DIY Insulation Tips

Winter is everyone’s nightmare, with raging draughts and uncontrollable fuel bills taking the leading parts. But there’s a lot you can do to make your home warmer — and reduce your heating bills as well.

If your house is cold in winter, or you find your fuel bills are too high, then thermal insulation may be the answer. However, it’s a fairly complex subject, and before you start worrying over much about how you do it, it’s important to know a little about why and where you should insulate.

Why should I insulate at all?

So long as the temperature outside your house is lower than the inside, your house will be losing heat — precious heat that you have paid for. You can’t stop this heat loss entirely, but you can slow it down by lining your house — or parts of it — with insulation materials. The slower the heat is lost from your house, the lower your fuel bills will be.

diy insulation

The most common way of insulating a space is to lay rolls of glass fibre. The material comes in suitable widths to fit in between the joist spacing

Should I insulate the roof space?

If you have no insulation at all in your loft or roof space, then you should certainly put some in — a lot of heat is lost through the roof, yet it’s one of the easiest areas to insulate. In the UK, you can get Government grants covering much of the cost of roof insulation, if there is none to start with.

For most people the best choice of material to use is glass fibre, or mineral fibre blanket, which is laid between the joists forming the ceiling of the room below the loft space. The material comes in rolls of a width that suits the normal joist spacing, and it is a relatively simple matter to unroll them directly into place in the loft. For safety, fix up a light in the loft and stand on a stout board laid across two or three joists — not on the joists them-selves, and certainly not on the ceiling which would not bear your weight.

Do I really lose much heat through my walls?

Yes, you do — perhaps as much as through a totally uninsulated roof. The problem is that insulating walls can be a very expensive job, so it is not nearly as worthwhile in terms of saving money as insulating the roof.

For houses with brick or blockwork external cavity walls, the simplest method is to fill the cavity with an insulation material.

This is a job best left to the professionals.

An alternative method, which can be used with almost any house construction, is to line either the inside or the outside surface of the exterior walls with insulation. You can line walls internally with panels of polystyrene bonded to plasterboard — for example, Gyproc thermal board. This can be fixed either with adhesive or by nailing. Or you can use the interlocking Epsicon polystyrene panel system. Another method is to nail battens to the wall, fill between with rolls of glass or mineral fibre loft insulation material, then nail plaster-board over the lot.

External insulation is very expensive, mainly because the materials have to be weatherproof. It is usually done by professionals, and is really not worth considering unless the house needs major repairs to the external walls anyway.


heat loss from a house

Shown above are the main trouble spots where you will lose heat from your home. Up to 20 per cent of your heating can be lost through the roof space — insulation can save as much as 16 per cent. There are a variety of methods you can use. The most popular is to lay insulation material —glass or mineral fibre—in between the joists over the top ceiling. Don ‘t insulate directly under the storage cistern as the heat that rises through the ceiling helps to prevent the water from freezing. Outside walls are responsible for 25 per cent heat loss. Insulating foam can be pumped through holes drilled into the mortar joints of cavity walls. If you have solid walls these can be insulated with panels of suitable materials fixed to

the inside face. FIot water cylinders should be lagged — quilted jackets are sold for this purpose. Windows and doors account for another 20 per cent heat loss. Windows can be double glazed; doors and letterboxes can be draughtproofed.

Floors don’t lose heat all that fast but can be insulated.

Suspended floors are easier — glass or mineral fibre is tacked to the joists. Solid floors can be insulated with polystyrene slabs which are then covered with flooring grade chipboard.

What about windows and doors?

Windows and doors are poor insulators, and lose heat rapidly — mainly because they are so thin. However, external doors do not form a large part of the house, so there’s no need to worry too much about insulating them.

Windows, on the other hand, can be re-sponsible for up to 20 per cent of the heat loss from a house. The usual method of insulating these is with double glazing, and there are many systems available for either do it your-self or professional installation — many of them, however, are expensive. A cheaper, and perhaps more attractive solution, is to hang heavy lined curtains at the windows. Provided you are conscientious about drawing these every night they are almost as effective as double glazing.

Shutters are another effective solution to insulating windows, but can be very expensive — and like curtains again, you have to remember to close them.

Is it necessary to insulate floors?

Uninsulated ground floors do not lose heat very fast but they can still be insulated and, because of the large area they cover, this can save significant amounts of heat.

Suspended floors are the easiest to insulate if you can get at the undersides. Simply tack glass or mineral fibre blanket to the joists, using garden netting to hold the lot in place.

Solid floors are more difficult. The usual answer is to lay slabs of polystyrene over the existing floor, and then cover the lot with sheets of flooring grade chipboard (you can get Epsicon flooring panels with the chip-board already bonded to the polystyrene).

Are there any other ways heat escapes?

Yes there are. As well as losing heat by conduction through the fabric of the house (walls, roof and so on) you lose it also by ventilation — the warm air in a house is continually being replaced with cold air from outside, which then has to be heated.

To reduce this heat loss, you have to slow down the rate at which warm air escapes from the house, by blocking off gaps — a process called draughtproofing or weather-stripping. Check all the house for gaps. As well as the obvious ones between the opening parts of windows and doors and their frames, you will probably also find gaps between window and door frames and walls; around loft hatches and where pipes and cables run into the loft; in ground floor floorboards, and round the skirting board. Letter boxes are also likely to be draughty, and so are open fireplaces.

