Proper loft insulation can transform your home by reducing heat loss, cutting energy bills, and boosting energy efficiency.
Whether you're looking to replace old insulation or insulate a loft for the first time, understanding the process is crucial to getting it right.
This guide will cover everything you need to know, from choosing the right materials to step-by-step installation.
Types of loft insulation material
Is installing loft insulation a DIY job?
How to install loft insulation: A step-by-step guide
When to call in a JustFix professional
Do you need loft insulation?
If your home feels drafty or your heating bills seem higher than average, chances are you could benefit from loft insulation. Properties without adequate insulation lose up to 25% of their heat through the roof.
Insulating your loft makes your house warmer and improves your property's energy performance certificate (EPC) rating. This makes your property more attractive to future buyers while helping to reduce carbon emissions.
Even if you already have some insulation, adding more to meet current standards can significantly improve energy efficiency.
For more ideas on how to save money on your heating bills, see our helpful guide.
Before you get started…
Before starting the installation process, evaluate your loft space and prepare for the job. Here are some key things to consider.
What do you do with existing loft insulation?
Before adding new insulation, assess the state of your existing insulation materials. If the current insulation is dry, clean, and still effective, you may not need to replace it. Instead, you can top it up to meet the recommended minimum thickness of 270mm.
However, if the existing insulation is wet, mouldy, or contaminated with hazardous materials like asbestos, it should be removed and disposed of properly.
Handling asbestos can be dangerous, so contact a professional removal service to ensure safety.
Even when dealing with non-toxic materials like old mineral wool, always wear protective clothing and a face mask.
Do you want a 'warm loft' or 'cold loft'?
Before installing insulation, decide how you plan to use your loft.
- Warm lofts are insulated at the roof level, keeping the loft space warm and suitable for conversion into a living area. This approach involves using rigid insulation boards or sheet insulation.
- Cold lofts are the more common option. In these, insulation is laid on the loft floor to keep heat in the rooms below. This is ideal for lofts used only for storage.
Each method has its advantages, but the installation process and materials differ significantly. If you're unsure, consult a professional roofer who's trained in installing loft insulation for guidance.
Weight limit
Loft joists have a weight-bearing limit, which is essential to consider when installing insulation or boarding. To avoid overloading the structure, it's recommended that no more than 25kg per square metre be stored in the loft.
Exceeding this limit can damage the structure or create safety hazards. Lightweight insulation materials like mineral wool or blown fibre insulation are ideal for maintaining structural integrity.
If you plan to add heavy storage boards, are using the loft as a storage space, or are converting the loft into a living space, consult a structural engineer to ensure your loft can handle the additional weight.
How much loft insulation you need
The amount of insulation material required depends on the size of your loft and the desired thermal resistance. Current building regulations recommend a minimum thickness of 270mm for most homes. This typically involves two layers of insulation:
- A 100mm layer between the joists
- A 170mm–200mm layer across the joists
For larger or older homes, you may need more insulation to achieve optimal energy efficiency.
Calculate the total square meterage of your loft using a tape measure, and consult product guides to determine how much material you'll need.
Types of loft insulation material
The choice of insulation material depends on your budget, the layout of your loft, and your insulation goals.
Blanket insulation
Blanket insulation, often made from mineral wool or glass wool, is one of the most popular options for loft floors. It's cost-effective, easy to install, and provides excellent thermal resistance.
However, it’s not ideal for awkward spaces or areas with obstructions.
Loose-fill insulation
Blanket insulation, often made from mineral wool or glass wool, is one of the most popular options for loft floors.
It's cost-effective, easy to install, and provides excellent thermal resistance. However, it’s not ideal for awkward spaces or areas with obstructions.
Blown-fibre insulation
Blown-fibre insulation is installed using specialist equipment, making it ideal for inaccessible loft spaces.
While it provides excellent coverage, it’s generally more expensive and requires a professional installer.
Sheet insulation/roll insulation
Rigid insulation boards offer superior thermal performance and are ideal for warm lofts or flat roofs. They can also support loft boards in cold lofts where storage space is a priority.
However, they’re more expensive and harder to cut and fit.
Is installing loft insulation a DIY job?
For a cold loft, installing insulation is often a manageable DIY project. With basic tools and some preparation, you can install loft rolls or blanket insulation without professional help.
