application of 1/2 lb with 2 lb | Ask Mason Knowles - SPF Consultant | Spray Foam Technical Questions and Answers | SprayFoam Magazine Q&A Forums

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Posted: Aug 23, 2008 02:39 PM	application of 1/2 lb with 2 lb Hi, I have a cold bedroom above an unheated garage. in MA, zone 5. My contractor wants to spray 2 lb closed cell foam on the garage ceiling between the joists and then cover that with 1/2 lb. He'd like to spray 2inches of the 2 lb for a R14 insulation, and then 4" of the 1/2 lb for a R16, which should bring us up to a R30 which should make the room above the garage warm. I haven't seen anything anywhere though about this practice. Is it possible, is it worthwhile or would the 1/2 lb foam do the trick for us? He has also recommended doing the same in our attics on the roof. One attic has a gas furnace though so is one type of foam better than another when a gas furnace is involved? The brand of 1/2 lb is LaPolla. Thanks for any help. Mary
mason Posted: Aug 24, 2008 09:36 AM	Both the 1/2 lb and the 2 lb foam would do the job. The 2 lb foam will give an R value of about 6 to 6.4 per inch while the 1/2 foam will be around 3.5 to 3.8 per inch. So, he is trying to get you a combination of R 26 - R 28 at a more reasonable price. (The 1/2 lb foam is less expensive per R value.) The 2 lb foam will give the structure more strength while the 1/2 foam is a better sound absorbing material. Sounds like the best of both worlds to me. The combination also will reduce air infiltration from your garage into your house thereby decreasing the potential harmful effects of carbon monoxide entering the room. I am going to do the same thing to my garage ceiling soon.

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Posted: Aug 23, 2008 02:39 PM

application of 1/2 lb with 2 lb

Hi,
I have a cold bedroom above an unheated garage. in MA, zone 5. My contractor wants to spray 2 lb closed cell foam on the garage ceiling between the joists and then cover that with 1/2 lb. He'd like to spray 2inches of the 2 lb for a R14 insulation, and then 4" of the 1/2 lb for a R16, which should bring us up to a R30 which should make the room above the garage warm. I haven't seen anything anywhere though about this practice. Is it possible, is it worthwhile or would the 1/2 lb foam do the trick for us? He has also recommended doing the same in our attics on the roof. One attic has a gas furnace though so is one type of foam better than another when a gas furnace is involved? The brand of 1/2 lb is LaPolla. Thanks for any help. Mary

mason

Posted: Aug 24, 2008 09:36 AM

Both the 1/2 lb and the 2 lb foam would do the job. The 2 lb foam will give an R value of about 6 to 6.4 per inch while the 1/2 foam will be around 3.5 to 3.8 per inch. So, he is trying to get you a combination of R 26 - R 28 at a more reasonable price.

(The 1/2 lb foam is less expensive per R value.)

The 2 lb foam will give the structure more strength while the 1/2 foam is a better sound absorbing material. Sounds like the best of both worlds to me.

The combination also will reduce air infiltration from your garage into your house thereby decreasing the potential harmful effects of carbon monoxide entering the room.

I am going to do the same thing to my garage ceiling soon.

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