What Are the Best Insulation Types? A UK Guide

Insulating your home is a key component of any energy-efficient upgrade. It helps to keep your home temperature regulated, providing warmth in the winter and cooling in the summer. Acoustic insulation can also help to reduce noise pollution, ideal for homes in dense urban areas. 

Various types of insulation are available on the market, each with advantages and disadvantages. However, picking the best fit for your budget and needs can require some work. That's why this complete guide by WhatCost will walk you through all you need to know about the different types of insulation available, including pros, and cons and how to decide on what is best for you.

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The best insulation types hinges on several important factors, such as the insulation project at hand, your budget, and other personal preferences. Nevertheless, here are some top contending materials on the market that are popular amongst customers:

When choosing the best thermal insulation, you will need to account for heat resistance and whether the type meets your needs. As a rule of thumb, more thermally efficient materials will cost more per m2. The best bet is to consult with a professional installer who can conduct a home insulation check and tailor the best course of action for your needs.

Insulating walls is a highly effective way to reduce energy consumption and lower heating bills. By insulating your walls, you can significantly reduce heat loss, potentially saving up to £370 per year for a detached home with cavity walls and up to £500 for a home with solid walls.

The type of insulation material you choose will depend on whether your home has solid or cavity walls, but some materials are compatible with both. Here’s a breakdown of the best options:

Made from recycled glass materials that have been woven into a blanket-like sheet, fibreglass is one of the most popular materials for all forms of wall insulation - cavity wall, internal wall, and external wall - and for good reason! 

It’s sustainable, flame and smoke-resistant, and budget-friendly at only £10 per m2. The semi-porous nature of fibreglass also allows for vapour to evaporate, helping to regulate moisture. The key downside of fibreglass is that it is highly irritating to the skin, eyes and respiratory system, meaning it must be handled with protective gear. 

Similar to fibreglass, but more thermally efficient, mineral wool is made of processed glass or rock that can be woven into blanket-like sheets, or denser insulation boards. Costing around £13 - £17.5 per m2, mineral wool boasts impressive qualities like flame and mould resistance, while also demonstrating an impressive heat retention. 

Mineral wool is also highly versatile, making it suitable for wall cavity insulation, as well as internal and external wall insulation projects. Like fibreglass, it must be handled with protective gear to avoid skin, eye or respiratory irritation. 

A newcomer to the market, EPS polystyrene can be found as beads, a favourite for cavity wall insulation, or as rigid boards. Costing around £10 per m2, this material is highly durable for weathering, moisture, and mould, making it a great choice for long-term comfort. 

As a downside, EPS polystyrene is less sustainable than its blanket counterparts, but in turn much more durable and long-lasting. While it takes more energy and resources to produce EPs polystyrene, the material can be broken down and processed into new products. 

Loft insulation is a crucial step in improving a home's energy efficiency. Uninsulated lofts can account for up to a quarter of home heat loss, driving up energy bills and reducing comfort. To maximise your energy savings, homeowners should consider various loft insulation options. Let’s have a look at the best loft insulation UK:

One of the most natural and hypoallergenic materials on the market today, sheep's wool is taken from farm excesses during the shearing season and treated for durability. This material is then compressed into sheets, perfect for loft floor and roof rafter insulation. 

However, sheep's wool comes with a higher price tag of £17.5 - £22 per m2 due to its seasonal collection, as well as impressive heat-retaining capabilities. 

Due to its lower cost of £13 - £17.5 per m2, and unmatched versatility, mineral wool makes for a great insulator even for loft spaces. The sheets can be conveniently cut to fit floor joists and roof rafters, as well as easily wrapped around awkward shapes and hard-to-reach crevices. 

As mentioned, mineral wool can cause mild to severe irritation if in direct contact with skin, eyes or respiratory system. This is why it's recommended to work with a professional installer. 

Made from a polyisocyanurate synthetic polymer, these rigid insulation boards are highly durable and exceptionally heat transfer-resistant. Costing around £5 – £15 per m2 depending on the material density, 

Most impressively, PIR boards boast a u-value of 0.022 - 0.028 W/m²K, making them one of the most effective heat insulators on the market today. A downside is that polyisocyanurate is a synthetic material that is energy-consuming to produce, and very difficult to recycle or dispose of.

While not all lofts are habitable, insulating your roof remains a worthwhile investment. It offers the same advantages as standard loft insulation, such as improved energy efficiency, reduced heating costs, and lower carbon emissions. Certain types of insulation material are specifically designed to be the best loft insulation between rafters, let’s have a look at them:

As one of the most affordable and versatile materials on the market, fibreglass makes for a great roof insulator, especially from the inside in between the roof rafters. Its decent heat retention capabilities and resistance to flame, smoke, moisture and mould make it a reliable option to work with if you are on a budget. 