However, insulating a warm loft or dealing with hazardous materials like asbestos requires specialist equipment and expertise.
In such cases, hiring a professional installer for your loft space is safer and ensures compliance with building regulations.
How to install loft insulation: A step-by-step guide
These instructions are based on the assumption that you've opted not to tackle the complexities of installing a warm loft yourself.
Instead, we'll focus on guiding you through the process of installing blanket insulation.
Tools you'll need
To complete the installation, gather the following tools:
- Rubble bag for debris
- Face mask to avoid inhaling fibres
- Tape measure for precise cutting
- Crawl boards for unboarded areas
- Handsaw or utility knife for cutting insulation
- Mobile workbench to support materials while cutting
Step 1: Grab crawl boards if necessary
If your loft isn’t fully floored, use crawl boards to create a stable surface. These boards prevent you from stepping through the ceiling and ensure safe working conditions.
Step 2: Check for recessed light fittings
Recessed light fittings, such as spotlights, require loft caps to prevent the insulation from contacting the hot back of the lights.
This ensures safety and maintains the integrity of your insulation.
Step 3: Cut insulation with a hand saw
Measure the distance between your roof joists (commonly 380mm or 570mm) and cut the blanket insulation accordingly.
Use a handsaw or utility knife while the insulation is still packaged for precise cutting.
Step 4: Lay the first 100mm layer of insulation material between the joists
Place the first 100mm layer of insulation between the joists, ensuring a snug fit without gaps.
Be sure not to push these all the way in so they touch the roof felt backing, as this can cause moisture issues. It's important to leave an air pocket.
Work methodically across the loft, nesting the insulation around obstructions like pipes or cold water tanks.
Step 5: Place the second layer of insulation material at a right angle over the joists
Lay a second layer of insulation, typically 170mm–200mm thick, perpendicular to the joists.
This creates a continuous, gap-free barrier that maximises thermal efficiency.
Start at the furthest point from the loft hatch and unroll the insulation towards the entrance.
When to call in a JustFix professional
While installing loft insulation can be a rewarding DIY project for some, there are certain situations where a professional roofer experienced in insulation installation is the best choice. If you're unsure about the type of insulation to choose or need help with the more complex aspects of installation, it’s always a good idea to call in an expert.
Our team of Fixers works nationwide, ensuring you have access to skilled roofers who specialise in loft insulation at fair, fixed prices. Whether you need help installing standard loft insulation, insulating a warm loft, or dealing with tricky roof spaces, our professionals have the experience to get the job done right.
When you book with JustFix online, we’ll connect you with a local roofer who can assess your loft space and recommend the best insulation solutions based on your needs. From roofers in London to roofers in Essex and beyond, we have you covered in areas all over England.
All our Fixers are fully qualified, ensuring high-quality work and giving you peace of mind throughout the process.
FAQs
Is loft hatch insulation worth it?
Yes, insulating your loft hatch is worthwhile. It can make a noticeable difference in your home's overall energy efficiency. Since heat rises, a poorly insulated loft hatch can let warmth escape, leading to increased energy bills.
Insulating the hatch helps to maintain the temperature inside your home, reducing heat loss and ensuring that your loft insulation remains effective.
Do I have asbestos in my existing loft insulation?
If your home was built before the 1980s, there’s a chance that asbestos may be present in the existing loft insulation. Asbestos is commonly found in older insulation materials, and it can be dangerous if disturbed.
If you suspect you have asbestos, it’s crucial to avoid handling it yourself. A professional should be contacted to assess and safely remove the material if necessary.
How much does loft insulation cost?
Loft insulation costs can vary depending on the type of material you choose, the size of your loft, and whether you're doing it yourself or hiring a professional.
On average, DIY insulation materials can cost between £200 to £400, while professional installation can range from £600 to £1,500.
It's also worth considering potential savings on energy bills, as loft insulation helps reduce heating costs in the long run.
Can I get free loft insulation?
Yes, it’s possible to get free or cheap loft insulation, especially if you qualify for government schemes like the Energy Company Obligation (ECO) or the Great British Insulation Scheme.
These programs offer free insulation to homeowners who meet certain income and property criteria. Check with your energy provider or local authorities to see if you qualify for these grants or schemes.
