Should I Insulate My Basement Walls?

This is the question for many people who are working on finishing their subterranean living space. The simple answer to that question is yes. Basement wall insulation is a must in most cases, and here’s the information you need to know for doing it.

Choosing The Right Product

There are different insulation products available on the market. Before the basement renovation begins, you must choose the product you will use to keep it warmer. This is because some, like foam boards, will go in before the framing is done and others, like rolls of batt insulation, will go in after the walls are framed. Here are the options you can choose from.

  • Foam board – Lightweight and easy to work with, foam board offers an attractive insulating value. It is installed before any of the framework.
  • Blanket – Installed before the framing goes in, this is easy to install with a helper and will provide a great deal of warmth.
  • Fiberglass wall – Designed to fit between studs, it’s inexpensive, effective and easy to install. However, there will be gaps and small, open areas that slightly reduce the overall effectiveness. This is installed after the framing; wiring and plumbing work is completed, but before the drywall goes up.
  • Spray foam – Whether you go with wet cellulose or closed cell spray foam, this is one of the best methods for insulation. However, it is expensive, messy and will require special equipment. If you’re not highly experienced in construction, you might want to leave one to the pros. Like fiberglass, this product will be installed before the drywall goes in place.
  • Blow-in – The tools required can be rented for a low cost, all the nooks and crannies will be filled and the process is relatively simple. This insulation is actually installed after the drywall is in place.

The Final Word on Vapor Barrier

Plastic sheeting that seals all other gaps and cracks; you will hear different advice about when vapor barrier should be installed. Some people say it goes against the concrete wall for a solid barrier. Others suggest putting it on the warmest side, between the studs and the insulation. Designed to prevent cool air from meeting warm air and forming condensation, the vapor barrier should go on the warmest side of the insulation. Thus, it should always be installed between the framework and the drywall.

Installing Foam Board

Rigid boards will provide a higher R-value. More flexible boards will have a slightly lower R-rating but will prove easier to maneuver into the basement. Choose yours based on the layout of your home and how easily the boards can be taken to the work area.

The boards are glued to the wall using special Styrofoam adhesive, available at your local hardware store. Installing them horizontally will make it easier for them to stay on the wall while the adhesive is curing. Seams should be sealed with Tyvek tape. Once they are in place, you are ready to start framing the walls. Vapor barrier can be installed on either side of the wall frame and may not be necessary with all types of foam board.


Ideal for unfinished walls, blanket insulation is great for people who want to warm up the area but aren’t interested in going to the expense of actually finishing the basement. It is held up against the sill plate by nailed furring strips along the top of the blanket. Because you will be working up against the floor joists of the house, you might want to wear a helmet during this process. While this is ideal for unfinished walls, it can also be done before the walls are framed.


Unfaced insulation is less expensive. Faced can be easier to work with if you are sensitive to fiberglass. It is installed between the studs, after the framing is completed, wiring is run and plumbing is roughed in. It is easy enough to install that one person can easily do the job in a day.

Unfaced insulation can be installed with special supports. Faced batt is easily installed using a staple gun.

Unroll the batt slightly to begin. Start by placing the free end at the top of one wall cavity, between the joists. Faced insulation should be installed with the paper towards you. There is a strip of extra paper on either side of the insulation. Fold this strip out and staple it to the studs. Unfaced insulation can be installed by placing the metal supports horizontally between the studs. When you have reached the bottom of the wall, use a utility knife to cut the insulation and start installing it at the next wall. You can also measure the wall cavity and then cut the exact length of insulation that is needed for a tight fit.


Should I insulate my basement walls before hanging drywall? Most people will do the insulation ahead of time. However, it is not a requirement. If you will be using blow-in insulation, you can install the installation after the drywall is in place.

There are several benefits to blow-in insulation. It’s affordable and easy to work with. It also fills all the crevices for a high insulating factor. On the downside, the process can be dusty and you will want to note any areas between the studs that have horizontal bracing or fire stops.

Using the screws in the studs as guides, drill a hole two inches in diameter in the drywall at the top of the cavity. Cut an X in the vapor barrier and fold the triangles to the exterior of the wall. Use a properly sized hole drill to make a clean hole.

You may want to have a partner help you with the chore. One person will hold the hose in place in the wall, with several inches of it inside the wall. The other person will turn the machine on and off and handle filling it with the blow-in insulation.

Once the cavity is filled, fold the plastic back into place. Seal the cut in the plastic as thoroughly as possible using special vapor barrier tape. The hole should then be patched. One option for patching the holes is to place them as high up on the wall so they can be covered with attractive, wood molding.

Should I apply waterproof paint first?

Waterproofing paint is not always necessary. Some basements are wonderfully dry and this step would be largely unnecessary. However, there is absolutely no harm in taking this precautionary step. It can provide an added layer of protection and peace of mind that you will appreciate.

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