Best Loft Insulation: Guide, Types and Tips 

Uninsulated lofts comprise more than a quarter of a home's total heat loss, making loft insulation an absolute essential for all property owners. Alongside reducing your domestic carbon footprint by a staggering 1 tonne a year, loft insulation can bring about significant energy bill savings of up to £445 in detached homes and bungalows alone. 

However, with all the options for loft insulation available on the market, choosing the best fit may seem like a daunting task. There are a variety of approaches to insulating a loft, each with its pros and cons, as well as suitability depending on your loft type, purpose and specifics. 

In this complete guide, we’ll walk you through all of the main loft insulation options available on the market, as well as which types of loft insulation material are best suited for what purposes and jobs. 

Ready to get your loft insulated? Look no further than GreenMatch UK to free you from the hassle of researching and vetting installers. Instead of spending hours a day on phone calls and websites, simply fill out our 30-second form and receive up to 3 free home-tailored quotes from our trusted installers in your area. No charges or obligations apply. Click below to begin! 

The best loft insulation for your home depends on many factors, most importantly what your existing loft is like, and what you want to achieve. The best insulation can also differ based on the quality you are comparing for, such as the best price, insulating effectiveness, or ease of installation.

To start, it's best to identify what you want to use your loft for, assuming you are to carry out a loft conversion insulation. This will largely determine the style of insulation you need. If you want to use your loft for storage purposes, you will likely require cold loft insulation, whereas if you want to use your loft as a living space, warm loft insulation is better suited to your needs. Both are discussed later in the article. 

A loft insulation cost can vary greatly depending on several factors. When it comes to the best budget-friendly loft insulation, homes with existing good-condition insulation that fall short of the recommended 270mm thickness are in the best position. In some cases, homes have up to 100mm of previously installed insulation in place, which topping up costs much less than starting from scratch. For homes with outdated insulation, perhaps a loft insulation replacement is in order.

To get the best idea of what suits your needs as the best insulation material, let’s start by checking out the main types of insulation there are.

You may be wondering; what is the best loft insulation to use? Does loft insulation make a difference? Before answering that, let's become acquainted with the four main types of loft insulation that are available; standard (blanket), loose-fill, sheet, and blown-fibre insulation. Each approach comes with its perks and drawbacks, as well as suitability depending on loft conditions and personal preferences.

Standard (Blanket) insulation

Arguably the most popular, versatile and cost-effective insulation, these are blankets or rolls of insulating material that are laid in between the joists of your loft floor and roof rafters. They come in several materials, including eco-friendly options such as mineral wool (rock and glass), fibreglass, and even sheep’s wool. 

Loose-fill insulation

An eco-friendly insulator that comes as lightweight granules made from sustainable cellulose insulation, mineral wool, or cork amongst other options. It is applied by being blown into loft spaces with an applicator hose and is very useful when topping up existing insulation.  

Rigid (sheet) insulation

These rigid insulation boards are highly effective in heat retention and are usually applied to the insides of sloping roofs, or stud walls in lofts. They come in synthetic materials such as Polyisocyanurate (PIR) or expanded (EPS) and extruded (XEPS) Polystyrene. Greener eco-friendly alternatives include straw, cork, and wood-based boards.

Blown-Fibre Insulation

This is a loose fibrous insulation material that is applied as blown in insulation. This is done with special industry equipment to reach hard-to-access lofts. It comes in several material types, most of which are eco-friendly and sustainable, such as cellulose, fibreglass, or mineral wool.

There are also sound insulation roof materials that differ a bit from thermal insulation materials if you are in the market for acoustic soundproofing.

Now that we’ve got a better understanding of the main types of loft insulation approaches, let’s look at which insulation is best suited for what purpose. 

Cold loft insulation is a cost-effective and efficient solution for homes that don’t plan to use their loft as a living space. This is when your loft floor is insulated, ensuring that your home below stays warm. In this scenario, your loft itself remains uninsulated, but can still be used for storage purposes if it is safe and easy to access.

There are several approaches to cold loft insulation, and the best option will depend on your specific budget and needs:

This is one of the best cost-effective options available, with the best loft insulation rolls in terms of cost being mineral wool. Your floorboards are lifted, and 270mm of blanket insulation is laid between and over the joists. A 50mm air gap is left to ensure ventilation before the floorboards are put back in place. Most loft floors lack depth for the insulation and air gap, so loft legs/joist extenders are purchased to elevate the floorboards. These are in most hardware stores or can be handled by a professional. 

Compressed batts instead of loose blankets are also available. They’re easy to fit, water-repellent, and breathable, making them ideal for minimising the risk of mould and rot.

This option is one of the most effective in retaining heat. The best loft insulation boards in terms of cost are Polystyrene (EPS) or PIR boards. Despite being costlier, rigid boards have far higher heat-retaining capabilities. Being half as thick as blanket insulation makes them very easy to install by fitting the boards in between your floor joists. Their slimness also means loft legs are unnecessary to raise floorboard height.

This option is best for lofts with existing insulation. Some lofts may already have insulation in place that is in good condition, but less than the recommended thickness of 270mm. Loose fill is a great solution that comes in bags and can simply be poured on top and in sparse areas. It is a very easy task that requires no professional installer if simply topping up. 

