An exterior envelope encases the living area of your home. This outer shell – which includes the floor, walls, and ceiling – is far from uninterrupted. Building material changes, wiring and plumbing penetrations, exhaust vents, windows, doors, and other home features create openings in the exterior envelope. Outdoor air can enter your home through these openings, impacting heating and cooling efficiency.
Windows have a particular impact on home efficiency because they’re quite large and are made of glass, which is a very poor insulator. This means that the entire window – not just where the frame meets the wall – affects air and temperature transfer in and out of your home.
Energy efficient windows are more expensive than basic options, but they should still be your first choice. When you choose windows with a higher efficiency rating, here’s how you benefit:
- Lower your heating and cooling costs by keeping conditioned air inside where it belongs.
- Decrease your home’s carbon footprint and do your part for the environment.
- Increase your HVAC system’s lifespan by allowing the equipment not to work so hard.
- Make your home feel comfortable with fewer drafts and a more even temperature from room to room.
- Reduce condensation to control moisture that could cause mold growth or home structure problems.
- Preserve the color of your furniture, carpet, and paint with window coatings designed to keep UV rays out.
Many features come together to make a window more energy efficient. They impact the window’s energy performance rating, which succinctly conveys how efficient the window is in different categories. The most prominent energy-saving features of high-performance windows include:
- Two or three panes of glass to slow heat transfer through the window
- Gas in-fills, such as argon or krypton, that are denser than air to slow heat transfer even more
- Insulating window frame materials
- Insulating spacers to hold the window panes a precise distance apart, thus reducing heat flow and minimizing condensation
- Low-emissivity (low-E) glass to reflect heat (and UV rays) out in the summer and back in during the winter
- Professional installation that includes caulking and weatherstripping to eliminate air leaks around the frame