Choose Your Insulation

How you insulate your attic depends on whether you want a "cold" or "warm" roof space. A cold roof requires insulation at joist level to stop heat escaping through the unused roof space. A warm roof is insulated between and under the rafters of the roof itself. The recommended depth for insulation has been increased recently, so you may have to increase the depths of the joists or rafters if you want to create usable platforms of storage space.

Recycled insulation
Recycled insulation is a green and non-itch alternative to conventional blanket insulation. The techniques for laying this are the same, but non-itch insulation makes it a more comfortable process. Check the instructions on the product to ensure that you install it to the right depth requirement.

Blanket insulation
One of the most widely used forms of attic-insulation, blanket insulation is simple to work with — although you should always wear protective clothing, as it can be uncomfortable to handle. Before starting, ensure that you have measured the surface area of your attic accurately, and that you bear in mind the recommended depth requirements and order accordingly (manufacturers supply blanket insulation in many different depths, so you must remember to order to the correct depth as well as to the necessary surface area). Always consider the recycled and natural alternatives to conventional blanket insulation.

Insulation Tips 01:26

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Step 1

Lay the Blanket Insulation

Sweep away any debris from between the joists. Determine whether a vapor barrier is needed. If the drywall surface is silver-backed, you won't need an extra membrane — if not, it is advisable to install one.

Roll out the vapor barrier, cutting and laying lengths in between each pair of joists. Staple the barrier to the sides of the joists using a staple gun (Image 1). Cut holes in the barrier to accommodate any electrical hardware.

Do not unpack the insulation blanket until you are in the attic (Image 2). This will restrict the presence of insulation fibers to the work area.

Roll out the insulation blanket between the joists, taking care not to compress it. Tuck it in against the sides of the joists (Image 3).

Butt the lengths of insulation up against one another, making sure that there are no gaps between each of the lengths (Image 4).

Cut a hole in the insulation blanket to allow for electrical hardware. This is an important step to prevent the electrical components overheating.

Lift any cables or wires above the insulation to stop them overheating. Any heat they do give off will rise harmlessly into the cold roof.

Step 2



©2007 Dorling Kindersley Limited

2007 Dorling Kindersley Limited

Build Up the Layers

If required by regulations, run a second layer of insulation at right angles to the first to increase depth.

Step 3

Pipework and Storage Decking

The initial application of blanket insulation is only part of the job. Many attic spaces contain pipework that needs to be protected from freezing during winter months. Insulating warm water heating or supply pipes will also save energy.

Many people want to use part of their attic space for storage purposes. This often means you need to build up the joist height to accommodate building boards, which provide a base for storage. Alternatively, storage decking is a 2-in-1 application that combines extra insulation with a rigid board for storage. Check the board sizes beforehand to make sure that they will fit through your attic hatch.

Using Sheep's Wool
As with the recycled non-itch alternative shown opposite, sheep's wool is a more user-friendly alternative to conventional material. Build up depth by laying subsequent layers at right angles to the preceding layer. Check the instructional literature for depth requirements.

Step 4

Insulate the Pipes

Custom-made pipe insulation is the best option. It can be bought in different diameters, depending on need. Split the pipe insulation along its length to slip over the pipe (Image 1). Keep the join facing upward. Although pipe insulation is non-itch, you should wear gloves to protect yourself from the blanket insulation.

Take care that each length is tightly butt-joined to the next one, so that no part of the pipe is exposed.

Hold the pipe insulation in position by taping it, or by using proprietary clips as shown here. (Image 2)

At corners, it is still necessary to keep a tight join. Use a miter box and fine-toothed saw to make accurate 45-degree cuts.

Make sure that the mitered sections of insulation meet precisely to avoid any gaps.

Secure the insulation in position using tape or clips (Image 3). Note how the corner has been secured with an extra clip across the miter. For any valves or stop taps, wrap the pipe with insulation but leave the valve handle exposed.

Step 5

Lay the Storage Decking

Cut wedges of blanket to insulate the join of the roof rafters and floor joists, but with non-breathable felt leave a gap behind the wedge (Image 1).

Lay the first board across the joists (Image 2). Butt the edge of the board up against the rafters. Be sure not to close the gap behind the wedge of insulation.

To hold the deck in position, use one screw to fix each section to the joist below. Board ends should join on joists (Image 3).

Glue the board edges with woodworking adhesive, then fit the boards together using their tongue-and-groove system.