Warm loft insulation is best if you intend to use your loft as a living space, but is more complex and costly than cold loft insulation. Loft insulation between rafters will ensure that your loft space retains heat along with the rest of your home.

This process involves insulating your roof rafters from the inside, as well as the stud walls of your living space to make sure heat does not escape to the uninsulated parts of your loft. Windows or skylights will also need quality glazing and draught-proofing.

There are several approaches to insulating your roof rafters and stud walls, each with its perks. Let's take a look at some of the best options:

This option again emerges as one of the most cost-effective options for loft insulation due to its wide availability and versatility. Coming in the form of blankets or batts (slabs) of mineral wool, fibreglass, or sheep wool, these can be installed in between your roof rafters and secured in place with netting before the plasterboard is added. The same can be done for stud walls. 

The best loft insulation roll in terms of affordability is mineral wool, whereas sheep’s wool is the most effective in retaining heat.

Just like in cold loft insulation, rigid boards are one of the most effective in retaining heat in your loft. Being very DIY-friendly, you can cut this loft insulation into the desired width and secure it between your roof rafters and behind stud walls before being covered with plasterboard to insulate the loft living space. While the costlier option, rigid boards are highly effective. 

Perhaps the most effective heat-retaining insulation on the market, spray foam is a synthetic expanding foam made from polyurethane and boasts some of the highest performance of all insulators on the market. It’s typically applied by being sprayed between the rafters from the inner roof of the loft. The downside is that it is very costly, unsustainable, and requires a professional installation.

So with all things considered, what is the best loft insulation to buy? If you are looking for the most cost-effective option that still successfully retains heat, then rolls of glass mineral wool would be your cheapest option. If budget isn’t a concern and you want the highest heat retention capacity possible, then spray foam insulation would be the way to go.

The best loft insulation material between rafters and joists will depend a lot on your budget, personal preferences, and the type of loft you are trying to have; a storage space or a living space. 

Rafters are the structural beams that support a roof structure or deck. They are normally vertical and common in traditional sloped roofs. Joists are structural beams that support floors and ceilings. They are normally horizontal. 

Insulating between joists is generally the more common and cheap method of insulation, but will leave your loft space uninsulated. It’s a relatively straightforward process in which insulating material (usually blanket insulation) is laid in the joists and covered with floorboards.

Loft insulation between rafters is a great step if you plan to use your loft as a living space. In general, it's advised to insulate both your joists and rafters if the loft space accommodates more than just storage.

Here are some ways you could do just that:

One of the most eco-friendly and sustainable approaches to standard (blanket) insulation is to use treated sheep wool. With higher heat retention than fibreglass and mineral wool, sheep wool is all-natural and recyclable, making it one of the best loft insulation between joists and rafters. You must source ‘treated’ wool so that it’s insect-resistant. 

Single or multi-layer foil is an aluminium-based sheet that is one of the most affordable and easiest-to-install approaches to loft insulation. It typically has two or more aluminium layers bonded to layers of foam insulation and can reflect up to 97% of radiant heat, making it a formidable choice for rafter and joist insulation. 

If you’re trying to figure out which is the best loft insulation material for your loft, you’ll need to identify what you’re working with and the needs that you have. From budget to loft type, there’s a whole range of factors to consider. Understanding these needs and the conditions of the loft you have will help narrow down your choices.

Additionally, you might wonder, is loft insulation fireproof? Fire safety is a paramount concern for homeowners, and knowing the fire resistance of your insulation material is crucial.

Here are our top tips to make sure you land the best loft insulation material for your needs:

Figuring out what you want to use your loft for is essential in narrowing down your insulation options. As mentioned before, storage lofts can suffice with cold loft insulation, whereas living space lofts will require warm loft insulation, which is a longer and more costly process.

Lofts that have issues with draught, dampness or mould must first identify and solve these problems before installing insulation. This is to make sure the material you install doesn't become damaged and ineffective, as well as to protect the structural integrity of your house.

If your loft already has previously installed insulation in place, it’s best to get it professionally assessed for effectiveness. If it is still dry and in good shape, your best insulation choice could be to simply top it up to the recommended 270mm thickness with some loose fill insulation, both cost and time-effective.  

Deciding whether to install with a professional or by yourself can narrow down your insulation material choice, as some insulation materials can only be installed by professionals. While a DIY loft insulation installation can cost two to three times less, professional loft insulation companies can ensure the job is done right and within loft insulation regulations, giving you peace of mind for decades to come.

Perhaps the most important tip we have is to not shy away from digging deep into some research. By reading reviews of insulation materials and professional installers in your area, contacting previous clients and comparing multiple quotes, you give yourself the greatest shot and land the best insulation material and bargain for the installation.

While easier said than done, researching and vetting can have you stuck in an endless cycle of phone calls and websites with no end in sight. Here at GreenMatch UK, we’d love to free you from the burden by handling the work for you!

By filling out our simple 30-second form, you can receive up to 3 free home-tailored quotes from our trusted network of professional installers in your area. The best part? Our services are completely free and with no obligation to accept any quotes. Maximise your chances at the best bargain and click below to begin!