“People usually end up making compromises when they try to build green,” said a contractor who quoted on our building project back in the summer. “And all of them are heartbreaking.”

He was talking about how  homeowners, when confronted with the real cost of building green, balked at the extra expense and went instead for the status quo. Either that or they were forced to adopt less-than-efficient technology because of a diminishing budget. When discussing our window choices, my impulse was to do the same. That is, until I learned about the important role windows play in energy efficient housing.

The cost of windows available on today’s market varies wildly, but so does what you get for each dollar spent. Wading through the literature and recommendations can be time-consuming, but we learned early on that there is no one-size-fits-all solution. Choosing the right window includes making decisions about frame material, opening style, air tightness,  glazing options, coatings, and gas fills, along with considering each window’s orientation and your local climate.

Our initial criteria was simple (or so we thought). We wanted high performance windows that we could afford. Here’s what we discovered.

Frames:

For us, finding something affordable meant opting for vinyl windows from Gienow. Gienow is a Canadian company who sells many of their windows to clients in Canada, Alaska and other northern and adverse climates. They have supplied many lighthouses in the Pacific Northwest, where the storms are so famous, they are now a tourist attraction.

They also have a 65 year history of excellent performance in harsh climates, both thermally and structurally, thanks to their multi-chambered design, multi-point locking mechanisms, and triple weather stripping. The sales representatives we encountered were knowledgeable about the various glazing options. The company also offer high performance glass. Overall, we liked the variety of options they had available. The value for money far exceeded other windows we considered.

While vinyl window frames were not originally our first choice, we decided to spend the bulk of our window budget on glazing options (more on that below) which have the greatest impact on energy efficiency. Through our research, we also learned that half of the ingredients used in making vinyl are salts. Making vinyl windows also uses less energy than aluminum, and vinyl can last for decades with very little maintenance (no toxic paints or stains required). At the end of its long life, vinyl can also be recycled. Although vinyl has some way to go before it can be considered a top environmental choice, the industry continues to make improvements in toxic emissions.

As for frame style, we opted for casement windows (which I discussed in a previous post), because they seal more tightly than other designs, leaking less of that precious indoor heat into the great outdoors.

Glazing:

Our favorite article about energy efficient windows discusses glazing options, which to the layperson, can often sound like another language consisting entirely of acronyms. But glazing is also the part you want to get right when building a home. Not just any window will do. In fact, according to Martin Holladay at greenbuildingadvisor.com, installing windows with the wrong glazing for your region will cost you unnecessarily for years to come.

As we learned more about glazing, we expanded our window criteria to include something that would work with our climate (the Pacific Northwest), save us money on energy bills and create a pleasant indoor living space (not too hot, not too cold…you get the idea). In order to achieve this, we wanted our windows to let the sunshine in (literally) on the south side of our house for most of the year, keep the heat in on the other orientations, and shield our rooms from overheating on the west.

To achieve that balance, we chose triple-paned windows with a heat shield on the north, east, and west sides of our house, and double-paned windows with a high solar heat gain coefficient or SHGC on the south (see what I  mean  about those acronyms).

The Gienow double-glazed, clear windows have a SHGC of 0.45, which means they let in about 45% of the available heat.  Carefully placed overhangs on the south prevent overheating through these windows in summer, when the sun is at it’s height. The same windows allow more heat to filter in through the south side in winter, when the sun shines below the overhangs.

The triple-glazed windows in our mix will increase the overall energy efficiency of the house thanks to a greater thermal performance. (The double-glazed, argon-filled windows are about R 3.4,  with an overall energy rating of 29, which is appropriate for our Zone A climate or the colder B and C zones, according to the Energy Star program. The triple-glazed and heat-shielded windows have an R-value of 4.4,  and a SHGC of 0.22).

Opting for double-paned windows on the south increases the amount of light and heat that will come through in winter. (To increase the R-value of these windows, you could add insulated blinds if desired, such as the honey-comb variety, which can add up to R5.) Added to this is an argon gas filling, plus different low-e coatings on various glazing surfaces to keep the heat in or out depending on orientation.

While our architect recommended triple-glazed windows throughout, our budget was limited. Many experts also said that they were not necessary for our climate. To compensate somewhat for this change in the thermal envelope, we eliminated several windows from the north and west walls, essentially converting about 30 square feet from R 4.4 to R40.

It turns out that contractor was right when he said we would end up making compromises (oh, for an unlimited budget), but thanks to high performance windows, they won’t cost us (or the earth) for years to come.

More on windows:

Gienow’s vinyl casement window specifications:

http://www.gienow.com/wp-content/uploads/2011/12/PDF_EStar_8VinylCsmt260.pdf

Natural Resources Canada Window Specification for many manufacturers

http://oee.nrcan.gc.ca/pml-lmp/index.cfm?action=app.search-recherche&appliance=WINDOWS

http://oee.nrcan.gc.ca/equipment/windows-doors/18017

 

 

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One Response to A Word About Windows

  1. “A Green Hearth | A Word About Windows” was a incredibly excellent posting, .
    I hope you keep publishing and I will continue to keep following!
    Thanks for your time ,Basil

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