As average temperatures rise, it’s becoming more common for people to use fans and air conditioning to keep cool in summer. However, there are other simpler, cheaper and more environmentally friendly strategies that can be used to maintain a comfortable temperature in the home.
Tips for keeping cool:
In the UK, the weather causes enough variability of the outside temperature for us to still need heating in winter even though climate change is causing a steady increase in global average temperatures. This warming is beginning to encourage some people to use air conditioning in their homes during the hottest part of the summer. The comfort zone for most people lies between 20 and 24°C depending on the humidity. When the outside temperature is more than a few degrees different from this range, the indoor temperature eventually begins to feel too hot or too cold.
Rather than using air conditioning or electric fans, there are other simpler, cheaper and more environmentally friendly strategies that can be used to maintain a comfortable temperature in the home.
The main ways to keep cool indoors in summer are to exclude the low sun, ensure that hot air is kept out and ensure there is a gentle circulation of air to promote evaporation and cooling of the skin. Insulating your loft and walls will help to keep your home cool in summer, as well as warm in winter. Further information and advice on ventilation and air quality in particular are available free from the Environment Centre in Southampton (02380 336172).
From the environmental point of view it is well worth giving the ideas presented below a try before installing an air-conditioner. An air-conditioning unit will come with its own embodied energy anyway, involving greenhouse gas emissions from its manufacture and transport, and may contain gases which, if they escape, damage the ozone layer.
If you live in the country, away from mains gas, and feel you need air conditioning, (in practice air-cooling), investigate reversible air or ground source heat pumps. These heat in winter and cool in summer. The Centre for Alternative Energy at Machynlleth low energy house had one powered by a wind generator. They provide good advice on heat pumps and much else at http://www.cat.org.uk.
If you have already installed air-conditioning or electric fans, but can avoid using them to maintain your home within the comfort zone, then you will save on electricity or gas (gas-fired air-conditioning units are available which cause less emissions than electrical systems and are cheaper to run) and therefore reduce your carbon dioxide emissions.
Avoiding the use of air conditioning and electric fans will obviously reduce your energy bills, as well as saving on installation and maintenance costs. Most of the methods that insulate homes and otherwise improve the thermal environment within the home cost less than £500. There may also be help through the Green Deal at www.gov.uk/green-deal-energy-saving-measures/overview..
Keeping cool is better for one’s health. It helps one to be more active during the day and to sleep better at night.
1. Simple ways to keep cool
Windows help to light up the interior of homes but at the same time they can let in low sunlight in the early morning or late afternoon which can cause a room to become uncomfortably hot. Not only does the window let in direct sunlight, but it will also trap heat that has been re-radiated from indoor floors and walls (the so-called greenhouse effect). Double glazing does little to reduce this effect.
In the day time, the simplest way to keep cool is to draw all the curtains and blinds on the sunny side of the home. It may even be worth closing internal doors to sunny rooms to exclude hotter air from the rest of the building. Close off any sun rooms, conservatories etc. from the main part of the house, otherwise they will let in hot air.
To encourage a flow of air through the home, open windows and/or external doors on opposite shady sides of the home and open internal doors to non-sunny rooms. Using outside openings at the highest and lowest points of the home will work best.
Avoid using electrical appliances that produce heat or increase the humidity other than a cooker.
Remember that as the sun moves round during the day you will need to close and open windows and blinds to get the maximum benefit. If you are out all day then it is best to keep all relevant curtains, blinds and internal doors closed.
At night, always use LED low-energy light bulbs: they give out less than one third of the heat of an incandescent lamp with the same brightness. Reducing the number of lights, and other electrical appliances, left on will also help to keep the air cool.
When sleeping, leave the bedroom window open, and other windows if safe to do so, to encourage a flow of air. If the bedroom is still too hot, move to another room on the north side of the house, which should be cooler, or to the ground floor (rooms under roof spaces tend to be warmer at night partly because hot air rises). In the worst case, sleep in a conservatory or out of doors, but be prepared to be too cold in the early morning!
The above suggestions involve no expense, only the adoption of certain habits to make your home more comfortable in hot weather.
2. Insulating the loft
Probably we have all experienced sleeping in a hot bedroom immediately under a roof space on a hot summer night. Just as, in winter, loft insulation helps to prevent heat loss from bedrooms so, in summer, loft insulation will also help to keep bedrooms cool. Indeed, loft insulation is the single most cost-effective, low risk, measure that can be used to keep homes cool.
Under pitched or sloping roofs, insulation is normally added between and over the horizontal joists across the floor of the loft. It is recommended that this insulation is 600 mm (24 inches) thick. A variety of materials can be used, in quilt or loose form, ranging from renewable cellulose and sheep’s wool to more energy-intensive mineral wool. The insulation material should not be pushed up against the sloping rafters: a gap of 25 mm (1 inch) must be left to allow air to circulate. If there is a cold water tank in the roof, insulation should be lapped up against it, and not placed underneath, to allow heat to rise under the tank and prevent the water freezing in winter.
