Tips, tricks, do’s and DON’Ts to keep a home cool in summer
The headlines
As a result of climate change, we are already seeing summer heatwaves that are more intense and with higher peak temperatures both in the day and at night.
Some homes though, are already experiencing intense overheating these days, especially during extended heatwaves.
Thankfully, there are many simple and well proven tips and tricks to keep homes more comfortable without the expense of air conditioning.
Some of the tips in this article just mean doing things a little differently around the home. Others need a little investment.
All homes are different though, and different tricks will be more suited to some people than others.
The best approach is to experiment with the "free" things you can try first.
The ideas below fall into one of the following sections below:
1) Keeping direct suns rays out
I've put this section first as it is the most important one. Doing may seem obvious of course, but research has shown that of all of the ways of keeping a home cool in summer BLOCKING THE SUN FROM COMING in is one of the best things you can do to keep comfortable.
If you are successful at keeping the sun out, you may not need to do much else.
Even if it is not that warm outside, direct sun flooding into a home will be heating the air indoors, even early in the morning.
1a) How best to use indoor curtains and blinds to keep the sun out
Keep curtains or interior blinds closed whenever the suns rays flood in regardless of the time of day.
Even if you don't have direct sun coming through, in the hottest part of the day keeping curtains or blinds closed will still act as a useful barrier to keep the heat out.
If you have both blinds AND curtains on the same window, close them both. The more layers of defense the better.
1b) Outdoor solutions to keeping the sun out
Shading or putting barriers of some kind on the OUTSIDE is by far the best solution. This is something that people in countries that are used to very hot weather do all the time.
Below are some ideas though what might be able to do.
Simple quick solutions
This looks dreadful but it was something I tried last summer using old sheets. It made a huge difference so I'm trying to work out how I can do something better for next time.
There are lots of pop up gazebos in the £25-50 range. Parking one in front of patio doors like this will can keep a lot of heat out of the house.
Exterior shutters.
These used to be common many years ago in the UK, although they were mainly to keep heat in rather than keep the sun out.
Exterior roller shutters
These are used all over Europe. They are great for keeping heat IN during winter too, and good for security.
They can be manually operated or electrically operated. I would expect the manual ones to be a pretty easy DIY job to fit.
They are less expensive than I thought they would be, as this made-to-measure web-site shows. If you Google "Outdoor roller shutters" you'll find loads of styles and colours.
They are available in any size and colour, including big enough to cover patio doors.
Exterior fabric roller blinds
These are similar to internal roller blinds but they are much more robust and suited to outdoors.
They simply mount on two fixings at the top (which could be hooks for easy removal) and come in a wide range of sizes. I priced up a 1m x 1.5m size here and it came to around £100 which I thought pretty good value.
Sun sail shades
The are an inexpensive solution and come a wide range of sizes and colours. They are very durable. This one is only around £70 on Amazon. The objective is to try to tie it as close as you can to the window or doorway you want to shield from the sun.
Don't forget to consider where the sun is at different times of day to make sure it is wide enough to keep the sun out as the sun moves across the sky.
This site allows you to enter any dimensions you want to have a custom one cut for you.
Retractable awnings
These come in all sorts of styles.
This one is about the cheapest and simplest designs I can find from Wayfair at under £90. There are smaller ones also. This one shows it mounting under an overhang but with a little bit of DIY creativity it might be made to work in front of a regular window or patio doors.
It isn't shown in this photo but this blind winds up around a roller at the top when not in use.
Wind out awnings like this are pretty common in the UK. These fix permanently to the house. They tend to be over £200 but I found this one smaller one at around £170. Some of these can wind out a really long way, so actually provide pretty decent rain shelter in summer to sit underneath.
This design below is nice and simple and they start for a little over £100 It's called a "half cassette". They are much easier to fit than wind out awnings.
To stow it you just lift the two arms and the fabric rolls up into the casing mounted on the wall. I suspect if you wanted to, it would be possible to work out a way of only lowering it part way down if you didn't want it as low as shown in this photo.
Retractable roman (or wave) blind roof
This uses tensioned stainless steel wires between the house and (in this case) a simple wooden structure.
