BD+C Annual White Papers on Sustainability

BD+C's award-winning series of white papers on sustainability

December 20, 2010
         
 

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Excellent white paper.

Excellent white paper.

Net Zero: how energy modeling prevents us from getting there

article submission for AIA chapter newsletter Hello, I would like you to consider the following article for submission to be used in your next AIA Chapter newsletter. It is a pretty important topic, about the consequences of receiving inaccurate information from energy modeling programs. As an adopter of the 2030 Challenge, we realize that a combination of good information and teamwork will help us meet our goals. Zapped by a (Design) Wizard: the Consequences of Inaccurate Energy Modeling Programs Increasingly, architects and engineers can sneak a peek at how the building in their head will perform on the day that the owner turns the key. Energy modeling program wizards help conjure building energy load predictions, allowing a variety of inputs, at the earliest stages of design. Program users can brainstorm and try a number of possibilities pretty quickly, and choose obvious winners. Hooray for wizards! But what happens when the wizard is a dunce? What if your wizard gives you inaccurate information about a crucial piece of the puzzle, say, the building envelope? You might just eliminate an easy to implement, energy efficient design strategy early in the design process. The result can be a building that leaves a Bigfoot carbon footprint instead of a Bambi carbon footprint. I must confess. I have been zapped by a wizard, my product declared a pumpkin, by designers who were under their wizard's spell. The result? Many millions of dollars per year in wasted energy, an amount that increases with rising energy costs. How could this happen? Just a brief background. A few years back, I met a guy who invented and patented a wall system that exhibits insulated thermal mass in a single wythe wall system. This insulated concrete block resembles a composite wall, which happens to be a very energy efficient wall configuration. It has two layers of concrete thermal mass that are completely separated by a layer of rigid expanded polystyrene. With over seventy buildings up, and excellent testimonials regarding energy efficiency, I happily figured I was the guy anointed (as a reward for clean living) to sell the building equivalent of a car that gets ninety miles per gallon. (Some of our buildings use about one third the HVAC energy as conventionally built structures.) Armed with positive anecdotal evidence, I set about to transform the landscape. Rejection after rejection ensued. It seems I was up against a legion of nonbelievers. Where is the proof, they rightly asked? It took me two years to find it, but I finally discovered that there is ample evidence to support our claims. Oak Ridge National Lab building energy research studies have shown that massive wall systems that exhibit insulated thermal mass insulation configurations have significantly better thermal performance than both conventional (interior insulated walls) and ICF (insulated concrete form) walls (with the exception of very low R-value walls). According to the experts, this is true across all climate zones, with the degree of thermal performance difference determined by steady state R-value and climate zone. For example, an insulated thermal mass wall configuration, with a steady state value of R-12, may have an R-value equivalent of R-30 in Phoenix, AZ, while an ICF insulation configured wall with a steady state value of R-12 may have an R-value equivalent of R-21, in Phoenix. A mass wall with interior insulation (conventional) with a steady state value of R-12 may have an equivalent R-value of about R-18 in Phoenix. Discovering the above information was huge relief. Here was the credible information, produced by world class scientists, that supported our claims of superior energy efficiency. To validate my find, I decided to employ the increasingly popular, easy to use e-QUEST energy modeling program. I performed a simple comparison between two same-sized buildings with mass walls, but different insulation configurations. I modeled the building