Regulars and Shorts

Eco House: Metal Roofs, Insulating Paint

By James Dulley

Lower those A/C bills.
-by James Dulley
I want to install a metal roof with a lifetime warranty, but I worry it will make my house hotter and increase my air-conditioning bills. Does the long life of a metal roof offset such disadvantages?

-Regina H.

You must have talked with an asphalt shingle salesman. Actually, installing a metal roof can lower your air-conditioning costs and improve your comfort. Also, since you will never have to install a roof again, the life-cycle cost of a metal roof is reasonable as compared to other materials.

Metal roofs are becoming a signature of expensive, top-end home builders. They cost more to install than shingle roofs, but the difference is not as great when reroofing. Metal roofs can be applied over several layers of old shingles, so the tear-off expenses are eliminated. They can look like tile or slate but the lighter weight metal will not require roof reinforcement.

The Florida Solar Energy Center built test homes with various roofs. In 90-degree weather, the attic temperature with a simulated cedar shake aluminum roof was almost 30 degrees cooler than one with asphalt shingles. This can result 33% less cooling load on your central air conditioner.

Another major advantage of metal roofs is they are fireproof. Fires are often spread from house to house by glowing embers carried by the wind. If embers settle on a metal roof, they will not start a fire. Houses with metal roofs may receive a discount on the homeowner's (fire) insurance.

The two most common metal roofing materials are painted aluminum (recycled from beverage cans) and steel. Both are strong enough to handle the weight of a person carefully walking on the roof. Copper and stainless steel are durable, but their cost is often outside of the budget of many homeowners.

Aluminum is an excellent material because it is easily formed to perfectly simulate cedar shakes, tiles and slate. Aluminum does not rust, so if there is an imperfection in the paint or it gets scratched, durability is not affected. The irregular surface eliminates noise from rain drops.

Simulated cedar shakes are most popular and are difficult to distinguish from real shakes. They are formed in multishingle panels to install quickly and they interlock to eliminate leaks and high-wind blow off. Many standard colors are available, and some use energy-saving (heat barrier) paint.

Most steel roofing is painted with tough Kynar as is aluminum. For the most authentic appearance, some include real stone granules in the final coat (10-coat process). Powder-coated Kynar, applied after the panels are formed, is most durable and attractive. Standing seam roofing is ideal on contemporary homes and simulated tiles create a "Western" appearance.

Download (from Update Bulletin No. 896-buyer's guide of 17 manufacturers of residential aluminum, copper, steel roofing, materials used and finishing methods, profiles and simulated styles, more. $3.

The walls in a few rooms and the exterior of my house need to be painted. I thought about using insulating paint on them to lower my utility bills and for comfort. Are these paints really effective?

-Carlos J.

The special insulating paints really do work and when applied, they resemble any other house or interior wall paint. I rolled insulating paint on the walls in the game room in my house. I did not install temperature sensors, but the room does feel more comfortable year-round.

Most of the insulating paints include a ceramic material similar to the heat shield tiles on the space shuttle. After the recent Columbia disaster, most people are aware of the insulating and heat dissipation properties of ceramic material. With a layer of ceramic powder over your hand, you can point a propane torch flame on your hand and not be burned.

Another advantage of using ceramic insulating paint is the dried paint film on the walls is thicker than with standard non-ceramic paint. This tends to fill tiny cracks and imperfections in the wall surface similar to using a thick primer coat first. Filling all these spots can improve the appearance, reduce air leakage into your home and improve sound-deadening qualities.

Ceramic insulating paint is available in one- and five-gallon cans similar to standard paint. The super-fine ceramic powder is already mixed in. If you already have the paint or like a particular brand, you can purchase a 32-oz. bag of ceramic powder and mix it in a gallon of paint yourself.

Whether you buy premixed insulating paint or stir in ceramic powder yourself, the paint rolls or brushes on thicker, so you need a little more. With its insulation qualities and the longer life of the thicker coating, it may be less expensive in the long run.

The ceramic material in the paint lowers the emissivity of the wall surface similar to efficient low-e window glass. The heat from your body, instead of passing through the wall, radiates back off the walls to your skin. This makes it more comfortable to sit near an outdoor wall during the winter.

During the summer, the greatest benefit is gained from painting the exterior of your house. Although the paint looks normal and is not reflective to visible light, it is highly reflective to sun's intense heat. All of the manufacturers also offer special roof paint that can keep your house cooler. It can be painted over shingles and will increase their life.

Most of the ceramic paints use microscopically tiny hollow ceramic spheres. Some paints also include solid glass spheres or ceramic platelets. As the wet paint dries and shrinks, these form a continuous efficient ceramic layer.

Download (from Update Bulletin No. 712-buyer's guide of 11 insulating ceramic and low-emissivity wall, house and roof paint manufacturers, typical application instructions, cleaning and maintenance, painting tips, chart showing the temperature of coatings and other materials in sunlight, more. $3.

Send questions to James Dulley c/o

This article was originally published on June 28, 2007.