DIY Guide: Building a Temporary Cover for Your In-Wall AC Unit Opening

As the seasons change, so do our home heating and cooling needs. For those with in-wall air conditioning (AC) units, the transition from warm to cooler months might highlight a not-so-insignificant issue: the drafty gap left by the AC unit. Not only can this lead to energy loss and higher utility bills, but it can also invite dust and pests into your home. A practical solution? Building a temporary cover for your in-wall AC unit opening. This guide will walk you through the steps to create an efficient, cost-effective cover that can help insulate your home during the months you’re not using your AC.

Understanding the Importance of a Properly Sealed AC Opening

Before diving into the construction process, it’s crucial to understand why covering your in-wall AC unit is beneficial. An uncovered AC unit can be a significant source of air leakage, which compromises your home’s thermal envelope. This can lead to increased energy consumption as your heating system works overtime to compensate for the cold drafts coming through the AC opening. By sealing this gap, you can improve your home’s energy efficiency, reduce your carbon footprint, and maintain a more comfortable living environment.

Materials You’ll Need

To start, gather the following materials:

  • Measuring tape
  • Insulation board or thick foam board
  • Utility knife or saw
  • Weatherstripping or foam tape
  • Decorative fabric or paint (optional)
  • Adhesive (if using fabric)
  • Sealant or caulk (optional for additional sealing)

Step-by-Step Guide to Building Your AC Cover

1. Measure the AC Opening: Carefully measure the height, width, and depth of your in-wall AC unit’s opening. It’s essential to measure accurately to ensure your cover fits snugly and provides effective insulation.

2. Cut the Insulation Board: Using your measurements, cut the insulation board or thick foam board to size. If your AC opening is particularly deep, consider adding an extra inch or two to the board’s perimeter to cover the entire depth.

3. Apply Weatherstripping: Attach weatherstripping or foam tape around the edges of the cut board. This step is crucial for creating a tight seal that prevents air leaks. Ensure the weatherstripping compresses slightly when the board is in place, indicating a good seal.

4. Decorate Your Cover (Optional): To ensure your temporary cover blends with your interior décor, consider covering it with decorative fabric or painting it. If using fabric, wrap it around the board and secure it with adhesive, making sure there are no loose edges.

5. Install the Cover: Carefully fit the board into the AC opening, pressing firmly to compress the weatherstripping and create a seal. If there are any gaps, consider applying sealant or caulk around the edges for an even tighter seal.

6. Removal and Storage: When it’s time to use your AC again, gently remove the cover and store it in a dry, flat place. This will ensure it remains in good condition for the next off-season.


Creating a temporary cover for your in-wall AC unit opening is a simple, cost-effective DIY project that can significantly improve your home’s energy efficiency. By following these steps, you’ll not only save on heating costs but also contribute to a more sustainable living environment. Remember, the key to a successful cover is ensuring it fits snugly and is properly sealed to prevent air leaks. With a little effort, you can enjoy a warmer, more comfortable home during the cooler months.

Share this:

Leave a Comment