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Why is orientation so important?

When Katrina and I were looking for our new home, it was imperative that our backyard was facing North (you would want it facing South if you live in the northern hemisphere).  Why?

First, a little about the sun

No matter where you are the sun rises to your east and sets to your west.  However, the tilt of the Earth’s axis as it orbits the sun creates the different paths and angles of the sun from summer to winter. 

In one half of the year the northern hemisphere receives more sun than the southern hemisphere (summer in the Northern hemisphere and winter in the Southern) with the reverse occurring in the other part of the year (summer in the Southern hemisphere and winter in the Northern).

Between these two extremes is the equinox, when both hemispheres receive the same amount  of sunlight.  At the equinoxes (21 March and 21 September), the sun rises exactly in the east and sets exactly in the west and it is directly above the equator or it’s zenith in relation to an observer at the equator.

Therefore, in Melbourne (Note: you should design and build FOR your climate…more on this in a later blog), which has hot summers and relatively cold winters with high diurnal (day/night) temperature ranges, you want to block out the summer sun with proper overhangs or shading when it is high in the sky (so your house stays cool during summer) and let in the winter sun when it is low and to the North (so your house heats up like a greenhouse).  This technique is called passive solar heating.

In order to capture this winter sun, you have to have lots of glazing (windows) facing North (South if you live in the Northern Hemisphere) and the sun must be able to reach this glazing, in other words, nothing can block your solar access to the North.  In Melbourne, the sun is as low as 29 degrees off the ground to the north during winter so the building wouldn’t have to be very big as long as it is relatively close in order to block my sun.

Passively solar heated

Furthermore, as Katrina and I were buying an existing home in areas that had heritage overlays, meaning you are not allowed to change the facade or the look of the structure for the first 9 meters from the street (quite a bit since our lot is only about 23 meters deep), we did not have the option of changing the front for passive design or the side as most lots are skinny (from 4 to 10 meters wide) with houses either attached or millimeters away on either side.

Therefore, your only option is to design your home to be passively solar heated towards the rear of your lot (that is if it faces north).

This is just a bit about the importance of orientation. Next time, I will write talk in further detail about passive solar heating and will touch upon passive solar cooling.