Keeping ZERO cool this summer

To keep your home cool this summer the simplest thing to do is to stop it from heating too much in the first place. Opening windows when it’s cool outside and keeping them closed when it’s hot can make a big difference, especially if, when it’s cool, you can open windows on two sides of your home to allow the air to blow through. Closing blinds and curtains during the day helps prevent the sun shining into the house and heating it up. If you want to do more to keep your home cool, or if, like us at ZERO, there aren’t curtains or blinds on all your windows, there are other things you can try. Last Zero Night our wonderful volunteer team helped set up an experiment on our south-facing windows to test how well two different ideas work.

The first idea we tried was using foil to reflect the light. We used radiator foil, but you could also use kitchen foil at home. We taped the foil to the windows with masking tape so that it will be easy to remove when the seasons change. Our team found this job quick and simple to achieve. One disadvantage of this method is that the foil blocks all the light coming through the window, so you might want to do what we did and combine it with other cooling methods to let in a bit more light if you are working with more than one window panel.

The second method we tried was painting yoghurt on our windows. This felt like quite a strange thing to be doing and our team had some fun making different patterns as they painted on the yoghurt. This was also quick and easy to do with paint brushes. We made sure to clearly mark the pot of yoghurt “do not eat” when we put the leftovers back in the fridge to use later! We found that the yoghurt dried quickly. It didn’t smell at all after it dried and it didn’t attract any insects. We painted the outside of our downstairs windows as it is better to reflect the light before it passes through the double glazing, but upstairs we painted the inside of the windows as there should still be a cooling effect due to reducing the light coming in.

We had fun setting up our experiment and are looking forward to testing our results with the thermal cameras that we use for home energy surveys as well as simple room thermometers. What have you done to keep your home cool during the hot weather? Do let us know what has worked well for you.

Your Summer Cooling Questions Answered

Does painting yoghurt on windows really help?

It can reduce the amount of sunlight entering through the glass, helping to keep rooms cooler. We're testing this at ZERO using thermal cameras and room thermometers to measure the results.

Should I apply yoghurt to the inside or outside of the window?

The outside is most effective because it reflects sunlight before it passes through the glass. Applying it inside can still help reduce heat.

Does dried yoghurt smell or attract insects?

We found that once it dried, it didn't smell or attract insects.

Does foil on windows keep a room cooler?

Yes. Foil reflects sunlight away from the window, reducing heat gain. The trade-off is that it also blocks natural light.

What's the easiest way to keep a home cool?

Open windows when it's cool outside, close them during the hottest part of the day, and keep blinds or curtains closed to block direct sunlight.

Can I get more advice on keeping my home comfortable?

Yes! ZERO's Home Energy Advice Team (HEAT) offers free home energy surveys with practical advice to help keep your home cooler in summer, warmer in winter, and more energy efficient all year round.