Insulating your home is one of the best things you can do to reduce your energy bills.
Need-to-know information about home insulation
Insulating your home is one of the best things you can do to reduce your energy bills and it'll make your house warmer and more comfortable, while also reducing its impact on the environment in the process.
What does insulation do?
Insulation - and draught-proofing - protects your home against cold in winter and excess heat in summer, and can even reduce noise pollution (like the sound from a road or passing aircraft). What's more, some key insulation measures are 'low cost', in that they pay for themselves in less than five years.
Other than low energy lighting, these measures have the best returns of all energy efficiency investments. Furthermore, if you decide to sell or rent your home, the rating that your home receives on an Energy Performance Certificate (EPC) will be improved.
|Home insulation measure||Cost||% saving on fuel bill||Money saved per year||Payback period (years)|
|Cavity wall insulation (100% funded by a grant)||£0||19.3%||£135||0.0|
|Cavity wall insulation (partly funded by a grant)||£49||19.3%||£135||0.36|
|Cavity wall insulation||£350||19.3%||£135||2.6|
|Loft insulation (100% funded by a grant)||£0||25%||£175||0.0|
|Loft insulation (partly funded by a grant)||£49||25%||£175||0.28|
|Loft insulation (DIY)||£50 to £350||25%||£175||2.0|
|Adding extra loft insulation (DIY)||£179||3.6%||£25||7.2|
|Floor insulation (DIY)||£50||6%||£42||1.2|
|Internal solid wall insulation||£5,500 to £8,500||63.6%||£445||19|
*These are estimated figures based on insulating a gas-heated, semi-detached home with three bedrooms. The installed cost includes a subsidy of around £250 available from the major energy suppliers under the Carbon Emissions Reduction Target (CERT). Source Energy Saving Trust
What is the difference in insulation between a new build and an older house?
Although new homes are now built to very good insulation standards, historically homes in the UK were insulated to a very poor standard, especially when compared to other European nations. If your house was built over twenty years ago, it's very likely that there are opportunities to 'retro-fit' insulation and improve its energy efficiency.
By contrast, some modern eco-homes are super-insulated and air-tight to the extent that they no longer need a heating system - they rely on heat from sunlight through the windows, and produced by the occupants and by electrical equipment in the home, with occasional top-ups from individual electric heating devices.
How does the heat escape from my house and the cold get in?
There are five ways that heat can escape:
Conduction - that's heat moving through solids like metal or brick.
Radiation - this is the heat you directly feel when you stand near a heat source. It is in fact infra-red radiation, and just another form of 'electromagnetic radiation' like radio waves, visible light, ultra-violet and x-rays - which all travel at the speed of light. If you take infra-red photos of your house on a cold, still night you can help see where heat is being lost.
Convection - this is the natural tendency of warm air or water or other gases and liquids to rise, while cold air or water falls. This often results in circulation of air and is the main principle behind central heating radiators.
Air movement - draughts are a common form of heat loss, taking warm air from within the home and letting it out into the outside (and typically replacing it with cold air coming in). Another example is a wind blowing past a house, which will generally have a cooling effect on it. Water movement has the same effect, but there are no known UK examples of systems to recover heat from water before it is put into the drains.
Evaporation - not a process that we naturally associate with heat loss, but if it rains on a hot summer day, after the rain stops, some of it may evaporate from the roof and walls, and this will cool the home considerably.
How do these methods apply to heat loss in my home?
In practice a lot of heat loss from your home will include a number of paths, each involving a combination of these methods. For example, in a bedroom, warm air can convect to the ceiling, the warmth will then be conducted through the ceiling, radiated or convected through the loft to the pitched roof, conducted through the roof tiles and then radiated or convected into the atmosphere.
On another path, heat from a radiator may radiate through the windows, while on a third, warm air might also be carried in draughts through gaps in the window frame and around the skirting boards. A fourth path could involve heat going through the inner 'leaf' of the cavity wall, being convected or radiated across the un-insulated cavity, conducted through the outer 'leaf' and then radiated, convected and conducted out into the atmosphere.
Where do I need to insulate in my home to protect myself from heat loss?
On a cold day, heat can escape from your home in all directions - up, down and sideways. So you should think about insulating the whole 'envelope':
windows and doors.
Many people make the mistake of assuming that heat only goes up - but only one form of heat transfer (convection) primarily moves up. In reality heat travels in all directions.
If you adjoin another home, either through shared walls or through a floor that is in effect another household's ceiling, or vice versa, you are fortunate as you will not suffer from heat loss, assuming the other side is heated as well. However, you will still need to heat your home, as you won't have heat gain either. The general rule is that the bigger the temperature difference, the greater the flow of heat. So, the colder it is outside, the greater the heat loss from your home.
Can I completely eradicate heat loss?
You cannot completely eradicate heat loss through any one part of your home's envelope. Beware of assuming that just because heat loss through, say, your roof will account for 25% of your heat losses, that you will completely eradicate that loss and reduce your bills by 25%. You can save a substantial chunk of that, but there will still be some loss through that 'face' of your home.
How much heat is being lost from different parts of my home?
This depends on the type of house you live in, whether it's detached or semi-detached, or if it's a terrace property, and if so, if it is mid or end terrace. If you live in a flat, the losses will be different again, and will depend on whether your flat is in the middle, at the top or at ground floor level.
For a typical house the walls will lose most heat, around 30% and up to 40%. The roof will be next at around 25%, probably followed by windows and doors at around 20%, and the floor (of your lowest storey, at around 10%). Quite a large loss will occur because of draughts, excess ventilation and lack of air-tightness. Of course, draughts can also be attributed to floors, doors and windows, the walls or roof.
Do I need planning permission for insulation work?
In most cases, insulation work does not require planning permission from your local council. The exceptions may include external wall insulation and, in areas where there are conservation schemes, glazing.
Even if you don't need planning permission, building regulations could apply, so check with your local council's building control department.