It’s hot. It’s airless. Everything you do brings you out in a sweat. Children can’t sleep, and you’re tired. You even begin to dream of grey, drizzly mornings in November. Surely, it doesn’t have to be like this?
Here are our best ways to cool your house down, starting with the things you can do today – through to the renovation jobs you should look at doing for next summer’s unexpected heatwave.
1. Aid a good night's sleep with a cooling pad or pillow
It’s all very well being hot during the day, but most of us need a bedroom to be under 21˚C to have a comfortable night. Beds can become heat sinks pretty quickly, with your hot bodies releasing heat into the mattresses and pillows.
Your hypothalmus controls body temperature – so keeping your head cool is absolutely critical to comfort. There are several ways of doing this artifically at night – one of which are pillow- or mattress-cooling pads (basically, they're slightly more hi-tech versions of mother’s cold flannel).
- The JML Chillmax Cooling Pad goes on top of the pillow and can be refrigerated before bedtime
- You could also go for a temperature regulating pillow itself such as Simba’s Hybrid Pillow, which aims to ventilate and regulate temperature through OUTLAST® technology
- Simba’s Active Cooling Pillow contains an integrated cooling pad for the best of both.
2. Try a room fan
As we all know, fans don’t cool air down, but they do move air around – which can help with comfort on hot nights. Oscillating fans work best. The ProBreeze oscillating 40 inch tower fan is a good place to start, offering remote control, a seven-hour timer (perfect for getting children to sleep) and three speed settings. They provide a significant improvement in comfort on relatively modest noise outputs.
3. Invest in air conditioning
One step up from a room fan, portable air conditioning units give the means to reduce the temperature of a room by around 5˚C is hugely valuable in a heatwave – but it’s not a cheap option, both in terms of upfront cost and running costs.
One of the best we found was EcoAir’s Artica MK2 Portable Air Conditioning unit, which delivers 2.3kW of cooling capacity and aims to reduce temperatures down to a minimum of 16˚C. It takes moisture out of the air (so the internal tank needs draining quite a lot in humid conditions) and has Wi-Fi functionality for remote operation. It’s relatively quiet at a typical dB output of around 50 – about the same as a floor standing fan.
Bear in mind the not insignificant running costs of 0.9kWh – depending on your energy supplier that equates to around 13p an hour. But it will get a hot room over the worst of the heat and give you a good night’s sleep – and sometimes, that’s all that matters.
4. Keep the sun out
The sun provides valuable extra warmth for most of the year, but in a heatwave it can serve to provide extra heat to rooms particularly on the southern elevations of homes.
The simplest solution on bedrooms and converted lofts is to look at so-called thermal blinds, which tend to have an aluminium-lined honeycomb construction designed to reflect up to 85 per cent of the sun’s heat. Try the DuoShade from Blinds2Go – they have the added benefit of keeping the light out on those early summer sunrises.
5. Upgrade your windows
All those are great ways to deal with the symptoms of a hot house – but how do really solve the problem in the long term? One of the major problems with modern homes is that our desire for natural light and connection with our gardens has created a higher window to wall ratio – meaning our homes have bigger windows and smaller amounts of walling. That’s great for light, but not so good for insulation – meaning that warm air can more easily penetrate the house.
It’s all a question of U-values: so a standard newly built wall will have a U-value of 0.1-0.2 (the lower the better for stopping heat transfer); while a standard double glazed unit might have a U-value of 1.6. This means that your window is letting in 8-16 times more heat than your wall. When windows take up a lot of your wall space, that’s a big problem. So ultimately you’ll have to look at your window performance.
Low-e (emissivity) window films such as the Enerlogic from ARC Window Films or Purlfrost's HRF 40 Heat Rejection window film (pictured top) can be easily applied and act to reduce solar gain. Ultimately, however, you might need to look at triple glazed windows; they can give U-values of around 0.7, so consider replacements on southern-facing rooms (bear in mind you’ll lose positive heat from the sun in the winter).
6. Add an overhang
There is a way to enjoy the best of both when it comes to the sun – overhanging. We tend to need the sun most when it is lower in the sky in winter; in summer, the high sun can cause overheating in rooms. That’s where the design principle of solar shading comes in.
This can be achieved in one of two ways. Firstly, the continuation of a roof structure over the facade of the house so that the high summer sun doesn’t ever get on to the windows or doors is a great house design trick, and can suit traditional style homes (verandas being the best example – designed specifically for homes in warm climates to be cool inside) or modern designs (with flat roofs cantilevered out an extra metre or two).
It has the added benefit of creating some transition space between inside and out, allowing you to sit outside on a rainy day, for instance. The other solution is a brise soleil, which is a feature that can be applied vertically or horizontally to a house (above a window) to deflect solar glare. It’s a kind of louvred awning, but makes an architectural statement in its own right.
7. Get air moving
Warm air rises, so it’s important to ensure that the windows at the top of the house remain open where possible. This is a very simple way of explaining ventilation theory – in particular, passive stack ventilation. Essentially, you should use a combination of cross ventilation, the rising of warm air and the venturi effect (suction created by air passing over flues) to feed warm air up and out of the house. It takes some design consideration, but can help to get air moving through the stillest of houses.
8. Address the structure of your home
There are a load of things you can do to your house to keep it cooler, but they do involve significant structural alteration. Many owners of homes built to the PassivHaus standard reported maximum internal temperatures at the height of the recent 30˚C+ temperatures to be no higher than 24˚C. This is because PassivHaus homes enjoy super-insulated walls, roofs and floors; triple glazed windows and high levels of airtightness, which means no inward leakage (gaps around doors, for instance) of warm air into the house – as well as a sensible approach to solar shading.
Insulation, of course, acts to keep warm air out as well as keep it in – so the more you can add, the better. It’s particularly important in lofts, which get the full assault of the sun throughout the day, seem to trap all the warm air generated through the house and get punctured with rooflights to allow extra solar glare in.