U.S. Department of Energy - Energy Efficiency and Renewable Energy

Building Technologies Office

Calculating Energy Savings of Cool Roofs Webinar (text version)

Below is the text version of the Webinar titled "Calculating Energy Savings of Cool Roofs," originally presented on April 22, 2010. In addition to this text version of the audio, you can access a PDF of the slides, a resource document, and a recording of the webinar.

Operator:
Welcome, and thank you all for standing by. At this time, I'd like to remind parties that your lines are in a listen-only mode. Today's conference is being recorded. If you have any objections, you may disconnect at this time. I will now turn the meeting over to Anthoney Perkins. Thank you. You may begin.

Anthoney Perkins:
Thank you, Rose. My name is Anthoney Perkins, and I'd like to welcome you to today's webinar, which is titled "Calculating Energy Savings of Cool Roofs."  The webinar is presented today by the Building Technologies Program at the U.S. Department of Energy, and we're excited today to have with us four speakers who will talk about cool roofs and their benefits. They'll also introduce a new Roof Savings Calculator to measure cost effectiveness and energy savings of cool roofs in both residential and commercial applications.

We're also going to learn about current research to develop innovative cool roof products and move them into the marketplace. Before we do that, we have some housekeeping items. First, you've already been told that everybody is in the listen-only mode. We will have a question-and-answer session at the end of the presentation, and you can participate by submitting your questions electronically throughout the webinar. To submit a question, use the Q&A link at the top of your screen.

You'll simply click on that, type the question in the box and click "Ask."  Make sure you click the "Ask," and not the symbol of the raised hand, so we can receive your question. Our speakers will address as many of the questions as time allows at the end of the presentation. Also the URL that's on your screen now — the www.buildings.energy.gov/webinars — is where you will find today's slides. And today's presentation is being recorded. So a video of the presentation will be posted in the near future, and you can also find links to past presentations and webinars there.

Finally, we have a few questions to ask you to help us learn more about the audience and target future presentations. We'll start with two questions now, and then we'll have two more questions at the end of the presentation before we go into the question-and-answer session.

[Next Slide]
So if you click on your screen to indicate the appropriate response — you should see your first question up now, which is, "At your location, how many people are participating in today's webinar?"  And we'll give you a few seconds to answer that. If you haven't voted, please go ahead and do so now. Okay — we're going to go ahead and move on to the next question.

[Next Slide]
And that question is, "What best describes your affiliation or organization. And we'll give you a few moments again to click on your answer. Again, if you haven't voted, please go ahead and do so now so we can close out this question. Okay — thank you for your participation.

[Next Slide]
Now I'll introduce you to your first speaker: Marc LaFrance. He's the manager for the Building Envelope and Windows R&D Programs at the U.S. Department of Energy's Building Technologies Program. Mr. LaFrance leads development of the next generation of these technologies. So with that, I'll turn the presentation over to Marc.

[Next Slide]
Marc LaFrance:
Thank you, Anthoney. So welcome, ladies and gentlemen, and welcome to this Earth Day. It's a great, great day to work on energy efficiency. So I want to discuss an overview of what we do for Building Envelope Research — the macro program overview. And then I'll get into some more details on what we're doing lately for cool roofs. And then, of course, the majority of the presentations today are involving the details of our brand new advanced roof calculator that we're launching today.

[Next Slide]
Okay — so first of all, I'm sure many of you on today's call are familiar with the Department of Energy's Office of Energy Efficiency and Renewable Energy. And as you can see from this chart, we have a pretty broad agenda, working on supply side renewables as well as energy efficiency. And of course, I work in the Building Technologies Program, which is a major part of the impact in the energy consumption of our country.

[Next Slide]
Here on this slide, you can see — you know, if you're looking at any way to mitigate energy consumption, you have to address the building sector. It's 39 percent of the primary energy in the country, 72 percent of electricity, 54 percent natural gas. So obviously, it's a major agenda item for the country to save energy and, you know, all of the building envelope is a major component of that as well.

[Next Slide]
Okay — so for those of you that have worked with the Office of Energy Efficiency and Renewable Energy, and specifically the Building Technologies Program, here's a little history on our funding situation. You know, going back not that long ago, we're only at the about $60 million per year for the entire Building Technologies, which is, like I said, 40 percent — almost 40 percent of the consumption of the country. And now we've had significant increases in funding. This particular fiscal year, we're up to $222 million for our core funding, but we also had this stimulus funding last year, which is still being administered, for $346 million, so significant investment for the Building Technologies Program. And fortunately, because of this funding, this is why we've been able to put a much greater emphasis on cool roofs.

[Next Slide]
And so when people talk about building envelope, we're talking about all of the components of the building envelope: roof, walls, foundation, windows. All of this has an impact of 57 percent of the loads of the building. So, for example, we can provide daylighting through windows, or we can provide natural ventilation through windows. So it's a major element. So if you're going to be trying to mitigate carbon or save energy, you have to look at the building envelope.

[Next Slide]
And so here's the funding history of the Building Envelope Program, and I'm not going to go through the details. Some of these slides today — I do have quite a few slides — some of them are here for reference, and you can go back and look at them. And of course, you can ask questions in the webinar, but also you can follow-up with my contact information after today's presentation. But here, you know, we were back at a funding level of about $8 million per year, and then now we're seeing significant increases up to $16 million in FY10, along with expectations of $20 million to $30 million for the stimulus funding to supplement this activity. And then our FY11 request actually includes $2.5 million worth of cool roof activity.

[Next Slide]
Okay, and so our long-term goal in the Building Technologies Program is to develop technologies that will allow us to achieve net zero energy homes by 2020 and commercial buildings by 2025. We also are very interested in existing buildings, and those of you that have seen the news information yesterday, the administration released our retrofit ramp-up results, and so there's a significant effort going on for the existing market as well as new construction.

[Next Slide]
So here on this slide, I'm showing some of the technologies we're working on for the next generation of windows. So we're working on highly insulating windows as well as dynamic solar control. So when we talk about dynamic solar control, these are relatively new windows that have been commercialized. They're still fairly expensive, but we will be seeing the price drop with more competition and more R&D. But here's an example of a pretty large example — I mean, a demonstration — I mean, an actual application for a full-scale building here on the left.

And so windows of the future will be both highly insulating and dynamic so that we can significantly reduce the consumption of energy in the window portion of things. Okay — going on to the next slide.

[Next Slide]
This is our thermal envelope research, which we're really looking for advanced walls, much higher in insulation value with an existing three and a half inch wall cavity as well as trying to go to the R30 walls from different strategies. We're also working on the next generation of attic and roof systems. So this is to reduce the consumption by 50 percent. Cool roofs can reduce the consumption about 10 to 20 percent. So we're really looking at going way beyond cool roof material for the next generation of attic systems. And a major part of the program includes the new material development.

So for example, we're looking at new types of insulation, new types of membranes, you know, all kinds of technology that you'd use to make up these different building envelope components.

[Next Slide]
So here when I talk about the next generation of attics, these are the technologies that we're integrating together. We're taking cool roofs along with the thermal mass benefit. There's a thing called above deck ventilation, which is whenever you have a roof, if you have a secondary roof you can have an airspace, or a classical application would be like a clay tile or cement tile that you actually have a ventilation below the tile deck. Of course, ratings been around for a long time, but we know that if we use them appropriately we can save significant energy and, of course, taking all of this together with advanced insulations and integrating it into what we call the next generation of attic and roof systems.

