Window furnishing tips for insulation

Windows are great for light, views and ventilation, but when it comes to insulating your home, they need to be fully dressed.

Bunnings magazine, July 2019

Keep your home warm in winter and cool in summer

The days when Australian homes had a single door leading from the kitchen to the backyard and a smallish window above the sink are long gone. Now, our love of open-plan design and indoor/outdoor living has brought us glazed sliding doors, bifolds and oversized windows. While these are positive assets from a lifestyle perspective, they’re less than ideal when it comes to keeping our homes warm or cool.

Underrated insulators

The insulating properties of standard types of glass aren’t great and, while double glazing improves that dramatically, it’s not uniformly used in Australia. A window loses 10 times as much heat as the same area of insulated wall; this needs to be addressed to keep your home comfortable and your power bills manageable.

If you’re building or renovating, consider orienting living spaces to the north to maximise light and warmth, and opt for window frames in timber or uPVC, which transfer less heat and cold than standard aluminium frames. For a retrofit fix, different window furnishings can make a big difference to your thermal comfort.

Drape expectations

Curtains are an ideal way to regulate the temperature of your house as they trap an insulating layer of still air between the window and the fabric. For best results, your curtains should include a pelmet at the top and a return at the ends (where the curtain bends around to meet the wall to create a seal). “If you’re looking for thermal control, you must have generous coverage,” says interior decorator Alix Helps.

The fabric you use will also impact the effectiveness of your curtains. “It’s possible to vastly improve the insulation and energy efficiency of your home by using curtains made from thermal fabrics,” adds Alix. “If you opt for a double curtain track, you can use a base layer (closest to the window) for thermal protection and light control, and a front layer to present a polished look to match your aesthetic – this might be a sheer or a semi-sheer. You can use them together, or just the sheer for light filtering and privacy.”

Blind attraction

Blinds also trap a layer of air that prevents heat transfer through windows. Where possible, install blinds so the edges are flush with the wall, rather than leaving a gap where heat can escape.

“The most effective method to block out heat or keep the home warm would be blockout fabrics in a Roman blind,roller blind or curtain,” explains Windoware’s Marcus Alexander. Honeycomb (or cellular) blinds are also thermal powerhouses; their structure traps air between the cells, creating a layer of insulation. Single, double and triple versions are available, and the thermal properties increase with each extra layer.

Open and shutters

A stylish choice for breezy coastal interiors, plantation shutters are most often chosen for their aesthetic appeal and capacity for controlling light and ventilation, but they’re a surprisingly good option for cooler climates, too. 

Timber shutters are slightly more efficient than vinyl or PVC, but all shutters fit tightly inside the window frame and prevent heat transfer, so are second only to curtains in terms of insulation. By contrast, Venetian blinds allow air to leak through the sides, as well as between the slats. If winters are particularly bitter, both shutters and Venetians can be paired with pretty curtains, which will create an additional barrier, enhance the thermal regulation and add visual appeal.

All in the timing

Window furnishings of all types are most effective if you put them to work before the outside temperature heats up or cools down. In winter, sunlight is a wonderful tool for heating the home, provided you close the blinds or curtains to keep in the heat as soon as the sun has passed.

Outside effects

Good insulation starts from the outside in, and anything you can do to stop cold air hitting the glass of your windows will make a difference. Outdoor blinds, enclosing alfresco areas such as verandahs and balconies, can be a great insulation tool in both summer and winter. “During the winter months they add an additional layer of insulation to glass windows and will keep some additional heat in,” says Marcus Alexander. By helping to block icy breezes, outdoor blinds can have a discernible impact on temperatures inside, with the greatest insulating effect offered by heavy-duty PVC versions.

A major advantage of both outdoor blinds and awnings is their flexibility; unlike fixed screens or solid awnings, they can be extended to block light or wind, then retracted in calm conditions to let in warming winter sunlight.

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How to choose your fabric

The type of fabric used for curtains and blinds will affect their thermal capacity. For example, while sheers are great for filtering light, they’re no good for keeping your home warm or cool. “There are two styles of fabric commonly used for light and temperature control,” explains Marcus. “A triple weave is a fabric that has a black layer woven into it – this style of fabric is popular due to its woven appearance, affordability and effective thermal properties. A blockout curtain is made from fabric that is coated with an acrylic backing – this is the most common curtain and it performs well in direct sunlight.” Many fabrics are available for custom-made curtains; if you can’t find a triple-weave or acrylic-backed fabric you like, use a separate thermal lining that can sit behind any fabric.

Window love

Once you’ve sized up and decided on which window furnishings will be the right one for your home, head into your local Bunnings store to pick them up. If you’re stuck for sizing, check out our article on how to measure your window for blinds or speak to one of our team members in store. 

Photo credit: Gap Interiors (Mark Scott and Tria Giovan)

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Health & Safety

Please make sure you use all equipment appropriately and safely when following the advice in these D.I.Y. videos. You need to be familiar with how to use equipment safely and follow the instructions that came with the equipment. If you are unsure, you may feel it is safest to consult an expert, such as the manufacturer or an expert Bunnings Team Member.

Grave health hazards are linked to asbestos, which may be in homes built up to 1990. Health hazards may result from exposure to lead-based paints in older materials and copper chromium arsenic (CCA) treated timber. For information on the dangers of asbestos, lead-based paint and CCA treated timber and tips for dealing with these materials contact your local council's Environmental Health Officer or visit our Health & Safety page. You can also use a simple test kit from Bunnings to indicate the presence of lead-based paint.
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