This UK company is a specialist, providing full kits cut to size (but not the frames). I priced up a 2m x 3m kit and it came to around £175. Another seller of this sort of blind here with lots of size options.
Alternative roman blind with frame
This is a pricier solution and is a complete kit with frame from Wayfair for £430. Clearly this is great for providing shade for sitting under as well as keeping direct sun out of the house.
Tinted or reflective plastic film applied to window glass
This is really easy and inexpensive to do. There are a whole range of plastic tinted and mirror finished films on the market. You just need a pair of scissors and water with a little washing up liquid in it to fit it. This very helpful Aussie guy shows you step by step in his Youtube video how to do it to get a very neat finish.
Window film will help if you use it on the inside but it is much more effective if you apply it on the outside. If you fit it on the outside, make sure you use a film that is specifically intended for outside use. Not all of them are.
This UK window film supplier has an online chooser guide to help you find the right one for you and the type of glazing you have. See here.
If you have double glazing with sealed double glazing units, window film is MUCH better for the windows if you install it on the outside.
Window film does reduce the amount of warmth coming through a window in winter though, which is something you might want to bear in mind. It will also reduce the amount of light coming through into the home.
Curtain pelmets
Yup, believe it or not these make a difference.
They make it harder for warm air circulate into a room, especially if you are keeping curtains closed to keep direct sun out.
This short video explains why, and also why pelmets are good at keeping heat IN in winter. There are numerous videos on Youtube on how to make a pelmet.
2) Ventilating, but in the right ways...at the right times
It is mightily tempting to open all the doors and windows all the time on a hot summer's day. However this usually the wrong thing to do if you want to avoid your home overheating.
To keep a home cool it is really important to prevent warm air entering when it is hot outside during the day. Ventilating during the hottest part of the day will make a house warmer, not cooler.
Ventilating only makes sense when it is cooler outside or at night.
So, ventilating at the right times in the right ways makes a huge difference.
Windows and doors
Keep doors and windows closed when it is warmer outside than inside. This is particularly important if you have hard surfaces outside like a patio. Hard surfaces create an island of heat around a home if they sit in the sun.
This is my patio. The patio heats up to over 45C and can stay very hot well into the evening. If I leave the patio doors and bedroom window open the heat billows in during the day and well into the evening.
I only open the window and doors late evening when BOTH the patio and the outside air has cooled down enough.
Avoid letting heat in from hot walls facing the sun
If you have a wall facing the sun, on a hot sunny day the wall underneath will get very warm. Unfortunately, opening the window is just likely to invite this heat in as it rises up, as shown in the image below. This will be particularly bad during the peak sunny part of the day.
It may actually be better to keep the window closed until a while after the sun has gone down and the wall has cooled down.
If in doubt, open the window and simply put your hand in the gap to see the air coming in is warmer or cooler than the air indoors.
Leaving the loft hatch open...but at the right times only
This is a well known trick. But, while it is tempting to think that leaving a loft hatch permanently open in hot weather will help, this is not the best approach.
Because hot air rises, leaving it open during the day, it will just suck up warm daytime heat into the house through gaps and draughts into the house. Every time you then open a window or door somewhere, hot air from outside will be sucked into the home making it warmer.
SO, only open the loft hatch when it is cooler outside than inside, typically during the evening and overnight. Close it first thing in the morning.
Cross ventilate if you can
If you are able to open windows on different sides of a home at night it will help cool air flow right through much better.
Leaving doors open a few of inches at night will help cross ventilation through a home when you are trying to encourage cooler air into the house. The wider the better.
A tip to avoid attracting mozzies into your bedroom at night
This was a great suggestion from Jan Anderson on Facebook:
When you go to bed turn your lights off for a bit before opening windows to avoid mozzies! If you open them and then watch TV or have lights on to read a book etc the mozzies are attracted to the light an will fly in and lurk around the light source and then bite you during the night so best to have a dark room before opening windows
3) Other indoor tricks
Curtain tricks at night
Make it easy for the cooler air to come in at night. If you are able to open windows overnight don't fully draw your curtains. Leave them drawn back a little like in this photo will help.