[Next Slide]
So here's a slide to show you — look at — if you — I know it's pretty complicated for a lot of people, but if you look at the top of the chart — the black line — that's what a conventional roof would have. And we're — we're — significant reduction in consumption of energy in a hot climate, and we can do all of this for about $2.00 a square foot for either a new roof or the replacement; when you go to replace your roof anyway, you could put on this new system, and this includes these strategies all combined. We are going to be coming out with an advanced attic roof design guide for hot climates later this year, and that'll be unveiled with a lot of the technical details of how do you achieve this performance that is going to be cost effective.

Mixed climates and cold climates are much more challenging, and we're still continuing to research in those areas, and that'll be something that we'll be launching in future years.

[Next Slide]
Okay — another major accomplishment was — we commercialized what we call dynamic insulation or, in this case, it's cellulose insulation that's been doped — or it's been added — we've added phase change material which will make our lightweight construction in the United States perform like a thermal mass wall. So it gives that thermal mass effect to significantly reduce the consumption in certain climates. It is very climate-dependent. A lot more work needs to be done to show the value in the marketplace of this dynamic insulation. But it is a significant accomplishment for the program.

[Next Slide]
Okay — another major area — many people on this call I'm sure have always heard of infiltration, and we all know that infiltration will save energy, but there still lacks a significant amount of knowledge about how — how and where we can save the performance of infiltration. So we have lots of new technologies. But yet it hasn't been fully implemented. And so this is a major study that we're working on right now.

[Next Slide]
Okay — and so our new interest in cool roofs basically — many of you have heard of Secretary Chu's remarks about cool roofs. We've been trying to promote this in the code, and then — so right now we're really looking at doing a lot of things. So one of the things today, of course, is this new calculator, which we're launching today, but we're also working on a retrofit guide that will be available for comment soon. We're also working on test procedures, and we're also doing things internationally. Now, I'll go more — into a little more detail of these items.

[Next Slide]
Here's a quick chart to show you the performance. When we start looking at cool roofs, the R-value, or the amount of insulations installed is a major factor in how cost effective the cool roof will be along with the climate zone, the energy rates, and then, of course, the type of cool roof. So as you can see, the energy savings of cool roofs is highly variable, and that's why having this calculator is so important.

[Next Slide]
Many of you have heard of a garden roof or a vegetative roof or a green roof, of course. There are a lot of different names. Basically what a garden roof is — it's a high-performing cool roof that has — that basically adds thermal mass to the roof and provides additional energy savings. Basically, this middle bar at zero would be a white roof. And, of course, the tall bar would be what a black roof would have, and all of these are different types of garden roofs to show you how the additional savings would perform.

[Next Slide]
Okay — today I didn't go into a lot of detail of what a cool roof is, and I was hoping that most people on this call know that. We do have a cool roof fact sheet that's widely available to people. Basically, you have white roofs, and then you have near infrared reflective pigments that are added to dark roofs for, let's say, residential asphalt shingles, for example. But all of these ratings are highly important to have to be rated by the Cool Roof Rating Council. And so we're working to try to basically accelerate the ratings. So instead of waiting three years, you can do that in six months, and this is being led by LBNL in cooperation with Oak Ridge National Laboratory with significant support from the California Energy Commission.

[Next Slide]
Okay — this next one is — okay, so we talked about the integrated cool roof calculator. This is a joint collaboration between Oak Ridge and LBNL for a number of years. The California Energy Commission — I want to thank them very much for helping support this financially. And then, of course, we've been doing it in collaboration with the EPA. So now before there used to be a DOE and an EPA calculator; now as of today we have one calculator for everybody to use. I already mentioned a little bit about the retrofit guide, and this is going to be available for stakeholder review very soon.

We also are looking at an opportunity for promoting cool roofs internationally, and we do have a draft study that's available. People can review it. It's not really — it can't be referenced yet because it hasn't been completed. But if somebody wants it after the call — after this webinar, you can always email me, and I'll make sure you get a copy. It will be posted for comment at some point, but it's not up on the web yet.

[Next Slide]
Okay — I'm getting pretty close to finishing. I know I'm going a little late here. So basically besides what we call the classical energy efficiency replacement of cool roofs — so whenever you're going to save energy in a building that's being conditioned, we also talk about urban heat island, or the direct global benefit from higher albedo. And this is where we think we need to do significant research to further understand these phenomena and also to help implement what we'd call basically cost abatement.

So basically, if you're putting in a measure that's not cost effective for the business owner, how much money would you spend to abate that carbon?  And so we're doing a critical review of urban heat island studies, which should be available any day, and we will be convening a scientific panel to help plan for our research roadmap for — to help plan our urban heat island and our direct global benefit research.

[Next Slide]
Okay — and when we talk about international implementation, there's lots of places in the world that it's extremely hot that have very little insulation. Perfect example is India, okay, and you can implement cool roofs very cost effectively, and we're doing a significant effort to try to go after these various areas I have listed here on this slide to really implement cool roofs internationally and also help U.S. companies sell these products as well as the global market for cool roofs.

[Next Slide]
And a lot of this is being done under the Asia-Pacific Partnership and — let's see — okay. Sorry. So basically, under the Asia-Pacific Partnership, these are a lot of the details we have here. But this shows you that we're working ahead, and this is where we had some proposals for the cool roof project with them.

[Next Slide]
Okay — and — okay, I go into the more details here. I think I'm not going to go through these details right now.

[Next Slide]
And then the final remarks — we have a significant investment in cool — in the energy efficiency, and we can play a major role in adopting cool roof technology and working in the future.

[Next Slide]
Okay — and with that, I'm going to turn it over to Bill Miller. Dr. Miller is an expert researcher at the Oak Ridge National Laboratory working on —

[Next Slide]
He's been working on the AtticSim model for quite some time, and he's really been a key player in all of the cool roof technology implementation and effective analysis of measuring the performance of cool roofs. So, Bill, I'll turn it over to you now.

[Next Slide]
Bill Miller:
Thank you, Marc. And to all out there in — listening to this webinar, I thank you for your participation in listening to us all as we talk about the cool roof calculator. I've gone to a slide that shows the computer tool that we're trying to develop. The project was one of collaboration — very much a team effort. The sponsorship from Chris Scruton of the California Energy Commission, and Marc LaFrance, who just spoke, from the Building Technologies Group, and a host of industry partners.

The work was done in collaboration between Lawrence Berkeley National Laboratory and Oak Ridge National Laboratory. And in developing this calculator tool there was a fair amount of bantering back and forth about how to set this thing up. And those folks who helped us who were sort of the glue that brought it together was the White Box Technology folks, Joe Huang and Ender Erdem.

[Next Slide]
Now, the objective in this project was to develop a web-based calculator that a consumer, a contractor or a distributor could estimate the cooling energy savings, and those cooling energy savings can be significant because there for buildings it's roughly 40 percent of the primary energy that you have so that you could better learn how to see what these savings are for installing cool roof products on a specific building, whether it is a commercial building or a residential building, whether it's the steep slope or whether it is a low slope.

