Energy Efficient Window Replacements For The Net Zero Home
Window upgrades are a routine household maintenance task. But if those new windows do not meet zero-emissions standards, they may not be worth your time or expense.
In the near future, all homes may be required to be net-zero energy.
The net-zero home produces at least enough energy to meet its own energy needs. The energy savings reduce the overall cost of homeownership. And if you produce more energy than you use, you can sell energy to your utility company.
Almost one-third (25-30%) of your home's heating and cooling costs come from the heat gain and loss through windows. Here's how to install energy-efficient window replacements that create high energy savings.
Install Triple- or Quadruple-Pane Windows
If you cannot feel a draft, you may be satisfied that your window is well-insulated. In fact, a draft only tells you that your window is very badly insulated, but not that it is well insulated. If the window is single- or double-paned, it is likely to have poor insulation.
The insulating power of a window is determined by the heat energy transmitted through a window. This performance metric is called thermal transmittance, or the U value. Direct light transmits directly into a room. But how much infrared light responsible for heat gain enters the room depends on the transmittance and reflectance properties of the glass.
Windows with low thermal emittance provide the best insulation. They reflect a low amount of IR light. Instead, this light is absorbed by the glass to create insulation. The thermal transmittance of your window panes will be provided by the window maker, as required for ISO certification.
Other factors affecting insulation include the following:
- Glass thickness – Thick glass has lower emissivity and thus higher insulation power.
- Tint color – Dark colors are better insulators because they absorb light. Cool colors reflect light.
- Coatings – Coating properties can be fine-tuned to control light reflectance to provide heat gain in the winter and cooling in the summer.
Use Low-E Coatings
Passive low-emissivity coatings absorb heat into a building. If you have double-pane windows, you may be able to treat them with a low-e coating to provide the insulation of a triple-pane window. This simple upgrade could save substantially on window replacement costs. Solar control e-coatings cool buildings by reflecting back solar radiation. Both types of coatings allow visible daylight in while blocking harmful ultraviolet light.
As we approach net-zero energy, window replacements should, at the very least, meet ENERGY STAR energy efficiency standards for windows.
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