I went to see a job a contractor was doing and was surprised the foam was not flush with the 2x4 wall. According to the installer the first 1" is responsible for 70% of the r value and the amount of foam that would be needed to spray would be a waste of money with no real benefit. After finishing the discussion he gave me a pamphlet where the foam was over applied and the excess was shaved flush with the studs. What is the industry standard?

Having started my career in foam insulation, this is fairly common. There is no way to perfectly fill a stud cavity exactly with the required depth unless you overspray and shave the cavity back to the studs, which means extra material and extra labor, which means extra cost. Foam is an addhesive and it sticks to itself when it expands. Thats why the adhesion to the studs tends to make the foam push out more on the edges than in the center of the cavity. If I was considering a insulation system for a new house I would go with either premium fiberglass either wet spray or cavity fill behind a product like Insulweb or cavity fill with an all borate cellulose. Your going to get more bang for your buck. I was just involved in an icf build where the owner was going to do the popular spray the roof sheathing thing, he found out that I had been involved in the insulation business and asked if I still had my insulation equipment. I do and he blew an r-60 cellulose cap at a cost of about $1 per sq ft compared to the $1 to $1.5 per board ft quotes he had for foam.

Thanks for the information. I thought about filling the cavity with cellulose but I figured with a 2x4 exterior the spray foam would do a much better job. It is not new construction but may as well be. It is a chinese drywall house bought in a short sale where the drywall and insulation must go The house is 2900 sq ft and the bid I am getting is $1.20 a board ft for open cell and $2.00 for closed cell in the attic. Since the hvac is on its 3rd or 4rth condenser I will probably have to replace it as well. Getting good information on spray foam has been difficult to say the least between the multitude of companies that sell spray foam as well as what type for what application. I am in the New Orleans area where the heat and humidity are very high. The contractor says closed cell in the attic and the head of the parish building permit office says nothing but open cell in the attic. At least they both agree on open cell for the walls. The bid also included caulking everything from the windows and doors to where the exterior walls meet the slab. I've still got 3-4 weeks to make a decision so I am going to keep asking around until I am comfortable with which way to go. Thanks again for your input.

Posted By finleyh on 14 Jun 2010 10:40 PM
Thanks for the information. I thought about filling the cavity with cellulose but I figured with a 2x4 exterior the spray foam would do a much better job. It is not new construction but may as well be. It is a chinese drywall house bought in a short sale where the drywall and insulation must go The house is 2900 sq ft and the bid I am getting is $1.20 a board ft for open cell and $2.00 for closed cell in the attic. Since the hvac is on its 3rd or 4rth condenser I will probably have to replace it as well. Getting good information on spray foam has been difficult to say the least between the multitude of companies that sell spray foam as well as what type for what application. I am in the New Orleans area where the heat and humidity are very high. The contractor says closed cell in the attic and the head of the parish building permit office says nothing but open cell in the attic. At least they both agree on open cell for the walls. The bid also included caulking everything from the windows and doors to where the exterior walls meet the slab. I've still got 3-4 weeks to make a decision so I am going to keep asking around until I am comfortable with which way to go. Thanks again for your input.

finleyh;

for proper mitigation, in addition to geting rid of drywall and insulation, you must remove all copper wiring, HVAC ductwork and HVAC airhandler.
any copper wtwer pipes are OK

Chris is correct. A point of clarifacation would be any plastic wiring such as Romex, low voltage, LAN, and A/V wiring would have to go I believe metal conduit can stay.....Eric