[Next Slide]
Our goals — we wanted to benchmark the measured energy savings to cool colored roofing products. We have done several experiments — field studies in California as part of the CEC Pier Project. We would like to take that benchmark data to give credibility to our calculator tool, then to use it to educate the consumers, contractors, engineers and architects on the benefits of cool roofing. We would also like to help the manufacturers of cool roofing products to deploy their products and to help the utilities and the public interest organizations refine their incentives.

There are already cool roof rebates out there on the market, but we'd like to be able to better refine those incentives — make them better, if possible.

[Next Slide]
AtticSim — what is it?  It's a computer tool. It's written in FORTRAN, and it is an American Society of Testing Material, ASTM, C1340 Standard that you see there in the screen, and it predicts the heat transfer going through the attic floor — the ceiling of your home — that has an attic on it. It is a code which you could go to ASTM and download if you wanted to. And so it'll perform calculations of heat transfer in a roof and attic such as you see here to the left for this California Energy Commission Public Interest Energy Research Project.

We did demonstrations at Fort Irwin; that's a United States Army Base. We had four houses that we set up with concrete tile. Two of those tiles were painted with infrared reflective or cool-color pigments. The other two tiles were placed above battened systems. And basically we did an energy balance for each of these respective roofs using the AtticSim tool. The tool was — has been very well validated. Petrie and Tom — Ken Wilkes did a study. That study is published, as you can see — looking at the effect of radiant barriers and attic ventilation with and without ducts in the attic.

Later the code was changed, and if you'll see this as I've changed it here, it is now showing a sort of a roof on a roof having an air cavity. This is what we call above sheathing ventilation. I developed correlations with colleagues from the University of Tennessee, and we were able to predict the heat flows that you would have in a roof system where you have above sheathing ventilation, which is commonly found on tile roofs and stone-coated metal roofs. They're placed on double-battens.

[Next Slide]
Now, the computer tool is one where you have a series of surfaces — everywhere from an attic floor to the gables to the eaves — the tool will do an energy balance on each of these surfaces and an energy balance on the interior surface, energy balance on the exterior surface. It solves for the temperatures. Given the temperatures, it then solves for the heat flows based on property data that you give for the building materials.

[Next Slide]
The code was very well validated in a study done for ASHRAE: ASHRAE Research Project 717. And I'm showing in this just some highlights of seven different sources of data. Owens Corning Fiberglass did studies with Oak Ridge National Laboratory in their large-scale climate simulator where they did test according to the ASTM protocol C976. And they are showing differences between — the percent difference between the predicted and measured heat flows for all these different tests, which were quite good — of the order of five percent in one case; 11 percent for the TVA project.

I'd like to highlight the one for Ocala, Florida. That was sponsored by the Mineral Insulation Manufacturers Association. It was an independent study where the results were very good for this calculator tool.

[Next Slide]
We took the data, and we benchmarked it against demonstrations at Fort Irwin, California, in the United States Army Base there. It's very new Barstow and very near the Mojave Desert, so it's a very hot climate — dry, hot climate. And what I'm showing for the south-facing roof deck, the heat flux going through the south facing roof of a tile roof that is applied direct to deck, and that tile roof has got reflective pigments on it, and so its solar reflectance is on the order of 42 percent solar reflective. And the symbols with a — sort of a light-colored pink in them — that is what AtticSim predicts.

This dotted line is the field measures. If I go to — this work has been published in a task report to the CEC. That was completed in March 31 of this year.

[Next Slide]
This is the heat flow that we're seeing through the attic floor, and this respective attic, if you look at it, it has trusses, and it also has a radiant barrier that faces into the attic. It's a Louisiana Pacific Tech Shield product. Now, the product — when I did this simulation, I did not simulate the gables — not the gables — the trusses within the attic, so there may be a timeline that I need to compensate for. The code has the ability for modeling trusses in the attic. That'll be a phase that I'll be doing soon.

[Next Slide]
Now, what we're wanting to do — AtticSim is one of several good codes. We feel it's an excellent code in terms of predicting the heat flows and the temperatures that you have in a roof or attic. But the fallacy of it is that it's not coupled to a whole-building. The difficulty with the DOE-2 engine is that that code does not do the greatest of jobs of the radiation heat transfer that you might have in an unconditioned zone, such as an attic. So to provide a state of modeling of the attic space that would include ducts or without the ducts, we decided to take AtticSim program and merge it into DOE-2.1E, and that code is now what we're using as the engine for this Roof Savings Calculator.

[Next Slide]
So at this point, I'd like to hand this presentation over to Joe Huang of White Box Technologies and allow Joe to explain to you just how it is he put this together. So with that, Joe, I'm giving you the floor.

Joe Huang:
Thank you, Bill. And I'd also like to welcome all the attendees in California. So it's actually early morning here. I'd like to spend a few moments and talk about the DOE-2 program and then talk a little bit about how AtticSim is integrated with DOE-2 and show you just a few preliminary results.

[Next Slide]
So DOE-2 — I'm not sure how many of you've heard of it. It's been around since the early '80s. It's gone through many versions. It's a whole-building simulation program that's hourly simulations. And this flow chart here shows the procedure that's used in DOE-2. You describe the building. It calculates the heat gains and losses in loads, then it calculates the distribution of heating and cooling through systems, the production of heating and cooling through the plant. Then it does an economic analysis, and then it gives you lots of outputs on energy use, energy costs, indoors conditions, etcetera. And then to run it, you need an hourly weather file.

[Next Slide]
So DOE-2 is an unbiased, well documented, public domain program for building energy analysis. It was developed by LBNL. Actually, I'm listed as White Box Technologies, but I was an LBNL employee for about 26 years. So it was developed at LBNL with support from the Department of Energy. The last federally supported version of DOE-2 is DOE-2.1E, and that was actually completed in 1993. Afterwards, there's been more work on DOE-2, and the latest version is DOE-2.2, and that's supported by — it was developed by a private vendor, and it's supported by Southern Cal Edison.

The source code for DOE-2.1E is — can be procured. The source code for DOE-2.2 is at this moment — it's proprietary, and I put this up mainly to explain while we're using 2.1E. It's the last publicly available source code version of DOE-2. DOE-2 is based on ASHRAE procedures for calculating heat flows and building loads. It's probably the most widely used simulation program in the U.S. and probably around the world, especially if you consider all the user interfaces that's come out, including eQUEST that is the interface for DOE-2.2, and then Visual DOE, Energy Pro — there's several of these interfaces for DOE-2.1E.

[Next Slide]
So what we've done with the Roof Savings Calculator is we're really harnessing DOE-2, and we're bringing it out as an easy-to-use web-based tool because DOE-2 by itself — it's an engineering program. It requires a fair amount of knowledge about how buildings are put together, how they're operated, and it really takes months of training before you can really use it efficiently. In its native form, DOE-2 uses a text-based input and output procedure, and just doing that, even if you know DOE-2 quite well, it's going to take you about a week or so to develop the input files, to debug it and then to evaluate the results.

What we've done with the web-based roofing calculator is we've developed template files — template input files that basically describe your building, and it's all predefined. And then what the user needs is only to provide, through the user interface, a few key building parameters — where you're located, the size of the building, type of building, etcetera — and then some more specific information about the building, attic and roof. And then DOE-2 does a run, and then it feeds back to the user interface the results that are then displayed on the screen.

