AIBU to paint south facing windows with chalk paint as a temporary shading hack?

[JennyForeigner]

Just curious. I was reading an article on solar shading and was surprised it doesn't mention good old fashioned limewash, or the modern equivalent - chalk paint.

I've got a garage full of Annie Sloan, which I already use on a bathroom window to obscure it. A very quick bit of research says painting the exterior of my south facing French windows with chalk paint would cut absorbed heat by up to 90% compared to 40-60% for closing the curtains, and would wash off at the weekend.

Obviously I would recommend it as a solution for people in upper story flats or anything, but have I hit on a genuinely affordable and useful idea? How to shade your home

If it's a brick house then you can hose down the outside to cool it. Bricks absorb a lot of heat and retain it.

Does it really wash off? I’ve seen it recommended for painting kitchen chairs and cabinets, surely that wouldn’t work if it washes off easily?

Do you not have blinds or curtains? Surely it’s only comparing heat reduction to plain glass in direct sun?

Just sellotape some A4 sheets of paper to the inside of the glass. That should do the trick. Or do what I did earlier in our bathroom and drape a towel over the frame, then shut the window to hold it in place.

There’s a similar thread somewhere recommending stick on blackout things from amazon.

It really does - I know to my cost how easy it is for my kids to scrape/wipe off the chalk paint I used to obscure a glass door 😂 (long story, I had to turn a downstairs room into a bedroom at short notice and never had privacy again).

This is proper old school chalk paint with nothing added though. I just hate the idea of buying something disposable from Amazon if I have a solution right here.

For anyone asking why not just draw the curtains... I have, but also this is the inside of the curtains from last year...

We’ve just blue tacked sheets of A4 printer paper to ours. No need to overthink or exert yourself outdoors painting in this heat.

My dad certainly uses a white mixture on his greenhouse in summer to avoid it overheating.

If using paper, is there not a risk of it scorching?

Covering the windows with foil would be more effective and less messy.

It's what they're doing in some parts of France according to the BBC :-)

"According to French newspapers, there has been a run on a chalky product called Blanc de Meudon, or Meudon Whiting, in DIY shops.
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."

https://www.bbc.co.uk/news/articles/cz0j87vpz79o

I’ve covered the outside of the windows with a combination of cardboard, towels and a foil camping mat. It’s definitely making a difference compared to just closing curtains. I’m not sure about paint though because surely the surface of the glass will still heat up? It’s not much of a physical barrier.

White surfaces have an excellent albedo effect (reflectivity). The darker the colour the more heat it will absorb.

I don’t think the French are using tins of Annie Sloan. It’s a powdered chalk that you mix into a slurry with water and paint on. We used it growing up overseas and it was the poor man’s version of tinted window film. You can just hose it off later. If you can arrange it, a towel hung outside the window can be effective- you want to keep the heat off the glass, so inside is no good.

When it was that super hot spell last time, I hung a white sheet in front if the windows. It really helped.

Please don’t!

Just get some foil bubble sheeting (comes on a roll) cut to size of glass and stick on the outside of your window or patio doors.

It’s reduced the temperature in my South facing rooms by 10 degrees C.

You can keep it to use for future heatwaves/ years too.

Just been inspired to tape some newspaper to the outside of our kitchen window and see if it helps with heat. The sun is hitting the window first thing and really warming the kitchen up. We don't have any blinds or curtains in the kitchen currently (though will be changing this but it's slightly awkward position for many blinds). This is the quickest solution. I will report in the morning if it works. The window faces the back of the house and isn't particularly overlooked. I don't think I'd tape newspaper on the front of the house for neighbours to see!

Sorry, is that a scorch mark? Did just the heat from the sun do that? If so why does literally every piece of advice about keeping cool tell us to keep the curtains closed?

I wonder if they had one of those garden mirrors or other shiny ornament that directed the rays towards the curtains.

I was just about to post the same! We even had the same temp reduction.

Definitely needs to be on the outside of the window, as BurntBroccoli highlighted.

Do you mean the bubble wrap thing for house moves?

I’ve just hung old towels and sheets on the outside of all of our south facing windows - has made a huge difference. The glass is very cool on the inside.

I love it! I was really happy when I thought of it as an alternative to plastic film for our damp old bathroom window. Generally I figure anything my grandpere and grandmere might have done is both chic and practical.

• Actually they were from Rickmansworth, but never mind.

No, no mirror or ornament or anything like that. A South facing outside glass door with a high ivy covered wall on one side and a large buddliea outside the door. I couldn't believe it when I noticed the scorch mark over the winter.