How do I Choose the Best Spray Foam Insulation?

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  • Written By: Nychole Price
  • Edited By: Bronwyn Harris
  • Last Modified Date: 10 November 2019
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Spray foam insulation is used in home improvement to increase the energy efficiency of the house, lowering the heating and cooling costs. When choosing the best insulation for your home, consider the climate in which you live, the size of your home, and how much money you can afford to spend.

This type of insulation is released as a liquid that is composed of a polymer, usually polyurethane or modified urethane, and a foaming agent. The process of applying this insulation material is relatively simple. A nozzle is inserted behind the wall, under the floor or in the ceiling, via a small hole. The liquid is sprayed through the nozzle where it turns into foam and fills the area completely. There are three main types of spray foam insulation: 3-pound foam (1.36 kg), 2-pound foam (0.9 kg) and 0.5-pound (0.23 kg) foam.


Three-pound (1.36 kg) spray foam is mostly used in roof and attic insulation. It is the most expensive of this type of insulation because it is also the most dense. The foam has an R-value (resistance to heat flow) of 6, meaning it can trap gases denser than air. Depending on the climate in which you live, this could be an advantage or a disadvantage. People who live in hot, dry climates would benefit most from three-pound (1.36 kg) foam, as it keeps the temperature in the attic within 10°F (12.22°C) of the temperature in the house. Houses located in wet climates should avoid this type of spray foam, as it may trap moisture between the roof and the insulation, causing the roof to rot over time.

Two-pound (0.9 kg) spray foam, also known as closed cell spray foam, has an R-value between 4 and 5, making it perfect for insulating walls and tanks. It keeps the heat inside during the winter and outside on hot summer days. This spray foam is most often used in small buildings where air and vapor control is necessary. The cost per R-value is higher than it is with half-pound (0.23 kg), because of the greater resistance to the leakage of air or gases.

Half-pound (0.23 kg) spray foam is the most cost-effective, and therefore most popular, spray foam insulation. It has an R-value between 2 and 3.5, making it about as dense as dormant air. It is used as the primary insulation material in the wall cavities of most home. Because of its low R-value, it is not approved for vapor and fume control, but still has the same insulation characteristics of the 2-pound (0.9 kg) foam.


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Post 5

Is that foam safe? If I want to buy it, how many kilograms can the foam take?

Post 3

Are these R values aged? I use Demilec, and it is 7.2 per inch. I would not recommend spraying foam by putting holes in the wall, and then spraying. Not only do you risk blowing out the wall, but you also risk it not curing properly.

Where are the off-gasses going to go? What if you have lath and plaster, and it overexpands?

As a drywaller and sprayfoam installer, I believe this method is very risky. Especially thin coat plaster. I wouldn't recommend it. Open cell foam is not waterproof, and in my opinion worthless, for the price you pay, anyway. I guess everyone has their own opinion. I'd say your info is misleading. --Jamie L.

Post 2

Half pound is "open" cell and simply is not code approved for applying to the bottom of the roof deck, when creating an unvented type attic the materials (foam) must be to a high level of air perm and moisture protection, the minimum requirements are 16 times tighter than open cell or 1/2 lb.

In your walls you may use open yet remember the open cell is cheaper yet your r-value is less than Half of 2lb or Closed Cell, so really best to use closed. the cost difference is balanced by the R- Value.

Your open cell contractor should give you a closed cell bid. If not, stay away from him, and never use Icynene. Big trouble.

Post 1

should i use the half pound or the two pound to insulate my house?

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