A quarter of all the heat loss in a home occurs through an un-insulated roof. Adding insulation into your loft is a very simple but effective way to reduce heat loss and save you money, and you can even get it installed free through the HHCRO Scheme. Even if you have loft insulation already installed, you may benefit from topping it up so that it reaches the recommended 270mm thickness.
How loft insulation reduces heat loss
Loft insulation works by reducing the amount of heat lost from your roof – reducing the amount of fuel you need to burn for heating and saving you money.
When your home is heated, a lot of that heat escapes through your roof, both through conduction and convection. laying loft insulation in your loft reduces the amount of heat that passes through your ceilings and reaches your loft space to escapes through your roof – it traps the heat inside the rooms below the loft, meaning that the air you heat stays in your home for longer. This means that you have to heat your home less to achieve the same temperature in your rooms, saving energy and money. The thicker your loft insulation is, the more effective it will be at stopping the heat from leaving your house – an insulation depth of 270mm is recommended.
Lofts with easy access can be insulated using layers of felt-like insulation material, usually mineral wool, that can be bought from your nearest DIY store.
If your loft is harder to access, you’ll need to install loose insulation material that is blown into your loft by an installer.
If you have access to your loft it is possible to install the insulation yourself, although it is often just as cost effective to get an installer to fit it for you, particularly if you are not confident about doing it.
If you are fitting yourself:
- Don’t squash down the insulation material. This makes insulation less effective.
- Make sure you don’t block any air vents, which are there to help prevent condensation.
- Keep all electric wires, cables and light fittings visible to avoid overheating.
- Always wear a protective mask and gloves when working with mineral wool insulation.
Exactly how you install your loft insulation depends on the features of your loft and how you are going to use it:
No storage or other use and the joists are regularly spaced: You can lay a layer of rolled insulation material, available from a DIY store, between the joists and a second layer over the joists. This will usually be mineral wool.
No storage or other use and the joists are irregularly spaced: You can pour loose insulation, available in granule form from a DIY store, between the joists. This can be mineral wool, paper (cellulose), vermiculite or cork.
No storage or other use and access is difficult: You can use blown insulation, which is loose, fire retardant insulation material – this should be done by a professional installer. This is usually either shredded paper (cellulose) or loose mineral wool fibre.
Storage or living space: You can either raise the joists so that you can fit enough layered (mineral wool) insulation between them, or you can fit layered insulation between your unaltered joists and add insulation boards over the joists. Some flooring material comes with insulation board already attached.
Alternatively, you could fit insulation boards on the underside of your roof – just cut them to size and fit them between the rafters. You will need to cover these pieces with plasterboard, and then fit more insulation covered plasterboard on top of the rafters.
Alternatives to mineral wool
If you’re short of space, you can fit rigid insulating foam instead, which has twice the insulating power of mineral wool, meaning you need half the thickness.
If you’d like a natural alternative to mineral wool, you can use sheep’s wool, hemp or cellulose (paper). It is safer to install than mineral wool, but is significantly more expensive and only equal to mineral wool in terms of insulating properties.
Loft insulation may cause other issues to worsen:
Loft insulation may make any damp problems worse, as it will make your loft colder. Try to solve any condensation issues before fitting insulation.
Similarly, a colder loft will make your pipes colder, so it is a good idea to to insulate these too to prevent freezing. Cold draughts may blow into your house from your loft hatch, so it’s a good idea to get an insulated loft hatch and draught proof the frame using adhesive draught proofing strips available from your local DIY store.
Costs and Maintenance
The cost will vary depending on whether you fit the insulation yourself or get a professional to do it. The Energy Saving Trust estimates that the cost for doing it yourself varies from £50 to £350 compared with £100 to £350 if you have it fitted. The actual cost will vary in these ranges depending on whether you’re getting full insulation fitted or a top up.
See how to fit loft insulation yourself on our how to fit loft insualtion page. If you are looking do more insulation and draught proofing work yourself we recommend you look at a DIY website like DIY Doctor who have a whole section dedicated to insulating and draught proofing projects.
The HHCRO scheme offers grants that fully fund loft insulation installations. The scheme available to all homeowners, but has a focus on helping poorer households, and is funded by the energy suppliers. You can see if you’re eligible for free insulation through the scheme and sign up by visiting our HHCRO Free Insulation page. If you are not eligible for the scheme, we are happy to provide you with competitive quotes for the work – you can request a quote here.
When loft insulation is fitted well, there is no maintenance, and the insulation should remain effective for at least 40 years, delivering you real long term savings!
How much money loft insulation will save you depends on whether you are insulating from scratch or just adding to existing insulation. By insulating from scratch you can save in the region of £175 per year, and top ups will save you around £25 a year, giving a pay back of between 2 and 6 years,
- How do I know if I've got cavity walls or solid walls?
- Most cavity walls are identified by two factors. They are about 10½ to 12 inches (270mm - 300mm) thick overall (You can measure this at a door opening) and all the bricks visible on the outside of the wall are all 9 inches (225mm) long (except at corners and openings) (i.e. are mounted lengthways, with 'headers' or the ends of the brick only visible at corners and openings). Solid walls have repeat patterns of 4 inch (100mm) wide bricks as well as 9 inches (225mm) long bricks over the main area of the wall. The walls are usually a little over 9 inches (225mm) thick, although in larger properties the walls can be 13½ inches (330mm) thick.
- I have lots of rubbish in my loft. Do I need to clear it out or will the installer do this for me?
- Yes, you will need to clear the roof of any rubbish or stored objects before the insulation is installed.
- How long does it take professionals to install loft insulation?
- It takes professional installers about 2 hours to install loft insulation in an average sized loft.
- Is it true that everyone in the UK is entitled to subsidised insulation?
- Yes, everyone is entitled to a subsidy and some people can even have free installation. Why? Because the UK Government is obligated to reduce greenhouse gas emissions by international environmental agreements. One of the easiest ways to achieve a large reduction in greenhouse gas emissions is through increased home energy efficiency. The Government has stated that cavity wall insulation and loft insulation are the most effective methods which is why they have legislated for power/energy utilities and power companies to provide subsidies.
- Do I need to provide extra ventilation to my loft space if I insulate it?
- That depends on whether it is adequately ventilated at the moment. Increasing the amount of insulation in the loft can lead to condensation of water vapour on any timber there. If your loft is not properly ventilated your installer will advise you, and can install simple vents that will ensure an adequate air flow through the loft.
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