Thermal Performance of Exterior Building Materials

Vinyl Siding

• Regular vinyl siding does not offer a great deal of insulation. Normal vinyl products have an R-rating of about 1.0. R-values are used in the building industry to describe how well a product stops the transmission of heat. For instance, regular fiberglass insulation has an R-value of about 3.14 per inch. Vinyl products with a solid core instead of a hollow-shell construction have an R-value as high as 4.0.

Brick

• Although the brickwork on many old buildings is very attractive, it is not a particularly effective insulator. Poor thermal performance is common in older brick buildings, which are often very expensive to heat. Brick has an R-value of around 0.44, but other factors can affect the thermal performance of a brick wall. For instance, the air-tightness of a wall affects the overall thermal performance without being directly tied to the R-value measurement. On older brick buildings where the mortar is starting to break down, a direct path is provided for more air and heat to move between the interior and the exterior of the house, compromising thermal performance.

Fiber Cement

• Most fiber cement products don't offer a building much additional insulation. The actual R-value of a given product depends on the exact formulation by the manufacturer, and certainly there are some higher-efficiency options that provide slightly improved insulation. A piece of 5/16-inch fiber cement siding has an R-value of about 0.15, according to Builder's News Magazine.

Wood

• Wooden sheathing and wooden siding products are used to provide a natural-looking building facing, but without additional insulation, it is not particularly beneficial from a heat perspective. The thickness of the wood affects the thermal insulation it provides to the building. Lapped wood siding provides about 0.80 R-value, while 3/4-inch plywood provides slightly more insulation.

Insulation-Added Products

• If the thermal performance of your walls is of the highest importance to you, then siding options that have insulation added are an option worth considering. This type of siding is available in fiberboard, vinyl, wood or metal varieties. Essentially, a layer of heat-resistant insulation is placed on the back of the siding material to provide another layer of protection to prevent heat transfer between the home and the outside air.