When selecting energy efficient windows, consider their ratings on energy performance in relation to the design of your home and your climate
By BRITISH SOLOMON
In efforts to save more energy, it is important that, as home builders, we do our part in choosing and installing energy efficient products to go into homes. This not only helps the home owner save energy and money, but significantly separates your construction company for your competition. Here are some tips on choosing and installing the best energy efficient windows for your next project.
How to select energy efficient windows
When you install energy efficient windows, the homeowner will benefit from low cooling and heating costs, and at times extend to low lighting costs. When you choose the right energy efficient windows, you are also going to add to the beauty and marketability of the home.
Now, before choosing new windows for your new build, you need to identify the type of windows that will best suit its climate and improve the energy efficiency of the home. It’s important to understand the energy performance rating of the windows based on the home design and the climate of your area.
For energy efficient windows that are labeled, ENERGY STAR has set minimum performance rating criteria for these windows, and categorized them by climate. However, the criteria do not involve the home design. Now, in areas that are dominated by heat, major glazing areas need to face the south to get the solar heat when the sun is low, and in the summer, other shading devices can prevent heat from getting into the house.
For a greater effect, windows that are facing south need to have a solar heat coefficient higher than 0.6 to gain the highest levels of solar heat during winter, a U-factor of 0.35 for heat reduction, and a high visible transmittance for the transfer of visible light. To learn more about energy ratings, check out Energy Performance Ratings.
Windows that are facing east, north and west, should allow some lighting when minimized. It is not easy to control light and heat through windows that are facing west and east during winter periods, and these windows need to be shaded or have a low SGHC. Windows that are facing North collect very low levels of solar heat, therefore they are used for lighting. When you install low-emissivity window glazing, you can control the gain and loss of solar heat in heating climates.
If you live in a cool climate, an effective strategy would be to include the preferential use of windows that are facing north and shade windows that are facing south. The best windows to use to reduce cooling loads are windows with low SHGCs.
To reduce solar heat gain, one needs some type of glazing to lower the windows SHGC. Windows with insulated glazing have Low-E coating that is microscopically thin, almost invisible metallic oxide or metal layers on its surface to control heat. A large portion of solar radiations is absorbed by tinted glass through a reflective coating to reduce solar radiation transmission and to select coating that filer between 40-70% of the heat that is transmitted through the glazing or the insulated window, as it allows transmission of full light. This kind of window, except for the spectrally selective, reduces a window’s VT. To learn more about coating, tint, glazing, and others, check out the windows types.
In case you are building a new home or remodeling it, incorporate your selection and windows design as an important part of the house design.
When you are choosing the type of windows you want to put in your house, there are several options to choose from. When selecting energy efficient windows, consider their ratings on energy performance in relation to the design of your home and your climate. Select windows that have low SHGCs and low U-factors to maximize energy savings in cold and heat seasons. Go for whole unit SHGCs and U-factors, compared to the center of glass (COG) SHGCs and U-factors. The energy performance of the product is accurately indicated by the whole unit numbers.
All the components of a window determine its energy efficiency. The frame of a window conducts heat, contributing to the overall energy efficiency of a window, in particular, the U-factor. Glazing has become advanced over the years, and designers specify the type of glazing for different types of windows based on the climate, orientation, design of the building, etc.
You should also consider the way a window operates because some have lower air leakage rates while some have high leakage rates.
Choosing the best energy coefficient windows depends on several factors, but will greatly improve the design and appeal of your next build.
British Solomon is a contributing writer and media specialist for Varco Purden Buildings. She regularly produces content for a variety of ecofriendly and construction blogs. She may be reached at vp.com.