Up to 30% of a home’s heat can disappear through the roof. But by tackling the easy task of insulating your loft, this heat loss can be reduced by up to 20%. The insulation itself should last for a good forty years, during which time it will pay for itself many times over. What’s more, you may also be eligible for a grant to pay for the materials. Whilst adding insulation is something that can be accomplished by a competent DIY-er, seeking professional help is recommended if you wish to board out your loft, or insulate a flat roof.
How Much Can I Save On My Roof?
By improving the insulation of your roof space, you can save cash and reduce your carbon footprint at the same time. According to the Energy Saving Trust (2015), assuming a 270mm layer of insulation, a typical three bedroom semi will save about £140 in fuel bills a year. This also amounts to a saving of 590Kg of carbon dioxide a year.
In the case of a four bedroom detached house, you should be able to save £240 in bills and 1000Kg of carbon dioxide a year.
For a three bedroom mid-terrace house, the savings are approximately £135 in bills and 560Kg carbon dioxide a year.
In each case, you should get back the cost of installation in about two years (even without a grant).
Insulating a pitched roof
If you have a pitched roof and you can get in to the loft space, the easiest option is to lay rolls of insulation between the joists. Simply unroll the insulation and cut the roll to length with a large pair of scissors. This will help stop heat escaping from the living area of your home, but will leave the loft uninsulated.
Insulation should be placed over any water pipes or water tanks (to prevent freezing in winter), but under any electrical cables. If the insulation will not go under the cables, you will have to leave that part of the loft uninsulated. Do not put insulation over cables.
Rolls of insulation can be purchased made from rock wool or glass wool (this is the only type of insulation for which you can claim a grant) and come in a variety of widths to match your joist spacing. The first layer is laid between the joists and the next layer is laid at right angles to the first.
It is recommended that glass wool is laid to a depth of 270mm and rock wool to a depth of 250mm.
Most joists are 100mm (4 inches) deep, so you will need 100mm rolls for the first layer, and then lay 200mm rolls at right angles to bring you up to the recommended depth.
If you already have some insulation installed, this can be left so you only need to add extra to bring you up to the minimum depth.
Don’t forget to insulate the loft hatch, and put strips of draught excluder round the edge of the hatch to prevent draughts.
What do I do if I want to use my loft for storage?
If the loft has been insulated to a depth of 270mm, you won’t be able to fit floor boards as the insulation will be over the joists. To avoid compromising on the depth of insulation, and on storage space, plastic loft flooring legs can be purchased to raise the height of the floor by 175mm. Floor boards can then be laid over these.
If you do plan to board out your loft, make a point of using a felt pen to mark out the routes of any pipes or cables as you lay the floor, then you will know which ones to lift if you need to do any maintenance. You may also wish to avoid using tongue and groove boards, because if you do need to take one up, you’ll end up taking half the floor.
Converting a Loft Into Another Room
If the loft area is being converted into part of the living space, then you will need to insulate the roof itself, rather than the loft floor.
There are a number of options here, depending on the size and shape of the loft space. For example, insulation boards can be fitted between the rafters. These in turn can be covered in plasterboard.
Other options include polystyrene slabs fitted between the rafters, or expanding spray foam which can be used in the more inaccessible spaces.
It is important to leave adequate ventilation beneath the roof tiles, or else a build-up of condensation could cause the rafters to rot. Missing or slipped tiles should be replaced before any work is carried out.
Whilst carrying out this work yourself is possible, bringing in a professional roofing contractor will ensure that any changes are safe, sound and up to building regulations. For more information on loft conversions, please visit our dedicated loft conversion page.
Insulating a flat roof
There are three types of flat roof insulation available, warm deck, cold deck or inverted roof.
Warm deck insulation is fitted above the main roof structure (the deck), but under the weatherproof layer. This can consist of a rigid layer of insulation board laid on top of the deck, with a new weatherproof layer on top. This is the method usually preferred.
Cold deck insulation is fitted below the roof deck, leaving a gap between the insulation and the deck for ventilation.
Inverted roof insulation is fitted above the weatherproof layer. This is generally finished with a layer of gravel. This method of insulation can prolong the life of the roof deck and weatherproof membrane by protecting against weather extremes and mechanical damage.
All new flat roofs must be insulated to comply with building regulations, so it’s advisable to seek the help of a roofing contractor at this time.
For more information on flat roofs, please visit our dedicated flat roof page.
If you’re looking to make changes to your roof to improve insulation and energy efficiency, please feel free to give us a call. Keay Roofing Services are Competent Roofer, NRFC and Which? Trusted Trader qualified.
You can contact us for any queries you may have about your roof on 01753 358267