Insulation, Comfort and Energy Savings (Part 3 Home Energy)

Now that we covered how to have an effective air barrier in part 2, we can work on the thermal barrier or better known as your insulation layer. Your thermal barrier, or insulation, will determine the ability of your home to retard heat flow. The slower your heat leaves your home, the less energy your heating system will use. Your air barrier and thermal barrier should be together and continuous for maximum efficiency. It is very important that you air seal before installing new or additional insulation. Insulation is another job where it is recommended to hire a BPI certified building analyst before tackling.

The typical insulation install in an existing home is installed in the attic. Sidewalls and rim joists can also be done in certain homes. It is important to do the proper attic prep before adding any insulation. This may include the following:

•             Determine amount (In most States, code is R-38: about 11 inches of blown cellulose or fiberglass.)

•             Check electrical (Watch out for knob and tube wiring, or any frayed wires or overburdened junctions.)

•             Make insulated boxes to go over any non-IC-rated recessed lights

•             Metal flashing with fire-safe caulk to keep insulation away from chimney or flue

•             Air sealing all intrusions into attic (If air sealing is not done, condensation can occur in attic, leading to mold, derated insulation, and ice dams.)

•             Ventilation (Make sure soffit vents have proper vents to train air flow to ridge vent and also make sure blocking is installed to prevent new insulation from clogging vents. Installing insulation without proper vents and blocking can lead to wind washing that will derate your insulation.)

•             Dams may need to be installed to prevent insulation from spilling over attic hatches, air handlers, and vents

•             Any roof leaks must be addressed

•             Watch out for vermiculite, as it has been known to contain asbestos, which can cause cancer. It should be removed by an asbestos-removal specialist.

Vermiculite insulation, also notice the knob and tube wiring that should not touch anything, and the poor installation of the rolled fiberglass on the roof deck. The insulation on the roof deck would not be effective as it is not continous.


Blowing sidewalls and floors can be a very difficult job, and the only houses that typically make sense to do this in are those without insulation that have large wall cavities and balloon framing. This is definitely a job for the professionals.


Rim joist insulation can be an effective install for those homes with un-insulated rim joists. Below is a nice video that shows where the rim joist is. A homeowner or even a contractor can simply use rigid board insulation friction fit and foamed on the edges with cans of spray foam, for sufficient improvement.


There are many different insulation materials and application methods. The most common are rolled fiberglass batts, blown loose fiberglass, blown loose cellulose, and closed cell foam. Loose blown cellulose insulation is essentially recycled newspaper. Unlike fiberglass it is non-toxic, resists air, and will seal small air leaks, where fiberglass will not stop air and is quickly derated when windwashing is present. Despite its shortcomings fiberglass is still an effective form of insulation with a low cost. Closed-cell foam insulation is the "new kid on the block." It is a perfect air barrier with a high R value, but it is expensive. It is a good to use if you are insulating a roof deck where you are bringing the entire attic inside the thermal envelope; for example, when you have ducts and an air handler in the attic. Some contractors combine the perfect air barrier of the closed cell insulation as the base of an attic, with the low cost of loose fiberglass to provide the bulk of the insulating inches.

A more complete list of insulating materials and applications can be found here.

Cellulose insulation burying recessed light.


ROI on insulation: AVG. 17%

(Varies depending on difficulty of the install, how much insulation is existing, and how expensive your fuel source is. The less existing insulation there is, the higher the ROI.)


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