Installing extra roof insulation

Insulation levels are specified by R-Value. R-Value is a measure of insulation's ability to resist heat flow.

The higher the R-Value, the better the thermal performance of the insulation. The recommended level for most attics is to insulate to R or about 10 to 14 inches, depending on insulation type. When adding additional insulation, you do not have to use the same type of insulation that currently exists in your attic. You can add loose fill on top of fiberglass batts or blankets, and vice-versa. If you use fiberglass over loose fill, make sure the fiberglass batt has no paper or foil backing; it needs to be "unfaced.

Insulating materials come rated by R-value. This refers to how well they resist the transfer of heat. R-value is determined by thickness, density, and material. Be aware that building codes determine the R-value of insulation required in each zone of your structure. Most people are familiar with the pink stuff that goes into your walls.

This insulation material comes in two styles: loose fill and batt. Loose fill, also called blown-in, can be packed into irregular spaces. This makes it good for attics with nonstandard joint spacing or low clearances. Bear in mind that this option requires a blowing machine, so you may find it advisable to enlist a professional. From there the job is pretty straightforward : hook up the hose to the machine and direct fill where you want it to go.

You may find it useful to cut and install barriers for this purpose and use your gloved hand as a guide. Conversely, batts come on a roll and cover the area like a blanket.

If using batts, unroll the fiberglass over the area. You want to cover the open ceiling plane and between any joists or studs. With a pair of pliers, cut wire mesh or sheet metal to size. This will become the barrier for the metal dome poking through the floor. Fit it around the recessed light and secure it with a staple gun. There are many safety considerations to make when tackling this kind of DIY. Be sure to put on a protective mask and safety glasses.

As you move around your attic, be sure to only step on the horizontal bars that support your ceiling. If you have the recommended level of loft insulation, you will no longer be able to store items by resting them on the joists.

Putting items on insulation weighs it down and reduces its effectiveness, and you won't be able to put boards onto the joists either. There are a couple of options you can consider though, although these wouldn't be included in any grant funding. You could put in some cross-joists so that any boarding will be able to accommodate the full mm of insulation.

This is probably a job for a professional joiner. There are some firms which specialise in providing a fully raised boarded loft, along with a loft ladder and suitable loft lighting, providing a very convenient storage space.

Alternatively, and probably more cheaply and easily, if you already have insulation in up to mm, you can add one of an increasing number of insulation products that have a polystyrene or a wooden layer on top of them. Those with a polystyrene top layer will not be as hard wearing as those with a wood finish, but polystyrene provides the best insulation performance.

In theory you won't be able to achieve the performance of mm of mineral or glass wool, but you will come close to it. If you want to match or exceed the performance of mm of a wool product, then you could consider a warm roof solution. For a warm roof solution you will need to install insulation in the plane of the roof pitch , that is, immediately below the sloping roof.

This will help to avoid your roof-space becoming excessively hot in summer or cold in winter, and will reduce heat losses from your roof. Assuming you don't have a room in the roof, and it is just a 'loft', then you should also implement all the 'cold-roof' insulation measures described above, including any raised boarding as appropriate. One important point to remember with a warm roof solution is the need for ventilation immediately below the roof tiles. This is to prevent any condensation build up, or water getting in through or around the tiles.

You need to create a space for air to flow parallel to the rafters and immediately under the tiles from one side of the roof the eaves to the apex and down to the other side, otherwise the roof structure may begin to rot.

The materials used to insulate under the roof include batts of mineral or glass wool insulation , held in place by 'battens' of wood attached to and across the rafters. Alternatively, polystyrene slabs , which are sometimes supplied foil-covered, can be fitted.

These usually have to be cut to size. Another option is EPS expanded polystyrene 'squeeze' products; these are manufactured with a 'concertina' shape and spring-like effect and can be pushed into place. There is an exception to the ventilation rule, and that's when applying polyurethane spray foams. These solutions, mainly professionally installed but also now available as a DIY measure, can generally only be applied where the underside of the tiles is bare and there is no roofing felt.

Spray foam may also provide additional physical strength where a roof is not in the best condition, by holding the structure together. However missing or slipped tiles must be attended to prior to applying the foam insulation. Warm deck or warm roof refers to a situation where the 'deck' of the roof, which is usually made of wood, is below the insulation. Cold deck or cold roof is where the insulation is below the roof deck and the associated joists.

Typically a gap will have to be left for ventilation - because this is a 'cold' area, condensation may form which can lead to rot. In both these cases the weather membrane, typically formed of roofing felt and bitumen, will be the topmost layer, protecting against rain. Inverted roof is where the insulation goes above the weather membrane, effectively protecting it from heat and cold which can shorten its life and that of the roof deck - it can even protect against wear and tear if there is access to the roof.

With an inverted roof, the top-most layer is generally gravel or similar. The lowest layer with any of these solutions - especially with the cold deck solution - is likely to be a vapour membrane, which is used to stop warm air rising and bringing moisture that will condense somewhere in the roof structure. The insulation of flat roofs nearly always requires professional assistance, and there are no associated energy-saving grants. A good time to insulate a roof is when it is being replaced, although in many cases a roof that is in good condition can be retro-fitted with insulation.

Dormer roofs are roofs that contain rooms and can present considerable challenges when it comes to insulation. Dormer bungalows, also known as Dutch bungalows, were built quite widely in the UK, particularly in the s and 70s. They have a conventional lower storey, along with an upper storey, with a smaller floor area, in the roof. Three storey town and detached houses have been built in the last few years, as builders attempt to build bigger houses in limited plots of land.

Their top storey is often 'in the roof', like an attic. However, due to modern building regulations, they are well insulated. But if you have an older property of this type, Victorian or Edwardian, many of which had attics, you'll need to install insulation; this may not be as straightforward as in a modern house.