air sealing and insulation materials

In most cases, air sealing and insulation have different scopes and demand proper materials that should be installed separately (air sealing first).

With some few exceptions, the general rule is that air sealing materials do not replace insulation materials, and vice-versa.

Air sealing vs. Insulation Materials

Air sealing concerns air leaks and their sources: penetrations, openings, cracks. Insulation involves thermal protection of large surfaces.

The scope of home air sealing and insulation is, in these cases, clearly different. And the materials used in these functions are also different.

However, since air leakage may also involve the home's shell - the floors, the ceilings, the walls -, in this case, insulation and air sealing may overlap, though often only partially. The materials used in this last case are mostly different (housewraps and sheet goods, that is, air barriers, in the case of air sealing).

Materials

Sealing electric outlet with a foam (Dow) Air sealing products include caulks (for smaller holes and cracks), foams, weather-stripping materials (namely for window and door movable parts) and air barriers for large surfaces and to provide a whole air leakage protection to the house shell, in the case of wood and steel frame homes.

Insulation materials involve common fiberglass and mineral wool, cellulose and a large set of plastic foams and special materials like ICF or SIPs.

Materials that can provide both insulation and air sealing

Sealing foams are used to seal medium and relatively large openings and penetrations. But in these case, foams are sealing products, not insulation ones.

Rigid Foam: Insulation and Air Sealing However, in some cases, where structural strength is provided by other means, some rigid foams (namely polyurethane foams...) can provide both sealing and insulation. They aren't exactly a two in one solution for all cases, and seldom are the best or the cheaper solution, but they can be excellent insulation and air sealing products.

Materials like EIFS or structural sheathing can also provide both air sealing and insulation.

Most insulation materials do not provide air sealing and Vice Versa

Common insulation materials (fiberglass, mineral wool or cellulose…) don’t stop air leakage. And vice-versa: sealing materials do not provide insulation...

If the insulation materials in your attic or walls are dirty, that is a very telltale sign of air leakage. In this case, the fiberglass or whatever the insulation material you have, it acting like a filter, collecting dirt without blocking significantly the air movement.

In places like walls or the attic, insulation can hide air leaks, making their identification and sealing more difficult.