Progress Report: Energy Efficient Windows

I’ve mentioned this before, but I’ll state it again for any newcomers (or those of you who may have forgotten): Our home is being built based on a passive solar design. Because of this, windows are an important element to reduce our heating, cooling and lighting needs. In order to maximize solar heat gain in the winter, our major glazing area faces south to take advantage of the sun in the winter when it’s low in the sky. The roof overhang was designed specifically to avoid excessive heat gain in the summer when the sun is high. You’ll notice both of these features in the photo below. (Note the windows just below the roof line that are barely visible.)


Window size and frequency is just as important on the east-, west- and north-facing walls. The photo below shows our north-facing wall. The windows on this wall are smaller and fewer than those on the south wall, on purpose. As our house sits, much of the winter winds come from this direction. Also, north-facing windows take in little solar heat. Therefore, they will mainly be used to provide ample daylight in back rooms of the house.


Our windows have a low-emissivity coating on them, which means they are a bit more expensive than regular windows, but according to the U.S. Department of Energy, they reduce energy loss by as much as 30-50%. They also meet or exceed Energy Star guidelines.

Originally, we were going to install Marvin windows in our house. But when we compared the Marvin/Pella windows side-by-side, we realized we could get the same quality windows for a heck of a lot cheaper.

I was also pleased to see a whole section on Pella’s Web site dedicated to their “green commitment.” Here’s what they say they are doing to help the environment:

• Recycling — Pella’s process minimizes our use of nonrenewable resources.


• Responsible Procurement — Pella uses sustainable sources and works with vendors who practice responsible harvest and replenishment.


• Pollution Minimization — In 2006, the EPA recognized Pella with its Pollution Prevention for Environmental Excellence Program honorable mention award for our responsible manufacturing processes.


• Reducing Energy Consumption — Pella offers the windows and doors rated #1 for energy efficiency among top national brands.

The company also claims to be FSC certified, offering the option of windows and doors made from wood certified to have been harvested from well-managed forests.

Why We Chose an Open Floor Plan

Making my way (ever so slowly) down the “About Our Home” list, I’d like to highlight now why we decided on an open floor plan for our home.

Let there be light. As mentioned in an earlier post, we built our home with a passive solar design in mind to take advantage of the sun’s natural light and heating capabilities. Our open floor plan compliments this design as fewer interior walls means more light reaching rooms on the North side of the house. Minimizing walls will make our space bright and open—and will maximize every inch of space. A good thing, since those inches are limited in our small footprint!

Air it out. We won’t have a need for air conditioning—our super-insulated home will work wonders to keep cool air in during hot summer days. At night, and on cooler days, an open floor plan will allow wind currents to bring fresh air into our home via strategically-placed windows.

Heat it up. According to Wood Heat Organization Inc., houses with an open floor plan and fewer separations between rooms can be heated entirely with a wood stove (depending, of course, on their size and energy efficiency). To maximize our stove’s highest performance, it will be centrally located in the middle of the main floor with the flue pipe running up and out of the roof. Heat will easily flow to the main living area, kitchen and loft above with this set up. A warm house in a mountain town that boasts more than 200 inches of snow a year? Yes, please!

Some home magazines point out a few disadvantages to having an open floor plan, namely inefficient heating and lack of privacy. As mentioned earlier, we plan on using our wood stove quite a bit during winter months, and our open floor plan will actually increase the efficiency of our heating. Lack of privacy doesn’t concern us either. Bathrooms and bedrooms (excluding the Murphy bed on the second floor) all have doors.

It’ll just be up to us—and any visitors—to shut them!

What Is A Passive Solar Design?

See that list on the right? The one titled, About Our Home? It’s pretty much the essential aspects we’ve chosen to make our home considerably more environmentally friendly than the average newly-constructed home. And I haven’t addressed anything on that list in detail yet. But that’s changing with this post. I think it’s important for you all to know a little bit more about each of these features, why we chose them and how they work to “green” our home. So, I plan on working my way down that list.

We are building based on a passive solar design, which means we kept the sun in mind at all times when planning our home. Our home is rectangular in shape and its long axis runs east/west. Our long wall will face within 30 degrees of due south. We will maximize the glass area on this south-facing wall to take advantage of the sun. Why?

Because sunlight offers us natural light. With our passive solar design, we’ll be able to rely entirely on sunlight in certain rooms for interior lighting during the day. The large, south-facing windows will allow a generous amount of light into our living and dining room. With our open floor plan, our kitchen should also receive ample daylight.

Because sunlight offers us natural heat. Solar radiation can directly penetrate our home via our south-facing windows and store within our living space (direct gain). It can also collect, store and distribute by way of a thermal mass (indirect gain). Thermal mass—or carefully-chosen materials that store heat—are key to a passive solar design. An example of thermal mass will be our flooring. A natural stone floor, such as slate, will be warmed passively by the sun during the day. At night, heat that is stored in the floor will be released back into the interior.

Because sunlight offers us natural cooling. The sun rises higher in the summer than in the winter; therefore, properly-sized window overhangs can create shading during warmer months and help to cool our home. (These overhangs are angled to permit sunlight through the windows in the winter.) Opening upper-level windows should allow naturally-rising warm air to escape as well. These elements, along with opening windows at night to let in cooler air, and closing the shades during the day, will reduce the need for supplemental cooling. In fact, we don’t plan on having a mechanical cooling system (or the energy bills that come from operating one!).

Here’s a quick run-down of passive solar design strategies (to maximize solar heat gain in winter and minimize it in summer) from the U.S. Department of Energy:

✓Start by using energy-efficient design strategies.
✓Orient the house with the long axis running east/west.
✓Select, orient and size glass to optimize winter heat gain and minimize summer heat gain for the specific climate.
✓Consider selecting different window sizes for different sides of the house (exposures.
✓Size south-facing overhangs to shade windows in summer and allow solar gain in winter.
✓Add thermal mass in walls or floors for heat storage.
✓Use natural ventilation to reduce or eliminate cooling needs.
✓Use daylight to provide natural lighting.

It takes a lot more thought to design with the sun. While our home design itself isn’t complex, it’s smart—and we owe it all to the experts. Our architects. Their knowledge of local climate, solar geometry and window technology, among other things, was mind-blowing. We learned so much just by talking with them. And I’m sure their wisdom stretches far beyond our conversations. We are forever thankful for their imparted knowledge and advice.