EXPERT ADVICE
Loft insulation: All you need to know
Updated 07/26
Installing loft insulation can improve your home's energy efficiency, heat, and comfort levels. Learn more about loft insulation with our complete loft insulation guide.
What's the best loft insulation
Loft insulation dos and don'ts
Build regs on loft insulation
How thick should loft insulation be
Loft insulation and boarding
Loft insulation grants
How to find a insulation contractor
Does your home feels cold in winter or your energy bills are climbing? Loft insulation could be the answer.
The Energy Saving Trust estimates that around 25% of a home's heat can escape through an uninsulated roof, making loft insulation one of the most effective energy-saving upgrades.
Read on for our complete guide, covering loft insulation types, installation tips, and the building regulations to know about.
What does loft insulation do?
Loft insulation prevents heat from escaping through your roof by trapping heat in air pockets. This allows your home to retain heat in the winter and keep cool in the summer.
Other benefits of loft insulation include:
Maintains consistent temperatures to improve comfort levels
Improves energy efficiency, which in turn reduces energy bills
Reduce draughts and cold spots
Minimises heat loss by creating a thermal barrier that stops heat from escaping
Lowers energy consumption levels
Reduces moisture and condensation levels to stop damp in your loft
Regulates the air to improve ventilation
Reduces noise from outside to create a quieter living space
Did you know, insulating your loft can also improve your home's resale value due to a higher energy performance certificate? Great to know if you're thinking of selling in the future!
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What's the best loft insulation?
Loft insulation is available in various materials, each with its own uses and purposes.
Deciding on the best loft insulation for your house depends on:
Your budget
Property age
Structure and type of property
How you plan to use your loft space
So, choosing the best loft insulation material can be a very personal choice. Let's get into it.
Loft insulation types
There are several main types of loft insulation that homeowners can choose from.
1. Blanket insulation
Blanket insulation is made from flexible fibres such as fibreglass, mineral wool, sheep's wool, and foil-backed felt.
Installation method: It's laid in sheets under and between the floor joists of roof rafters and then secured
Pros: Easy to install, widely available, cost-effective, and won't stop you using your loft
Cons: Breaks down over time, can retain moisure if not installed correctly
2. Sheet or board insulation
These rigid boards are most often made of polystyrene, polyurethane (PIR), polyisocyanurate (polyiso), or phenolic foam. Made of synthetic or natural materials, they're best for insulating the underside of your roof.
Installation method: Is secured to solid walls between rafters and the floor, before sealing any small gaps with expanding foam and foil tape
Pros: Can be decorated, excellent thermal insulation, provides structural support, and is great for loft conversions
Cons: Sheet or board insulation can come with a pretty price tag and is best professionally fitted
3. Loose-fill insulation
Loose-fill insulation is usually made from cork granules, cellulose fibre, mineral wool, or even cellulose (recycled paper).
Installation method: Quick to install with a blowing machine or pouring directly into joist gaps by hand
Pros: Lightweight, eco-friendly, can be used to top existing insulation and is great for hard-to-reach and irregular spaces
Cons: This type of loft insulation is not always easy to install and is not as secure as others
4. Blown-fibre insulation
Blown-fibre insulation is usually made up of cellulose or mineral wool.
Installation method: This loft insulation is installed by blowing loose materials between joists
Pros: Excellent for nooks and crannies, can be used to top up existing installations, and provides premium thermal insulation
Cons: Not suited to draughty lofts (as it's only a partial solution), best professionally fitted
5. Spray foam insulation
This loft insulation is made from a Polyurethane foam.
Installation method: Sprayed directly into loft spaces
Pros: Airtight sealing and easy-to-fill gaps
Cons: More expensive, requires professional installation, improper installation can lead to ventilation and mortgage issues
It's worth noting that prices vary widely depending on the material you choose. Fibreglass and cellulose tend to be the cheapest, while PIR foam boards tend to be more expensive. Our insulation cost guide has all the details.
Or if you're ready to discuss your plans with a trusted loft insulation installer, just search your postcode below.
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How to insulate a loft
How to insulate a loft depends on the property type, the type of insulation material, and how the loft is used.
You might be able to install blanket insulation as a DIY project. In this instance, you only need to lay rolls of blanket insulation between joists.
Here are the basic steps:
Assess the space
Choose the correct insulation based on property type, size, and intended use
Clear and clean the loft
Remove any current insulation that's no longer needed, or keep it if it’s being topped up
Depending on the insulation, you can lay, spray, or fit it between the joists
Attempting to install loft insulation yourself? Using the correct PPE equipment (dust mask, goggles and gloves) is a must. Fibrous insulation materials such as fibreglass and mineral wool can cause skin, eye, and lung irritation if not installed safely.
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Starting to think this is a job best left to a loft insulation contractor? To price up for the job, download our free mobile app and connect with tradespeople we've checked and approved.
Loft insulation cost: Job estimator tool
Want to learn more about the costs involved before contacting an insulation contractor? Try our free interactive cost calculator for an instant estimate or read on.
