How does spray foam work?

A two-part mixture is applied by trained professionals to the inside surface of exterior walls, to the underside of the roof, and beneath floors in basements and crawl spaces.The spray mixture expands rapidly to fill all cracks and voids, completely and permanently adhering to wood, masonry, metal studs and joists.

How does Spray Polyurethane Foam (SPF)  reduce energy use in buildings?

SPF provides a continuous air barrier.
SPF prevents moisture infiltration through air leakage.
SPF minimizes dew point problems and condensation.
SPF avoids thermal bridging.
SPF resists heat movement in all directions.
SPF provides reliable performance under varying conditions.

What is the difference between low density, open cell SPF and medium density closed cell SPF?

1/2 lb Spray Polyurethane Foam (SPF)

Low density, open cell SPF refers to a generic spray polyurethane SPF that weighs between 0.4 to 0.6 lbs per cubic ft when fully cured. It is spray applied to a substrate as a liquid and expands about 100-150 times its original volume to form a semi-rigid/flexible, non-structural SPF insulation. The SPF has an R-value around 3.5 per inch and typically uses water as the blowing agent.

Medium Density, Closed Cell Spray Polyurethane Foam (SPF)

Medium density, closed cell SPF used in interior applications typically refers to generic spray polyurethane foam that weighs between 1.5 to 2 lbs per cubic ft when fully cured. It is also spray applied as a liquid to a substrate and expands about 35 to 50 times its original volume to form a rigid, structural SPF insulation with a compressive strength between 15 to 25 PSI. The SPF has an R-value of around 6.0 per inch (aged R-value) and uses high R-value blowing agents.

Similarities: Both products are excellent air barriers in buildings, provide great insulation, can assist in the control of condensation within buildings and have great environmental benefits.

Won’t sealing my house lead to indoor air quality problems?

Your house does need to be ventilated. Most house design professionals will advise you to seal the house structure as tight as possible and provide the necessary ventilation through the heating and air conditioning system. Many systems employ an "air exchanger" which is designed to pre-condition (either warm or cool) the incoming outside air with the outgoing exhaust air. In this manner, you can build an extremely energy efficient exterior shell using spray polyurethane foam while still providing controlled and energy efficient ventilation.