[Next Slide]
So I don't want to go too much into the engineering details. This is for the people that are more familiar with DOE-2. We've actually coupled AtticSim into DOE-2 systems. And the reason we do that is we want to capture the actual air temperatures of the attic and the room below. And then we also want to get a correct feedback between the ducts and the attic space as well as on the HVAC system. So this little flowchart shows that as we're looping through DOE-2 systems — as we're looping through the zones, when the modified program sees an attic space, then what it does is it builds an input file for AtticSim. It sends those input file to AtticSim.

AtticSim then does the simulation for that hour, sends back the results to DOE-2. So it, again, in essence, replaces the attic simulation in DOE-2, and it gives — AtticSim gives back to DOE-2 the attic floor conducted energy to the room below. And then it also gives it the attic temperature and the duct losses both to the attic as well as to the HVAC system.

[Next Slide]
And now in the roofing calculator we've considered two types of roofs: a low-slope roof and steep-slope roof. And the low-slope roofs, we have three prototypical commercial building types. Low-slope roofs are really on commercial buildings. Steep-slope roofs, we've done two prototypical buildings. One is a residential building — really a house. And then we've also done steep-slope roofs on a prototypical commercial medium-sized office building.

[Next Slide]
So this is — these are the building types that we covered for the low-slope roofs. It's a medium office, a big-box retail and warehouse. And what you see here are just representative photographs of these types of buildings, and then below that are the template prototypical buildings that we have in the roofing calculator. These are actually taken from DOE's commercial building benchmark models, something I was involved in several years ago. And there's a reference for them below.

[Next Slide]
So for the low-slope roofs, we're looking at three building types. We're looking at four roofing systems, either single-ply, concrete paver, bitumen or built-up roof. We look — we allow you to look at three vintages of the building and the HVAC system: pre '80s, '80s to '90s, and then post '90s. And then we look at three — we allow for two types of heating system, either a furnace or a heat pump. And then we also assume that there is a air conditioning system. Then as far as the roof itself, we look at nine levels of roofing ceiling insulation, seven levels of roof solar reflectance, six levels of roof thermal emittance, and then the results come out as the annual and monthly heating and cooling energy use.

[Next Slide]
So for the steep-slope roofs, we have a house — a residential building. It could be either one-story or two-story. And then we have a medium office. And by the way, all these prototypes are scalable. So you put in the size — the floor area of the building and the number of floors, and you will — the template file will adjust for that.

[Next Slide]
And then for the steep-slope roofs, we have two building types: a house and an office. We have three levels of roofs thermal mass, whether it's tile, metal or asphalt shingle. We — with a steep-slope roof, we also consider whether there are ducts in the attic, and that's actually an important factor that AtticSim is able to model. We also can model radiant barriers and then also above sheathing ventilation. And the other things are grayed out because they're the same as what I said earlier for the low-slope roofs.

Okay — this is a preliminary set of runs that we were doing on the same Fort Irwin house that Bill mentioned earlier. And the difference here is now we're looking not just at the AtticSim simulation, but we're looking at AtticSim as coupled to DOE-2.1E. And you see here the solid line is the attic air temperature, the dotted — purple dots, that's what AtticSim has simulated, and then the — well, these figures are kind of small — these symbols — but we have two sets of symbols for the DOE-2 AtticSim simulation. And the difference between them is that one of them assumes that this has natural ventilation, so it has low — that's the top one.

It has a small inlet — IA stands for inlet area, and the OA stands for the outlet area. So this really assumes that the roof is ventilated, but it's all through natural ventilation. Unfortunately, when Bill looked at the roofs and looked at the data, it turned out that this attic actually had a solar driven — I mean, solar motor driven power ventilation, and that's one of the complications you get when you actually look at real data — that things are more complicated than anticipated. So we also did a run where we simulated the power ventilation by increasing the inlet area and the outlet area, and you'll see that when we did it that way the results are almost right onto the measured data.

Of course, some of the cynics out there will probably say, well, I'm just fudging the numbers to make them match. And we realize that, and Bill and I are now also looking at other data that may not have this complication.

[Next Slide]
So with that, that was the last of my slides, and so now I would like to introduce our final speaker: Joshua New. He's a Computer Science Specialist at Oak Ridge. Dr. New was instrumental in developing the design and implementation of the Roof Savings Calculator, and he will actually explain the tool's applications. Here's Joshua now.

Joshua New:
As Bill Miller and Joe Huang have discussed, the Roof Savings Calculator integrates AtticSim for advanced modeling of modern attic and cool roofing technologies with DOE-2.1E, so we have the fast whole-building energy simulations where we can actually show the savings from the HVAC unit. The integrated simulation engine can perform an annual simulation of hour-by-hour performance using local TMY2 weather data.

[Next Slide]
And it can do that — an annual simulation of hourly performance — in about 30 to 40 seconds. We'll go over this in more detail in subsequent slides, but at a high level the inputs required are general location and building details, heating/cooling unit information and roof/attic information, which is the key focus. Now output is annualized energy and cost savings with monthly information available for subsequent analysis. This is a screenshot of the Roof Savings Calculator, and, unfortunately, that'll be as close as you get to the URL until the end of the demo. So I'll give you that little teaser there.

The Roof Savings Calculator was developed to handle the average load based on comparable web services, one to two users a minute, not the peak concurrent load of the 900-plus registrants we had for this webinar. So we've ordered additional hardware to handle this kind of peak load, but the compute-intensive simulations prevent us from sharing the URL until the very end. And we have a few mechanisms I'll discuss on how to make sure you get your results.

[Next Slide]
So the Roof Savings Calculator was designed as an industry consensus tool. As Marc LaFrance mentioned, there was a DOE calculator and an EPA calculator, and now we're combining that into one Roof Savings Calculator. The industry consensus tool unifies best practices identified by the previous DOE calculator and EPA's Energy Star Roof Calculator with modern roof and attic technologies identified by the California Energy Commission's Project Advisory Committee and several subsequent teleconferences. The managers of the two previous calculators have agreed to take down their calculators and promote use of this new calculator tool.

There are a total of 17 questions per building which encompass the two previous roof calculators and the Project Advisory Committee recommendations with the exception of HVAC schedule, internal load and days of operation per week, which we use those template files that Joe was talking about since we believe we have good estimates for that. There's also a concern that biased users could use those parameters to game the system and report unrealistic savings estimates. The Roof Savings Calculator also can't handle condition space under roof, such as a cathedral roof, and is a potential future addition to AtticSim.

Building America profiles were used as the statistical basis for selection of the default answers, so the only necessary input you even have to give is just the location of the building in question. We also provide a lot of other details that you can define, and I'll go through those one by one later on. Some questions have links for additional information, such as if you don't have good building data handy you can look at your utility pricing by state and other things like that.

[Next Slide]
We use several dynamic web technologies in the development of this Roof Savings Calculator. It was designed for building owners, manufacturers, distributors, contractors and practitioners so that they could easily run complex simulations. The latest web technologies and usability design were employed to provide an easy input interface which minimizes the number of questions the user must answer. The web technologies include a veritable alphabet soup. This is mostly for the computer scientists in the group and cognitive experts.