However, fibreglass does have a comparably lower insulation capability, as exemplified by its lower cost. This means that you’ll require 270mm or more of insulation thickness to achieve similar heat retention to around 100mm of PIR board or other efficient materials. 

One of the reigning champions of heat retention, phenolic boards boast an unmatched efficiency, as seen by their remarkable u-value of 0.018 W/m²K. A phenolic board is a rigid type of insulating with a 95% or more closed-cell structure, making it nearly impervious to moisture.

As a downside, this material is by far one of the most expensive price ranges on the market, at around £12 – £45 per m2. While the overall investment is much higher, so is the capacity for heat retention.

Rigid PIR boards make a great roof rafter insulation material due to their durability and impressive heat retention capabilities. Their rigidity can also help strengthen the structural integrity of a pitched roof. PIR boards are also great solutions for flat roof insulation, whether internal or external. 

The only downside is that PIR is not a malleable material, like mineral wool or fibreglass. This means it’s not easy to insulate crevices and awkward shapes, only flat surfaces.

Uninsulated floors can account for a significant portion of heat loss in your home, often around 8%. By investing in proper floor insulation, you can significantly reduce energy consumption and lower your heating bills. 

There are two primary types of floors: solid and suspended. Solid concrete floors are common in modern homes, while older houses often feature suspended timber floors.

Mineral wool is back on our list due to its remarkable versatility, making it one of the best underfloor insulation materials. Sheets of mineral wool can be fitted and secured between floor joists for suspended timber or solid floors under concrete slabs or above with a layer of screed.

As a downside, mineral wool is not as moisture-resistant as some other alternatives. This could be a headache for solid concrete floors, as damaged insulation will require tearing up the floor to remove.   

Polyurethane (PU) spray foam exhibits one of the most impressive heat retention properties, with an u-value of around 0.022 - 0.028 W/m²K. In addition, it's practically moisture-impervious and very sturdy. While its difficulty to remove is a serious problem for loft insulation, it’s much less of an issue for floor insulation. 

As a downside, spray foam costs around £21.5 + per m2. In addition, it is highly unsustainable, difficult to replace, and cannot be recycled or disposed of safely. 

Rigid insulation boards - especially PIR - boast rigidness, durability, and remarkable heat retention, making for perfect floor insulation, whether solid or suspended timber. Sheets can be cut to fit in between floor joists, or laid directly over concrete floors and covered in screed.

As a small downside, PIR insulation boards are very sturdy, and cannot bend around awkward shapes, or fit comfortably into tight crevices. It’s usually recommended to pair rigid insulation with other draughtproofing measures for an optimal finish, which can cost more. 

The main distinction between acoustic and thermal insulation lies in their density. Acoustic insulation, designed to block noise, is typically much denser, successfully creating a barrier that can absorb or even reflect sound waves entirely.

While thermal insulation excels at regulating temperature, its lighter weight often limits its soundproofing capabilities. Conversely, acoustic insulation may not always provide optimal thermal performance, depending on its specific composition.

Here are some of the top-performing acoustic insulation materials on the market today:

Mass-loaded vinyl (MLV) is a highly dense and thin vinyl sheet that boasts remarkable sound insulation capabilities. Due to its concentrated density, MLV can easily reflect sound waves. It costs around £10 - £20 per m2 and can even be installed as a DIY project.

As a downside, MLV is a synthetic material that requires lots of energy to produce and is not very easy to recycle or discard.  

Dense acoustic cotton is one of the most effective soundproofing materials available today. At a density of around 55 kg/m³, it provides impressive noise-cancellation performance while also being entirely natural and recyclable.

Acoustic cotton costs around £10 - £14 per m2, and can be found as boards, sheets or batts. It’s important to note that acoustic cotton does not provide sufficient thermal insulation.

Acoustic fibreglass is similar to normal fibreglass, just much denser. Costing around £10 per m2, it’s made from recycled glass products that are woven into a blanket-like structure.

While it may provide a small degree of thermal insulation, acoustic fibreglass is optimised to reduce sound transfer, not heat transfer. Therefore, it’s good to know that acoustic fibreglass cannot double as effective heat insulation.

With all the options on the market, deciding on the best insulation type for your home may seem a little daunting. The truth is, that each home will have its own best fit, depending on factors like your budget, home type, installation complexity and other specific needs.

To help refine your choices, follow these key pointers to efficiently choose your best insulation material options:

Make sure to invest in professional installation. A certified installer will ensure proper workmanship, optimal performance, and long-lasting results that bring your home comfort for decades. Sadly, most prospective customers find themselves stuck in an endless loop of researching and vetting with no bargain in sight. Luckily, WhatCost can solve this for you!

Instead of spending endless hours searching online, spend just 30 seconds filling out our simple online intake form and receive up to 3 free home-tailored quotes from our network of trusted professionals. No costs, no obligations. Click below and find the best bargain for you today!