One study estimates that a single-pane window allows 10 times as much heat to be transmitted through it, compared to a similar sized insulated wall.
Another report states that about 35% of the heat will seep through walls, gaps, and crevices, in and around windows.
That also means 35% of your cooled, air-conditioned air, is escaping out your window. And warm air from the outside is coming back into your room.
The recommendations we’ll we talking about can save you 20-30% on annual energy costs, or about $400 each year for an HDB owner and easily $1,000 living in a bungalow.
That is definitely unnecessary cost incurred. And that can be fixed with a window? How easy!
The science behind heat transfer and energy saving
- Conduction: You touch a hot pan. You burn.
- Convection: You boil a pot of water – considered a “fluid” in thermodynamics – water is heated throughout
- Radiation: You put your hand near a pot of boiling water for a period of time, you feel the heat too.
For the ease of explaining, let’s pretend you are in your home sitting on the couch with your aircon switched on.
But little do you know that while you’re enjoying the cool air, your windows are letting the cool air escape and allowing heat to enter.
To put it simply, we feel hot under the sun mainly because of radiation.
Well, same concept here too. Heat is transferred into your home, and especially if you have a fair bit of glass, it creates somewhat of a glasshouse effect.
Around ⅔ of the energy lost through the standard, non-energy efficient window, is by radiation through the window glazing.
So while your aircon cools the air in your rooms, the air is concurrently being heated by the sun…No wonder you’re decreasing the thermostat and increasing the fan speed!
This quite obviously one of the biggest ways you can save your electricity bills.
Recommendation: Coat with Low-E
Windows equipped with Low-Emissivity (Low-E) glazing reflect heat, rather than absorbing it, while still allowing sunlight to enter.
It is a multi-layer coating (aka glazing) that is applied to the interior pane(s) of glass during the manufacturing process. The Low-E coating has to be microscopically thin if you still want to see through your windows, but look really closely and you’ll notice that it does give them a slightly grey tint.
This coating can minimize the amount of ultraviolet and infrared light that passes through the glass in your windows.
A small amount of energy is also lost through convection within the glazing cavity.
As we know in science, warm air rises and cooler air sinks to replace it, thus setting up a convection current which transfers heat from the inner pane through to the outer pane(s).
To prevent this convection current from being created, we want to limit the air between from being heated as much as possible.
Recommendation: Install Double-Glazing
Built like a sandwich, with a layer of gas (usually Argon or natural air) between two glass sheets.
Since air is an insulator of heat, it significantly reduces the amount of heat transferred from panel to panel.
Plus, in order to maintain the air padding, the panes must be sealed shut by a hermetic seal that prevents any air from entering or escaping. An added benefit is that the tight sealing prevents unwanted airflow too. Which brings us to the next point…
After radiation, air leakages is the next biggest culprit of energy loss, mainly due to old windows or poorly installed windows.
Air leakage, also known as air infiltration, is the measurement of air that passes through the window assembly itself. This means that cool air can easily escape your windows through tiny gaps around the frame or between the wall and your window.
If you’ve ever experienced strong winds and heard your windows rattling…that’s a sign that your windows aren’t fully secure and air is passing in and out of your home. That’s money creeping out your window!
Recommendation: Employ Casement Windows
Of course, in this case, fixed windows would be the best to prevent air leakages since they cannot be opened at all. But if you want an operable window, simple casement windows or lift & slide windows perform the best.
These windows typically use corner connectors which allow them to be closed very tightly. By the way, it’s so tight that it blocks out noise by up to 80%.
Cooler homes, quieter rooms, lower bills, better sleep, here we come!
If you take a look at the window frames around you, high chance that it’s made from aluminium. While aluminium is versatile and cheap, it conducts heat very easily. Which means it heat enters your house easily too.
Different materials have unique properties that affect a window’s insulation properties. Incorporating certain materials within the frames of your windows can help ensure a more consistent temperature throughout the room.
Recommendation: Use composite materials for frames
Composite materials like Unplasticized Polyvinyl Chloride (uPVC) are ideal choices because Because of its physical properties, they practically disperse heat before it enters your home.
uPVC frames have air chambers that can be filled with insulation, which helps in reducing the transfer of heat and cold through the window frame. It is also easy to maintain and needs no regular upkeep. By the way, this seals so tightly that it creates sort of a soundproof environment.
Air conditioning a poorly insulated house with little shading is expensive and futile. You can improve the comfort and energy efficiency of your living space with the strategies mentioned above. To learn more about how to maximise your home’s energy efficiency, you can read more about energy efficiency here.