in the Phoenix climate zone, where insulated thermal mass insulation configurations perform especially well. The first wall had insulated thermal mass, where thermal mass is exposed to the interior, and the second wall had isolated thermal mass, where there is a layer of insulation between the thermal mass and the interior. Guess what? The heating and cooling load results were almost identical, when one would expect a significant difference. I contacted the e-QUEST designer, and he told me to " make sure you are describing the walls with mass (layers with mass not just R values) for layers other than the insulation. That is the only way any calculation can see a difference." I double checked that I had done just that, and then I ran a number of other simulations just to be sure, and got the same results. According to the program, there is no significant predicted thermal performance difference between mass walls that have the same R-value, regardless of insulation configuration. The problem? This is in direct contradiction to the laws of physics. So, the energy modeling program that I was using was flawed. Past events began to click in my head. The architects and engineers for some of the world's biggest retailers had scoffed at my claims that insulated thermal mass walls systems are thermally superior to conventional and ICF wall systems. They told me that the energy simulation programs that they used showed no significant difference. A few went so far as to attack me personally, saying that I was just a snake oil salesman, and a poor one at that. At the time, I did not have the information at my fingertips to refute their claims. That was before I discovered the fine research done at Oak Ridge National Lab, and then learned how to use the e-QUEST energy modeling program. Now, I know that science is on my side, and the wizard is not. Even though one can input several options, it does not mean a modeling program values them accurately. Misinformation can waste a lot of time and energy. If the engineers would not have been misinformed by their energy models, perhaps today their companies would have a much smaller carbon footprint. Had I known then, what I know now, instead of just having the anecdotal evidence from some very satisfied customers, I could have alerted designers to the wizard's pitfalls. Of course, if I was a better snake oil salesman, I would not have the need to write this, as my smooth talking would have already won the day. Seriously, though, the facts speak for themselves, but you have to place yourself within earshot. Either one of two things is true: the Oak Ridge National Lab scientists are wrong, or the e-QUEST energy modeling program does not accurately differentiate between different insulation configurations in mass wall systems. The evidence points to the latter. This is a pretty important piece of information. Imagine specifying a conventional wall (which, according to the evidence, consumes much more energy), instead of an insulated thermal mass wall, time after time after time, based on flawed information. End result? Needlessly wasted energy. For the architect and engineer who may use the e-QUEST program to compare mass wall systems, one must realize that the results may not reflect the careful research produced at Oak Ridge National Lab. To determine if your energy modeling program works correctly, I would suggest that you do your own testing. Run a simulation with two R-12 mass walls in an Arizona climate zone (where the difference in thermal performance should be very significant). Simulate one wall made up with 2" rigid EPS interior insulation, and a 12" exterior heavyweight cmu with partially filled cores; the second wall, have an interior portion with a 6" partially grouted heavyweight cmu, with 2" EPS rigid EPS middle layer, and a 4" partially grouted heavyweight cmu as the wall exterior. If there is no significant difference between predicted heating and cooling loads for these walls, then your energy modeling program does not accurately differentiate between isolated (conventional) and insulated thermal mass walls. Designers need to know the limitations of the tools they use to get to net zero. Marty Walters NRG Insulated Block www.energyefficientblock.com

