Another heatwave is looming for the UK, and after struggling with high temperatures in May and June, homeowners are racing to cool their homes before the next hot spell hits. While portable air conditioners are tempting, experts advocate for low-cost, sustainable alternatives that are effective and environmentally friendly.
Why passive cooling comes first
Tom Greenhill, an engineer, environmentalist and author of the Heatwave Toolkit website, says: “Air conditioning will cool the privileged but will not work for the many – or the environment.” Even if you do buy an air conditioner, powerful passive measures such as shading windows will make it more effective, he adds.
Stuart Dantzic, vice-president of the British Blind & Shutter Association, emphasises the importance of blocking solar heat: “We don’t heat a building without insulating it so why are we cooling a building, whether that’s with a fan or air conditioning, without shading it first?”
Start in the loft
Where you place shading matters more than the product. External shading can reject up to three times more solar heat than an equivalent internal blind. Greenhill recommends covering skylights first, as they receive direct sun most of the day. He bought £80 Velux external awning blinds for his Victorian terrace loft and found his space cooler. “I looked up the product code for our Velux roof window and ordered the corresponding awning blind. I installed it within half an hour of DIY. Now, it takes 20 seconds to deploy or hide away as necessary.”
Velux offers manual anti-heat blinds promising temperatures “up to 4C cooler inside” for £110 for a standard window. Their more expensive anti-heat blackout shutters reduce solar heat by up to 5C indoors, costing £530 plus £166 for electric control, with professional installation required.
For renters or those on a budget, a £5 fitted sheet from Ikea can work. Bojana Bajzelj from Exeter used a king-size Bärglim sheet to cover her skylights, estimating it made her kitchen 2C to 4C cooler while still allowing daylight through.
Set sail with solar shades
For large bifold or patio doors, which act as one-way heat traps, a solar sail – a sturdy fabric suspended between walls – is an effective solution. Greenhill says: “It will be super effective – that’s why you see it in streets across Europe. You can get something that looks really smart and well-designed for about £20.”
Kemp Sails, a Dorset-based company, sells chic shades starting at £136 for a one-metre by two-metre rectangle. Cheaper options are available on Amazon, with a two-metre by two-metre shade for under £20. Unlike solar-reflecting film, these sails can be removed in winter to allow heat and light back in.
Rig up a camouflage net
A cheap and cheerful option is a camouflage net, available on Amazon for about £10 in various sizes. It blocks direct sun while allowing daylight and ventilation. It can be draped over windows or skylights or used as a makeshift awning. Doubling it over blocks more sunlight. Shade cloth used for plants is also useful as a mesh that remains see-through.
Clip shades on sashes
After neighbours with a baby were hospitalised with heat-related illness during the June heatwave, Greenhill suggested they buy Shaded’s £89 mini awnings that clip onto windows from the inside. The product, created by founder Aimée Daniels, is currently sold out but will be restocked in a fortnight, with 10% off for purchases of two or more.
Invest in external blinds
External blinds and awnings don’t lower existing temperatures but stop them rising, says Dantzic. For an average set of bifold or patio doors, an external roller blind costs around £3,000–£4,000. Adding a weather sensor for £250 allows the blind to close automatically in response to light levels, preventing overheating. “Sensors don’t add a lot of cost but having the blind do what it needs to, when it needs to is worth its weight in gold,” Dantzic adds.
Awning it
Awnings project out from the facade, allowing continued use of doors while creating shaded outdoor space. They cost between £4,000 and £6,000 for a typical set of bifold or patio doors. Dantzic notes that modern buildings designed to retain heat make awnings a valuable long-term investment.
Get flash with shutters
Motorised metal or manual wooden shutters are common in hotter climates. David D’Ambrosio, director of the Scottish Shutter Company, says demand is growing but external shutters are still not widely used in the UK. Interior wooden shutters start at £550 for a typical 1.2m by 1.4m living-room window, while external roller shutters cost £1,100 and aluminium shutters £1,450 for the same size. External products work best when incorporated into the building design, D’Ambrosio explains, recounting a customer in Perthshire where solar heat gain was so intense that the plastic coating on a kitchen island peeled off. They opted for internal blinds due to outward-opening windows and lack of recess.
