There's A New Myth in Town
There's a new myth in town, and it's name is spray foam insulation. Actually, that's not fair. Spray foam insulation has many benefits--air sealing at the top of the list. But there is a myth being propagated by some in the home performance industry that it is the silver bullet that some have been looking for.
Many proponents of the product would like you to ignore r-values. But R Value is still R Value, that is, it is still a measure of resistance to energy flows. The leading Building Scientists propose an R-60 or above for our region. The energy code for our area is R-49. But many selling spray foam in our region claim that an attic only needs 4 or 5 inches of spray foam, that anything more is just a waste. Even with a high r-value claim of R-7 per inch, 5 inches of spray foam will only yield an R value of approximately R-35, well below the code mandated R-49. Especially for those foams that are only R-5 per inch, that yields about an R-25 for the attic, about 50% below code, and also meaning that heat losses are about 50% below code mandates.
The argument will come back that spray foam "performs better" than an R-49 attic with fiberglass or cellulose insulation. Partly true. But it's like the weather man saying "partly sunny". That also means it's partly cloudy. And for our attic, it's only half the story. The spray foam will "perform better" than attic of higher R Value that is not air sealed. Remember that one of the biggest benefits of spray foam is its air-sealing ability. But a properly air-sealed attic with cellulose at R-49 will perform better than the spray foamed attic at R-25.
Don't misunderstand me. I love what spray foam does. It air seals well. The closed cell variety has a high R Value. But it is substantially more expensive than cellulose insulation. And it's not the only way to air seal. I've used spray foam in attics as air barrier followed by a blow over of cellulose to attain an R Value to 60-70.
So y'all be cool (and warm).
Posted by COASTLINE BUILDING at 5/2/2010 12:26 PM 
Categories: Energy
Tags: green building home performance energy efficiency R-Value
Categories: Energy
Tags: green building home performance energy efficiency R-Value
They're either trying to sell their stuff, or they are just misinformed. The latter seems to be the problem, since they certainly are not trying to advertise or sell their products because saying that less would be enough would actually lessen their total sales because people would be using less. I hope they read this article.
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I don't really know why sellers are doing this. It is clear that they are wrong about they are saying about their products, but why do they still keep saying that 4-5 inches are enough? I think they have been misinformed. I will try to inform a few local sellers in my area about this so that they will know the next time someone buys from them.
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From the sellers perspective, I think it's more of a marketing issue for them. It is a premium option compared to fiberglass or cellulose insulation, so they try and sell less that performs better per inch. The way that it performs better is through it's air sealing capabilities, so in performance testing, it does better than non-air sealed fiberglass or cellulose insulation. But the foam companies ignore R-value, which is the other part of the equation. And R-value is still the resistance to energy loss. An attic that is air-sealed that is R-60 will perform (have less heat loss) twice as well as one that is R-30. Also, blanketing an area in spray foam is not the only way to air seal that area. Spray foam is an excellent product, but it can't overcome the physics of the equation
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Nice post interesting and informative too. looking for other informative post.
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Clearly, there's some kind of misconception in here. I don't believe that it's all about marketing since some of these people only do what they are told to do. If they are told to tell customers that a particular product is like this and like that, then they will.
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This is somewhat confusing, that's because, if they are selling their product like this then it would have an adverse effect on their sales since people would be buying less due to the fact that spray foam covers a much wider area in contrast to what people say. This is weird.
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Thank you for your comments. It does appear confusing that they would be trying to sell less. But because the foam is expensive, even at the reduced depth levels of the spray foam, it's cost its still much higher than even twice as much depth as cellulose insulation. So what they sell on is that it performs better than more cellulose that is not air-sealed. So when an air leakage test is done on a home, the spray foam seals the house better and doesn't leak as much unsealed areas with other insulations.
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It's nice to know that there are different benefits that we will get in this new product of Spray foam insulation. This really helps us to clean some areas that are so dirty.
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It air seals well. The closed cell variety has a high R Value. But it is substantially more expensive than cellulose insulation.
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I love what spray foam does. It air seals well. The closed cell variety has a high R Value. But it is substantially more expensive than cellulose insulation.
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The energy code for our area is R-49. But many selling spray foam in our region claim that an attic only needs 4 or 5 inches of spray foam, that anything more is just a waste.
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So if an attic is properly air sealed, whether spray foam or other approaches--and there are many, then that R value comes into play.
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But it's like the weather man saying "partly sunny". That also means it's partly cloudy.
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Now spray foam insulation is an good alternative to usual building insulation like fiberglass. A two-component mix comes together at the tip of a pistol, and produces an expanding foam that is sprayed onto concrete, into walls, or through holes drilled in into a cavity of a wall.
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I think they have been misinformed.
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