Glass is a poor insulator, which is why windows tend to be the main source of heat loss in any home. When temperatures are colder outside than inside, glass conducts the heat from inside the house to the outside where it quickly disperses. The air next to the glass inside, having lost it's heat, becomes cold and dense and falls to the floor drawing in new warm air from above. This cycle continues until you lose all your warm air outside. Here are some ways to ensure you’re doing everything you can to reduce the amount of heat loss through the windows.
Seal any gaps
The very first thing to check is if you have any gaps around your windows that are letting cold air leak in; check both inside and outside. Gaps are easy to fix either by caulking them or applying rubber weather seal tape where appropriate; this is available fairly cheaply from any hardware store and it’s easy to install; here’s a handy how-to video from Bunnings.
Upgrade to multi-layered glazing
Double-glazing is proven to reduce heat loss through windows. It works by trapping a pocket of air – which is not a good conductor of heat - between the two panes of glass.
You can even get triple-glazing nowadays! With quite incredible insulating performance, triple-glazing does come with some disadvantages such as needing an extra wide frame to accommodate the extra thick window panes, it doesn’t let in much solar heat so you would have to rely almost completely on a heat source within the home, light transmission can be quite low and for the most part, retrofitting cannot be done. To install double or triple glazed windows throughout your whole house would be an expensive (albeit worthwhile) task so here’s a cheaper option:
Insulating window film
The cheapest option is to go the DIY route with a kit from the hardware store. 3M make a product that you can install yourself with nothing more than a tape measure, scissors and a hairdryer. There’s a useful how-to video on the Energywise site.
Low-E window film
This is a thin polyester film with a micro-thin metal coating that sticks directly to existing glass to reflect radiant heat back into the home. It works best in homes that don’t experience condensation though; find out if it’s right for your home on the Energywise website.
Thick, properly lined curtains or blinds
Thermal lined curtains and blinds can significantly reduce heat loss through your windows. According to Energywise “Good curtains and blinds can reduce heat loss through windows by 60% for single glazed windows, and 40-50% for double glazing.”
- A thick, closely woven fabric will offer the best heat loss reduction.
- Ensure a snug fit on both sides of the window and at the top of the curtain or blind to stop warm air sneaking down behind it.
- Install a pelmet above the curtain rail. This then creates that pocket of air, which helps to reduce heat loss. Or use curtain tracks that curve at the end and bring the curtain into direct contact with the wall to create a seal.
- Make sure you keep curtains and blinds open during the day to let in any sun and close them at dusk to keep that warmth in and block the cold glass.