So far, I've interviewed two new contractors. They had very different styles. The first, a licensed general contractor, arrived exactly on time, asked questions, said little, left in 30 minutes, and delivered a written estimate the next day. The first estimate included metal roof and foam insulation. I suggested those, and the contractor didn't debate them at all. Actually, a little more discussion would have been nice.
The second contractor I interviewed last week was very reluctant to do foam insulation, so I said I would also accept fiberglass batts, as on my written specs (because that was what Ronnie wanted to do, and he convinced me it was OK). However since then, I've decided I must do closed cell 2 lb foam insulation as mentioned by the first contractor (though strangely not included in his estimate, apparently I agreed to 0.5 lb foam because of better acoustical properties). Foam insulation is by far the best, and 2 pound foam is the best of the best (see below) for thermal insulation, though 0.5 is somewhat better for acoustical insulation.
The second contractor I interviewed last week was very reluctant to do foam insulation, so I said I would also accept fiberglass batts, as on my written specs (because that was what Ronnie wanted to do, and he convinced me it was OK). However since then, I've decided I must do closed cell 2 lb foam insulation as mentioned by the first contractor (though strangely not included in his estimate, apparently I agreed to 0.5 lb foam because of better acoustical properties). Foam insulation is by far the best, and 2 pound foam is the best of the best (see below) for thermal insulation, though 0.5 is somewhat better for acoustical insulation.
Here's a great link recommending 2 lb spray foam insulation.
Here's an even better link with all the technical data:
Open cell (0.5 pound) vs Close cell (2 pound):
R Value per inch:
Open 3.9
Closed 6.9
STC (Sound Transmission Class)
Open 51
Closed 43
Noise Reduction Coefficient
Open 0.7
Close 0.2
The really relevant number is the STC, that's a complicated measure of how sound is attenuated as it passes through a structure, very roughly speaking, the dB's of loss in transmission. The NRC is a measure of how well a material prevents sound from reflecting, therefore it is more applicable to surface treatments (studio foam panels, traps, acoustical ceilings, drapes, etc.) than wall structures. Normally STC needs to be evaluated as a complete structure, because leakage through any part (such as, the studs) can compromise the whole, so it's not entirely clear what the above specifications mean (were they evaluating a pseudo-wall of nothing but foam, and if so, how thick was it, or were they evaluating a real wall, and if so, what were the other materials and how thick?).
But it seems both types of foam have excellent STC. The STC of a standard uninsulated interior wall is 33, the STC of a typical insulated exterior wall should be above 40. 44 is the STC of a cinderblock wall 4 inches thick.
Although no doubt 0.5 pound foam is better for acoustical insulation, 2 pound foam is not shabby, and it's hard to know how much difference it would make inside a wall structure.
Here's an even better link with all the technical data:
Open cell (0.5 pound) vs Close cell (2 pound):
R Value per inch:
Open 3.9
Closed 6.9
STC (Sound Transmission Class)
Open 51
Closed 43
Noise Reduction Coefficient
Open 0.7
Close 0.2
The really relevant number is the STC, that's a complicated measure of how sound is attenuated as it passes through a structure, very roughly speaking, the dB's of loss in transmission. The NRC is a measure of how well a material prevents sound from reflecting, therefore it is more applicable to surface treatments (studio foam panels, traps, acoustical ceilings, drapes, etc.) than wall structures. Normally STC needs to be evaluated as a complete structure, because leakage through any part (such as, the studs) can compromise the whole, so it's not entirely clear what the above specifications mean (were they evaluating a pseudo-wall of nothing but foam, and if so, how thick was it, or were they evaluating a real wall, and if so, what were the other materials and how thick?).
But it seems both types of foam have excellent STC. The STC of a standard uninsulated interior wall is 33, the STC of a typical insulated exterior wall should be above 40. 44 is the STC of a cinderblock wall 4 inches thick.
Although no doubt 0.5 pound foam is better for acoustical insulation, 2 pound foam is not shabby, and it's hard to know how much difference it would make inside a wall structure.
All spray foams have one thing in common, unlike old fiberglass insulation (which gets worse over time in this regard) they much better seal against airflow. But in that regard, closed cell foam is the best.
Contractor #2 also didn't like the metal roof idea, and tried to convince me to use composition shingles instead. It's cheap now and cheap to replace in 20 years. No, that's not what I want to have to do, I don't want a roof of rotting shingles. So I gave him some links. Here's a great list of metal roofing manufacturers in Texas, several in or near San Antonio.
Here's one in San Antonio, Berridge, which seems to make top quality 24 gauge Class IV galvalum roofing. Here's the Berridge color chart, showing that both natural white and almond meet Energy Star and LEED 2.2 requirements for low slope roof (2:12 or less). Natural white has higher reflectivity but almond has higher emissivity. Combining the two in SRI, White is naturally the best overall at 93 but almond close at 82. Above 2:12 slope, actually most colors qualify for Energy Star and LEED, despite typical SRI's in the 30's.
Another roofing manufacturer with branch in San Antonio, MCBI, also has white and almond colors. However, they only offer almond in their higher end Signature 300 series which uses Kynar and/or Hylar. In the Signature 200 series, which uses a proprietary siliconized polyester, the SRI's are generally lower so that the white (a non-pigmented polyester) actually has lower SRI than the Almond in the 300 series. And it has no almond, only a similar Light Stone which brings the SRI significantly down to 58.
Another roofing manufacturer with branch in San Antonio, MCBI, also has white and almond colors. However, they only offer almond in their higher end Signature 300 series which uses Kynar and/or Hylar. In the Signature 200 series, which uses a proprietary siliconized polyester, the SRI's are generally lower so that the white (a non-pigmented polyester) actually has lower SRI than the Almond in the 300 series. And it has no almond, only a similar Light Stone which brings the SRI significantly down to 58.
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