Wood vs. Insulation Between Shingles and a Metal Roof

Metal Roofs

• Metal roofs come in a variety of colors and styles to suit any home design. Installation can be either with fasteners exposed or hidden to give the roof a seamless design. Contrary to some people's expectations, metal roofs can weigh even less than asphalt or other roofing materials and are no noisier than other types. Metal roofing can be repaired if necessary and can last 30 to 50 years with routine maintenance. Soap and water is generally all that is required to keep metal roofs looking attractive. These roofs generally have UV-protective coatings to protect their color.

Metal Roof Installation

• Though roofing companies often install the metal roofing, the home do-it-yourselfer can also install the new roof with simple tools such as a hammer, screw gun, metal snips, chalkline, tape measure and nails or screws. Panels can be cut with a circular saw with a metal cutting abrasive blade.

Metal Roof Over Asphalt Shingles

• It is not always necessary to remove old asphalt shingles when installing a new metal roof. If the shingles are in good condition -- that is, if they are not broken, curled, crumbling or otherwise in a state that might adversely affect the metal materials -- they can be left in place. In fact, the asphalt layer serves to help insulate the roof against heat loss. Generally, an underlayment is placed on top of the asphalt. A layer of felt material or tar paper is often used, but other synthetic products may also be used, according to the Absolute Steel website.

Wood Under Metal Roofs

• Wood fiber insulation boards were one of the first industrially made insulation materials used for residential energy conservation. One of the advantages of wood is that is environmentally sustainable. Wood fiber protects well against summer heat, according to the PazRoofing and Waterproofing website. Moisture that builds up over time releases readily. Wood fiber boards may be impregnated with binders to increase their insulating properties.

Insulation for Metal Roofs

• Metal roofs can develop condensation under the roofing material. To prevent this problem, a foil-backed barrier insulation is generally used. A fan-fold insulation is another choice for this purpose. Some companies offer a bubble-type insulation that traps a layer of air between the foil and roof to block 97 percent of the radiant heat energy, according to the A&E Roofing website. The R-value of this insulation -- that is, the amount of heat transfer it blocks -- is approximately 9.2, one of the higher values in insulation materials. Insulation can often be used in combination with other materials, such as asphalt shingles that are left on the roof.