How Thick Should Spray Foam Insulation Be In Attic

A lot of builders and homeowners are going with spray foam insulation because of the airtightness benefits but then the questioner mentioned that the spray foam contractor had intentionally left big holes to the outside by not sealing the gable vents.

How thick should spray foam insulation be in attic.

This is more common with closed cell foam but it happens with open cell foam too. Allowable of the spray foam in an attic is 6 inches. Nothing unusual about that. Unvented attics sometimes called sealed enclosed or encapsulated attics feature insulation on the underside of the roof decking rather than on the attic floor.

Earlier this year i got a question about a home that had spray foam insulation in the attic. I have recently had close cell insulation sprayed in a metal building the contractor was suppose to install 2 of foam and states they sprayed 5 coats of insulation however the actual thickness is 1 1 1 8 he is claiming the foam did not expand as it should have but that the material for a 2 of foam has been sprayed. So to answer the question how thick should spray foam insulation be the answer depends on certain factors. Although spray foam insulation has been in use since the 1940s primarily for aircraft for the past 30 years continual product innovation has seen the increased adoption of spray foam insulation in residential and commercial construction.

The rapid growth of sprayed foam insulation in building construction thanks in part to its immediate and long term. It is also essential to examine the degree of moisture permeability that is needed. Since closed cell foam has a higher r value per inch installers generally spray 2 in walls and 3 in rooflines to meet the energy code requirements of r 13 and r 19 respectively. Spray polyurethane foam is a chemical product that is created by two materials isocyanate and polyol resin that will react with each other when they are mixed and will expand up to 30 to 60 times its liquid volume as it is sprayed in place.

Since the protocols for testing u and r values don t take into account nearly 0 infiltration losses of foam compared to fiberglass or loose fill insulation. Department of energy recommends insulation levels relative to the climate zone and part of the structure being insulated. Spray foam insulation thickness study the sciene of spray foam and you find it s not necessary to spray more than 4 inches of closed cell foam in any installation. So if the ideal r value for your home is r 40 your contractor may only need to spray five inches of foam insulation.

Spray foam isn t thick enough. The unvented attic space is considered the most effective and up to date building practice particularly by the spray foam industry.