If the loft space has been converted into a living space, then insulation has to be applied between the sloping rafters on the underside of the roof. Suitable materials include mineral wool and polystyrene in various forms including spray foams, rolls and rigid slabs. Where space is limited, you can use multifoil insulation. In most cases a 50 mm (2 inch) ventilated airspace must be provided between the upper surface of the insulation and the tiling underlay.
Flat roofs can also be insulated but it is most cost effective to add or replace the insulation in a flat roof when the roof covering needs renewing.
Find a registered installer through the National Insulation Association (NIA) .
You will save on emissions in summer only if insulating your loft prevents you from using air-conditioning or fans. However, you should also need less heating in winter which will reduce your emissions further.
The cost will depend on how much loft insulation you already have and its condition. If you install the insulation yourself it costs around £4.50 per square metre to lay 250 mm thick glass fibre and around £20 per square metre to use wool.
Grants are available to cover the total cost of insulation (including fitting) for those aged 70 or over, or in receipt of certain benefits, and discounts may be available to others.
Loft insulation will also help to keep your house warm in winter.
3. Insulating the walls
Insulating your external walls will keep out much of the sun’s heat.
If you live in a house built since the 1920s it probably has “cavity walls”, i.e. an air cavity at least 50 mm (2 inches) wide between the inner and outer skins of the building. This cavity can be filled with a solid foam that traps air in tiny bubbles and therefore insulates the wall. Cavity wall insulation is the second most cost-effective, low risk, measure (after loft insulation) that can be used to keep homes cool.
Cavity wall insulation can be installed without major disruption to a building’s occupants, usually in a single day, and it needs no maintenance. The installation has to be done by a specialist company and involves drilling a series of one-inch diameter holes between the bricks in the outer wall and then injecting wool fibre through them under pressure.
If your house was built before about 1923 and has a solid brick wall (you can tell from the pattern of the external brickwork: in a solid wall the bricks are laid alternately end-on and sideways-on ), insulation can be applied either from the inside (making the rooms slightly smaller) or the outside. These are more complex undertakings and you should seek professional advice before deciding to go down this route. Find out more here.
You will save on emissions in summer only if insulating the exterior walls prevents you from using air-conditioning or fans. However, you should also need less heating in winter which will reduce your emissions further.
It costs around £1000 to install cavity-wall insulation but it can pay for itself within 5 years.
Grants are available to cover the total cost of insulation for those aged 70 or over, or in receipt of certain benefits, and discounts are available to others. You may be able to obtain a Renewable Heat Initiative (RHI) grant for electricity used by an approved heat pump installation.
Insulating external walls will also help to keep your house warm in winter.
4. Reducing heating from the sun through glass (windows and conservatories)
Windows help to light up the interior of homes, but at the same time they can let in low sunlight in the early morning or late afternoon which can cause a room to become uncomfortably hot. Not only does the window let in direct sunlight, but it will also trap heat that has been re-radiated from indoor floors and walls (the so-called greenhouse effect). Double glazing does little to reduce this effect.
You could fit an internal light-coloured roller blind or vertical or horizontal slatted blinds which can be adjusted as the sun moves. Some opaque blinds made of metallised low-emissivity (“low-e”) material are specially designed to reject 60% of the sun’s heat. Conservatories can be fitted with special roofing panels that are said to reject 80% of the sun’s heat. You can also use low-e films which you can apply to the inner surface of the window yourself and that can reject up to 69% of unwanted solar energy. Low-e films block most of the sun’s heat while letting through most visible light. External blinds are more effective because they largely prevent heat passing through the window.
The cheapest options are fitting roller blinds and applying low-e film to your glazing. The savings involved are hard to estimate because every home is different.
The conservatory roofing panels mentioned above will also help to reduce heat loss through the conservatory roof in winter.
5. Providing external shade
Another approach to keeping cool is to shade the exterior of the home.
For example, if you can plant deciduous trees or shrubs to the east and west of the home, which will throw shade on the windows and walls when the summer sun is relatively low but still strong enough to warm up the home, then this will reduce solar heating. On the other hand, when the leaves fall off in winter you will still get plenty of light.
It is not a good idea to plant trees and shrubs close to the south side of your home because they may block off the low winter sun which will help to heat the home. Windows on the south side can be shaded by installing exterior awnings, canopies or louvres (some times called ‘brise soleil’, literally meaning ‘break sun’ in French) which are set away from the wall and prevent the low sun from heating the interior. Further information can be obtained from the British Blind & Shutter Association.
Planting trees and shrubs is an environmentally sound option which will help to absorb carbon dioxide from the atmosphere.
Planting trees and shrubs is relatively inexpensive. Installing awnings, canopies or brise soleil will be much more expensive (c £3,000 for a motorized 3 metre blind). However, it is difficult to estimate costs here because almost every requirement will differ.
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The information on this page is provided in good faith and reflects our understanding of the underlying science and technology at the time of writing, but we cannot guarantee that it is wholly accurate. All figures for costs, savings and other matters are estimates: the actual figures will depend on your particular circumstances and may differ (perhaps significantly) from those shown. Although we have included links to various organisations, we are not recommending these organisations: it is your responsibility to check that they are suitable for your needs. Nonetheless, if you experience difficulties with any of the links or organisations, or believe that any of the information presented here is inaccurate, please let us know and we will update this page if we consider it necessary.