But we used Dynamic Hypertext Markup Language, which includes use of the HTML Document Object Model, Cascading Style Sheets, which allow site-wide formatting changes in seconds for cleaner code, reduced load time and caching, better separation of content versus presentation and improved search engine placement. We use AJAX, or Asynchronous JavaScript and eXtensible Markup Language for client-side interaction and asynchronous client/server communication through JavaScript Object Notation, or JSON, packets.

And we used then the Personal Homepage language, PHP, for data transfers and generation of dynamic waiting and result pages as well as the jQuery and jQuery user interface, JavaScript libraries. One compatibility is the jQuery Steamroller which allows you to create your own theme which you can apply to this webpage. One trick to using — writing a grant proposal is to Google terms and find out what the highest returned results is, and that shows you what the most popular phrasing, and that method was used to determine the name for technologies which come under various different names for different reasons.

For each question, the answers are typically ordered with the most energy efficient at the top and the least energy efficient at the bottom so you can get a rough estimate of how this is going to affect the final simulation as you're making changes. We minimized the predicted time required to rapidly move from a — to a target area by using radio buttons. Those take up more screen space, but they allow less cognitive overhead since you can immediately see all the choices, and they require fewer and less accurate clicks than drop-down boxes. One of the most highly cited papers is George Miller's 1956 paper.

If you try to memorize these 18 letters, you'll probably find it difficult if you're an average human until you realize that those are a combination — you can group those into three letter governmental agencies, at which point there's only six of those groupings, and most people can remember them. So cognitive overhead — you can usually remember seven, plus or minus two, logical groupings of elements.

[Next Slide]
So at this point I'm actually going to give a live presentation of the Roof Savings Calculator so you see it up and running, and then I'll give the URL at the end so that you can play with it yourself. I'm getting disconnected here. Does — can I get feedback on you seeing the screen?  I'm assuming you can see the Roof Savings Calculator.

Jenni Sonnen:
Yes.

Joshua New:
This is the main page of the calculator. There's a feedback option here which I wanted to call out where the — as we make simplifying assumptions as to the inputs that you can provide, that we're necessarily removing handles that an experimenter or someone in the field might actually want to play with. So if you would click that feedback link you can go to a form where you can post feature additions, and we welcome your feedback, your praise, your complaints, any comments you have. I'd also like to call attention to the Cool Colors Project — CoolColors.LBNL.gov.

Jenni Sonnen:
Joshua?

Joshua New:
Yes?

Jenni Sonnen:
I'm sorry. This is Jenni. We are getting feedback that people can't see the screen, so maybe you'd want to just take a second and maybe open it in a new window and load a new window?

Joshua New:
Okay. I apologize for the technical difficulties. That's the nature of demos. Okay — I'm going to go back to the slides and see if I can go back to sharing the Roof Savings Calculator — see if that refresh will work.

[Next Slide]
Okay. Did that work?  Can I get feedback on that?

Joe Huang:
Yeah, that worked.

Joshua New:
Okay. So here's the Roof Savings Calculator. There's a feedback link here that I was discussing previously, and also the CoolColors.LBNL.gov, which has details on kind of the grandmother project of which the Roof Savings Calculator was a deliverable. And you have two choices here; you have the residential calculator and the commercial calculator. You choose the building type that you want to look at.

[Next Slide]
Then once you get into the Roof Savings Calculator, we have an advanced mode which I'll enable for the sake of this presentation.

[Next Slide]
The first question here — the closest location — you really want something that's with similar weather, so if there's several locations nearest you, you can think about whether they're on a mountain or not, and you select the closest location to you. The building type — this is where if you chose residential, but you want commercial, we have the different options here. So we have residential, office, warehouse and box tour that Joe Huang had talked about; different underlying assumptions and building models are related to that.

We have the conditioned floor area, which you can adjust freely. There's also a link here if you want to know what the average U.S. home was during a certain year. You can put in the number of floors — one floor or two floors — how many ever you need for your residential or commercial home. We have a window-to-wall ratio, which is an advanced mode option. It's something that most people don't know what their window-to-wall ratio is, but if you happen to be an energy expert, that's important to you. You can plug that in.

And many of the feature requests we expect to be getting we could be putting into the advanced mode option. The year of construction, as Joe Huang discussed, is pre-1980, 1980 to 1990 and post-1990; again, different assumptions underlying that. That was also details related to the primary building. So when you get to the heating and cooling unit, that's another grouping here, and you can select the different type of heating equipment you have. If you have a heat pump, then you only need electrical price — utility price information. Natural gas and then fuel oil for the northern colder climates.

If you happen not have your billing statement handy, we have the units here and a link next to it which links to the prices, on average, for your state, and you can break down in more detail there. Another important element of the heating and cooling unit in your home is the efficiency of the unit. So we have AFUE and numbers. There's other numbers out there, such as EER, and the link here will show you the mathematical equation to translate between those two. So with those two sections, we get to really what's the heart of the Roof Savings Calculator, and that is the roof and attic system.

So we have two examples here. One is the existing roof for a house as it is now or a building that's undergoing planning, and then on the right side we have the white roof comparison. So how much better could this building do it if it had a white roof with these certain properties?  So going through the questions one by one, we have the common types for residential is tile, metal and asphalt shingle. If I come up here to change it to office, you can see the roof type has changed to the single-ply membranes, concrete pavers, modified bitumen and built-up roofs.

I'll go back to residential just to finish this presentation. Now, two elements of the roof type that are most important for energy efficiency is solar reflectance and thermal emittance. So these are indented up under the roof type, and in this example the default situation if you only select your location will be a difference between a 20 percent reflective roof and a 50 percent reflective roof. So these are numbers that are age three years; oftentimes, manufacturers report their initial reflectance numbers. We use the age three years number because we're trying to model real-world performance, and things do degrade over time.

Also, we have — we have solar reflectances here that comply to different standards. We also have a custom option, so if you have a certain roof type that you're interested in with a known solar reflectance, you can put that in. That's true for several examples throughout this calculator. Thermal emittance — almost everything is other materials. It has a 90 percent thermal emittance. Only Galvalume and more exotic products will allow you to get the lower thermal emittance on your roofing system. Again, we have a custom — so if you have a new product, and it has a certain known thermal emittance, then you can plug that in and see what kind of energy savings we estimate.

There's above sheathing ventilation, which Marc talked about. It's the idea of a roof on a roof with an air cavity between. It's also applicable to tile and other types of metal offset membranes, for example, roof on double battens. Most people don't have that, so we defaulted to "no."  The pitch is the inclination. So is it a steep-slope or a low-slope roof. Here we give custom options for what high, medium and low is as far as the amount of rise and run, but you can put in your own slope if you know the slope of your roof system. Radiant barriers — we only allow yes and no.

Currently, the radiant barrier is modeled as the radiant barrier on the underside of the rafters facing the attic assembly. So if you don't know what a radiant barrier is, it's like aluminum foil with the shiny side facing toward the open area: so a low-emittant surface. Attic insulation — we have the standard regulation agency recommended amounts here, but you can, again, put in your own custom R-value for your attic insulation if you wanted to do a comparison. The duct location we allow to be either in the conditioned space or in the attic. A conditioned space is more energy efficient than the attic.