Net Zero: How energy modeling can prevent us from getting there.

Zapped by a (Design) Wizard: the Consequences of Inaccurate Energy Modeling Programs. Increasingly, architects and engineers can sneak a peek at how the building in their head will perform on the day that the owner turns the key. Energy modeling program wizards help conjure building energy load predictions, allowing a variety of inputs, at the earliest stages of design. Program users can brainstorm and try a number of possibilities pretty quickly, and choose obvious winners. Hooray for wizards! But what happens when the wizard is a dunce? What if your wizard gives you inaccurate information about a crucial piece of the puzzle, say, the building envelope? You might just eliminate an easy to implement, energy efficient design strategy early in the design process. The result can be a building that leaves a Bigfoot carbon footprint instead of a Bambi carbon footprint. I must confess. I have been zapped by a wizard, my product declared a pumpkin, by designers who were under their wizard's spell. The result? Many millions of dollars per year in wasted energy, an amount that increases with rising energy costs. How could this happen? Just a brief background. A few years back, I met a guy who invented and patented a wall system that exhibits insulated thermal mass in a single wythe wall system. This insulated concrete block resembles a composite wall, which happens to be a very energy efficient wall configuration. It has two layers of concrete thermal mass that are completely separated by a layer of rigid expanded polystyrene. With over seventy buildings up, and excellent testimonials regarding energy efficiency, I happily figured I was the guy anointed (as a reward for clean living) to sell the building equivalent of a car that gets ninety miles per gallon. (Some of our buildings use about one third the HVAC energy as conventionally built structures.) Armed with positive anecdotal evidence, I set about to transform the landscape. Rejection after rejection ensued. It seems I was up against a legion of nonbelievers. Where is the proof, they rightly asked? It took me two years to find it, but I finally discovered that there is ample evidence to support our claims. Oak Ridge National Lab building energy research studies have shown that massive wall systems that exhibit insulated thermal mass insulation configurations have significantly better thermal performance than both conventional (interior insulated walls) and ICF (insulated concrete form) walls (with the exception of very low R-value walls). According to the experts, this is true across all climate zones, with the degree of thermal performance difference determined by steady state R-value and climate zone. For example, an insulated thermal mass wall configuration, with a steady state value of R-12, may have an R-value equivalent of R-30 in Phoenix, AZ, while an ICF insulation configured wall with a steady state value of R-12 may have an R-value equivalent of R-21, in Phoenix. A mass wall with interior insulation (conventional) with a steady state value of R-12 may have an equivalent R-value of about R-18 in Phoenix. Discovering the above information was huge relief. Here was the credible information, produced by world class scientists, that supported our claims of superior energy efficiency. To validate my find, I decided to employ the increasingly popular, easy to use e-QUEST energy modeling program. I performed a simple comparison between two same-sized buildings with mass walls, but different insulation configurations. I modeled the building in the Phoenix climate zone, where insulated thermal mass insulation configurations perform especially well. The first wall had insulated thermal mass, where thermal mass is exposed to the interior, and the second wall had isolated thermal mass, where there is a layer of insulation between the thermal mass and the interior. Guess what? The heating and cooling load results were almost identical, when one would expect a significant difference. I contacted the e-QUEST designer, and he told me to " make sure you are describing the walls with mass (layers with mass not just R values) for layers other than the insulation. That is the only way any calculation can see a difference." I double checked that I had done just that, and then I ran a number of other simulations just to be sure, and got the same results. According to the program, there is no significant predicted thermal performance difference between mass walls that have the same R-value, regardless of insulation configuration. The problem? This is in direct contradiction to the laws of physics. So, the energy modeling program that I was using was flawed. Past events began to click in my head. The architects and engineers for some of the world's biggest retailers had scoffed at my claims that insulated thermal mass walls systems are thermally superior to conventional and ICF wall systems. They told me that the energy simulation programs that they used showed no significant difference. A few went so far as to attack me personally, saying that I was just a snake oil salesman, and a poor one at that. At the time, I did not have the information at my fingertips to refute their claims. That was before I discovered the fine research done at Oak Ridge National Lab, and then learned how to use the e-QUEST energy modeling program. Now, I know that science is on my side, and the wizard is not. Even though one can input several options, it does not mean a modeling program values them accurately. Misinformation can waste a lot of time and energy. If the engineers would not have been misinformed by their energy models, perhaps today their companies would have a much smaller carbon footprint. Had I known then, what I know now, instead of just having the anecdotal evidence from some very satisfied customers, I could have alerted designers to the wizard's pitfalls. Of course, if I was a better snake oil salesman, I would not have the need to write this, as my smooth talking would have already won the day. Seriously, though, the facts speak for themselves, but you have to place yourself within earshot. Either one of two things is true: the Oak Ridge National Lab scientists are wrong, or the e-QUEST energy modeling program does not accurately differentiate between different insulation configurations in mass wall systems. The evidence points to the latter. This is a pretty important piece of information. Imagine specifying a conventional wall (which, according to the evidence, consumes much more energy), instead of an insulated thermal mass wall, time after time after time, based on flawed information. End result? Needlessly wasted energy. For the architect and engineer who may use the e-QUEST program to compare mass wall systems, one must realize that the results may not reflect the careful research produced at Oak Ridge National Lab. To determine if your energy modeling program works correctly, I would suggest that you do your own testing. Run a simulation with two R-12 mass walls in an Arizona climate zone (where the difference in thermal performance should be very significant). Simulate one wall made up with 2" rigid EPS interior insulation, and a 12" exterior heavyweight cmu with partially filled cores; the second wall, have an interior portion with a 6" partially grouted heavyweight cmu, with 2" EPS rigid EPS middle layer, and a 4" partially grouted heavyweight cmu as the wall exterior. If there is no significant difference between predicted heating and cooling loads for these walls, then your energy modeling program does not accurately differentiate between isolated (conventional) and insulated thermal mass walls. We need to understnd the limitations of the tools we use to get to net zero. Marty Walters www.energyefficientblock.com