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How to Insulate Your Basement

From preparation to installation, here's a breakdown on basement insulation.

Whether you use your basement primarily for storage or as a recreational space, insulating this section of your home can yield significant financial benefits. According to the U.S. Department of Energy, insulating your basement walls can save up to $350 annually in some regions. This is especially true in “tight” homes with a strong seal around upstairs windows and doors, where a large portion of heat loss comes from an uninsulated basement.

Prepping for Basement Insulation

The most important concern to address before insulating your basement is moisture. To ensure there’s no dampness seeping through the walls, conduct a simple test using plastic sheeting and duct tape. Tape a small piece of plastic sheeting to a bare concrete wall with an impermeable duct tape border and wait 48 hours. After sufficient time has passed, check the interior and exterior of the plastic sheet for condensation — this will determine if water is seeping through.

Additionally, ensure the tie rods embedded in the concrete (once used to hold the form of the home’s foundation as it was being poured) are sufficiently sealed. To do this, use a masonry hammer and center punch to tap the tie rods below the surface of foundation wall. Next, mix up a batch of hydraulic cement to fill the tie rod holes.

This type of cement sets quickly, so work with it in small amounts. When properly mixed, the cement should reach a peanut butter-like consistency. Before applying the hydraulic cement, spray down the tie rod holes with water—this will prevent the concrete walls from leeching moisture from the new cement. Force the cement into the sunken tie rod holes using a margin trowel.

Step-by-Step Basement Insulation Installation

  1. After the cement is set, apply a foam board adhesive to the rear of a polystyrene insulation panel, then press the panel to the wall. Make sure your adhesive is free of solvents, which can eat away at the foam insulation. Adhere and apply the remaining panels.
  2. Next, you will create a wood grid that will hold the drywall. Begin by measuring three inches from the top and bottom of the floor and ceiling of the room. Mark these measurements, then snap five equidistant horizontal chalk lines across the polystyrene panels. This will provide a guide for creating the grid. Then, take a 1x3 spruce board and hold it on the chalk lines you created.
  3. Using a hammer drill and a 3/16-inch masonry bit, drill 5-inch holes through the 1x3 and into the concrete wall. You will fasten the 1x3s with 4-inch-long spring spikes, which appear like nails with no point and a kink towards the tip. This acts like a spring that tends to straighten out and anchor the spike into the concrete wall.
  4. Once the horizontal boards are attached, screw vertical 1x3s to the horizontal 1x3s with 1 ⅝-inch drywall screws. This will create a vertical and horizontal gap for any future electrical wiring to be installed. Space the horizontal 1x3s 16 inches on center, and finish installing the vertical boards.
  5. Once your grid is in place, you can install your drywall. For basements, moisture-resistant greenboard is best.

Selecting Between Mesh and Paper Tape

To finish the drywall, there is some debate about the use of paper or versus mesh tape to hide the seams in the panels. The advantage of mesh tape is that it comes adhesive-backed and does not require an initial layer of joint compound before application. Paper tape, on the other hand, necessitates a layer of joint compound before being smoothed on with another layer of the compound.

While there is no hard and fast professional preference among contractors, in some circumstances, paper tape is a superior choice. Paper tape allows for an easier-to-achieve seamless finish along corners and is better suited for large-scale applications.

On a project smaller than 1,000 square feet, fiber mesh is easier and faster to use.


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