The Insulation Needed for a Concrete Block Wall

Spray Foam

• One widely used type of insulation for the hollow cores of concrete blocks comes as a spray that expands to fill out the cavity. The foam forms a tight bond with the concrete, but also maintains some flexibility. Spray foam cannot be left open to the environment after application. A barrier of some kind, such as drywall, must go up around it. Spray foam typically costs more than some other types of insulation, such as fiberglass batts, but can make up for the extra expense in reduced utility bills.

Vermiculite and Perlite

• Two other materials used for insulation the cavities of concrete blocks, vermiculite and perlite, come in the form of small pellets. Both natural minerals expand when heated to a high temperature, making them effective, lightweight insulating materials. Vermiculite has become a problematic insulator because of concerns that it might contain asbestos. The U.S. Environmental Protection Agency reports, however, that only a few sources of vermiculite contain any appreciable quantities of asbestos.

Exterior

• Insulating the outside of the concrete block as well as the hollow cores creates an additional layer of energy saving material in the wall. Traditional fiberglass batts, or blankets, do not work well when applied directly to concrete block walls. The cold, damp concrete can cause mold to form in the batts. A better alternative, placing polystyrene insulation panels over the concrete, allows you to thoroughly cover the wall with a moisture-resistant material.

Alternative

• An alternative method of achieving strong concrete block insulation involves using blocks made of materials that have strong insulating qualities. A concrete product called autoclaved aerated concrete, or aac, contains an expansion agent that causes it to expand when the aggregate mixes with the cement. The expansion creates a block made up of about 80 percent air, according to the Portland Cement Association. The lightweight blocks make excellent thermal insulators, but need the application of a finishing material, such as stucco, to improve their durability.