Basement Insulation - Evaluate Your Free Space

In the pioneer days having a space below ground was useful for storing food in a cool place, keeping it away from animals and protecting valuables that might be compromised by the elements. In addition it was a precious space to plains-dwelling settlers in case their area was hit by a tornado.

Later, in Victorian times, basements became common for use as a large bin for coal that was dumped in through a cellar door and also for storing extra furniture and tools. However, not all homes had a complete basement. Many just had a crawl space to accept piping and electrical lines. During the mid to late stages of the 20th Century the furnace, water heater and electrical supply panel were added to this space.

It wasn't until the 1950's that the basement began to emerge as an important, livable area of the home. This, of course, was the case only if the space was dry or had a system to direct water away from the foundation. Otherwise, since cement is porous, moisture could keep creeping in and the basement would be always damp.


One of the main considerations for a basement, either partially or totally beneath the surface of the ground, is keeping it dry. In older homes basements were not waterproofed or provided with drains so, to compensate, many had a sump pump below the basement floor. In the spring and fall when rainfall was heaviest, water in the basement was pumped out. Sometimes this process was performed below ground so that the basement floor never saw any water.

The best way to keep a basement dry is to drain the water away before it hits the ground. This is accomplished by a good gutter and downspout system that will send the gallons of water away from the foundation. New builders make sure that their foundations will not excess water by placing a perforated drainpipe all around the footing. Any water seepage will enter the pipe that is directed toward a storm drain. In addition builders will waterproof the basement walls by either coating the exterior with a waterproofing compound or wrapping it with a membrane to shed the water.


By its very nature concrete is a “thermal mass.” This means that it stores heat energy and will suck heat out of your basement and transfer it outside. That is why the basement feels really cool on a hot day and it one of the advantages of having a basement space.

Basement heat loss can make up as 20 to 35% of the total heat loss for the home. In an older home this is compounded with air leakage through windows sills and cracks between the foundation and the house level, the result of wood shrinkage and house shifting. There are four types of insulation:

1. Inside Batt Insulation

This is the most common type of basement insulation. It requires building a stud frame much like the regular walls and then putting in fiberglass or rock wool insulation between the studs. These are then covered with vapor seal and drywall, and then finished. In some cases there is a vapor seal between the cement and the studs to protect from moisture but this depends on how moist the basement gets. Having two sets of vapor seal may provide a good place for mold and mildew to infest. The R-values for fiberglass batt is 3.5 per inch, meaning 12-15 for a wall.

2. Inside Rigid Foam Insulation

Rigid board insulation for walls comes with prefabricated channels for framing to hold the insulation in place. This makes the profile almost half that of traditional wood framing which can be 3-5 ½ inches. This can be important where space is limited. In addition, rigid foam board gives you the option of insulating on the exterior of the foundation.

MEPS Foam Board: Molded expanded polystyrene (MEPS) is a material used in coffee cups and is also known as beadboard. For wall insulation the R-values range from 3.8 to 4.4 per inch of thickness.

XEPS Foam Board: Extruded expanded polystyrene (XEPS) is similar to MEPS except it is injected through a shaping die making it a more sturdy product and less subject to penetration by moisture. Because of this it is more expensive. The R-value is about the same same as MEPS.

Polyisocyanurate and Polyurethane Foam Board: These types of foam boards are more flexible and have a smooth finish. In addition they have a greater R-vale per inch at 5.5 to 8.0.

3. Outside Rigid Foam Insulation

If the soil is easily removes insulating an outside wall can be a great way to go. Because once you have the dirt aside you can waterproof the exterior and readjust the drainage. In addition, you can finish the basement without the deep profile of inside insulation gaining more space. The best part for heating and cooling is that the cement mass can now be used as a thermal mass to provide an even heat for the upstairs.

4. Spray Foam Insulation

Like the foam insulating spray in the small cans, spray foam machines shoot liquid foam onto the surface where it adheres to the cement as it dries. To get the best results you should frame your basement walls and get the spray foam in between. Since it is waterproof, and gets into all the spaces, there will be no condensation and therefore no mold or mildew. The foam expands at a terrific rate and the installer cuts off the excess after it dries and the drywall goes on over top. The r-value is rated at 7 per inch but the added savings in heat costs will be greater because of the sealing effect of the foam.

With the moisture and heat problems behind you then you can begin planning your new space.

Posted by: TrustedPros
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