Insulating Exterior of Home Has Advantages

QUESTION: I think I should add some insulation to the exterior of my house. Is exterior wall insulation as effective as standard insulation inside a wall and what is the easiest way to add exterior insulation?

ANSWER: Insulation on the exterior surface of a wall is the best location, and it is actually better than standard inside-the-wall insulation. You will notice the greatest benefit in the summer as it blocks heat gain through the walls.

Exterior insulation is more effective because the entire wall structure under the insulation stays cooler in summer and warmer in winter. It becomes a thermal mass that moderates indoor temperature changes. Also, the insulation seals many gaps in the exterior surface to reduce outdoor noise transmission and dust.

The easiest and most common way of adding exterior insulation is by attaching several inches of foam insulation board on the outside of your walls. The insulation values of foam boards range from about R-5 to R-7 per-inch thickness. A 1 to 2-inch thickness is often added.

There are several companies that manufacture and market special exterior insulation systems. Some are only applied by licensed contractors and others can be done by the do-it-yourselfer. The companies can sell you all of the materials needed or you can purchase some locally. This type of insulation system is also effective for new construction.

First you must attach the foam board insulation to your existing walls. You can attach the foam board with special adhesives, mechanical fasteners into the existing wall or a combination of the two methods. The foam board is easy to cut, so you can fit it neatly around the openings for doors and windows.

Next, you apply a reinforcing mesh over the joints between the pieces of insulation board. This adds strength to the joints and minimizes the possibility of any cracks forming.

The most commonly used type of finish coating is a special flexible stucco-like coating. It looks and feels just like stucco, but it is made of an acrylic polymer that remains flexible. It is easy to apply and durable due to its flexibility. You select among many colors and it can improve the appearance of most houses.

You can apply the coating with a trowel or a roller, depending upon the surface finish you desire. One-sixteenth of an inch is the recommended thickness. You should trowel it on around the corners and window trim right up to the masonry or block-exterior surface for a finished look.

You can write to me for Utility Bills Update No. 049 showing a list of manufacturers of exterior insulation systems, information on the do-it-yourself system and materials, and small sample pieces of cured stucco finish coating. Please include $1 and a self-addressed business-size envelope. Send your requests to James Dulley, c/o Los Angeles Times, 6906 Royalgreen Drive, Cincinnati, Ohio 45244.

Is Window Coating a Health Hazard?

Q: I have heard that the new energy-efficient low-E glass uses a metal coating that contains mercury. Can that be dangerous to my family’s health if we install new windows?

A: Energy-efficient low-E glass uses a microscopically-thin invisible coating of metallic compounds on the glass surface. It is very effective for blocking heat loss in the winter and heat gain in the summer. The metal compounds don’t have mercury in them and the metallic surface is sealed on the inside surfaces of the thermal double-pane glass.

Attic Vapor Barrier Not Always Needed

Q: I am in the process of insulating my attic, but I accidentally tore the plastic vapor barrier I laid down first. Is it really necessary to repair it?

A: In your warm climate, an attic vapor barrier isn’t absolutely necessary. Therefore, unless the tear is very large, don’t bother repairing it. The two edges should lay close enough together to adequately block the water vapor.

However, if you want to fix it, tape the two edges together with standard furnace duct tape. Also, if you have some of the plastic vapor barrier left over, lay a 2-foot-wide strip over the tear. The weight of the insulation above it should hold it down.

Letters and questions to Dulley, a Cincinnati-based engineering consultant, may be sent to James Dulley, Los Angeles Times, 6906 Royalgreen Drive, Cincinnati, Ohio 45244.