Spray Foams and their insulation value

Spray insulation foams come with different insulation values (R-value); they are mainly used in walls, foundations and roofs, whenever high-energy efficiency, strength and sealing is important.

Polyurethane and polystyrene foams

Most spray foams are made of liquid polyurethane or polystyrene, also found in small aerosol cans and used in refrigerators and water heaters (see: Green insulation).

High and low-density foams

Sprayed on foam Typical insulation foams are 1) high-density or 2) low-density.

High-density polyurethane has a superior R-value (R-6 to R-7 per inch), and the best structural strength, air sealing and adhesion. It's also the most expensive.

Because high-density sprayed insulation provides a particular high insulation value (R-value) per inch, it makes possible to use 2x4 exterior walls (instead of the 2x6), which means savings on framing costs.

Low-density polyurethane has a much lower insulation value (an R-value around half the value of high-density polyurethane) and is excellent to insulate closed cavities.

Low-density foams are very flexible, but most demand protection from fire and heat (drywall, when installed close to the inside residential walls).

Spraying foam Icynene When expanding (after being sprayed into open wall cavities), these foams will fully seal and fill cavities but may also damage the walls (due to over expansion). To avoid it, some proprietary foams can expand very slowly. Some proprietary foams can also be fire-resistant.

Uses

Home sprayed foam insulation is an alternative to consider to traditional insulation materials in walls, roofs and foundations whenever high-thermal insulation values (R-values), structural strength, air-sealing capacity and moisture resistance is highly important.

They are largely used in enclosed existing walls, and in open new wall cavities, and also in unfinished attic floors.

Low-density foams - with their "medium" insulation value - are excellent for filling window jambs, rim joist areas, small stud bays, and other penetrations where traditional insulation materials (e.g. fiberglass batt insulation) are difficult to use.

See:
Insulation materials
Insulation best

How spray-on foam insulation works

During installation, when expanding, the resins associated to the foams combine with the blowing elements of the mixture (often HCFC gas or CO2), incorporating the tiny gas in itself, which results in a high insulation value (R-value) of the spray.

Some of that gas will be lost during the first months or years, lowering the foam insulation value, though not in a very significant degree. The effectiveness and the spray foam insulation value remains always sufficiently high.

Application

Sprayed or foamed-in-place insulation is pumped into closed cavities, and molds itself to the surfaces, filling and sealing them thoroughly.

Spray foam insulation fills and seals all the miniscule cracks and seams in walls and other surfaces, eliminating any energy loss by air filtration. That's explains the spray foam insulation value...

Some foams are applied using small spray containers, as a pressure sprayed product. Also in this case, the product molds itself to the surrounding surfaces (by expansion) conforming to the shape of the areas, filling and sealing them.

Prices and Spray Foams insulation Value

Sprayed-foam insulation is more expensive than traditional fiberglass, cellulose and mineral wool batts - though less costly than rigid insulation panels.

Prices vary from $0.50 to $2 per square foot for each inch of thickness, depending mostly on the foam insulation value...

Foam insulation deserves its price whenever higher R-value, structural strength, air-sealing capability or moisture resistance are required...

Installation

Sprayed and injected foam installation demands special equipment and skills, unless in the case of small insulation jobs, using small spray containers. In this case, just follow the manufacturer's instructions.

Warranties

Some manufacturers provide a lifetime limited warranty for their spray foams.