Window, Skylight and Door Basics -- Increasing Energy Efficiency
- By Staff Writer
- Published 05/12/2008
- Unrated
Putting it all Together: Guidelines for Your Windows and Skylights Project
If you are planning to completely replace your windows, meaning removing all parts including the frame down to the building rough opening, or to install replacement windows or sashes with a sash replacement kit into the existing frames, then the following characteristics should factor into your window choice:
1. U-Factor and SHGC. LEED for Homes certification requires that homeowners maximize the energy performance of windows by installing windows that meet certain minimum Energy Star windows requirements for U-factor and Solar Heat Gain Coefficient factor depending on the climate zones in which the house is located. LEED for Homes sets out the following window requirements and are good guidelines to follow whether or not you are going for LEED certification:
Northern Climate (including NYC, Boston and Chicago): Select windows with a U-factor of 0.35 or less and any SHGC.
North/Central Climate (including Washington DC): Select windows with a U-factor of 0.40 or less and SHGC of .45 or less.
South/Central Climate (including San Francisco): Select windows with a U-factor of 0.40 or less and SHGC of .40 or less.
Southern Climate: Select windows with a U-factor of 0.55 or less and SHGC of .35 or less.
2. Number of panes. The greater the number of panes, the higher the insulating value and sound control offered. Choose double or triple panes.
3. Gas Fills such as argon or krypton, as discussed earlier in this Article.
4. Low-e coating, as discussed earlier in this Article.
5. Tinted coatings, as discussed earlier in this Article.
6. Frame type. If your brownstone or townhouse is in a landmarked area in NYC then the type of windows you are able to use will be strictly regulated by the New York City Landmarks Preservation Commission for any windows visible to the street (in the public domain). Typically windows will need to be the same size and style as existing windows with wooden frames. If you have windows that are not regulated by the NYC Landmarks Preservation Commission, then when making your choice you can take into consideration how the type of framing you choose may affect the window’s energy efficiency. Aluminum frames are lightweight and strong and virtually maintenance free, but aluminum conducts heats rapidly and can have a negative impact on U-factor and CR. Wood frames insulate well and expand and contract less than other materials but may require more maintenance because they weather with age, however choosing a vinyl or aluminum clad exterior (if not landmarked) can reduce maintenance. Vinyl frames are also lightweight but may expand and warp in high temperatures and can discolor over time. Fiberglass offers good insulation value and a relatively low degree of expansion and contraction, and fiberglass windows can be made with a wood veneer. Vinyl windows can also be obtained with a fiberglass core.
But remember, replacing the windows themselves is not enough if you don’t also ensure adequate insulation around them. See our Article Insulation and the Building Envelope: Controlling Heat Loss and Gain for an in depth analysis of insulation issues.
1. U-Factor and SHGC. LEED for Homes certification requires that homeowners maximize the energy performance of windows by installing windows that meet certain minimum Energy Star windows requirements for U-factor and Solar Heat Gain Coefficient factor depending on the climate zones in which the house is located. LEED for Homes sets out the following window requirements and are good guidelines to follow whether or not you are going for LEED certification:
Northern Climate (including NYC, Boston and Chicago): Select windows with a U-factor of 0.35 or less and any SHGC.
North/Central Climate (including Washington DC): Select windows with a U-factor of 0.40 or less and SHGC of .45 or less.
South/Central Climate (including San Francisco): Select windows with a U-factor of 0.40 or less and SHGC of .40 or less.
Southern Climate: Select windows with a U-factor of 0.55 or less and SHGC of .35 or less.
2. Number of panes. The greater the number of panes, the higher the insulating value and sound control offered. Choose double or triple panes.
3. Gas Fills such as argon or krypton, as discussed earlier in this Article.
4. Low-e coating, as discussed earlier in this Article.
5. Tinted coatings, as discussed earlier in this Article.
6. Frame type. If your brownstone or townhouse is in a landmarked area in NYC then the type of windows you are able to use will be strictly regulated by the New York City Landmarks Preservation Commission for any windows visible to the street (in the public domain). Typically windows will need to be the same size and style as existing windows with wooden frames. If you have windows that are not regulated by the NYC Landmarks Preservation Commission, then when making your choice you can take into consideration how the type of framing you choose may affect the window’s energy efficiency. Aluminum frames are lightweight and strong and virtually maintenance free, but aluminum conducts heats rapidly and can have a negative impact on U-factor and CR. Wood frames insulate well and expand and contract less than other materials but may require more maintenance because they weather with age, however choosing a vinyl or aluminum clad exterior (if not landmarked) can reduce maintenance. Vinyl frames are also lightweight but may expand and warp in high temperatures and can discolor over time. Fiberglass offers good insulation value and a relatively low degree of expansion and contraction, and fiberglass windows can be made with a wood veneer. Vinyl windows can also be obtained with a fiberglass core.
But remember, replacing the windows themselves is not enough if you don’t also ensure adequate insulation around them. See our Article Insulation and the Building Envelope: Controlling Heat Loss and Gain for an in depth analysis of insulation issues.