So just like with the R-value, more insulation is better, so more energy efficient options are at the top, and less efficient at the bottom. And same for duct leakage — so duct location — if you're an energy auditor, you know the duct leakage is a very important aspect of the quality of the energy preservation for the home. So we have the uninspected amount, which we relegate to 14 percent, and a really good inspection of 4 percent leakage; but you can specify, again, your own custom amount. At the bottom here, this is something I wanted to call out during this webinar.

I had already highlighted we don't have the computing power to run all the simulations for everyone in this webinar. So if you want to make sure you get your results, I recommend you put your email address in this box so that the server can email it to you. When you've selected everything, it will — there's some cursory error checking. So you have to put in the location. That's the only thing you have to put in, and I rerun my simulation.

[Next Slide]
And while this is going on, I figured I would highlight a few things that we're — we've talked about doing — some future work. We don't have a very good system for telling how long a user is having to wait. We want to develop a queuing system, and that's not implemented yet. That'll give you statistical basis for how long you have to wait for your actual simulation. The simulations, again, take 35 to 40 seconds, with a little bit of post-processing overhead on top of that. But we're talking less than a minute.

[Next Slide]
So here we've gotten our simulation results. We save $93.00 a year for a Birmingham, Alabama, roof going from 20 percent to 50 percent solar reflective. We have the total energy savings reported as well as the cooling and the heating. You usually take a penalty because of the cool roof. You're reflecting energy, so in a colder climate like Alaska it's not something you would want to do. So you take a penalty there, but usually you save more energy during the hot months.

We break it down into monthly savings for more details, so you can see again it's on the hottest months that you save the most money, and — because you're reflecting the heat energy rather than having to run your HVAC to cool the house. And then we break it down into monthly performance for the retrofit case, or the white roof case, and the base case, or the existing house case.

[Next Slide]
We also have links to the data so you can see, okay, this was a house in Birmingham, Alabama, a residential house, had all these parameters that were sent to the simulation. Same for the comparison — so the white roof had a different reflectance.

[Next Slide]
And then the raw output — so this is an easy mechanism to get some DOE-2.1E output. You have the whole energy simulation here, so if you're an energy expert and you want to dig into the code and the output and detail, there's plenty for you to look at right there.

[Next Slide]
So then I'm going to switch back to the presentation.

[Next Slide]
Some future work that we're still talking about is the queuing system, already mentioned; mouse-over tool tips — so there may be a few things that you're not comfortable with or you don't know. We want to provide more information on that so that you get an idea of what this technology is, how it works and how it does what it does. We want to enable on-peak and off-peak pricing models. Also we want user input for scheduled usage profiles. So how do you set your thermostat? Do you cut it off when you got to work or when you go to sleep? That would be a nice handle to have for most people.

Also, this is — all these energy savings are based upon the heating and cooling load from the heating and cooling unit. It's not plug loads. But in some places of the world, especially the 40 percent of the population between the Tropics of Cancer and Capricorn, a lot of them don't have HVAC units. So it'd be good to know if we put a white roof in a third-world country how much would it decrease the temperature in that tropical area inside that home. We want to allow additional building types.

We have just a handful now, but as future requests roll in we'd be interested in knowing what the community wants in this calculator. Also, ductwork above a roof plane, advanced mode options, which are all those feature requests we hope to get from you guys, and there's also a possibility we could open source at least part of the calculator. So we'll have a polling question on that later to just gauge the interest in the community of having some of this code available to the public. And with that, I'll turn it over to Jenni.

[Next Slide]
Jenni Sonnen:
Great!  Thank you so much, Joshua. My name is Jenni Sonnen, and I work with the Building Technologies Program, and I'll be helping with the final polling questions and also to introduce the question-and-answer period.

[Next Slide]
So we just have a few polling questions to wrap this up before we move to Q&A. The first one should be on your screen now. This one is about the Roof Savings Calculator, and if you have an interest in having the code made available open source. If you don't, we do have an indifferent category if you'd like to answer that. So please take a minute and answer this, and we'll move to the next question. All right, I'm going to move to the next question, so please answer. Great!  Thank you.

[Next Slide]
And then this question is based on the demonstration you saw today. How well do you think the Roof Savings Calculator will meet your needs?  So please answer that. And if you'll answer that, I'll move on to the next question. Okay — great.

[Next Slide]
So this question just wants to find out a little bit about what you were hoping to learn from today's webinar. So take a minute and answer that one. Okay. I'm going to move to the next question. This is the last question, just wanting to know how well your expectations were met today. Okay — great. And with that, I think we will go ahead and — thank you for responding to those. We'll go ahead and turn it over to Q&A right now.

[Next Slide]
So you can submit your questions based on the directions on the screen here. And Marc, did you want to kick it off?  Do you have any questions you'd like to address?

Marc LaFrance:
Yeah — sure, sure. Thanks, Jenni. Okay — first of all, I just wanted to clarify one thing. At the end of my presentation, some of you might have noticed that I was hesitating a little bit on some of my slides. That's because there was a little bit earlier version that was loaded. So for reference, we will be putting up the latest version on there. And one of the questions that actually came in was addressed by my original — my final presentation, and that is people keep saying, "How do you cool roofs play in with photovoltaic cells?" 

And the simple answer is — I always tell people that cool roofs are ready today. They're economic today, and PV, even though many people are putting them in because of rebates or tax credits — you know, PV's really available for the future. And so that's the big difference. Of course, cool roofs are going to be available or going to be needed in widely spread for developing countries for many years. It may take 20 or 30 years before PV is truly cost effective for other countries. One last thing is whenever you have PV on top of a roof, if there's a gap that allows for the cooling or the airflow below the PV panel, then that's the most effective roof system so that the heat doesn't penetrate into the roof.

But of course, some of our advanced technology that we've shown today with the radiant barriers and the above deck ventilation, you could put a thin film PV right on the roof surface but have actually a cavity behind the roof surface that actually would prevent that heat from getting into the building. Okay. I'll — and that was one of the — another question here was, "Are all white roofs the same, or how do they perform?"  Okay — basically, a critical element of this is the Cool Roof Rating Council, and so the biggest difference between one white roof and another white roof is the long-term performance or the aged value.

So after three years, some particular white coatings may have a very small reduction in performance, and other ones could have a significant reduction. So it's very important that you have an aged value for your rating on the white roofs. And maybe I'll take one to two more quick ones, and I'll turn it over to the next person. There are quite a few questions that go beyond the cool roofs, and maybe in our second round of questions we can get to some of those. Another key measure was about — it seems like there's several questions coming in about the performance in hot climates and the heating penalty, and that is why we have this calculator.

As you can see from the demo from Josh, there's so many parameters involved, and climate is a major element of that. So, for example, our retrofit guidelines — it's not going to be one size fits all. It's going to be, "Here are some of the types of roofing measures you need to consider."  But we always will refer people back to the calculator to determine if it is cost effective for their application. I think there was also another question regarding application in cold climates, let's say, for a residential building that maybe is not an urban heat island.

All of the stuff that we're putting in here currently for our policy does not include any kind of benefit of urban heat island or direct global benefits. It's all about energy efficiency. Now, we need to conduct research that will decide whether or not we should have appropriate benefits or value that we can place on it, but today we don't have those determined yet. So all of the applications will be applicable to energy efficiency for energy savings. And so in a cold climate, it may not make sense for energy efficiency. Now, it may — it could make sense for an urban heat island, but that goes beyond where we are today for our implementation tools.

