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Home insulation make your home energy efficient

Home insulation

Insulating your home doesn't just make it more energy efficient, it is also one of the best things you can do to reduce your energy bills (next to switching to a cheaper energy deal, of course).

Insulating your home will 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.

How does the heat escape from my house and the cold get in?

There are five ways that heat can escape:

  1. Conduction - that's heat moving through solids like metal or brick.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

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':

  • The roof

  • The walls

  • The floor

  • The 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.

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.

What types of insulation are there?

Good insulation types

Good insulators include many products that typically have a structure similar to wool. In effect a good insulator will trap tiny pockets of air within a material which itself is also a good insulator. These include the very common mineral and glass wools, which come on rolls in blanket form, or in a somewhat denser form as batts or slabs.

Sheep's wool is of course a great insulator, as are other natural fabrics like hemp and cotton - so curtains are good insulation products. Some mineral and glass wool style products are 'higher density' and therefore have greater insulation effect, typically about 25% greater.

Most wood and wood based products, for example, MDF, plywood, and hardboard, are also fairly good insulators - so wooden doors and wooden loft boards help keep warmth in the home.

Not surprisingly, paper is another a good insulator, including recycled paper, and cellulose from other sources such as crop wastes. Although flammable in its untreated form, it is treated to make it fire resistant for use as insulation. This is supplied in sealed sacks, but once opened is in loose form, which makes it suitable for installing in circumstances where blankets or batts won't fit.

Polystyrene and similar products are generally good insulators. Polystyrene is sometimes referred to as EPS (expanded or extruded polystyrene slab) form. These products are also usually fire resistant, and much denser and heavier than the sort of polystyrene that is used for packaging. EPS is typically 50% more effective, for the same depth, as standard mineral or glass wool products.

Closely related are spray foam solutions, which are typically polyurethane based. The foam forms on the mixing of two chemicals and it hardens, trapping tiny pockets of air. Because the foam fills crevices and gaps, it can also eliminate draughts and provide strengthening to existing building structures, for example roof tiles. Other foam solutions include adhesive strips for insulating around windows, doors, or loft hatches.

Some 'insulators' work by stopping the flow of air (draughts) through cracks and gaps, such as sealants (mastics). One of the cheapest sealants is papier-mache, which you can make yourself from torn-up paper and wallpaper glue.

Another method of insulation is reflection. There are now multi-foil products, which are generally a sandwich of metal foils and plastic style insulators. These can be used to reflect radiated heat (infra red) and are designed to insulate where there isn't the space for wool, batt and EPS type products. Some polystyrene and other products are also coated with foils.

Good insulation material doesn't just slow the process of heat loss, depending on its specific use, there are other properties that are important too, such as physical strength, fire resistance, resistance to mould, and non-toxicity; cost is another important consideration too.

Poor insulation types

Unfortunately, many materials with physical strength and which are therefore used in building construction, including metals (such as copper, steel, and aluminium), stone, brick, tiles, and concrete, are bad insulators . However, some more modern versions of these materials have been designed to have construction strength but lower heat transmission than in the past, for example, modern breeze blocks.

Water is also a bad insulator, which means that anything that soaks up moisture will usually conduct heat away quite quickly. Moving air also takes heat away quickly even though air that is prevented from moving, generally when trapped in tiny pockets, makes a good insulator.

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