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Why Spray Foam Insulation Is Not Always The Best Choice

Spray Foam insulation is without a doubt the best insulation material available for insulating a new home, block of apartments, retail store or commercial building in most instances. But is italways the right choice? There are instances where traditional insulation materials such as fiberglass batts and blown insulationsimply make more sense.

So what are the tradeoffs

Closed cell foam insulationhas an extremely high R value (R=6 per inch of thickness) and provides both an air and vapour barrier, meaning heat is less likely to escape through gaps and the performance isnít degraded by drafts or moisture. However, it is expensive and must be installed by aninsulation contractor to get the true benefits.

Fiberglass batts is cheap to buy and while best installed by an expert, can be installed by homeowners. It can be installed both horizontally and vertically. Typical theoretical R values are R=2.7 per inch. However, because the insulation is installed in rolls between wooden joists and has to be cut accurately to fit complex shapes, gaps are quite common. Also the insulationís properties are degraded by compression (cramming into gaps), moisture from condensation or water leaks and is susceptible to drafts. Batts insulation that is no longer pink and is turning grey has most likely absorbed moisture reducing the insulation value. Also batts takes up the most space to achieve the same r value.

Blown insulation, such as blown cellulose or fiberglass is cheap to buyand while best installed by an expert, can be also installed by homeowners. With an R value of R = 3.65 per inch it is of medium density. Because the insulation is blown it provides a more uniform layer and can be blown over the top of attic joists. It is also less susceptible to moisture and drafts than fiberglass batts. However, blown insulation is really only suitable for large flat horizontal areas with lots of space and good access.

Which is the best attic insulation for my house?

When building a new house and the budget is available to pay the extra cost, spray foam insulation is the best solution because it will give the greatest energy cost saving for the entire lifetime of your home. Itís estimated it can save up to 40% of the annual heating and cooling costs and given the way heating costs are rising that could add up to a substantial amount.

If the budget wonít stretch to 100% spray foam then a hybrid approach is a good compromise. This is achieved by spraying 1-2 inches of foam, to create an air and vapor seal, then finishing off with blown insulation to a total r value of r=50. This approach provides the best of both worlds, excellent insulation at a reasonable cost.

For existing homes the rule of thumb is to top up what is already there (excluding vermiculite, asbestos or other prohibited substances). If fiberglass battsare present, then add more rolls over the top in the opposite direction to the first layer. If blown fiberglass or blown cellulose is in place, blow in some moreof the same. Measure what is there, estimate the current R value and add sufficient new insulation material to achieve a total of r=50 for Canada and Northern US Sates.

Which is the best insulation for basements?

If the basement is unfinished and the extra budget is available then spray foam insulation is the best solution. According to Environment Canada up to 30% of heat loss occurs through the basement, so once again it is worth paying for the best.

If budget is limited then the most important location to apply foam insulation is the crawl space. Traditionally fiberglass batts has been used to insulate the basement crawl space, but the confined area, lack of space and complexity make it difficult to achieve a consistent covering without gaps or compressed insulation. To save costs consider having the crawl space insulated with foam and the walls insulated with fiberglass batts.

The best advice about insulation

Every home is unique, and while us homeowners now have a wealth of information available online, there is no substitute for consulting an expert insulation contractor that can supply all your insulation needs.