You can design and build an energy efficient home to be naturally warm in winter and cool in summer.
A comfortable home that saves money and is better for the environment.
In this article I’ll talk about how to take advantage of the world’s most significant energy source, the Sun.
The Sun And Its Path
Each square meter of sunlight provides us with up to a thousand watts of energy on a summer’s day. That’s the equivalent heat to what a radiator like this provides each square meter.
By following some straightforward rules when designing and building, we can capture this free energy in winter when we need it and block it out in summer, when we don’t.
The position of the Sun varies throughout the seasons.
In winter, the Sun moves across the southern sky at a relatively low angle of elevation.
In summer, the Sun is high in the sky and almost directly overhead at midday, but at a low angle in the east and west in the morning and afternoon.
So what should we do to make the most of the changing position of the Sun?
Let’s look at glazing, shading and building layout.
Normal glass allows up to 90% of the sun’s heat directly into the house. As a result, the location, size and type of glass is a critical aspect of design.
As a general rule, install more glass on the south facade where it is easy to let in the Winter Sun, and less on the east and west where it is difficult to block out the hot Summer Sun in the morning and the afternoon.
The solar heat gain coefficient or SHGC is a measure of the amount of solar heat that passes through the glass.
The higher the SHGC, the greater the heat that passes through. So in temperate climates, install glazing with a high SHGC on the southern side of the house to allow the Winter Sun in.
In summer, it is the glazing on the east and west which is exposed to the Sun. So install shading, and if that’s not possible, use low SHGC glazing to keep the solar heat out.
Check the label to help select the right glazing. It contains the SHGC at the bottom of the label, as well as other measures such as U-value.
High performance glazing is important, but especially on the east and west, external shading will be even more effective.
On the east and west horizontal shading such as eaves do not block any Summer Sun at lower angles.
So shading must be vertical, with good options being shutters, pulldown awnings, shade cloth and vegetation.
On the southern side, horizontal shading such as eaves will sufficiently block the direct summer sunlight whilst allowing the low angled Winter Sun to get in.
As a rule of thumb, shading should extend out no more than half the height of the window.
Adjustable shading is a good option, allowing occupants to control solar heat gain, depending on comfort at any time of the day in any season.
The vegetation is also useful as it shades well in summer but let the Winter Sun in. Such options may be used to block summer glare, which is bounced off outside objects.
The Sun also heats up roofs and walls which will eventually transfer heat into the house.
Shading of east and west sides of the building using vegetation can be very effective at keeping the house cool in summer months.
Colors of the roofs and walls affect how much of the sun’s energy that is reflected or absorbed.
So in cold climates choose darker colors to absorb solar heat, and choose lighter colors in warmer climates to reflect solar heat.
A building’s shape and orientation will have a big impact on its comfort.
If you have any role in design here are some tips.
South facing areas are a good spot for living areas.
Locating the garage or laundry on the western side will create a heat barrier to the rest of the house in summer afternoons.
A longer southern layout allows more solar gain in winter than summer.
If the block has a narrow southern aspect, other solutions exist.
For example, the house can be split into two sections: providing every room with south facing glazing.
So, to build with the Sun in mind, allow sunshine through glazing in winter, shade glazing in summer and plan the building layout to take advantage of the southern aspect.
Note: These advises about house plan are for northern hemisphere. For Australia, New Zealand, and other countries on southern hemisphere it has to be reversed. I mean you should place the living room and etc. to northern facade of your house for taking advantage of the Sun.