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K High Posted: Nov 04, 2015 02:02 AM	Is the foam in my attic thick enough? Hi Mason - We just had foam installed today in our attic which has 2x6 rafters and 2x4 framing on the gable ends. The contract specified: * Install R-36 closed cell spray foam in the attic roof rafters. * Install R-20 closed cell spray foam in the attic gable end walls. Although no roof sheathing is visible and the foam comes up to the surface of many of the rafters right next to them, there is definitely a substantial "hollow" in each rafter bay. The majority of the surface is about an inch short of the underside of the rafter, with many areas that are as much as two inches from being "full". The result is that most of the roof space probably has 4-5" of foam, and the gable ends have a consistent 3" of foam. If the R-value is 6.0 per inch, it seems like the contractor may not have applied enough to have really hit the goal. I will contact the contractor tomorrow to ask about it, but would also appreciate the expert opinion of a disinterested party. Since I can't attach pictures here, I'll email them to you Mason in case that's helpful. Thanks in advance for your help.
mason Posted: Nov 04, 2015 01:27 PM	You really can't tell the thickness of the foam without physically measuring it. Rafters can mislead you. In order to measure the foam thickness check the foam depth with a thin wire or ice pick with duct tape wrapped at the 5 inch mark. I would expect a typical closed cell foam application to vary an inch when sprayed at an average thickness of 5 inches. So, some foam might be 6 inches, some 5.5, some 5, some 4.5 and some 4 inches. Take measurements at random spots checking both apparent low spots and apparent high spots in addition to what appears to be the average. Once you have the average thickness, then you can calculate the total R value of the foam. Obtain a technical data sheet of the foam you have had installed and see what the measured R value of the foam. Most SPF closed cell foams have an average of 6.5 R value per inch, some a little more. For example if the average is 5 inches then a 6.8 R value would have an R value of 34, pretty close to your R 36 requirements. However if the average is 4 inches then you only have an R value of 27 which is not enough.
K High Posted: Nov 04, 2015 05:04 PM	I appreciate your prompt response, Mason. The rep from the insulation company just came out to look at it and agreed that the sprayer went a bit too thin in a few places, so they are going to come back out and apply a bit more. Although he was very accommodating and agreeable, feeling like I had done my homework certainly made me more comfortable with the conversation. Thanks for your help!

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K High

Posted: Nov 04, 2015 02:02 AM

Is the foam in my attic thick enough?

Hi Mason -
We just had foam installed today in our attic which has 2x6 rafters and 2x4 framing on the gable ends. The contract specified:
* Install R-36 closed cell spray foam in the attic roof rafters.
* Install R-20 closed cell spray foam in the attic gable end walls.
Although no roof sheathing is visible and the foam comes up to the surface of many of the rafters right next to them, there is definitely a substantial "hollow" in each rafter bay. The majority of the surface is about an inch short of the underside of the rafter, with many areas that are as much as two inches from being "full". The result is that most of the roof space probably has 4-5" of foam, and the gable ends have a consistent 3" of foam.
If the R-value is 6.0 per inch, it seems like the contractor may not have applied enough to have really hit the goal. I will contact the contractor tomorrow to ask about it, but would also appreciate the expert opinion of a disinterested party. Since I can't attach pictures here, I'll email them to you Mason in case that's helpful.

Thanks in advance for your help.

mason

Posted: Nov 04, 2015 01:27 PM

You really can't tell the thickness of the foam without physically measuring it. Rafters can mislead you.

In order to measure the foam thickness check the foam depth with a thin wire or ice pick with duct tape wrapped at the 5 inch mark. I would expect a typical closed cell foam application to vary an inch when sprayed at an average thickness of 5 inches. So, some foam might be 6 inches, some 5.5, some 5, some 4.5 and some 4 inches. Take measurements at random spots checking both apparent low spots and apparent high spots in addition to what appears to be the average.

Once you have the average thickness, then you can calculate the total R value of the foam. Obtain a technical data sheet of the foam you have had installed and see what the measured R value of the foam.

Most SPF closed cell foams have an average of 6.5 R value per inch, some a little more. For example if the average is 5 inches then a 6.8 R value would have an R value of 34, pretty close to your R 36 requirements. However if the average is 4 inches then you only have an R value of 27 which is not enough.

K High

Posted: Nov 04, 2015 05:04 PM

I appreciate your prompt response, Mason. The rep from the insulation company just came out to look at it and agreed that the sprayer went a bit too thin in a few places, so they are going to come back out and apply a bit more. Although he was very accommodating and agreeable, feeling like I had done my homework certainly made me more comfortable with the conversation. Thanks for your help!

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