And that was a few questions. Then if there's a second round, I'll go through a few more. And I guess at this point, Joe — I'm going to turn it over to Joe so he can respond to a few of the questions that he received, or I guess we could — I'm sorry. I'm sorry. Let me go to Bill, because Bill's next on the list, about the AtticSim questions. Okay, Bill, can you answer a few, please?

Bill Miller:
Sure — I sure can, Marc. Thank you. There's a couple questions that popped up for me, and the one question came up, "Can one set of cool roof guidelines work for the whole country?"  And an issue there is — and the gentleman further elaborated saying most studies show that cool roofs in northern climates — say Zone 5 and higher — add little to no value in energy savings. And that's a very true statement. This calculator tool is a cool roof calculator tool, but as you have now see, the tool can be used to not only model a cool roof.

It can be used to model a roof that has different levels of insulation. It has the ability to model a roof that has a ventilated airspace. It has the ability to model a radiant barrier so that you can take these options and utilize them to try and see what makes the best sense in your respective geographic location. I've always looked at this in terms of minimizing energy for that respective geographic location. Cool roofing can be a part of that. As an example, if I'm in Chicago or in, say, New York City, those are very predominantly cold climates. However, they have very hot summers.

And so what if you had the cool roof, but you also implemented other strategies that made that roof work well in the winter?  This tool — our desire is that this tool can be used to show the benefits of different strategies working in unison to minimize energy use. The next question, "Does AtticSim work with Energy Plus at all?" AtticSim is a standalone code that was written in FORTRAN. Energy Plus is its own standalone code which is written in FORTRAN 90. AtticSim uses response factors. Energy Plus can use response factors, or it can do a finite difference type calculation.

But the bottom line is, no, you have to do what we did. You would have to take and merge the attributes of AtticSim into Energy Plus to make this work. Now, Energy Plus does model a radiant — the radiation exchange in an unconditioned zone. It does have in it the ability to model a duct system. The reason — I don't know how well that is benchmarked, but the main reason we went with AtticSim is because of the speed of the process when you have a duct system in an attic.

If you're on the web, and you're running a simulation, the speed, as you saw from Josh showed, is the order — for a full year of data, the order of about 45 seconds with that — 45 to a minute with that duct system in the attic. So, you know, bantering back and forth on this, we went with AtticSim and DOE-2. Those are the two questions that I had and I've tried to answer. Joe, would you like to field some of the questions you've got, please?

Jenni Sonnen:
Actually — oh, I'm sorry. Joe, this is Jenni. I'm sorry to interrupt.

[Next Slide]
We did have — one of the polling questions we had, we had a teeny bit of a problem on and weren't able to get the votes, and I was just wondering if I could jump in real fast and ask people to vote to the question that's on their screen now. Just take a second. Sorry to interrupt.

Joe Huang:
That's okay.

Jenni Sonnen:
Okay — great!  Yeah, please go ahead and take a minute and vote. Great!  Thank you for that. And Joe, with that, I'll turn it back over to you.

Joe Huang:
Okay — thank you. So I'm looking at several questions about — about simulations.

[Next Slide]
The first one is, "Is AtticSim for commercial and residential?"  And I think our presentations have already clarified that; it does both steep-slope residential as well as steep-slope commercial and low-slope commercial for three commercial building types. There was another question on, "Where and how can I access DOE-2, and where can I get weather files?"  Well, the DOE-2 program's been out for a long time, and you could get the root program or the native program from the energy software or technology center in Oak Ridge.

You could also get the eQUEST program, which is free public download. And that actually runs DOE-2 behind the eQUEST interface. That's DOE-2.2. That's not 2.1E; that's 2.2. Weather files — there are also plenty of weather files around. DOE maintains a large database on the web of Energy Plus weather files. The commercial DOE2.com also has lots of weather files for DOE-2. And then you could also get publicly available weather files in their own form — the TMY2's, the TMY3's — and you could convert them to DOE-2 and run it. So I don't think that's a problem.

If you're thinking of using it with AtticSim — with DOE-2/AtticSim — just keep in mind that we've already got all the DOE — 239 DOE-2 — I mean, the TMY2 weather files already installed on the web version. Another question is, "Difference between DOE-2 and Energy Plus?"  Well, that could take a long time to answer. Fundamentally, they're two different programs. DOE-2 is a 1980's vintage; Energy Plus is a later generation program. They're very different. They have some fundamental similarities, but their solution methods are different, and that's all I want to say about that.

"Why did I use DOE-2.1E and not Energy Plus, which is supposed to replace DOE-2?"  Bill already covered that in some detail. I'd reiterate that one of our concerns was both runtime — for DOE-2, to do a single building it takes less than a second. And actually when Bill says that the AtticSim — the roofing calculator simulation's taking about 40 — I was hearing 30 to 40 seconds. Actually, 99 percent of that time is for AtticSim, not for DOE-2. DOE-2 itself is very fast. And we were concerned that running Energy Plus would slow it down even more.

Another practical reason is I'm much more familiar with DOE-2 and not as familiar with Energy Plus. And also there's really no significant difference in the capabilities of — in this application because — keeping in mind that the attic is modeled in quite some detail with AtticSim, and DOE-2 is just providing the HVAC requirements of the building below. So, let's see, I have another question, "What about high-rise commercial buildings with very little roof area?"  That's certainly true, although I would say if you look at it on a per-square-foot basis it's really not that different.

It's just that if you consider the amount of roof, you may say that roofs are not very important. But then if you look at it per roof area, it's really not that different. Those are the only questions that I see in front of me. So I'm going to — oh, I got another question forwarded to me from Joshua. It says there was a question about, "In my city, many homes are 100 to 300 years old. Do you have tools for these?"  Well, I mean, you could certain use AtticSim for them. You may want to first evaluate if the model that we're building for the roof is appropriate.

You may have to take the DOE-2 input itself and then adjust them. But there's no fundamental reason why the DOE-2/AtticSim won't work for a 300-year-old house. So with that, I'm going to turn it over to Joshua, because I see he's got a — the longest list of questions.

Joshua New:
Yeah, and I can summarize most of them. There were a lot of questions — and I could go through all of them, but most of them involved, "Well, what about modeling this?"  So some examples where building orientation, hip roofs, wood shingle roofs, buried ducts, the older homes question that are 100 to 300 years old — all of these things are things that are not currently modeled — not a handle that — well, I should say they are modeled. They are in the building models and can be simulated. They are not in the web interface.

So we don't give you the handle by which you can change or use these things. So it's — I would like to reiterate — I didn't make a good enough point of it, but if I can go back — I'm going to go back to my presentation here.

[Next Slide]
The URL is RoofCalc.com, and if you've been to that you saw a "Coming Soon" link. But that is now open. So feel free to go to that website, and you can actually use the calculator yourself. On that main page, at the very bottom underneath the two images, there's a feedback link. If you click that feedback link, you can submit all these things that you want — wood shingle roofs, older homes, buried ducts, hip roofs — all these things we encourage you to submit through that form so that we have one source that we can go to and say, "Okay, what does the community say is important for them?"  So that should address that question and let you know that that website is alive and you can go there now.

