Stop cranking up your AC in a heatwave — this 'chalk on window' hack can keep your home cool
With another heatwave hitting the U.S. right now, staying cool isn’t the only concern — the looming cost is just as stressful. Running your AC on overdrive to stay cool leaves you with a tough choice. Do you face a massive energy bill, or suffer through the sweltering heat?
Aside from blasting your AC, there are lots of ways to stay cool in a heatwave, from using the free wind tunnel method, which I favor, to staying cool with a fan, and even covering your windows with aluminum foil.
But I’ve recently spotted another method to stay cool in a heatwave, which I first saw mentioned in a BBC News article, and it made me want to find out more. It’s how applying chalk to your windows can help to reflect the sun and keep your house cool.
Reflect the sun with chalk
The BBC reports, “According to French newspapers, there has been a run on a chalky product called Blanc de Meudon, or Meudon Whiting, in DIY shops.”
And the article continues, “The powder is mixed with water and then painted on windows, thus diminishing the power of the sun’s rays and in theory bringing down the inside temperature. It does actually seem to work.”
I found the idea of using chalk to reflect sunlight intriguing, and I wanted to learn more about this method and its origins.
What is Meudon whiting?
Meudon whiting is composed of calcium carbonate — the main component of chalk and limescale — and it also contains a small amount of clay. It takes its name from the quarries on the outskirts of Paris, where it was first thought to be extracted in the 18th century. You may also hear it referred to as Spain whiting, Champagne whiting, Troyes whiting and ‘white polishing stone’.
Artisans and households first used the powder to polish delicate surfaces, such as glass, marble and silverware. It’s also been traditionally used as a base pigment or additive in paints and putty.
Apart from these uses, it’s also been painted on greenhouses to reduce the sun’s intense glare, with Sortir à Paris stating: “In favorable conditions, drops of 3 to 7°C [5 - 12°F] could be expected.”
Now that I know it’s been used on greenhouses to reduce the sun’s heat, I’m surprised we haven’t already been using this on our windows to beat the scorching sun.
How to apply Meudon whiting to your windows
The fine powder needs to be mixed with water before it’s applied to the exterior of your windows. The standard ratio is one part powder to two parts water. Once applied, it will leave an opaque-like film on the glass, helping to reflect the sun’s rays from your home and reducing heat inside.
The benefits of using this whitewashing-effect on your windows?
Meudon whiting is a natural, biodegradable product that is safe to apply to your windows. What’s more, it’s an economic way to shave a few degrees off the indoor temperature during a heatwave, without being left with the worry of an extortionate energy bill.
I’d be interested to know whether you think it’s a good way to reduce the heat in your home during a heatwave, and if you’ll be giving it a go?
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