Improve Home Performance with Spray Foam Insulation

Published on: August 16, 2012


Spray foam insulation is an incredibly useful product when it comes to sealing and insulating walls and providing attic insulation. It can make a huge difference in building energy efficiency by insulating small and awkward spaces.

However, spray foam is even more impressive when used in large projects. It can prevent the tricky problems with moisture and condensation that often haunt insulation upgrades, and it can create amazingly effective wall insulation in previously uninsulated buildings framed with 2×4 lumber. Spray foam can bring an old house up to the modern building code standard for energy efficiency.

The closed cell variety of spray foam insulation blocks the passage of both air and heat, and the open celled type is an excellent acoustic insulator.

Attic insulation – spray foam under a hot roof

Many houses in areas of the U.S. with warm climates have air distribution ducts routed through their attics. When you consider the fact that the attic floors are usually insulated and the fact that the attic above, where the air conditioning ducts are located, is therefore as hot as an oven, you have to wonder whether insulating the attic floor is really such a good plan.

Insulation contractors in the southern states are choosing to use spray foam insulation on the underside of the roof rather than placing attic insulation at the joist level.

Attic insulation – spray foam under a cold roof

In cold climates, it’s currently standard practice to provide full length ridge and soffit vents in the roof and to insulate the attic floor. This provides the ventilation needed to prevent the warm, moist air that inevitably finds it’s way into the attic from the home’s interior from condensing on the underside of the cold roof and rotting its structure.

However, older homes do not have full length ridge and soffit vents. When their attic floors are insulated, their roof structures often end up being plagued by rot and mold because of chronic problems with condensation.

Using closed cell spray foam on the attic floor can seal the openings that allow moist air from the interior to gain entrance to the attic: electrical openings, recessed lighting, and mechanical penetrations. Using closed cell spray foam on the underside of the roof structure can provide greater energy efficiency while protecting the wood from moisture. The roof is still cool enough to prevent ice damming, but the attic can remain unvented.

Spray foam in an existing 2×4 wall

Batt insulation, which is used in between studs to insulate walls, has an R-value of approximately 4 units per linear inch, and it tends to sag, leaving an uninsulated area at the top and decreasing the energy efficiency of the wall. The most non-toxic spray foams have a similar R-value, but do not leave gaps. That improves their performance considerably. The spray foams with the best insulative properties are more than twice as effective as fiberglass batts.

Modern building codes require that new houses in cold climates be constructed with 2×6 exterior walls or added foam insulation board in order to meet the minimum requirement for wall R-value. Spray foam can bring an old house right up to the modern code level of energy efficiency, while preserving the integrity of the interior finishes and the exterior cladding.

Spray foam for windows, doors and sill plates

Spray foam can be injected into spaces that would normally be impossible to insulate. Some types of spray foam are water resistant and can even be used in protected areas that are exposed to the exterior. Spray foam can be used around window and door frames, and it can seal the openings where electrical, telephone, and cable wires enter the house. It can also be used to seal the space between the sill plate and the foundation wall.

Spray foam and health

Older spray foam formulas, popular 15-30 years ago, have been associated with respiratory problems. However, today’s spray foam insulation is a great improvement on what was available in the past. Choosing the right formulation for the right application is still important, but modern spray foams do not off-gas once they have cured. Formulas that are completely non-toxic, even during installation, are available. We can advise you on the best product for your application.

Whether it’s used as attic insulation, to fill gaps around wall penetrations, or to seal the foundation, spray foam insulation can improve the energy efficiency of an existing building like no other product. An experienced insulation contractor can tell you which type of spray foam is best suited to your needs.