Wet towels or sheets
Hanging a wet towel or even sheet in front of a window at night will help cool a room if you can do it. This will be especially effective if it is in front of an open window. The wet fabric takes heat away from the air in the room as it dries.
Wet towels on an airer
This is a variation on the previous idea. A clothes horse allows you to have more wet towels and sheets helping you. This would help in any room but is best in a room where you can open a window open so that moist air doesn't build up in the room.
Keeping certain doors shut through the day
If you have rooms that you cannot prevent from getting sun on them during the day, it is usually best to shut those rooms off from the rest of the home.
Block the bottom of the door to prevent a warm draught creeping into the home.
Keeping conservatory heat out of the house
If you have a conservatory that gets hot in the sun, and their are doors that shut it off from the rest of the house, it is probably best to keep the doors from the conservatory into the house closed if you can.
Even if you open the outside doors to the conservatory, leaving the internal doors to the conservatory open will still send a lot of heat into the house.
USB powered fans
These are incredibly cheap to buy, and only cost around a penny to run for 6 hours. Some like the one shown here run for several hours on an internal battery.
They are ideal for personal cooling. For many people, just keeping a face cool can make a big difference to comfort, especially at night.
Mini 'portable cooler' - I wouldn't bother
These products are basically just a low power fan that blows air over water that is held in an internal tank to reduce temperature of the air. I've not tried one but doubt they will cool you any better than just a simple fan. So if you have a fan, just use that and save your money.
In particularly humid hot weather these will probably make you feel stickier or muggier than just a simple fan too.
Make yourself a DIY air conditioner - Definitely don't bother
This looks dead simple to do. I've seen online articles suggesting this. They suggest a small fan blowing air over ice, or ice blocks immediately in front of you.
I've tried this a few different ways. The best I got was around a 1C reduction in the temperature of the air reaching my face. The ice blocks only stay frozen for an hour or so too.
So, my recommendation is not to bother!
Use a fan to suck the warm air out of the room at night
If you can find a way of mounting a fan like the one shown below, this can be used at night to blow the heat out of the room.
Some modern homes, particularly ones with small windows overheat more easily than traditional homes. This sort of trick is going to be particularly useful if this is your situation.
This will not work well if you just do this alone. You have to leave the door to the room open, and one open a window somewhere else in the house to let cool air IN to replace the warm air you are blowing OUT. If you just perch a fan by a window and keep the bedroom door shut it will achieve very little.
If you sleep near a window, another variation on the above theme is to do the reverse of the above, to blow the air from a cool window directly at you as you sleep. It will work best again, if you leave the bedroom door open and open another window somewhere for the warm air to get out.
Using a typical desktop fan will cost around 12p to run for 10 hours. This assumes it is a 40 Watt motor running at maximum speed and a typical 30p/kWh energy tariff.
Ceiling fans
These are particularly brilliant in a bedroom at night. As well providing movement of air to cool you directly, they help get warm air out and cool air into a room if you have windows open.
They can normally be fitted exactly where a conventional central light fitting is fitted, so are usually very easy to install. They often have a central light and a remote control.
The larger they are and the more elegant the blade shape is, the quieter they are. I have this one at home and it is really quiet to others I have experienced.
The running costs of these are low. The most powerful one I can find costs a little under 2p an hour to run on full speed. Good ones start at around £75.
I find they are best use in "blow downwards" mode rather than "suck upwards" mode.
In general, they are much quieter than desk fans or other similar portable products.
Pedestal fans
These are obviously a great too and very cheap to run. I have seen some situations where they are pointed in some random direction in a room, or oscillating around a room. The reality is that unless they are pointing at YOU or SOMEONE, then you might as well turn them off.
Tower fan/heaters
These products are really designed to be heaters for cold weather but will operate in just fan mode. In my experience they are pretty useless in summer as they don't really push out enough puff to be useful.
4) Insulation
Lofts get REALLY warm in summer, so having the right amount of loft insulation is really useful at keeping the heat out of the house below.
The recommended depth of loft insulation is around a foot (300mm). Untidy or badly laid loft insulation will let heat through rooms below also. See my other article about loft insulation, and how it should and shouldn't look. Also, see my other short article showing you just how warm ceilings get if they don't have loft insulation.
