Choosing the Right Spray Polyurethane Foam (SPF) Insulation for Air Sealing
Low Pressure Two-Component SPF: For mid-size projects, there are low pressure two-component kits (typically less than 250 psi or pounds per square inch) and systems (e.g., refillable tanks). This foam works because the chemicals in the two tanks are mixed together on site, chemically reacting very quickly and expanding to fill gaps and cracks. These two-component kits can be used to insulate and air seal small to mid-size areas around the home, such as attics, crawl spaces, and rim joists. These kits are primarily used by weatherization professionals and spray polyurethane foam contractors.
Insulating Foam Sealant: Another product used in weatherization projects is a sealant with insulating and air sealing properties generally referred to as insulating foam sealant. This is also a spray polyurethane product (one-component foam) and it is readily available at home improvement stores in a small can (typically 12-24 oz). These products are intended for use in a “bead type” application for air sealing or adhering. Their small volume, ease of use, and portability make them ideal for smaller projects tackled by the weatherization professional (and often Do-It-Yourselfer).
The different formulations for low pressure spray polyurethane foam products are designed to expand to different degrees, providing the right amount of expansion for gaps and openings of varying sizes. Low expansion and low pressure varieties are available for air sealing around window and door frames that will minimize the pressure exerted against the frames. Other foams are available that will expand more aggressively to fill larger gaps. Some formulations are made to meet specific building codes. Read the product label to help you select appropriate foam for the job at hand.
In addition, it is helpful to understand that low pressure two-component foam requires very different handling procedures, personal protective equipment, and other procedures than insulating foam sealant. Insulating foam sealant is applied in accordance with manufacturer’s instructions on the can, and can be applied by a Do-It-Yourselfer with modest preparation and the kinds of PPE, like gloves and safety glasses, that are readily available at a home improvement store. Low pressure two-component foam is installed with specialized equipment, with more sophisticated ventilation procedures, professionally available PPE including respiratory protection, and other measures. Workers who have previously worked only with the “foam in a can” products need to understand that the low pressure two-component product has completely different handling procedures – read the Safety Data Sheet carefully, and first, before attempting to use the material.
For details regarding high pressure two-component SPF insulation used by professional SPF contractors when insulating large areas, like walls and roofs, in new construction or major renovations, see the “I’m an SPF contractor/building and construction professional.”