Foundation Wall Insulation by AEA, LLC.

The Benefits Of Insulating Basement Walls

We want to address the foundation walls specifically because, unlike insulating other parts of the home which already considered good practice by the majority of contractors, many contractors unfamiliar with weatherization do not understand the benefits of insulating foundations. New studies by building scientists have proven to get the full benefits from a home's thermal barrier it needs to include the basement walls to give you the highest energy efficiency (if the basement is conditioned).

A properly insulated basement can greatly reduce your energy costs. New building science studies have shown that a conditioned basement that is NOT insulated may represent up to 50% of heat loss in a tightly sealed house that is well insulated above grade. Many existing homes fall into this category since foundation walls were mostly overlooked when a home was insulated during construction since old building practices did not have an understanding of much energy is lost with uninsulated foundation walls.

Annual Energy Savings

The energy cost savings of basement wall insulation vary depending on the local climate, type of heating system, fuel cost, and occupant lifestyle. The graph below shows the annual savings of a 1,500 square-foot home with a conditioned basement heated by natural gas costing $0.72 per therm with R-10 insulation on the foundation walls.

Advantages and Disadvantages

In most cases, a basement with insulation installed in the exterior basement walls should be considered a conditioned space. Even in a house with an unconditioned basement, the basement is more connected to other living spaces than to the outside. This connection makes basement wall insulation preferable to insulating the basement ceiling.

Compared to insulating the basement ceiling, insulating basement walls has the following advantages:

Requires less insulation (1,350 square feet of wall insulation for a 36 x 48-foot basement with 8-foot walls, compared with 1,725 ceiling)
More easily achieves continuous thermal and air leakage boundaries because basement ceilings typically include electrical wiring, plumbing, and ductwork.
Requires little, if any, increase in the size of the heating and cooling equipment. The heat loss and air leakage through the basement ceiling is similar to that through the exterior walls of the basement.

Adding insulation to the interior of the foundation is often more cost effective for an existing building. Interior insulation has the following advantages and disadvantages.

Advantages:

Interior insulation is much less expensive to install than exterior insulation for existing buildings
Almost any insulation type can be used, giving a wider selection of materials
The threat of insect infestation is eliminated
The space is isolated from the colder earth more effectively than when using exterior methods

Disadvantages:

Many insulation types require a fire-rated covering since they release toxic gases when ignited
Interior insulation reduces usable interior space by a few inches
It doesn't protect the damp-proof coating like the exterior insulation
If the perimeter drainage is poor, the insulation may become saturated by moisture weeping through the foundation walls
Superior air-sealing details and vapor diffusion retarders are important for adequate performance

Types of Basement Insulation

Once you have determined the insulation R-value you'll need for either adding insulation to an existing basement or new home construction, you can choose the type of insulation, including the following:

Blanket (batt or roll) insulation
Foam board insulation
Loose-fill insulation (a good choice for finished basements, drill into and fill the wall cavities)
Spray foam insulation (also a good choice for finished basements, but generally more expensive)

The installation of insulation in your basement will depend on the type you choose and the best way to control moisture in your particular climate.