With the new building codes in the city and county of Boulder, homeowners and building professionals are coming into our showrooms with many questions regarding windows and doors for their remodel or new construction projects. The questions generally ask “which window or glass do I need to use to achieve the HERS (Home Energy Rating System) Score required for my building permit.” My answer is always the same and invariably unexpected. As long as the windows are Energy Star rated for this region (the vast majority of commercially available windows are) nearly any window will do.
I go on to explain that the larger the house, the lower the required HERS Score. Since insulation, air infiltration, HVAC systems, and lighting loads make big and very cost effective contributions to lowering HERS Scores, their contributions will always be maximized. The irony is that the more energy efficient the overall building, the less difference a given window makes!
I further explain that if you are just aiming at a HERS Score, someone could sell you a very low quality vinyl window that is gas filled and the result would make the requisite contribution to achieving the given HERS Score target.
I think there is a lot of data and comparatively little information “circulating in the air.” From our perspective, window and door selection is about the interplay of aesthetics, performance, and price. Aesthetics speaks to the contribution windows make to exterior and interior beauty, as well as ease of operation. Performance includes the embodied energy of production and delivery, impact on heating and cooling loads, product life cycle, and recycling opportunities at the end of useful life. The new building codes add important and beneficial elements to the performance aspect but do not change the fundamental pros and cons, or the trade-offs associated with the interplaying factors.
Any quality window or door company should be able to help you to understand the aesthetics, performance, and price choices available to you and do so in context of your project, building permit requirements, and budget.