Step 6

Laying Loose-Fill Insulation

Loose-fill insulation can be used as a direct alernative to blanket insulation. Which one you choose is a question of personal preference. Bear in mind that bags of loose-fill insulation are easy to handle and are simpler to transport into the attic than their blanket insulation equivalent. Also, where an attic is awkwardly shaped in its joist design and layout — it may have lots of blocking and inaccessible voids between the joists, for example — loose-fill insulation can provide a more user-friendly, easily installed alternative to common blanket insulation. Be aware that there are conventional and recycled alternatives.

Using Recycled Paper
Arguably, the greenest option in loose-fill insulation is shredded recycled paper. This is sometimes used in wall insulation, but it can also be blown into attic spaces using a purpose-made applicator. Ensure that an adequate depth has been achieved to ensure thermally efficient results.

Step 7



©2007 Dorling Kindersley Limited

2007 Dorling Kindersley Limited

Laying Loose-Fill Insulation

First, sweep the voids to remove any debris. To stop the loose-fill leaking out under the eaves, create a barrier where the joists meet the rafters using a small section of blanket insulation, as shown here. If your roof is covered with non-breathable felt, leave a 2-in (50-mm) gap between the roof and the blanket to allow air to circulate freely.

Carefully pour loose-fill insulation into the areas between the joists. Pour in enough to reach the top of the joists. It is best to start at the eaves on one side of the roof and work across to the other.

Cut a section of plywood to the same width as the gap between the joists. Sweep the fill away from you, using the offcut to level it off. Move excess loose-fill to areas that need to be built up.

When leveled off, you should have an even coverage across the entire attic space. The blanket insulation at the eaves will prevent "creeping."

The depth of the loose-fill will determine any further requirements regarding regulations. If you have electrical hardware, such as a recessed light from the ceiling below, build a wooden frame around it to keep the loose-fill insulation out.

Should you require a deeper layer of loose-fill, you will need a platform from which to work, so that you can safely move across the attic space, as the insulation will obscure the joists from view. A further wedge of blanket insulation may be required at the eaves.

Step 8

Deep Filling

Deep filling can be achieved with loose-fill, but a more practical alternative is to use decking boards above the loose-fill, combining the two to achieve regulation depth, and creating a useable storage space in the attic. Always think about combining insulation — even if you don’t create a large storage area, the decking will provide safe access.

Step 9

Insulating Rafters and Walls

If you are converting the attic area into a living space, there are strict regulations on the amount of insulation required. Rafter depth is an issue, as there is often not enough depth to fit the required insulation — you may need to increase the depth of rafters by adding wood to their undersides. The drywall will probably need to be insulation-backed; framefoil varieties will need to be stapled across the rafters before applying drywall. An air gap is generally required for this, which is achieved by battening of the framefoil — always pay close attention to a manufacturer's specifications. Remember to consider green insulation materials, such as recycled batts.

Using Recycled Batts
Recycled batts are a good alternative to blanket insulation for rafters and walls. They are more eco-friendly, and are often easier to position (blanket insulation can sag before it is secured in place by drywall). Either type may need to be cut to fit the exact space between rafters or studs.

Step 10

Insulating Rafters

In many cases, a dwarf wall is used to partition the eaves area. This makes a more practical space for positioning furniture and fittings. The area behind the wall is treated as a cold insulated roof even though it is a relatively small space. Insulation is laid at joist level to reduce heat loss from the floors below.

Fix lengths of treated lumber along the inside edge of each rafter right up against the roof felt (Image 1). These furring strips maintain the ventilation gap when non-breathable felt is in place. Even when using breathable felt, it is still good practice to leave this ventilation gap.

If necessary, increase the depth of the fill space by fixing 2 x 2 in (50 x 50 mm) wooden battens along the roof rafters. Screw them into position (Image 2).

Infill the space by wedging the blanket between the furring strips but do not compress the insulation against the underside of the roof (Image 3).

Wedge the insulation in the gaps between the studs in the dwarf wall. A tight fit is required to ensure that the insulation doesn’t fall backward. Nails can be tapped in along the back edge of the studs to prevent this. Alternatively, use a rigid insulation board instead of blanket insulation.

Cover the rafters and the lower dwarf wall with vapor barrier, then staple the sheets to the joists.

Fix thermal drywall to the dwarf wall, butting the boards up against one another (Image 4).

Stagger the joins between subsequent boards to ensure you have complete coverage, and screw boards to the rafters as you go (Image 5).