Retrospective #15: The Multiple Functions of Windows

Many of the things I’ve written about over the last three months can be described as the low-hanging fruit of saving energy at home. In other words, they represent low investment and rapid payback. Taken in isolation, each of these works, but taken together there results a synergy where the whole is greater than the sum of its parts.
A home is a system of interacting elements. The greater our understanding of how the elements work together, the higher levels of energy performance our homes can achieve. For us, the consistent $20 – $30 (including line charge) power bills are the result of a holistic approach to renovation. While science and maths play a large role in eco-thrifty renovation, we did not apply any scientific or mathematical formulas when setting goals for the project. We simply wanted to take the worst house possible – a drafty old villa with 12 foot ceilings and no insulation – and see what we could achieve.
Eco-thrifty design is just one type of ecological design. Ecological design – by definition – is holistic. It treats the relationships between elements of a system as important as the elements themselves. Ecological design aims to be as robust as the natural ecosystems it mimics. When we look at native bush in New Zealand we can see that no plant or animal fills only one niche, and that no niche is filled by a single species.

In an ecological design system called permaculture, these dynamics are summarized by the principles of multiple functions and redundancy. In other words, each element of a system (plant or animal) should serve multiple functions (niches), and each function (niche) should be fulfilled by multiple elements (plants or animals).
Graphics for Holmgren’s permaculture principles.
In eco-design we take the lessons we learn from nature and apply them to human environments. The term ecology comes from the Greek word oikos, meaning home. My home (and gardens) is my ecosystem. (With a major renovation, a huge landscaping job, and a PhD thesis I bloody never leave it!)
In our home, as well as yours, windows serve multiple functions: they allow the passage of light and heat; they provide views in and out; and, some can be opened for ventilation. In our home, and I hope yours, there is more than one window to allow these functions.

Here is where the science and maths come in: at this time of year the path the sun travels across the sky (science) means some windows are net energy gainers and some are net energy losers (maths). In other words, northerly windows gain more heat than they lose and southerly windows lose more heat than they gain.
Recognizing this, we “manage” our southerly windows differently than we “manage” our northerly windows. By manage I simply mean when we open and close curtains (if at all) and when we put up and take down window blankets (if at all).
Additionally, the recognition of relationships between seasonal sun angles, windows and heat flow helped us make design decisions about where to add glazing and where to remove it. One of the major aspects of our renovation – requiring consent and now requiring a qualified builder – was adding and subtracting windows and doors. Here is an example of applied eco-design thinking.
Where the kitchen was located when we bought the villa, the window over the sink faced to the southwest. At this latitude, that window was as a heat loser in winter and a heat gainer in summer. Oh boy, the worst of both worlds! Could you imagine working at the kitchen bench in January with the late afternoon sun streaming in? That kitchen would have been unbearable for cooking tea during summer.
Before: Southwest side with old kitchen window (yellow part) bringing in too much summer afternoon sun, and losing heat in winter. 
At the same time, the toilet was located in the northernmost corner with just one tiny frosted window for ventilation. And we can’t even blame this solar-illiteracy on the builders 100 years ago because the villa was moved to this location in the 1980s!
After: Southwest side with old kitchen window removed. Result: cool in summer and warm in winter. 
The eco-design solution (some might say common sense solution) was to swap the location of the kitchen and bath, and to relocate the southwest window to a northeast position. A northeast window is a heat gainer in winter and neutral in summer. In the end there was the same amount of glazing, but in a location supported by sound science and maths. 
New northeast window brings winter morning sun into the relocated kitchen. 

Peace, Estwing

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