Window Comparison Spreadsheet

Comparing Energy Efficient Windows.

CLICK HERE to view the Window Comparison Spreadsheet.

Whether you are building new or remodeling an existing building, you should be thinking about High Performance windows for improving comfort, health, and energy savings. Energy Efficient Windows are ones with very good insulating and air-sealing properties. (for the purposes of our comparison chart we are defining “Energy Efficient” as having a U-value of less than 0.30). Not only can these save significant amounts of energy and money spent on energy bills, they can also substantially improve the comfort and indoor air quality inside buildings.

Improve comfort.

Homes with really good windows tend to “feel” warmer because the inside surface of the glass stays closer to the temperature of the inside air. Passive House standard likes to see no more than 3degrees difference between the two. This is because of the dramatic improvement in comfort that people experience when they are surrounded by surfaces that are at an even temperature. If there is a cold window in a warm wall, the window will suck heat from the occupants of the building and they will not feel comfortable.

Reduce condensation, moisture, and mold.

The higher temperature of the glass also helps to greatly reduce the amount of condensation which forms on the inside of the glass which reduces the likelihood of mold growth inside the home. This, in turn, can lead to better indoor air quality and healthier buildings. Typically, if you add insulating blinds to poorly insulating windows, you increase the potential for condensation on the glass because you lower the temperature of the glazing. With high R-value windows you can add insulating blinds (which makes them perform even better) without necessarily creating a lot more condensation. Of course there is still some potential for condensation but it is greatly reduced with high-performance double-glazed or better yet, triple-glazed windows.

Reduce noise.

Highly insulating windows also help to reduce noise from outside and make the inside of buildings quieter. If you have a home or other building near a busy street or noisy location you will definitely want to consider high-performance windows and contact the manufacturers regarding the noise reducing abilities of their windows.

Save money.

Really good windows tend to be expensive, sometimes very expensive. So how can we justify the additional construction or window replacement costs? In many cases, using better windows can reduce the heating or cooling loads enough to allow the mechanical equipment to be downsized and/or simplified. This can sometimes reduce construction costs substantially. And, of course, really good windows help to lower utility bills which means that the added cost during construction can be paid back many times over during the life of the building. And there are the added benefits of improved comfort, durability, and health that stem from using better windows that are impossible to put a monetary value on but make a huge improvement in to the occupants of the building.

New or Replacement Windows

In both new and existing building, the windows are typically the weakest point in the “Thermal Boundary”. In new construction the walls are typically insulated to about R-21 while the windows are usually about R-3. And in older existing homes the walls are often only about an R-3 or 4 but the windows are lucky if they are an R-1. So you can see that the windows are likely to lose a lot more heat in the winter and let a lot more heat through in the summer. By spending a bit more on high-performance glazing you can dramatically improve the energy, comfort, and condensation resistance of your home or commercial building.

And choosing Energy Efficient units for your replacement windows can be one of the most cost effective upgrades you can make to an existing building. CLICK HERE to read about a study that shows that replacing old windows with high R-value replacement windows can be a very cost effective option.

Selecting the right energy efficient windows.

Using the best information we could gather from the window manufacturers listed we have come up with a chart that directly compares the U-values, R-values, SHGCs, VLTs, cost (for a 2′w x 4′h casement), cost per sf, and cost per sf per R(value). This is a simple way to compare how much energy performance you get for your money and will help you with choosing the right energy efficient windows for your situation, climate, and budget.

Obviously this is based on information that is likely to change often so we would like to ask for your help. If you contact any of the companies listed on the spreadsheet, please take a minute to verify that the information we have is accurate and up-to-date. If it isn’t, please take another minute to let us know what the correct information is via the “Contact Us” form to the right.

Also, if you know of another window manufacturer that can meet the “less than 0.30″ criteria for a casement window please let us know and we will add their information to the list.

By working together we can ensure that this resource is kept current, correct, complete, and available to everyone.

CLICK HERE to view the Window Comparison Spreadsheet.

For a wealth of information about energy efficient windows please click on the following link to visit the website of the Efficient Windows Collaborative http://www.efficientwindows.org/index.cfm

To read an excellent article that explains window performance data please click on the following link from the Building and Construction Technology program of the Department of Natural Resources Conservation. http://bct.nrc.umass.edu/index.php/publications/by-title/windows-understanding-energy-efficient-performance/

To read another excellent article about super-high performance windows for Passive House standard construction please click on the following link from Green Building Advisor.com http://www.greenbuildingadvisor.com/blogs/dept/musings/passivhaus-windows

CONTACT US – Energetechs, Inc., – ph.