Window Insulation Is Key to Your Home’s HVAC Efficiency

When it comes to your home and bills, HVAC efficiency is essential to keeping bills in check and your family comfortable. Windows are a major source of heat loss and heat gain. Roughly 25% to 30% of residential heating/cooling energy use can be attributed to window performance, according to It can literally make your home unlivable if your windows aren’t properly insulated. Proper window insulation can both make your home comfortable and save you money.

While, glass has no insulating properties of its own, a lack of sealing around your windows has the opposite effect of good insulation. Poorly insulated windows have impacts such as:

  • Lower Heating Efficiency: Heat passes through glass in a process called conduction, forcing your heater to work harder. It also rises toward cool glass, being cooled in the process, and pushed to the floor, while any heat remaining near the window conducts outside.
  • Poor Cooling Efficiency: Heat can enter your home in summer the same way it escapes in winter. Single pane windows are the most vulnerable, while gaps around the frame don’t help. Your HVAC system must work harder to compensate for a hotter interior.
  • Drafts: Conduction sometimes feels like a draft, but a true draft originates from cracks or gaps around the window’s edges. This also makes it harder for your HVAC system to maintain a stable indoor temperature no matter what you set the thermostat to.
  • Humidity: HVAC systems help remove excess moisture, but struggle to regulate humidity if there’s an influx of air from outside or air is escaping. Too much moisture can increase mold, dust, and allergen levels, and damage your home; to little can leave you with dry skin, dry eyes, and nosebleeds.

How to Insulate Your Windows

There are several methods of insulating windows that can be beneficial for your AC and heating system, as well as home air quality. The most effective ones include:


Weatherstrip seals, made of vinyl, foam, or silicone, fill gaps around the windows. They can withstand temperature extremes and block drafts.


Rope caulk is a putty that you can cut and press into place in any crack or hole you find.

Bubble Wrap:

Is an effective insulator. Apply it by spraying some water onto the window, and the wrap will stick and act as an extra layer of glass.

Blackout Curtains:

Curtains should be closed at night to block out colder air in winter and opened during the day to let in warmth. In summer, close curtains on south- and west-facing windows when the sun is out.


Insulating shutters provide an effective barrier for summer heat. While keeping your home cooler, they are also decorative and come in many different styles.

Reflective Insulation:

Reflective film bounces light off your windows, so it does not heat the interior. It also protects the window from damage.

Cellular Shades:

Feature built-in air pockets that trap air and provide an insulating effect; cellular shades are decorative as well.

Properly installed and insulated windows open and close smoothly, have smooth caulking with no cracks, no gaps between the windowsill and frame, and are free of water damage or fog/condensation inside the pane. If you notice otherwise, it’s time to take measures such as those above or contact a professional to identify and address the problem.

Contact Black Hills Inc. Home Services

If your home has issues with heating or cooling, we can determine the source of the problem. Your HVAC system may be working fine, yet issues such as poor window insulation can be reducing performance and efficiency. Allow us to determine the best solution if your AC/heater could be performing better. Request service online or call 888-538-5821 today.