Marc LaFrance:
This is Marc. I was going to — Joshua, you finished or you want me to just go for a couple more items?

Joshua New:
Marc, could you say that again?

Marc LaFrance:
Josh, are you all set, or — answered most of the questions or —

Joshua New:
Yeah — I have a couple more.

Marc LaFrance:
Okay — go ahead. I'm sorry.

Joshua New:
I'll turn it over to you as soon as I'm done. So I had some other questions which were involving solar panels and how that affects the cooling of the roof. I think Marc talked a little bit about that. There's a lot of articles out there. There's a July article in the Insulation Magazine from Scott Kriner that talks about how do thin-film PV systems affect the cooling loads on a building?  There's a lot of publications in that respect, so I would refer you to the existing literature for that kind of question. But PV systems are not currently modeled in the calculator tool.

"Do you have any general guidance on what heating or cooling dominated climate ratio is the breakeven or neutral benefit point for adding a reflective roof?"  I think that's a good question, and that's something that we're not answering with this calculator. We basically give you the tools where you can do a comparative analysis for yourself and see, "Okay, cool roofs are great in Hawaii."  That would make sense. "But they're not so good in Alaska."  Well, that makes sense.

So we haven't gone through multiple emulations of this simulator to answer those kinds of big questions as far as the energy performance goes. Now, a related question is, "What does a lifecycle cost analysis look like, and how do you do it?"  We're not looking at — we use utility prices to calculate the savings on the HVAC unit usage. We aren't doing a breakeven analysis or a return on investment of how much does a cool roof cost and to have the material as well as the labor.

Those are things that are really tricky and hairy to get into, and that's something that we're not looking at at this time. Those are most of the questions I've had. If you want to jump in, Marc, go ahead.

Marc LaFrance:
Okay — yeah — and I just want to reiterate one critical thing, and that is that this calculator is basically assessing the energy efficiency component of cool roofing. It does not include urban heat island or the direct global benefit, which are things that we want to research — we want to continue doing work in that area. But this just gives people the fundamental energy efficiency performance data that they need to get. And it does it in a much more elaborate way and a much more detailed way than they've ever had before.

So we're really taking some of these sophisticated modeling tools and bringing it to a basically layman user without having to have a full knowledge of the simulation tools. Now, obviously, in doing that we can't solve all the problems. People can still go back to full simulation and do their — do that type of manner to get their numbers anyway. But it's really taking the sophisticated modeling to many more people. And so one of the things that — one of the questions that also came in was, "Okay, what are we doing for other countries — so, for example," they said, "Mexico, Canada and other parts of the world?" 

Right now, I believe there's Canadian cities, so — and the Canadian building stock is very similar to the U.S. Mexico would be more of a developing country building stock, and we also were looking at trying to expand things to possibly India, China, other areas that will require additional building types and benchmark analysis. But one of the things we do plan on working on is expanding this calculator so that it can be used by other countries around the world. Let's see — there's — there's also a couple of non-cool-roof questions.

I don't want to get too crazy here, but one was for the dynamic insulation. You know, it's commercialized today. It can be used in a commercial building. But it's mostly useful in a climate like — a hotter climate with a larger change in temperature. So, for example, the Southwest would be perfect, even the Southeast. One thing about this dynamic insulation — people that don't understand the way that it works is if you can imagine the sun's energy beating on a wall, and normally the insulation slows that heat flow and then it still makes its way into the building.

Well, if you have a storage capacity, whatever energy gets stored, okay, that is going to delay the heat flow into the building. And so what happens is whatever energy doesn't make its way into the building would be peak savings. So it eventually gets in there a little later, but it's been shaving the peak. And then whatever energy — because the outside temperature now has dropped — the ambient temperature on the outside has dropped, so that stored energy flows back outside of the building, and that is the energy savings.

So you have both peak shaving and energy savings from dynamic insulation. Another quick question was — we talked about R-value of walls today, and we — our goal is to get to R20. So typical walls in most homes in the United States are R10, which would be like an R11 or an R13 cavity insulation with a thermal shorts — get you somewhere between an R8, R9, R10. There are walls in the Northwest United States that have had code for a number of years at R21 cavity insulation. So in essence, an R20 goal is doubling the effect of typical walls today.

And I think that covers most of them, but I don't know if — Jenni, if we have any new ones coming in as a response to some of our questions, or if people have anymore to go over?

Jenni Sonnen:
All right — Bill and Joe and Joshua, did you cover everything that you wanted to cover?

Bill Miller:
Well, there's just one little question here that I'm seeing. It might not have been hit. It said, "Did I hear the current version of the calculator will not model cathedral/vaulted roofs?"  And the answer is we gave certain styles of buildings, which Joe went over, and those styles did not include a roof that had — that was with a cathedral roof. We limited it to roofs that had an attic plenum. Now, that does not say that the combination of AtticSim and DOE-2 could not do a cathedralized roof.

It's just simply saying that for this calculator tool and this first step we are limiting certain building types. But as Marc alluded to, there can be more buildings that could be added to it so that, yes, indeed, we could get a vaulted ceiling in there and study that. Okay.

Jenni Sonnen:
Great!  Well, we're actually — oh, was there something else?

Joe Huang:
Yeah — this is Joe. I just want to make a comment about the roofing calculator — that what we've tried to do is to simplify the I/O — to simplify the input and output. But the modeling itself is actually quite detailed, and it's about the most detailed as I can — I've seen for the attic. And one thing that I like to point out is a lot of the time that AtticSim is using is to model the duct system, which includes air leakage as well as conduction losses. And I've noticed that if you run — if you run the program with the ducts in the condition space, it actually speeds up by a factor of three.

So I just want to make those two points. One, the modeling is actually, in my opinion, state of the art, and, two, that if you don't have ducts in the attic you'll see the results in less than ten seconds.

[Next Slide]
Jenni Sonnen:
Great!  We're getting close to the end of our time here. Does anybody have anything else?

[Next Slide]
Marc LaFrance:
Jenni, I guess there was one question that I guess I missed — is one that said, "How do we define a hot climate?"  In essence, the one thing about a hot climate, of course, is — the guideline will give you the design strategies as to how to install an advanced next generation of roof/attic system in a hot climate. And, you know, in essence, a mixed climate is basically a hot climate for part of the year. So the technology will still work for a mixed climate. The issue comes back to economics. So definitely Zones 1, 2 and 3 — but you start getting into Zone 4, you may lose your economics.

But certainly, the design practices are still pretty rigorous, and then what'll come out in a design guideline would be provisions as to run the simulations to show whether it's cost effective or not. So when I say, "We're going to unveil this next generation of attic roof guidelines for hot climates," it's really more along the lines of being economic and cost effective. As far as the energy savings attributes, it still would make sense in a mixed climate; it just may not be as cost effective. So hopefully that clarifies that question from somebody.

Jenni Sonnen:
Great!  Well, thanks for that, Marc. And thank you to all of the speakers for your time today. We really, really appreciate it, and we'd like to thank everybody who called in and listened and participated. We will be posting updated slides at the URL you see on the screen: buildings.energy.gov/webinars.html. We apologize for the confusion with Marc's slides, but please do check back to that webinar for the updated slides and also for information about future Building Technologies Program webinars. This concludes our presentation for today. Thank you, again, and goodbye.

[End of Audio]