Are your floors, ceilings, and interior walls cold to the touch? Are your energy bills higher than they should be? Do you notice mould, pests, or condensation around your home? Then it’s most probably time to upgrade or install proper insulation.
Cold surfaces mean heat is escaping, forcing your heating system to work harder and raising your energy bills in the process. Meanwhile, moisture buildup from inadequate insulation can lead to mould growth and attract pests, while also causing structural damage over time. Spray foam is a leading cause of issues here, but you might not even be sure what type of insulation you have. Find out if you have foam insulation in our how do I know if I have spray foam insulation guide.
In this guide, we discuss the different types of insulation, their benefits and drawbacks, and the best options for each area to determine what is the best insulation for your home.
How Is Insulation Measured? Understanding R-Values
When purchasing insulation, you’ll often come across a measurement called “R-value.”
R-value tells you how well a material resists heat flow, which directly affects how much energy your home will save on heating and cooling. The higher the value, the better the insulation is at reducing heat transfer.
In the UK, R-values are expressed in square metres kelvin per watt (m²K/W).
- M² (square metres): the area of the material being measured
- K (kelvin): the temperature difference across the material
- W (watt): the amount of heat energy that passes through the material
Let’s say an insulation material has an R-value of 3.0 m²K/W and there’s a 1°C temperature difference inside and outside the house. This means that for every square metre of that insulation, only about one-third of a watt of heat will pass through.
It’s important to note that higher R-values don’t always equal better insulation. Generally, the ‘right’ R-value depends on the location of the insulation and its intended purpose.
Walls, for instance, usually require lower R-values than attics or roofs because they lose less heat in comparison. Attics and roofs are directly exposed to the outdoor environment and have a large surface area, so they need higher R-value insulation to keep your home warm in winter and cool in summer.
How High Should My Insulation’s R-Value Be?
Every house has different insulation needs, so it’s best that you contact your local insulation contractor to determine how much insulation you need for your climate.
Generally, though, the recommended R-value for different parts of the home is as follows:
- Walls: R-2.5 to 3.5 m²K/W
- Roofs and attics: R-5.0 to 7.0 m²K/W
- Floors: R-1.5 to 2.5 m²K/W
R-values are usually printed on the wrapper or sticker attached to the insulation roll, board, or bag.
Common Types of Insulation Materials
To understand what the best type of insulation is for your home, you must first understand the options available. Insulation comes in varying materials, including:
Fibreglass Insulation
Fibreglass insulation, also known as glass wool insulation, is one of the most common and affordable insulation materials in the UK.
As the name suggests, fibreglass insulation is made from fine glass fibres. It has an R-value of between 2.2 and 4.3 m²K/W and usually comes in batts, rolls, or loose-fill.
Fibreglass is fire-resistant and works well for smaller areas like attics and basements, as well as walls. Loose-fill fibreglass, in particular, is best suited for nooks and crannies because fibreglass particles can be “blown in” into these spaces with specialised equipment.
You can learn more about fibreglass insulation in our fibreglass comparison guide vs spray foam insulation.
Cellulose Insulation
Cellulose insulation is made from recycled paper products and treated with chemicals like boric acid to make it pest-resistant, fire-resistant, and mould-resistant. This type of insulation has an R-value of R-3.1 to R-3.7 m²K/W.
Foam Board Insulation
Foam board insulation consists of rigid panels made from materials like extruded polystyrene (XPS or blue board), expanded polystyrene (EPS or beadboard), polyisocyanurate (ISO or polyiso), or expanded polyurethane (EPU). It’s often used to insulate roofs, walls, and foundations.
Foam board insulation has high R-values (around R-6 to R-6.5 per inch), good moisture resistance, and is relatively easy to install due to its lightweight nature. It also provides structural support to walls, floors, and roofs, and has excellent soundproofing qualities.
Foam board insulation is the most expensive type of insulation, but it’s often the preferred choice for areas that require high thermal resistance and moisture control, like basements, flat roofs, external wall cavities, and crawl spaces.
Mineral Wool/Rockwool Insulation
Mineral wool insulation, also known as rockwool insulation, is made from natural rock (usually basalt, a volcanic rock) or industrial slag melted and spun into fibres. It has excellent fire-resistant and soundproofing qualities, plus it’s resistant to water, mould, fungi, and vermin.
You can read more about our mineral wool or rockwool comparison insights in our detailed guide.
Types of Insulation
Here are the types of insulation based on how they’re installed or applied:
Loose-Fill and Blown-in Insulation
Loose-fill and blown-in insulation consist of small particles like cellulose, fibreglass, or mineral wood, which are poured or blown into cavities using an insulation blowing machine. This makes them particularly suitable for attics, gaps, and irregular spaces where batts or rolls may not fit.
Rigid Foam Panels
Rigid foam panels are pre-formed boards made from materials like polystyrene, polyisocyanurate, or polyurethane. They offer high R-value per inch, good moisture resistance, and some structural support. They’re generally more expensive than blanket or loose-fill insulation.
Spray Foam Insulation (Not Recommended)
Spray foam insulation is a liquid polyurethane foam that expands and hardens into a lightweight, stiff, insulating layer. It’s applied using a specialised spray gun. Since it starts as a liquid, it can be applied to gaps, corners, cracks, and irregular surfaces.
Spray from insulation comes in two main types: open-cell foam and closed-cell foam. Open-cell foam is flexible, lightweight, and easy to work with. Meanwhile, closed-cell foam is denser, more rigid, and has a higher R-value per inch (up to R-7, one of the highest in the market).
That said, spray foam insulation isn’t a popular choice among homeowners for several reasons.
