Get your sun shades on: external blinds and shading
In most climates, appropriate sun shading is as important to successful passive solar design as orientation and window placement. Anna Cumming looks at how to keep the sun out when it’s not wanted.
North-facing windows, good ventilation and thermal mass to help regulate the internal temperature of our homes: the basics of passive solar home design are pretty straightforward. Shading for sun control is no exception. Well-designed shading lets the sun’s warmth into your house in winter, and keeps it out in summer. Something as simple as an eave, a vine-covered pergola or an external blind can block up to 90 per cent of the heat generated by direct sun, reducing the need for active cooling, cutting energy consumption and making a home more liveable and more sustainable.
When direct sunlight hits a window, radiant heat passes through the glass and is absorbed by walls, floors and furnishings. This heat is then re-radiated back inside the room, heating it: a desirable outcome in winter but one to be avoided in summer. Blocking the sun before it reaches the glass is the most effective way to control this unwanted heat gain.
If you are building from scratch, you have the opportunity to design shading systems in conjunction with carefully considered window size and placement. But even if you are retrofitting an existing home, shading can help mitigate problems like too much solar heat gain through west-facing windows.
What shading where? Consider your climate
When thinking about shading, your geographical location and climate are important factors to consider. In temperate climates the magic direction to start with is north, says ATA technical expert Mick Harris. “The north side of a home has the most solar energy available and it is the easiest to control. All you need is the right width eave or other horizontal shading to stop the sun in summer and let it inside in winter.” [Ed note: Your Home provides a simple formula for calculating eave widths.]
For east and west windows, a different shading solution is needed as the sun is lower in the sky. Architect Emma Scragg recommends adjustable vertically-placed blinds, screens or louvres. “They work best to control sun for the short time it’s needed, and then open up again to daylight, views and breezes,” she says.
In hotter climates – roughly north of Brisbane – shading is important all year round, including on the south side of your home. In colder parts of the country, winter heat gain is the priority so it’s vital to ensure any shading doesn’t impede solar access in winter.
Local site topography also plays a part in deciding the amount of shading needed, explains architect Graham Anderson. “For example, a south sloping site may need slightly less shading for a longer period of the year.” [Ed note: For more information, see Your Home’s ‘Shading’ fact sheet.]
There are plenty of choices for effective shading, from cost-effective and easily retrofitted blinds to custom-designed automated systems. External blinds, shutters and screens can also provide security while inner doors and windows are open for ventilation.
Mick Harris’ mantra is to tackle the easy things first. “Correctly designed eaves are simple and cheap,” he says. With no moving parts, eaves and fixed awnings and screens are simple and easy to maintain. They can be made from a range of materials from fibre cement sheet to Colorbond, aluminium and timber.
Brisbane architect Stephanie Skyring favours fixed awnings for windows in the sub-tropics and tropics: “They are cost effective and allow you to keep the windows open when it’s raining.” However, they allow for less active sun control and flexibility than adjustable versions. For western and eastern facades where the sun is intense at a low angle for a short time she recommends retractable fabric awnings. Other adjustable shading options include blinds, louvres, sliding screens and roller shutters. Louvres, shutters and even pergolas with adjustable angled blades allow sun control while admitting breezes.
Emma Scragg is a proponent of trees and plants as shading. “A living sunshade is the most eco-friendly shading available,” she says. “Evergreen trees and vines are ideal in areas where year-round sun shading is desirable. Carefully chosen deciduous screen plants and overhanging trees provide summer shade and winter sun.” Lyn Beinat of energy efficiency consulting company EcoMaster agrees. “A pergola with deciduous vines is a functional thing of beauty.”
If the budget stretches, pergolas with motorised blinds or complete louvre roof systems such as Vergola may fit the bill. Archisoul director Sue Connor notes that such systems can help create the effect of an outdoor room and allow your home’s internal spaces to feel larger.
However, sometimes external shading is not a viable option. As Scragg explains, it tends to be more expensive, access for installation and operation may be difficult, and internal sun controls can be much easier, especially if you are a tenant. “Internal blinds and curtains are easy to operate, can double as thermal insulation to keep warmth in and are not subjected to as much weathering as external options.” For more effective interior sun control, choose a blind with a metallised back to reflect sunlight coming through the window.
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