As the nights draw in and the temperature drops, a warm home becomes a priority. One of the simplest and most effective ways to keep the cold out is to make sure your loft is properly insulated.
Heat rises, and in a home without loft insulation, around a quarter of the heat can escape through the roof. Good loft insulation keeps that warmth where you want it, helps your heating work less hard and can make a noticeable difference to your energy bills.
Here's what you need to know before winter really sets in.
Signs Your Loft Insulation Isn't Doing Its Job
You may need to top up or replace your loft insulation if you notice:
- Upstairs rooms feel cold even with the heating on
- Your heating seems to run constantly to keep the house warm
- Energy bills are higher than you'd expect for the size of your home
- Frost or snow melts quickly on your roof compared with neighbouring houses — a sign heat is escaping
- Insulation is thin, patchy or flattened when you look in the loft
- Insulation is damp, dirty or mouldy
- You can see the tops of the ceiling joists — meaning the insulation is too shallow
How Much Loft Insulation Do You Need?
The recommended depth for mineral wool loft insulation in the UK is 270mm. Many older homes only have 25mm to 100mm, which was standard decades ago but falls well short today.
A quick way to check: pop your head into the loft and look at the joists. If you can see the tops of the joists, you almost certainly need more insulation. Use a tape measure to check the depth in a few places.
Types of Loft Insulation
Mineral Wool (Blanket) Insulation
The most common choice. It comes in rolls of glass wool or rock wool and is laid between the joists, with a second layer laid across the joists to reach the recommended depth. It's affordable, effective and widely available.
Sheep's Wool and Natural Insulation
A more eco-friendly option made from natural fibres. It handles moisture well and is pleasant to handle, but usually costs more than mineral wool.
Insulation Boards
Rigid boards such as PIR (polyisocyanurate) give high performance from a thinner layer. They're often used between the rafters when a loft is being used as a room or for a future loft conversion.
Blown (Loose-Fill) Insulation
Loose fibres or granules are blown into the loft space by a professional. It's useful for awkward lofts with low headroom or hard-to-reach areas.
Spray Foam — Approach With Caution
Spray foam insulation applied to the underside of the roof is sometimes sold as a quick fix. Be careful: it can trap moisture against roof timbers, make roof inspections difficult, and some mortgage lenders and surveyors have raised concerns about it. Get independent advice before going down this route.
Don't Forget These Important Details
Insulating a loft properly is about more than just laying rolls of insulation. Make sure you or your installer:
- Keep the loft ventilated. Don't block the eaves or vents, or you risk condensation and damp in the roof space.
- Insulate and draught-proof the loft hatch. An uninsulated hatch is a big gap for heat to escape through.
- Insulate pipes and water tanks in the loft. Once the loft is insulated, the space above the insulation gets colder, so exposed pipes and tanks are more at risk of freezing. Lag them properly, but don't insulate directly underneath a cold-water tank — leave that area clear so a little warmth can rise to stop it freezing.
- Keep clear of electrics. Don't bury cables or downlighters under insulation without checking. Recessed lights may need fire-rated covers.
- Plan for storage. If you use your loft for storage, don't squash the insulation with boards laid directly on top. Raised loft boarding legs let you board over the full depth of insulation.
DIY or Professional?
If your loft is easy to access, dry and free of damp or pest problems, laying mineral wool rolls between and across the joists can be a manageable DIY job. Wear gloves, long sleeves, goggles and a dust mask, and take care to step only on the joists.
It's worth calling in a professional if:
- Your loft has low headroom or is hard to access
- There are signs of damp, leaks or condensation in the roof space
- You want to insulate between the rafters or plan a loft conversion
- There's old insulation that needs removing
- You need blown insulation or insulation boards fitted
- You're unsure about ventilation, wiring or downlighters
A good installer will check the whole roof space, make sure ventilation is right, and leave the job tidy and safe.
Is There Help With the Cost?
Government and energy supplier schemes to help with the cost of insulation come and go, and eligibility often depends on your income, benefits or the energy rating of your home. It's worth checking the latest schemes on GOV.UK or with your energy supplier before you book the work.
Get Your Loft Ready Before the Cold Sets In
Loft insulation is one of the most cost-effective home improvements you can make. It pays for itself over time through lower heating bills, and you'll feel the difference in a warmer, more comfortable home straight away. The best time to sort it is before the coldest weather arrives.
Need your loft insulated? Post your job for free on Compare My Builder and get quotes from verified local insulation installers. Compare profiles and reviews, and choose the right tradesperson to keep your home warm this winter.