Uncontrolled sunshine through windows will not only fade your carpets and furnishings and make for uncomfortable living conditions, but will also have a huge impact on your home’s energy efficiency. Unprotected windows account for roughly 50% of the unwanted heat absorbed by an average house in summer, so with that in mind, here are some practical ways to protect your windows from heat gain and the sun’s harmful UV rays.
External shading is a far more effective cooling method than internal window coverings, reducing heat gain by as much as 80%, compared to just 20% with curtains or blinds. External shading can be either fixed, in the form of verandas, eaves and pergolas, or adjustable, such as awnings and shutters.
While fixed shading is suitable for north facing windows, adjustable shade provides much more flexibility, with the advantage of being able to extend or reduce the amount of shade required according to comfort levels, the angle of the sun and the time of year. External shades and awnings come in a wide range of fabrics and colours and can be rolled back during the winter months to protect them from the elements.
One thing to remember with external shading is that, to effectively block low-angled morning and afternoon sun, it should extend out to at least twice the height of the window being shaded.
In combination with external shading, curtains and blinds can significantly reduce heat gain through your windows. On their own, however, they are less effective. For maximum protection, choose drapes, Holland blinds or Roman blinds rather than Venetians, as they provide a better seal around the window and, if properly fitted with a box pelmet above, will trap a layer of still air between them and the window, which will reduce heat flow through the glass.
Modern internal blinds come in a range of elegant options that can reduce heat and glare without restricting your views, and they can be manually operated or fully motorised.
Another way to prevent heat gain is to treat the glass of the window itself, and there are several ways this can be done:
- Tinting — this is where a tint is applied to the glass during manufacture to reduce heat gain, without greatly reducing visibility. The darker the tint, the greater the heat protection.
- Reflective films — these can be applied to new or existing windows and can reduce heat gain while also providing additional privacy due to their reflective outside surface.
- Glazing — new glazing technologies include photochromic glazing (glass darkens when exposed to sunlight) and thermochromic glazing (glass becomes less light-penetrable as temperature rises). These technologies are largely used in commercial applications at present, but will find their way into domestic use as they become more affordable.
- Low-E glass (low-emissivity glass) — this is glass with a special coating applied to it that reduces the transfer of heat energy by filtering the sun’s short-wave radiation.
- Windows are necessary to see out and to allow light and air to enter our homes, and by using one or more of these methods, you can enjoy the benefits of your windows without the penalties of the harsh summer sun.