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Loft insulation grant
Are costs working out more than you hoped?
Before scrapping the project entirely, make sure to look into grants you might be eligible for. You may be able to reduce the cost of loft insulation through a government-backed energy efficiency scheme.
Current schemes include:
ECO4 Scheme: The Energy Company Obligation scheme, which requires energy suppliers to fund energy-saving measures for eligible lower-income or vulnerable households
The Warm Homes Local Grant: Replaces some previous schemes and helps eligible households with energy-saving home improvements
Learn more about the current green grants available and costs in our guide.
Green home grants available in 2026
Looking to make your home more eco-friendly and energy-efficient? Discover the latest green home grants that could help you save money while reducing your carbon footprint.
Loft insulation dos and don'ts
Insulating your loft might seem straightforward, but some aspects need extra attention. Don't forget these dos and don'ts:
Loft insulation dos:
Leave a loft insulation ventilation gap (of around 50mm between the insulation and roofing felt to prevent condensation build-up)
Add insulation boards or a raised platform (to avoid compression and improve thermal effectiveness when flooring over insulation)
Make sure you have enough vents (to prevent moisure build-up)
Loft insulation don'ts
Don't block your eaves gaps (or you won't have enough airflow and may have damp issues)
Don’t compress insulation (when laying flooring over it)
Don’t block air circulation (which leads to moisture and mould)
Did you know that too much loft insulation can lead to ventilation issues? Creating this moisture trap can lead to condensation, mould growth, wood rot, and damage to the roof structure if left untreated over time.
An experienced loft insulation contractor will ensure there is adequate ventilation in your loft area via roof vents or soffits.
How to find approved loft insulation installers near you
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Find insulation installers registered with recognised organisations, such as the National Insulation Association, on Checkatrade. Before you choose a contractor, read our guide on how to choose a loft insulation contractor so you know what to look for.
Build regulations on loft insulation: What you need to know
If you're insulating a loft for the first time or upgrading existing insulation, it's important to follow current UK Building Regulations. Here are the key points to know:
1. How thick should loft insulation be?
Current UK guidance recommends 270mm of mineral wool insulation. This is usually achieved by laying 100mm between the joists and 170mm across them, helping your home meet modern energy efficiency standards.
2. Loft insulation and boarding
If you're installing loft boarding at the same time, make sure your installer uses a raised loft boarding system. This prevents the insulation from being compressed, allowing it to stay at the recommended depth while still creating useful storage space.
3. Do I need Building Regulations approval?
Simply topping up existing loft insulation doesn't usually require Building Regulations approval. However, if the work forms part of a loft conversion or involves significant structural alterations, Building Regulations will apply.
Learn more about the building regulations of lofts here.
But if in any doubt, speak to a checked loft insulation installer. They can assess your existing insulation and recommend what's needed.
If your loft already has insulation, topping it up to the recommended depth is often much more affordable than starting again from scratch.
Need help with your home insulation? At Checkatrade we have a number of resources to help with your decisions, such as eco-friendly choices and planning guides.
Frequently asked questions
Loft insulation is a layer of insulating material installed between or over the joists in your loft. It helps reduce heat loss through the roof, making your home warmer, more energy efficient, and cheaper to heat.
Yes. Loft insulation traps heat inside your home by reducing heat loss through the roof. This helps maintain a more comfortable indoor temperature while lowering heating bills.
Loft insulation helps reduce heat loss, improve energy efficiency and lower heating costs. It can also make your home more comfortable year-round, reduce your carbon footprint and help prevent condensation in the loft.
No, loft insulation isn't completely fireproof, but most modern insulation is fire-resistant. Mineral wool, fibreglass and stone wool are non-combustible, with mineral wool offering the highest fire resistance. For the best protection, choose insulation with an A1 fire rating.
Most modern loft insulation is non-flammable and designed to resist fire. Materials such as mineral wool, fibreglass and sheep's wool require very high temperatures before they burn or melt, making them safe for use in homes.
Loft insulation is designed for horizontal installation in loft spaces, while cavity wall insulation is specifically made for vertical wall cavities. Using the wrong type of insulation can reduce its effectiveness.
Loft insulation is available in several materials, including mineral wool (rock wool), fibreglass (glass wool), sheep's wool, hemp, recycled polyester and multi-foil insulation. The best option depends on your budget, insulation needs and sustainability goals.
Current UK guidance recommends a minimum loft insulation depth of 270mm. Topping up older insulation to this level can significantly improve your home's energy efficiency, and some homes may benefit from around 300mm.
The amount of loft insulation you need depends on the size of your loft, the existing insulation depth and the type of material used. As a guide, most UK homes should have at least 270mm of loft insulation for good thermal performance.
Yes, you can have loft insulation and boarding, but it's important they're installed correctly. Compressing insulation beneath loft boards reduces its effectiveness and can lead to heat loss. The best solution is to use raised loft boarding systems, which create a gap above the insulation. An experienced loft insulation installer will make sure both the insulation and boarding are fitted correctly.
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