Experts increasingly recommend insulating between roof rafters, rather than at the floor of the attic. This results in a conditioned attic space which greatly increases the efficiency of your HVAC system (since attic ductworks are within heated or cooled space), and increases the lifespan of those family heirlooms stored in the attic!

Fiberglass batts finished with sheetrock.

Cellulose blown into the attic.

Finished Shirazi home: quiet and energy efficient.

Insulation is an increasingly coveted element of an energy efficient home.

Not only does insulation create a barrier to air leaks and temperature extremes, it also provides a barrier for sound, insects, etc. We followed up with Reza and Naghmeh Shirazi, whose interior renovation was completed by CG&S Design-Build in September 2008. Spray foam insulation was used in their exterior walls and attic spaces. According to Reza, “the new insulation has made a huge difference. The street noise level is significantly lower and the house stays cooler or warmer longer between HVAC cycling.”

While there are many manufacturers of insulation, there are generally four broad types: batt, blown-in, spray foam, and SIPS. They are all rated for their R value, a measure of thermal resistance, with the highest value providing the best insulation characteristics. Coverage is also an important factor, with higher air infiltration leading to higher energy costs. Choosing which type of insulation to use depends on the project, budget, and installer’s expertise.

Batts are generally made of fiberglass, however there are greener materials now available such as recycled denim and other natural fibers. Batt insulation is most often used in small projects because it’s inexpensive and easy to install, especially in ceilings. It comes in rolls of precut widths and is fitted between the framing studs; holes are cut for electrical outlets and wiring. The insulation values range from R3 to R5 per inch. One drawback of using batts is the potential for gaps and reduced energy efficiency.

Blown-in insulation is typically composed of loose cellulose, fiberglass, or polyester, to name a few. It can be installed wet or dry and should be applied by a professional. Wet cellulose can be blown into framing that is open, while dry insulation is often blown into existing sheetrocked walls through a series of holes, or applied to attics for added insulation value. Because of its size, blown-in insulation can fill small holes and gaps, providing complete coverage and increased R value. Its insulation values range from R3 to R4 per inch, with prices comparable to fiberglass batts. Blown-in insulation can settle over time resulting in a reduction of the effectiveness of the insulation value.

Spray foam in the attic.

Spray foam insulation prior to sheetrock.

Spray Foam insulation is most commonly used in new construction, large additions, and attic spaces. A specialized, licensed subcontractor should be used for the installation. Applied as a liquid between open framing, the nontoxic polyurethane foam expands to fill every gap, nook, and cranny and dries to create an airtight barrier. Excess foam is trimmed before the sheetrock is installed or if used in an attic space, is sometimes left as is. The insulation values range from R4 to R6 per inch of thickness. Pricier than batting or blown cellulose, the return on investment is quickly recovered through lower energy costs.

SIPS (Structural Insulated Panels) are wall panels that are custom manufactured at the factory and shipped to the job site ready to install. They are usually constructed of polystyrene sandwiched between two sheets of plywood or OSB (Oriented Strand Board) and are designed to lock together to create finished walls. They are ideal for new construction and major additions and should be installed by trained framing crews. Their insulation values range from R3 to R5 per inch. While initial costs are higher, savings are recovered by lower framing labor costs, stronger walls, and less waste. Reduced framing members result in a tighter building envelope and lower energy costs.

Can insulation really make that much of a difference in the cost of running a home? Along with HVAC and window upgrades, insulation is at the top of the list of best improvements for potential energy savings and it provides the quickest payback!