There are many types of draught proofing equipment. For gaps between opening parts of windows and doors, use some form of flexible strip; for many other gaps, a proprietary filler or mastic is best.

Can I save on heating hot water?

If your hot water is heated in a hot water storage cylinder, then you must make sure this is properly insulated. If the cylinder is bare, then insulate immediately: if you already have some insulation, but less than about 75mm, its a good idea to top it up.

The usual insulation for the traditional British hot water cylinder is a special lagging jacket. Alternatively, you can build a box around the cylinder with plywood or some-thing similar, and fill the space between this and the cylinder with some form of loose-fill insulation — but this is a dearer method.

Cold water pipes that pass through insulated lofts, or under insulated ground floors must be insulated — otherwise they may freeze and burst in cold weather. It is probably also worth insulating hot water pipes that run through these areas, to save on heat loss. It is rarely worth insulating pipes that run through the house itself, though.

You can insulate pipes either with pipe wrap (long strips of glass fibre insulation that you spiral round the pipe) or foam plastic tube with a split along one side that you simply slip over the pipe. Pipe wrap is cheaper, but probably more fiddly to fit.

Water cisterns in the loft must also be insulated to prevent their contents freezing —cover the sides and top with blanket insulation. But don’t insulate underneath — this is difficult anyway and the heat rising from below is useful because it stops the water getting too cold.

What is the most important area to insulate?

The purpose of insulating is to save fuel and cut your heating bills — or make you warmer without spending any more money on heating bills. So there is rarely any point in insulating unless the savings you make on your bills quickly repay the cost of the insulation.

Unfortunately, it is not too easy to predict how much you will save by any particular piece of insulation; it depends on your house construction, the amount you heat, and what fuels you use.

In general, though, the priority for people living in the UK should be:

  • lag your hot water cylinder, or increase the insulation on it, draughtproof thoroughly,
  • put in some loft insulation if you have none already — you should be able to get a Govern-ment grant to cover most of the cost, consider cavity wall insulation if you can use a cheap form of material.

The following things will be much less worth while doing in financial terms, unless, perhaps, you heat the whole of your house to a very high temperature all day, and use one of the more expensive fuels:

  • increasing the amount of loft insulation, if you have some already,
  • installing floor insulation,
  • installing interior wall insulation,
  • fitting double glazing, unless it is of the cheapest kind — using, for instance, plastic film rather than glass.

Are there any problems with insulation?

Unfortunately, insulating your house can give rise to many problems. Perhaps the most common is condensation. Particularly if you draughtproof too well, there may not be enough ventilation to get rid of steam and moisture from cooking, bathing, heating appliances, and just living and breathing. The answer in most cases is to fit a powerful extractor fan in the kitchen and bathroom. And not to use mobile gas heaters and paraffin stoves that do not have a flue. Another safety point you should remember is not to use an extractor fan if there is a conventional-flued boiler in the room.

Heating appliances (except electric ones, and balanced-flue heaters) need a flow of air to burn properly. If you over-do draught-proofing, they may not get enough air — the result is a build-up of toxic or explosive gases that could kill you.

After insulating the loft, there is a greater chance of condensation forming on the roof timbers, which could give rise to rot. To prevent this, you should ensure the loft is well ventilated. Drill plenty of holes along the length of the soffit, and on the sides of the roof. When laying the insulation, don’t tuck it under the eaves, but makes sure there’s a gap between the roof and the insulation material.

If you insulate walls by fixing timber battens to them, make sure that these are pressure-impregnated with preservative.

Cavity wall insulation can give rise to damp on the inside of walls if the material has been installed incorrectly. In the UK, you should have no problems if you use a firm that has an Agreement certificate, or who holds BSI registration.

The cheapest and most widely used cavity wall insulant is UF foam.

This gives off a gas for a week or so after filling, which some people may find irritating to breathe. But so long as UF foam is used only in traditional UK-type brick or block cavity walls, then there should be no long-term problem.

The problems of solid wall or block insula-tion are mainly ones of installation. The material can thicken walls and floors by up to 100mm or more — so doors and architraves will have to be moved and shortened, and skirting boards and possibly electric sockets repositioned. This can involve a lot of work.

Some double glazing makes it more difficult to open your windows.

You must make sure that this doesn’t reduce your chances of escape in case of fire.

Is my newly-built house adequately insulated already? The newest of new houses are very much better insulated than those built only a few years ago. In many cases, there will be very little extra that is worth doing. But it’s a good idea to check that the draughturoofing is well done — check especially areas like the loft hatch cover, cracks in upstairs ceilings, letter boxes and so on.

Don’t worry if your cavity walls are not filled — the builder might have used highly-insulating blockwork to give an effect which will be nearly as good.

If you are in the process of having a house built, then it would be worth checking what levels of insulation are to be adopted, and to see whether it would be worth increasing them — it is easy, for example, to incorporate insulation in the floor during building.

Are there any rules and regulations governing insulation? If you are living in an older house, there is nothing compelling you to add any insulation to what (if anything) is already there.

Newly-built houses have to comply with the current building regulations, which lay down insulation levels for lofts and walls and so on. These are minimum levels and as such are uprated from time to time.

Leave a Comment