All types of insulation are not created equal

A licensed contractor blows insulation into an attic space. By Ryan Davies
CEC Energy Services Supervisor

There are many types of insulation products: fiberglass batts, blown fiberglass, cellulose, rockwool, rigid foam products, spray foams, etc.  While some products perform better than others, more importantly others are more cost effective in specific locations than others.  Each house is unique, and the following options are not the only options but are the most commonly installed and cost effective.

The first locations we will analyze are the walls of the home.  In 1973, the State Building Codes required a minimum R-11 to fill the 2” x 4” framed wall cavity.  In 1992, the State increased framing requirements to 2” x 6” as well as the insulation to fill that cavity to an R-21.  In either case the wall cavity is filled and physically will not allow further insulation to be added inside the cavity.  Homes built prior to 1973 could have an empty framing cavity, and if that is the case could be filled with insulation.  Blown cellulose and blown fiberglass are both cost effective options for a retrofit scenario, that can be blown into and fill the cavity.

Most homes in Central Oregon have at least a marginal amount of insulation in the attic space.  In 1973, State Building Codes required a minimum of R-19 insulation in the attic.  Today’s Energy Star standards would require a minimum R-38, and many times R-50+ is recommended.  The attic is most often a blown material, either cellulose or fiberglass.  The most common and cost effective being a blown fiberglass.  Fiberglass batts are an option; however they do not install or conform as nicely as a blown material around framing and other obstacles in the attic space.  No matter what type of insulation your attic started with you can add more on top of it, ultimately utilizing what is in place and compounding the end value.

The crawlspace of homes can be unique, depending on the way it was originally constructed.  In Central Oregon most often we see a framed crawlspace that has foundation vents around the perimeter.  The floor of the home is supported by framing, or floor joists.  Those floor joists can be various sizes, or depths, and therefore the insulation inside them (if any is installed) may or may not fill the cavity.  It is extremely important for the insulation to fill the cavity and be in contact with the floor.  It was not until 1979 when the State Building Codes required a minimum R-19, and depending on the floor joists depth this may or may not fill the cavity.  The most common and cost effective option is an un-faced fiberglass batt filling the floor joist cavity, and supported at the bottom of the floor joist.  Another option, though significantly more costly, is installing spray foam in the floor joist cavity.  This provides a better R-Value, air sealing, and a moisture barrier all in one.

Typically a home built in 1992 or newer was weatherized close to today’s minimum standards at the time of construction.  Essentially the State of Oregon required certain levels of insulation post 1992 that are most often adequate.

If your home was built before 1992 you would be eligible for a free energy assessment performed by one of CEC’s Energy Specialists, and potential cash rebates to help pay for various insulation and weatherization measures if eligible.  Contact us or visit our website for more information.