Cavity wall insulation is generally likely to help keep a home cooler in summer also.
5) Minimise the amount of heat generated indoors
Kitchen appliances
All the following items generate heat, so the less you can use them, the less heat you will be generating indoors.
Dishwasher
Washing machine
Condensing and heat pump tumble dryers
Hoovers
Irons (especially steam irons)
Steam mops
Cooking is obviously a significant source of heat indoors. Ways to reduce this are:
Switch to salads or cold dishes, especially during the day
Cook meals that take less energy and time (especially avoid use of ovens)
Cook later in the evening when it is cooler and the windows are open
Reduce heat from lighting
Halogen, traditional, and even fluorescent bulbs or fluorescent tubes produce a lot of heat.
In most weather conditions we are not aware of it. But in hot weather it can really make a difference to heat building up in a home.
Either:
Minimise how much you use these sorts of bulbs in hot weather, or
Switch to LED alternatives. This will eliminate most of that heat and save you money on energy costs too.
Heat leaking into the home from a hot water tank
Hot water tanks and the plumbing around them give off quite a lot of heat when the tank is hot. This will be the case even if you have a well lagged modern tank.
Tips to reduce this heat are:
Only heat the tank when you know you need hot water. This will save you money anyway. Having a constantly hot water tank wastes between £60 and £100 a year if you heat your hot water using an electric immersion and save you between £15 and £25 a year if you heat your water of mains gas. (This assumes energy tariffs from Oct 2023)
Lag your tank if it isn't properly lagged
Lag ANY pipes around the tank that get warm, with the thickest insulation you think you can fit
6) Garden features that can make a difference
Green features, plants, and garden ponds close to a home all make a big difference. They either soak up the sun, or provide shade or both.
Garden ponds in particular are useful as they soak up a lot of heat and as the water evaporates they cool the air above them.
In contrast, hard landscaped areas around homes such as patios CAUSE heat problems in hot weather, particularly if they are south facing and soak up the sun all day long. The larger the patio, and the nearer a home it is, the more a problem it will be.
DIY patio cooler pond
I don't yet have a garden pond but I DO have a patio that gets very hot.
This idea below is for an "instant DIY" pond that might help you keep the patio cooler on hot days. It uses just a handful of bits of scrap wood and an piece of tarpaulin.
In just a few minutes, hey presto, I have a 2 inch deep pond!
Ok, it isn't pretty but it works well as a quick way of reducing the amount of paved area that gets hot. It also gives me some instant water cooling effect as the water around the pond will be cooled as the water evaporates.
If you are on a water meter the cost of doing this works out at around 13p in this example.
It obviously won't suit every household (especially if you have pets or toddlers!) but if the above idea appeals to you, you can make one of these any size you like. Thick polythene is an alternative to tarpaulin and both are readily available and cheap online or in builders merchants.
A smarter alternative
A paddling pool is a better looking way of hiding a hot patio near the house from the sun and give even more of an evaporative cooling effect if it is a decent size. They come in all shapes and sizes, including this monster at 10 feet diameter for only around £40 at Argos.
A note about air conditioning
This is obviously an expensive solution. Even portable air conditioners which are relatively cheap to buy, can be very costly to run, especially if not used in the right way.
I will do a separate article on air conditioning practicalities in the future. In the meantime the ideas in the article above should help many householders to make a big difference to their own situations without that expense.
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Thanks.
Mark Thompson
Get Energy Savvy - simple practical home energy efficiency information
We have plants that grow outside in the summer and shade the downstairs windows. Much cooler in the rooms with plants. We have some shrubs that grow up in the summer and we cut back in the winter and two wisteria plants that grow between the ground and first floor windows. These shade the windows from above. You can make a 5 degree difference with shading with plants between rooms with and without.
We went for the house sail option and found it works really well, wasn't too hard to set up, relatively cheap and easy to put up or take down as needed. It doesn't have to be fully tensioned either if it's only going to be up for a few days. Ours was tied to a small tree at one corner and into the ground using a stake for dog leads on the second (our garden is higher than the back door) then the other two attached to the house.