Do Windows Affect Your HVAC?

Do Windows Affect Your HVAC?

Keeping larger buildings cool during the scorching summer months can be challenging, especially in older buildings. Summer heat always makes your HVAC system work harder, and we’re projected to break heat records over the next few years. Since July is Air Conditioner Appreciation Month, though it officially lasts from July 3 through August 15, now is a good time to assess your building’s windows and ways to reduce their impact on its internal environment.

Do Windows Affect Air Conditioning?

They certainly do, and in a number of ways. Windows allow heat to enter and exit your building relatively unimpeded and can account for up to 10% of the total heat lost. This is why structures that include modern glass facades put such a higher caseload on their HVACs and attendant power bills. Glass facades and HVAC make for a visually appealing but expensive proposition.

The primary reason for this effect is called thermal bridging, which is the term for how heat moves across a material that conducts heat better than the surrounding materials. If you have ever noticed a cold spot on a wall or window, often identified by visible condensation, you are seeing this process in action. Thermal bridging most often occurs on windows when they are framed with a material that conducts temperature easily. For instance, glazed windows can only be so helpful when they are framed with aluminum which conducts heat out of your structure.

With new construction, it is best to remember this process during the design process. Consider triple glazing on the windows and frame them with low-conductivity materials. When possible, place windows so that they allow maximum light and heat during the winter and minimize heat loss through glass the rest of the year.

How Much Can Windows Affect Heating and Cooling?

Windows are one of the primary paths through which heat can enter and leave your building, and not just because of thermal bridging. The summer sunshine pouring in through the windows can generate a massive spike in your HVAC system workload and energy bills. Likewise, during the cold of winter, heat escapes through the glass in the reverse of that process.

If your building has residents or staff that leave the windows open, this can also have several serious effects. Besides allowing hot air in and making your system work harder, doing so also puts you at risk of desensitizing your thermostat, which can cause it not to recognize proper start and shut-off temperatures.

Future HVAC Advancements

Since windows are such a significant factor in green construction, there is extensive research attempting to mitigate their downsides without eliminating them. Some of the promising areas currently yielding measurable results include: 

  • Thermochromic microparticles that react to temperature conditions, blocking up to 70% of the sunlight entering.
  • High transparency silica gel placed between windowpanes, increasing insulation by 50%.

In the meantime, while we wait for new technologies to mature, it is well worth considering an evaluation of your HVAC and related systems, including the windows.

Henick-Lane, New York’s HVAC Experts

For more than six decades our talented, hardworking technicians have provided premiere service to the New York City area. Whether it’s new construction or a high-rise building, our LEED-accredited team can provide the assessments and services you need. Call us at (718) 768-7277, contact us online, or email for a consultation or quote.