Loft Insulation
What is
Loft Insulation
Loft insulation refers to the installation of insulating material in the space between the ceiling of a building’s top floor and the roof. This is the space we usually refer to as the loft or attic.
The primary purpose of loft insulation is simple – to reduce heat loss from the interior of a building to the exterior, especially during the colder months of the year.
The most common form of loft insulation, comes in rolls of rock, glass or mineral fibre. Other options include foil-backed felt, sheet insulation and loose fill, blown or sprayed insulation.
Insulating your loft properly is extremely cost effective – especially when you consider that up to 25% of heat is lost through the roof in an uninsulated home!

Loft Insulation Example
What are the main benefits of loft insulation?
There are several significant benefits to having properly installed loft insulation:
- It will save you money. Your heating bills could reduce by up to £330 for a mid-terrace property and £590 for a detached house per year (Energy Savings Trust 2023).
- The value of your home will increase. Increasing the energy efficiency of your home makes it more valuable. When you come to sell your home you will require an Energy Performance Certificate (EPC) and the lower the EPC band the more it adds to the value of your property and the easier it is to sell.
- Properly installed insulation could improve your health. Poorly insulated lofts can cause damp and condensation which, in turn, can lead to mould. This can result in respiratory problems and allergies.
- It helps our environment. Loft insulation reduces CO2 emissions therefore you are doing your bit for the environment and the planet!
- More efficient heating and greater comfort. Your boiler won’t have to work as hard and it will be easier to keep an ambient, consistent temperature in your home in an efficient manner.
Do I need loft insulation?
If you can get into your loft the answer should be simple. Is it already insulated? If so then measure the thickness and, if it’s not at least 270mm thivk then consider topping up to at least that thickness in line with the current building regulations recomendations that have been in place since 2003.
If you can’t get into the loft then do some detective work … Are your enegy bills high compared with similar properties? Do you notice a lot of birds on the roof in cold weather? Does snow on your roof melt faster than your neighbours? All these are signs that your loft is warm and would therefore benefit from insulation.
How thick should loft insulation be?
Since 2003 the current building regulations recommend a 270mm minimum thickness of mineral or glass wool insulation in the loft. Go thicker if you can but use this as a starting point.
From 1995 until 2003 the recommended depth was 200mm and pre 1995 it was a mere 100mm. So, if you have historical lofft insulation there.s a very good chance it will benefit from being topped up.
How long does loft insulation last?
Loft insulation is designed to last … 40 years or more depending on the insulation itself and how well it was installed and if properly maintained. It therefore pays for itself many times over its lifespan.
Ways to insulate your loft
There are two main ways to insulate your loft:
1: Cold Loft: This is what we mainly associate with loft insulation and is the easiest and cheapest option for DIYers. This basically involves covering the floor of the loft with insulation hence preventing heat from rising into the loft area itself hence keeping the loft cold.
2: Warm Loft: In this case the insulation is not placed on the floor but is installed to the underside of the roof itself … between and underneath the rafters. This means the loft space will warm up as hot air rises but the heat will not escape through the roof.
Loft insulation - what to check for
Although loft insulation is designed to last it should be regularly checked to ensure it remains efficient. Apart from the age (it loses effectiveness with age) check for:
- Thickness: you’re looking for at least 270mm on insulation
- Moisture: either caused by a leaking roof or lack of ventilation. Ensure the insulation is not wet or damp which can lead to mould and health problems as well as reduced insulation properties.
- Dirt and debris: any dirt or debris settling on the top of the insulation can reduce the effectiveness of the insulation
- Compression: Don’t let the insulation get squashed as it won’t insulate as well as it should and you’ll lose more heat.
- Ventilation: You’re not looking to make the loft air-tight! Loft insulation still requires adequate ventilation to prevent damp and condensation
- Coverage: make sure the insulation covers the whole loft – don’t leave any cold spots.
- Damage: always check for damage as this will affect the effectiveness. Pay particular attention to anything caused by birds, pests and rodents who may have made an unwelcome home in your loft.
Is it OK to compress loft insulation?
The simple answer is NO … make sure your loft insulation is not compressed or squashed down in any way as this will prevent it from perfoming how it should and potentially lead to significant problems.
Often the insulation will be placed below loft boards and it’s especially important that these do not squash down the insulation and that there is room for the air to flow between insulation and the boards themselves otherwise you’ll losse thermal efficiency, put a strain on the ceiling below, leave yourself open to condensation on the underside of the boards resulting in moisture and damp.
Can I add additional layers of insulation?
Absolutely! If your existing insulation is in good order you can add additional layers directly on top of it. Remember, you’re ideally looking for at least 270mm thickness in total so top up as thick as you are able to do making sure it’s installed correctly.
Can I install loft insulation myself?
If you’re talking about a cold loft then it’s a simple process adding insulation to the floor.
Make sure you follow the manufacturers installation instructions and follow health and safety guidance … wear a dist mask, ensure the loft is well lit and ventilated, wear knee pads and work from crawl boards if the loft is not boarded. You should also be wary of any asbestos containing roof products which may be present in older (pre 2000) properties.
For warm lofts we would always suggest getting the job done professionally.
Which loft insulation is best?
We can’t really answer that because it very much depends on the project itself but there are 4 main options:
- Blanket Insulation – typically made of rock, glass or mineral fibre and comes in rolls. It’s very easy to fit and not expensive at all.
- Loose Fill Insulation – this consists of a loose, lightweight material that can be packed in between the joists.It’s very cheap and is available in many different recycled materials such as cork granules, cellulose fibre or mineral wool.
- Blown-Fibre Insulation – great solution if you need to get insulation into hard-to-reach places. Machine applied and hence not for the DIYer.
- Sheet / Roll Insulation – expensive and not for the DIY market but required if you are looking to insulate the roof / rafters and create a more specialist warm-loft.
How much does loft insulation cost?
If you’re looking at standard blanket type insulation it needn’t cost much at all – packs of insulation start at less than £10 a roll so you can easily do the job yourself for very little. To have it installed you’re looking at around £5 per sq metre upwards.
Grants may be availanble