Energy efficient window coverings: the best ways to keep the heat in your home

We talk a lot about the temperature in Canberra. Our altitude and southern inland position make our summers dry and hot and our winters downright frigid.

As such, insulation is a critical household energy efficiency consideration. And often the biggest weakness in a household’s insulation is its windows.

The good news is we can counter this to varying degrees with window furnishings. But note that not all window coverings are created equal when it comes to insulation.

There are two things worth understanding when deciding which options are best suited to your spaces, according to Regency Knights owner Martin Smith.

“Firstly, there are two different types of heat that we’re trying to keep in certain places, and they behave differently and have different insulation requirements,” he says.

“When you’re inside your home in winter all the heat that’s generated when you’re using a heater, cooking and doing all the things you do is your ‘thermal heat’, and you want to keep that in.

“When the sun beats down on your home, all the heat that’s trying to get into the house is ‘solar heat’, which you want to insulate against in summer.

“Secondly, when you’re heating a room, the warm air rises, travels across the ceiling and down the wall. This should factor heavily into your window furnishing choices if insulation is your priority.”

1. Curtains and pelmets

When combined with a “pelmet” (the horizontal headboard running across the top), a curtain can be one of the best insulation options.

As warm air travelling across the ceiling comes down the walls, a curtain with no pelmet will allow it to continue down to the window glass where it will cool. That now cold air will continue to the floor, eventually being reheated as it travels across the room and starts the cycle again.

This means your air is constantly being reheated, requiring more energy to maintain the temperature set on your thermostat.

The top of a pelmet will block the warm air from the glass behind the curtains, forcing it in front of the pelmet “fascia” (the part of the pelmet used to conceal unsightly headrails) and in front of your curtains. As a result, the air follows its usual path down but remains warm.

Note that cold air may still seep out of the bottom of the curtains, but overall your air maintains its temperature much better with a curtain and pelmet in place, requiring less energy to maintain your desired temperature.

2. Hinge shutters

These shutters have their own frame that fits inside your existing window frame, blocking light at the back of the panels.

Because they’re fitted inside the reveal, the top of the window frame acts like a pelmet. This means when the warm air goes across the ceiling and down the shutter, that window frame prevents it from getting onto the glass behind the shutter blades and cooling.

Though they’re not airtight, there are very few gaps in shutters, even around the sides and the blades, and they remain one of the best insulators in window furnishings.

Note that while timber is a good natural insulator, a PVC (polymer) product is usually 50 to 70 per cent more effective.

3. Honeycomb blinds

Honeycomb blinds get their name from the formation of the fabric which is made up of “cells”. The air filling these cells produces the blinds’ insulation qualities, making them particularly effective at keeping your thermal heat inside.

Fitting them inside the window frames maximises insulation because the tops of your window frames act like pelmets, preventing warm air from getting behind the blinds and onto the cold glass where it will cool.

Honeycomb blinds come in several light filtering and room darkening fabrics, with the former providing light filtering that yields good insulation for keeping thermal heat in.

Room darkening fabrics have the same qualities as the light filtering fabrics, but with the addition of a silver foil lining the cells to insulate against solar heat coming in.

Hints

1. If you’re very serious about insulation, consider a shutter with its own built-in room darkening honeycomb blind, which fits in the frame at the back of the shutter frame and functions like a regular honeycomb blind. Not only is it one of the best combinations for shutting out light whenever needed, but you’re also purchasing two of the better window furnishings for insulation for the one window, yielding superior results.
2. If opting for a honeycomb blind for a living space, consider a light filtering fabric. It will provide good thermal insulation in winter and in summer, will still provide reasonable insulation against solar heat from outside while allowing through some filtered light when closed, so you won’t feel like you’re living in a cave.

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