In the era of building science and energy modelling, there’s increased awareness, within the industry, of the effect windows have on the thermal performance of buildings.
How significant is that effect?
It’s quite startling, actually, to see just how much a window can lower the R-value of a whole wall. BuildingGreen, an online-based independent publishing company, recently released the timely report “Better Window Decisions: Mastering the Performance and Cost Options”. This document contains valuable information for anyone faced with choosing windows. It includes a comprehensive overview of glazing options, along with practical advice and cost-saving strategies.
Here’s one particularly eye-opening fact shared by the authors:
“If the effective R-value of the opaque area of a wall is R-30 (accounting for thermal bridging through the framing), and clear, double-glazed (U-0.5) windows are installed covering 12% of the wall area, the effective whole-wall R-value will drop by 60% to about R-12.”
In fact, most windows tend to be 10 times less energy efficient than the wall area they replace.
At Biostruct, our main focus has been on developing and marketing a hemp-lime bio-masonry wall product, including both prefabricated and do-it-yourself versions. Currently we are in the final stages of testing and piloting our wall system, which we believe will “stand tall” among building products of the future. At the same time, we recognize that it’s pointless to incorporate solid, high thermal-performance walls in a project if those walls aren’t matched with good windows. This is the reason we’ve looked for energy efficient glazing companies with which to partner.
Energy efficiency is the fuel of the future!
The cost of fossil fuels will inevitably continue to rise; it’s predicted, in fact, that by 2050, the price of oil may go as high as $220 a barrel. But what does that mean for you and me?
Petroleum products are embedded in so many of the things we use–including the food we eat, the buildings we inhabit, the vehicles we drive…even the pharmaceuticals in our medicine cabinets. It’s critical, therefore, that when we select a material for a project or renovation, we choose one that is purposefully designed–not for “planned obsolescence” (the intended fate of the majority of the products we purchase) but for longevity and durability.
Currently, PVC has a huge lead in most window markets. Yet it’s also found on various materials red lists (inventories of substances considered “worst in class” from the standpoint of human and/or ecological health), including the Living Building Challenge Red List. Vinyl “qualifies” for inclusion on these lists because, in addition to containing heavy metal additives intended to keep the plastic from breaking down rapidly, it’s known to create toxic by-products such as dioxin. Even from a purely practical standpoint, PVC windows miss the mark. When compared to other frame options, such as fiberglass or wood, they have higher rates of expansion and contraction; the depressing result, over time, is that seal integrity and window durability are compromised.
So why has PVC taken such a big chunk of the window market?
The vinyl and petroleum industries have huge lobby groups in Washington and around the globe; it’s largely due to their efforts that a “worst in class” product has been able to maintain its large market and subsidies, even as many health and environmental consultants are recommending that its use be phased out. Companies like Apple and Nike started removing it from their products years ago, so why do we still accept it in windows and many other buildings products? Let’s just say “no” to vinyl!
According to the World Business Council for Sustainable Development, buildings worldwide account for a surprisingly high 40% of global energy consumption; the resulting carbon footprint is significantly bigger than that from all forms of transportation combined.
“Large and attractive opportunities exist to reduce buildings’ energy use at lower costs and higher returns than other sectors. These reductions are fundamental to support achieving the International Energy Agency’s (IEA) target of a 77% reduction in the planet’s carbon footprint against the 2050 baseline to reach stabilized CO2 levels called for by the Intergovernmental Panel on Climate Change (IPCC).”
Obviously, one way to aggressively reduce energy consumption, and vastly improve thermal performance, in new and existing buildings–and, by extension, to support the achievement of the IEA target–is through widespread use of better wall and glazing systems. In regard to the latter, specifically, not only do efficient windows save you (or your client) money every month–they also reduce your building’s contribution to climate change, while increasing the comfort level of its inhabitants.
Save money. Save energy. Inhabit the future now.