Selecting the right insulation for the job hinges on five key points: the initial cost of the insulation material; the installation cost; the ease of installation; and what additional building components are required to achieve the installed R-value. All of these factors can be tracked, tallied, and compared in an effort to select the right insulation and installation method for your home.
Coverage and Cost
Coverage, like density, affects how efficiently any insulation performs. Leaving uninsulated gaps creates thermal leaks that may make for increased heating or cooling costs. However, achieving the required coverage, maintaining it, and gauging it are very difficult for homeowner and professional alike, particularly in a retrofit. It is nearly impossible to tell how much insulation settles in a wall or how compressed blankets and batts become. So, the ease with which an insulating material can be installed to achieve complete coverage is an important consideration for the homeowner and contractor. The more time a pro spends on the job, the higher the installed cost of the insulation.
Ease and savings often combine to make blown-in applications the most cost-effective option for retrofit installations, because they can usually be completed with no disruption to interior walls. Unseen framing obstructions or existing insulation might interfere with the application, however, making coverage and R-value a real wild card. Spray-in-place foam, blown-in cellulose or fiberglass applications are typically performed by professionals, so the installed cost is higher. On the plus side, little or no surface repair is needed after installation, which adds to the long-term energy savings.
Keep Air Out and Heat In
Other components may be needed to achieve the rated R-value, and this can affect both the installed cost and the overall efficiency of your insulation installation. Air infiltration reduces insulation efficiency, and can be blocked by housewrap or rigid foam installations. A layer of rigid foam board, with taped joints, may be applied to the exterior of the insulated wall. This layer adds R-value to the insulation while serving as an air infiltration barrier. Housewrap is commonly used in new construction and on re-siding jobs to reduce air infiltration. Again, the joints must be carefully taped, which means time, money, and increased installation costs on a contracted job.
Hype and Homework
Service life, or the length of time a material will effectively perform its job, is a factor in making an insulation choice, as is flammability. But whatever it’s made from, most types of insulation are designed to function in sealed cavities that are nearly air-free, protected from sunlight, moisture, and sources of heat. Given these conditions, any insulation should perform satisfactorily throughout the building’s life.
Credit: Renovate Your World