Tardissing the Space – Part One – Sun Path

It all just boils down to sun, soil and water, and on a small, urban site, sun is the limiting factor. So this is the first in a series about making 500m² seem much bigger than it would appear, by tackling this most limiting factor.

There’s a lot of sun in Australian sub-tropics. But we can use a lot of sun – passive solar heating, solar panels, tree crops, garden beds, clothes line, even just a nice place to sit with a book. The sun is the original source of just about all energy. There’s a finite limit to the sunlight available and lots of competition for it. Tree crops in particular are greedy for sun harvesting space, but I want mangoes, and avocadoes, and macadamia nuts. OK, I’ll give in on the bunya nuts, but surely we can fit in a lychee somewhere?

In Yeoman’s Scale of Permanence, climate and land form are the top two in the scale, and there’s a reason for that! Soil is (relatively) easily fixed and water can be stored and managed, but the sun is a given, and how a site faces it conrols the amount of energy from the sun that can potentially be harvested. This is a neat little site to see the sun’s path – you can zoom right in to your own address. This is another one, in 3D (It’s a little bit complicated – worth watching the Youtube tutorial about it). Something simpler? Here’s a shadow map app.

If I play around with the times of day and times of year, I can watch where the shadows fall throughout the day, over whole year. I can see that the north side of our house is always in sun, morning and afternoon, summer and winter. Whose stupid idea was it to put the garage on that side!

The south facing wall is always in shade. It’s not just that it gets less light – the south facing wall gets no direct sunlight through its windows at all. Trees planted along that wall get no direct sunlight on their leaves unless they can get up above the roof height.

Our site is near flat, but the effect is much more pronounced on sloping sites. The shadows are much longer on the south side of a hill, shorter on the north side. When we were looking for our site, one of the major criteria for a good suburban permaculturing site was no tall neighbours to the north. Shorter things to the south of taller things are in constant shade. A tall building or tree uphill to your north will cast such a long shadow it will make finding enough sun for warming the house, growing food, powering solar panels really difficult.

So this is the trick for fitting a couple of mango trees, a couple of avocado trees, a macadamia tree and a lychee on our little block. (We’ll keep them pruned to a much smaller size than they would naturally grow, but they will still end up 4 metres or so tall anyway). But if they are all positioned on the southern boundary, right on the southern boundary, they will not shade all the other trees, gardens, verandah, clothes line, solar panels to their north. Lucky for us, there is a laneway down our south side, so they won’t shade the neighbours out either.

Not only that, but the canopy size can be nearly halved by making use of the sun’s angle. A carambola tree is tucked in under what will eventually be the mango’s canopy on the north side, and a grumichama under that. Coffee bushes make use of the partial shade under the east and west canopy. Everything tall is to the south side, shorter on the north side. A sort of tiered sunlight harvesting system that ideally keeps the ground always in shade – summer and winter, morning and evening. And captures every ray, on leaves, solar panels, floors that need warming, clothes that need drying and skin that, as we head into spring, is hungering for a bit of sun.