Is there really a need for double-glazed windows and doors in South African homes? Our weather can hardly be compared to that of colder climates where this is an essential feature. And yet, there are more benefits to installing this type of window and door in our homes than we might realise.
Such windows and doors are a popular feature on green homes. That’s because they contribute to the overall energy efficiency of a home. And with the rising cost of electricity, more home buyers are looking for features that reduce heating and cooling bills. Whether looking to buy a new home or thinking about retrofitting an existing home, here’s what we need to know about double-glazing.
What are double-glazed windows and doors?
It is simply a window or door made up of two layers of glass with a gap between them. This gap is usually filled with air, although in some cases it may be filled with Argon or Xenon gas. The two panes of glass are separated with an aluminium spacer and the unit is sealed with silicon. A secondary coating of silicon or bitumen is applied to ensure the glass is completely waterproof.
The air trapped between the two panes of glass acts as a layer of insulation. This makes it more difficult for the cold air outside to pass through the glass and into the home, and vice versa with warm air. This is what makes double-glazed windows and doors more energy efficient.
How energy efficient is double-glazed windows and doors?
Single-pane glass accounts for as much as 40% of the energy lost in a home. Double-glazed windows and doors reduce this figure by as much as 50%. In the winter, double-glazed windows and doors reduce and regulate thermal loss from the inside. While in the summer they prevent solar heat from entering our home from the outside. That means our home will be warmer in winter and cooler in summer.
The use of dehydrated air to fill the cavity between the two panes of glass is what makes these windows and doors so effective at retaining warmth. Heat is normally lost as warm air molecules move from the inside of a window pane to the outside, where it’s colder. Because the molecules of dehydrated air are less mobile than normal air molecules, the heat loss is a much slower process, the same, though in reverse, with cool air in the summer.
What are the other benefits of double-glazed windows and doors?
Not only do double-glazed windows and doors help save energy and cut down on heating and cooling bills—they have many other benefits worth mentioning such as:
- Reducing noise pollution: Double-glazing helps reduce the amount of noise that may enter our home from outside. This makes them ideal for homes located next to busy roads or even in windy areas. They also help soundproof our home from the inside out.
- Draught proofing: Double-glazed windows and doors are well-sealed and fitted which means that little air gets through. Even in areas with high wind, the all-round rubber seal stops any icy draughts from finding their way into the home.
- Reduced condensation: Because heat is reflected back into the room, and the inside pane is warmer, there’s less chance of condensation forming on double-glazed windows and doors. This means there’s less chance of mold and mildew developing in the bathroom or kitchen.
- Added security: Two panes of glass are much harder to break so double-glazed windows and doors act as deterrent to intruders. It’s not only the thickness of the window; it’s also the composition that makes it difficult to smash this type of window and door.
Double-glazed windows and doors let in just as much light as regular glass, with added benefits. Why would we want regular glass when we could have something that functions just the same, though makes our home safe, quieter and retains the interior temperature; warmth in winter and cooler in summer?
What to be aware of when installing double-glazing
There are a few things to bear in mind when considering double-glazing. While many green homes include them as a standard feature, retrofitting them requires some consideration. This is what to look out for:
- The right kind of window and door frame: Bear in mind that frames affect the insulation properties of double-glazing by up to 30%. It’s worth spending the money for high quality frames. Timber frames are a popular choice for their aesthetics. Timber requires some maintenance, and especially when double-glazing is fitted.However, aluminium frames require little maintenance. With these frames we need to consider the thermal break. This is a plastic or resin section in the centre of the aluminium joinery made from an insulating material such as uPVC or wood. This type of frame is less likely to attract condensation and will lose less heat than a standard aluminium frame.
- Low-emissivity (low-E) glass: It’s worth ensuring that the double-glazed windows and doors use this kind of glass because it cuts heat or cooling loss by about 10% more than those with regular glass.
- Multiple layers that are well sealed: It is essential that the double-glazing is perfectly sealed. This way they will keep out draughts, moisture and noise effectively. Also ensure that the joint between the frame and the window is well sealed.
