In last month’s article 3 Golden Rules for an Energy Efficient House I mentioned winter sun as a valuable source of energy.
It can however, be so much more than that.
I was born and educated in Australia where solar control really is an issue. Even in the southern hemisphere where the sun is in the wrong side of the sky and summer nights are dark, the sun is still significantly lower in the sky during the winter.
Perth, Western Australia has a Mediterranean climate, one where winter sun is a delight yet summer sun can be a hazard. North facing walls in Australia are the equivalent of south facing walls in the UK and are ideal but need serious control from overheating in the summer. Simple canopies, pergolas or awnings do this job perfectly. Louvre systems also help, because if angled correctly they can let in the low winter sun whilst preventing the higher, more extreme summer sun from getting through.
Here in the UK however, things are different. We love sun and so we should. Winter sun, summer sun, sun in the spring and autumn, just bring it on and in abundance. This is most likely to do with the relatively low average ambient temperature throughout the year, so sun is the perfect antidote.
Short winter days are transformed when the sun shines and long, balmy summer evenings are a delight.
The only down side of a south facing wall or courtyard in the UK is that in the summer, the evening sun sets in the north west so the south facing wall misses out. My illustration shows an approximation of the winter and summer paths for central England. At the winter solstice (21st December), the sun has a low arc, rising in the south-east and setting in the south-west. The longest day in the year is the 21st of June where the sun rises in the north-east, then follows a long, wide arc, high in the sky, before setting in the north-west.
When choosing or designing a house, the orientation of the main internal and external living areas cannot be underestimated. We often hear of the benefits of the ‘south facing garden’, and yes, a south facing garden is a delight.
We can take this one step further however by analysing the actual path of the sun in the UK throughout the year, but first there are two main factors to consider.
When is it most likely that you are going to be able to enjoy the sun in your home in the winter or summer?
I would say that for most families, it is towards the end of the day. This is largely dictated by our hectic lifestyles educating our children and earning a living.
Secondly daily temperatures tend to peak in the afternoon/early evening, so although the sun may be shining in the morning, it may not necessarily be comfortable outside.
So why is south-west best? A south-west facing wall, garden or courtyard is the only place where the following three things can be experienced: The winter sunrise, the winter sunset and the summer sunset. So when considering the design of a new house, or the purchase of a building plot, make sure that the orientation is right. It can make all the difference.