The Aspect Effect: using the sun’s energy intelligently

“In the southern hemisphere, houses should be oriented to the north”

I first learnt this concept way back in high school geography classes, but never thought that I would ever get to apply it to the construction of my own house. And obviously, with so much more understanding of why this is so important.

So often people make the mistake of adapting the house design and orientation to the lay out of the property. Our plot of land is a rectangle with the long sides oriented east-west, thus it would make sense to build the house facing either east or west so that you can make the most of the view of the entire plot. While many of our neighbours have built this way, it is a big NO-NO from an energy efficiency perspective.

In the southern hemisphere, a north-facing house means that the main living areas (lounge/dining rooms, bedrooms etc) face north and with ample windows will be able to maximise natural light as the sun moves from east to west during the day. This access to sunlight significantly affects the temperatures in the house throughout the year. In the winter, when the sun is at its lowest, this energy can be considered “free heating”.  Yet in the summer, the challenge is to ensure that the house doesn’t overheat.

The north side of the house, with the bedroom, living room and dining room windows

Given that we moved into the house in January before the external siding and the patio was finished, the first few weeks we experienced first-hand the impact of the sun on bare north-facing windows. But thankfully in February we started work on the patio structure. It is important to not only consider the orientation of the house, but also the kind of patio structure you want. Shade in the heat of summer is great, yet shade in winter defeats the purpose of facing north if the windows can´t soak up all that good energy. So what kind of patio can you have that suits both seasons…

Once again we need to take geography into account and determine the angle of the sun in different seasons (Photo source: Folleto Calificación Energética de Viviendas, MINVU, Chile)

We decided on a mixed approach with a permanent eave, 72cm wide, above the windows on the north side of the house. The eave is not a solid structure, but is made of 2×1 poles with 3cm gaps between the poles to give the eave a bit of transparency.

Salomon, our metalwork contractor and his assistant Christopher installing the first eaves over the bedroom windows
Eave installed and the shade it provides over the windows may not seem like much, but the effect is tangible

In front of the living and dining rooms we designed a mixture of the permanent eave and a canvas roof structure that can be opened during summer and closed or removed in winter. This will allow the sun’s light to enter during the winter months.

First canvas installed, with the eave above. This produces a great, solid shade in summer to help cool the living and dining room which with such big windows is at high risk of overheating
Finished patio roof – very happy with the finished product after 2 solid days of sewing (I sewed over 180m in the end, and with such big pieces of quite heavy fabric, it was quite a physical workout).
One of the canvases closed
Full view of the finished patio

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