Thermal Window Energy Efficiency
October 11, 2010
Thermal windows can improve both the comfort and the energy efficiency of your home. As such, they represent a long-term investment that can pay off for years to come.
How Thermal Windows Can Improve Energy Efficiency
The glass surfaces of your home--windows, skylights, and glazed doors--can account for over 25% of a home's heating and cooling bills. Thus, while thermal windows may be more expensive, they have the potential to make a significant impact with each monthly energy bill.
Choosing thermal windows for energy efficiency has such a big impact because heat can transfer into or out of your home via your windows in three ways:
- Conduction, and other forms of heat transfer by contact between the window and outside air of a different temperature
- Solar radiation, which occurs as a result of sunlight streaming through your windows
- Airflow, which can cause temperature transfers due to ventilation or unintended gaps in window materials
Thermal windows can improve energy efficiency by seeking to reduce temperature transfer from any or all of the above sources.
Choosing Thermal Windows
Thermal windows can derive energy efficiency from different designs and materials, and companies may use different standards to describe the energy efficiency of their products. This can make thermal windows difficult to compare, but some standards have been formulated to help consumers make these comparisons.
The National Fenestration Rating Council (NFRC) is a non-profit collaboration between public and private entities, and they have created a labeling system to help consumers compare window products. NFRC labels rate products based on:
- U Factor: heat transmission due to temperature differences
- Solar Heat Gain Coefficient: the rate of solar heat flow through the window
- Visible Light Transmittance: the portion of visible light which transfers through the window
- Air Leakage: a measure of the air that can flow through a window
So, look for the NFRC label and you will be able to make direct comparisons when evaluating thermal windows.