- Spacers made from plastic or stainless steel: This refers to the spacers used to separate the two panes of glass in the window or door. When made from plastic or stainless steel (as opposed to aluminium) they aid in reducing heat or cooling loss and condensation at the glass edge.
- Inert gas for the filling: Gases such as Argon or Xenon make better insulators. When used for the gap between two glass panes in a double-glazed window and door they reduce heat and cooling loss by an extra 3%. It may not seem like much but when it adds to saving energy—every little bit counts.
How much does double-glazing cost?
Double-glazed windows and doors are considerably more expensive than regular, single-paned glass. The final cost depends entirely on the requirements. How many windows and doors are required? What are the sizes? These are factors influencing the price when looking at the cost of double-glazing.
Why double-glazing works best in conjunction with other insulation methods
On their own double-glazed windows and doors go a long way to reducing the overall energy consumption. The expense of fitting double-glazing to an existing home would not be as effective if done in isolation. It needs to be considered in conjunction with the other insulation, like insulating exterior walls, floors and ceilings. Comprehensive insulation might not be practical or cost-effective. These points need to be considered as a whole.
In green homes they form part of the methods used to keep energy costs low. This is one part of comprehensive insulation to reduce electricity usage, whether drawn from the grid or from photo-voltaic solar panels. In green homes, they complement the floor, ceiling, water pipe and wall insulation. And when combined with the Hydronics Radiant heating and cooling system, the result is a home with a perfectly maintained indoor temperature throughout the year. The savings on [the water and] energy bills in a green smart home are momentous thanks to this holistic approach.
But when retrofitting an existing home there are some possibilities to improve insulation along with fitting double-glazing. For example:
- Check for draughts and seal them up: It’s a simple matter of looking around the home and making a note of the areas where air leaks in or out. Around windows and under doors is a good place to start. Use sealing strips and caulk to seal any gaps.The idea is to stop warm air from escaping and cold air from entering, and vice versa, so best is to scrutinise every frame, window and door. Even sealing up these little gaps helps to make a home comfortable in summer and winter.
- Insulating the ceiling: lots of heat escapes through the roof so it’s worth adding insulation to this vulnerable area. There are many different kinds of insulating materials to choose from. However, opt for a green alternative rather than the traditional fibre-glass or paper options. Not only is it kinder to the environment, it’s also healthier for the whole family.One such material, Isotherm ticks all the boxes. It’s made from recycled plastic bottles and can be recycled again itself. It is dust and water resistant, non-flammable, non-toxic and lasts longer than many other insulators.
- Use thicker curtaining: We usually switch out the light summer duvet for something thicker and warmer in winter, and the same applies to glass windows and doors. Thick curtains will add an extra layer of protection from the cold and stop draughts from getting into the homeUsing this option for windows and doors contains the costs of adding double-glazing everywhere. That way a home is better insulated and the double-glazing installed is effective.
- Close internal doors: When not using a room, rather keep the door closed. Limiting the airflow within a home goes a long way in keeping the heat and/or cold in and cuts down on electricity usage. Keep in mind that when a room is not in use, it is advisable to balance the electricity spending with maintaining the temperature.Bathrooms are particularly chilly in the winter because they’re filled with tiles that don’t retain heat very well. Keeping the bathroom door closed in winter stops the cold air from seeping out and affecting all heating efforts, and vice versa in summer.
Keeping in mind, when deciding whether it’s worth investing in double-glazing, due to the cost, considering the saving such an investment brings about to heat or cool down our home, and that over the course of their lifespan they pay for themselves many times over. And when implementing comprehensive insulation, further savings are achieved, which recoups the initial investment faster.
A further point is the different experience in summer when the home becomes a cool and quiet haven, or when in winter it is a warm and quiet haven. Not many renovations reduce electricity costs while providing the benefits that double-glazing does. They’ll also add to the value of our property when selling it on. Well worth the extra expense, double-glazing is an excellent investment.