Basement Insulation

First of all, we know that not all homes have basements.  But if you do have one, it may be an energy pig.

Top 3 reasons to insulate your basement:
  • Because heat flows naturally from a warmer to a cooler space, you are probably experiencing heat loss from your first floor living space into your basement.  During the summer, the opposite occurs—heat flows from outside to your house interior and gets stuck in the living spaces.
  • So the heat you lose to your basement in winter must be replaced by your heating system and the heat gained in you living space in summer must be removed by your air conditioner—or simply endured.
  • When you insulate basement ceilings, walls, and floors, you provide effective resistance to the flow of heat. You’re more comfortable, more energy efficient, and you save money.

What Are the Choices for Insulating Basement?

basement insulationHow you insulate your basement depends on whether it is conditioned (meaning that it is heated and cooled—generally the case in finished basements)—or unconditioned, with the space left raw. So you have some choices here—you can insulate the walls, the ceiling, the floors, or all three.

If you have a conditioned basement, first find out whether it has been insulated. (A home energy assessment will let you know this.) Once you’ve located the placement and amount of insulation, you can make improvements (unless, of course, your basement is perfectly insulated.)

Most conditioned basements can use insulation in the walls and floor. In unconditioned basements the best choice is going to be to insulate the ceiling. Not only will it save you energy but it was also make the floor of the first floor feel warmer; your feet won’t be so cold.

Questions to Ask A Contractor

For a conditioned basement:

  • What’s the best way to add insulation to my walls and floor? For walls, contractors usually recommend the “drill and fill” method, where loose filling insulation such as cellulose is pumped in. When it comes to your floor, a contractor can place insulated pads underneath the floor (provided the floor can be easily lifted) or you can add foam layers underneath rugs or other floor coverings.

For an unconditioned basement:

  • What type of insulation will you be using, and where will it be placed? If you can see the joists in your ceiling, the contractor may recommend batts, also known as blanket insulation. Or, you might be offered sprayed foam, which expands to fill the unconditioned space.
  • What can I do if I have plaster covering my walls or ceiling? You’ll probably want to consider the same “drill and fill” method used for conditioned spaces. Either way, count on a fairly short and not very expensive process. (Worried about the “drill and fill” method causing plaster or wallboard to crack or break? Under normal circumstances, this should not be a concern, since these materials are very heavy and the insulation is light. However this is another area to discuss thoroughly with your contractor.)

No matter which type of basement you have:

  • Be sure to complete the job with air sealing, which is one of the key ways to maximize insulation effectiveness.
  • And as long as you’re in the basement, why not insulate the outgoing pipes on your hot water heater? (Pipe insulation is sometimes included free in a home energy assessment.) If you have an older hot water heater, you may also want to insulate it with a hot water heater blanket, although most newer hot water heaters are already adequately insulated.
  • Talk with your contractor about moisture control and venting, which can be a bit tricky in basements. All venting should be to the outside, not to conditioned spaces.
Behind the Walls
Innovation Center
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Cambridge, MA 02142