According to YourHome.gov, up to 40% of a home’s heating energy can be lost and up to 87% of its heat gained through windows. Improving the thermal performance of your windows can reduce your reliance on heating and air conditioning, save you money on your power bills and improve your home’s energy efficiency.
The amount of heat absorbed through your windows is determined by a number of factors including:
- The size and orientation of the windows
- The type of window glass and glazing treatment
- What type of window coverings you have
- Your local climate
- External shading
While some of these factors can’t be changed, like the size and orientation of your windows, there is still plenty you can do to reduce heat gain through your windows.
1. Install appropriate window shades and coverings
When it comes to reducing heat gain through your windows, the first thing you want to do is minimise the amount of direct sunlight that reaches your windows in summer. For north or south facing windows, fixed horizontal shades like eaves and pergolas will help to block out the direct summer sun.
For east and west facing windows, you can make use of adjustable external window coverings like blinds, awnings and roller shutters. These coverings help to absorb the sun’s heat before it reaches the windows, thereby minimising heat transfer into the house. In terms of preventing heat gain, external window coverings work much better than interneral curtains or blinds.
2. Install window tinting
Adding window tinting films to your windows is a great way to reduce heat gain without compromising the view from your windows. Tinted or toned glass can reduce the amount of UV energy getting through your windows, which means less heat is getting in. Reflective coatings also work to reflect sunlight and UV rays, reducing the amount of heat that is transferred through your windows.
3. Install double glazing
Double glazing can reduce heat gain through your windows by up to 30% compared with single-glazed windows. Double glazing consists of two panes of glass separated by a vacuumed layer of air or inert gas. Since air is a poor heat conductor, the heat is transferred through the first pane of glass and trapped by the gaseous layer.
Double glazing can be pricey to install, but it can deliver serious long-term savings on your power bills, effectively paying for itself over time. Some glazing companies will even be able to retrofit double glazing to your existing windows, which means you don’t have to replace your windows to enjoy the benefits of double glazing.
4. Upgrade your window frames
Together with the glass, your window frames will also have a significant effect on the thermal performance of your windows. The material your frames are made from will affect how easily heat is transferred into your home. Timber, for example, doesn’t readily conduct heat, making it an energy efficient option. Aluminium, on the other hand, is an excellent conductor, meaning aluminium frames will transfer a lot of heat.
Combination frames use low-maintenance aluminium as the external and structural elements of the frame and timber as the internal core. This creates frames that are durable and lightweight, but have a timber insulating core to prevent heat transfer.
While not a cheap or simple option, upgrading your window frames will help with thermal performance and energy efficiency and is worth bearing in mind if you are renovating or building.
5. Draught proofing
On a hot day, even a small draught can significantly increase the temperature inside. When it comes to your windows, draughts are generally caused by improperly sealed window panes or frames. Any hot draughts will heat up the inside of your home, making your AC system work harder to cool the room down. And that will increase your energy costs.
Make sure any gaps around your windows are properly sealed to prevent draughts. If you have timber window frames, be aware that the timber can expand and contract with the moisture in the air. As a result, timber window frames require larger tolerances, meaning they are more prone to draughts. In this case, you want to make sure your window frames are properly weather stripped.
6. Passive cooling
Passive cooling involves using non-mechanical techniques to help keep your home naturally cooler. It is the least expensive means of cooling a home in both financial and environmental terms. The main passive cooling techniques for reducing heat gain through windows include using shade to block direct sunlight from hitting your windows and placing water features like ponds or pools outside windows. Using deciduous trees can be a great option for passive cooling. During summer they will block the sunlight from reaching windows, but in winter when they lose their leaves they will still let in the maximum amount of precious winter sun.
When it comes to improving your home energy efficiency, your windows are one of the most important elements to consider. Making smart choices can help to make your home more comfortable while dramatically reducing your power consumption.