For one, they’re expensive. Open-cell spray foam costs between £20 and £30 per square metre, while closed-cell foam costs between £40 and £55 per square metre.
Two, they’re harmful to the environment. They’re made from unsustainable, petroleum-based materials, and release PFAS (“forever chemicals”) and Volatile Organic Compounds (VOCs) that contaminate the air, soil, and body.
There’s also the fact that poor installation can cause it to shrink, pull away from surfaces, or trap moisture, leading to mould and structural issues.
Because of this, homeowners who have spray foam insulation go to great lengths to have it removed from their homes.
Spray foam insulation is notoriously difficult to remove, not only because it’s tough but also because it can release harmful chemicals when disturbed. Therefore, it’s always best to call professional removers like those we work with at National Spray Foam Removal to do it safely and efficiently.
If you’re planning to have yours removed, fill out this form to receive competitive, no-obligation quotes from our spray foam removal experts.
Blanket Batts/Roll Insulation
Blanket batts are pre-cut or rolled sheets of insulation, usually made of fibreglass, mineral wool, or natural fibres like sheep’s wool, cotton, hemp, or cork. They’re fitted between studs, joists, or rafters and are ideal for walls, lofts, and floors. There are many roll insulation pros and cons that are worth considering, but by far they tend to be the easiest type of insulation to install and they’re affordable and effective.
Reflective / Radiant Barriers
Reflective or radiant barrier systems are insulation made with reflective foil-faced kraft paper, cardboard, polyethene bubbles, or plastic film.
Radiant barrier insulation can be installed between joists, beams, rafters, and wood studs, as well as ventilation ducts and unfinished walls, floors, and ceilings.
How Much Does Insulation Cost?
Insulation costs vary depending on the insulation material, insulation complexity, and property type. Here’s an overview of what to expect:
| Insulation Type | Cost |
| Fibreglass Insulation | £10 per m² |
| Cellulose Insulation | £10 to £12 per m² |
| Foam Board Insulation | £20 to £50 per m² |
| Mineral wool Insulation | £13 to 17.5 per m² |
| Spray Foam Insulation (open-cell) | £20 to £40 per m² |
| Spray Foam Insulation (closed-cell) | £40 to £55 per m² |
You can use our free spray foam removal cost calculator uk to get an accurate estimate about spray foam removal costs prior to replacing it with a new form of insulation.
Factors to Consider When Buying Insulation
When buying insulation, consider these factors:
Type of Insulation
The type of insulation you choose depends on the area you want to insulate.
Foam boards offer high thermal performance and moisture resistance, but are more expensive.
Mineral wool and fibreglass are affordable, easy to install, and provide good thermal and sound insulation, but are generally less moisture resistant.
Fibreglass insulation is a good all-rounder, suitable for large areas without a high upfront cost, and offers sufficient R-value for most standard applications. It doesn’t seal gaps, though, so it’s best paired with a vapour-permeable underlay.
R-Value
As discussed earlier, r-value measures how well a material prevents heat from moving through it. Higher R-values equal higher insulation. Here’s a look at the R-values for common insulation materials:
| Insulation Material | R-Value |
| Fibreglass Insulation | R 2.0 to 3.7 m²K/W |
| Mineral Wool Insulation | R 2.5 to 3.7 m²K/W |
| Cellulose Insulation | R 3.0 to 3.7 m²K/W |
| Foam Board Insulation | R 4.5 to 6.5 m²K/W |
| Spray Foam Insulation (open-cell) | R 3.5 to 4.0 m²K/W |
| Spray Foam Insulation (Closed-Cell) | R 5.5 to 7.0 m²K/W |
Attics and roofs often require the highest R-values—around 6.0 to 7.0 m²K/W for cold roofs or 5.0 to 6.0 m²K/W for warm roofs—because they lose heat the most.
Walls, on the other hand, need moderate R-values of 2.0 to 3.0 m²K/W for solid walls and 2.5 to 3.0 m²K/W for cavity walls, depending on whether insulation is installed internally or externally.
Floors require the lowest R-values, around 1.5 to 2.5 m²K/W.
You can use multiple layers of insulation to achieve a higher R-value. For example, if one layer of fibreglass has R-2.0, three layers stacked could give around R-6.0, assuming they’re properly installed and not compressed.
However, it’s often more efficient and cost-effective to use a higher-performance material instead of multiple thin layers.
Durability and Maintenance
With proper maintenance, insulation can last between 80 and 100 years.
Fibreglass, which is the most commonly used insulation type in the UK, can last up to 100 years if properly installed and maintained. The same is said for mineral wood insulation. Cellulose and spray foam insulation, on the other hand, can last up to 80 years.
Insulations made of cheaper or lower quality materials degrade faster, with some losing effectiveness in as early as 10 to 20 years.
What Are the Best Insulation Options for Different Areas of the Home?
Ready to install insulation in your home? Here’s what to look for:
- Attics and Lofts: Fibreglass or mineral wool batts and rolls are ideal for standard loft spaces, while loose-fill or blown-in insulation works well for irregular areas or around obstacles.
- Walls: Cavity calls are best filled with mineral wool, cellulose, or rigid foam boards, while solid walls may require internal or external rigid insulation to achieve the desired R-value.
- Basements and Crawl Spaces: Basement and crawl spaces often face moisture issues, so you’re looking for rigid foam boards (EPS and XPS) or mineral wool. Fibreglass is also a popular choice since it doesn’t retain water, but it should be paired with vapour underlays so moisture doesn’t get trapped within it.
- Floors: Floors work best with mineral wool, rigid foam boards, and fibreglass (paired with a vapour-permeable underlay).
