What type of roof insulation is best?

Dec. 16, 2024

Best Roof Insulation: A Complete Guide to Roof Insulation Types

About 21 million homes in the UK have outdated or insufficient insulation, causing significant heating challenges for 41% of UK adults.
To find the best roof insulation, you must consider your roof type, your budget, and whether the loft space will be used for storage or as a living space.
Proper roof insulation can save up to £230 annually on energy bills and reduce the carbon footprint by 0.6 tonnes.
The most cost-effective roof insulation is fibreglass at £10 per m2. It is suitable for roof rafter insulation and cold and warm insulation for pitched roofs.
Sheep wool and cellulose roof insulation are the most eco-friendly options available.

About 21 million homes in the UK have outdated or insufficient insulation, causing 41% of UK adults to struggle with heating their homes due to poor insulation and high living expenses. Uninsulated roofs can account for one-quarter of heat loss in your home, making roof insulation crucial.

Insulation for your roof can improve your home&#;s energy efficiency and help you save up to £230 annually on energy bills. Additionally you can potentially reduce your carbon footprint by 0.6 tonnes. Nonetheless, selecting the right roof insulation can be overwhelming. With various insulation types available, each with unique benefits and installation methods, it can be challenging to determine the best option for your specific requirements.

This comprehensive guide will explore the most effective roof insulation materials, including traditional options like fibreglass and cellulose and modern solutions like spray foam. By grasping the advantages and disadvantages of each type, you can make well-informed decisions to ensure that your home stays well-insulated, comfortable, and energy-efficient all year round.

Once you've found the perfect roof insulation, comparing quotes from various roof contractors is crucial to ensure you secure the best deals that fit your needs and budget. However, sifting through multiple quotes can take time and effort.

GreenMatch can provide you with up to four free, non-binding quotes from trusted local installers. Complete a quick 30-second form using the link below. Click now to receive your quotes with no obligations and no hidden fees.

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What is the best roof insulation?

Choosing the best insulation for your roof is a critical decision that requires careful consideration of various factors. These include the type of roof, budget, roof structure, and the depth of the rafters. Consider whether the loft will be used for storage or living space, as this significantly influences the decision

There are several types of roof insulation, each suited to different structures and compatible with flat or pitched roofs, as well as warm or cold loft insulation. For example, fibreglass batt insulation is popular for standard rafter spacing due to its affordability and easy installation.

Spray foam insulation is ideal for complex roof structures as it offers excellent thermal resistance and effectively fills gaps. Rigid foam insulation works well in spaces with limited rafter depth due to its high R-value per inch.

Cellulose insulation, made from recycled paper products, can be blown into roof cavities for good coverage. Mineral wool insulation provides excellent fire resistance and soundproofing, making it a durable choice for increased safety.

It's important to remember that what works for one roof may not be the best option for another. Factors such as roof design, climate, and specific insulation requirements must be carefully considered to find the optimal solution. Sustainability is also a crucial consideration.

Some insulation materials, like cellulose and mineral wool, are more environmentally friendly. In contrast, others, such as certain types of foam, are less sustainable. Therefore, selecting the best insulation for your loft involves thoroughly evaluating these factors to ensure the best fit for your unique situation.

Best roof insulation for flat roofs

When choosing the best insulation for flat roofs, it's important to consider materials that offer strong thermal performance, moisture resistance, and durability due to the unique challenges of flat surfaces.

The structure of a flat roof will significantly influence the insulation materials you can choose from. Flat roofs, unlike pitched roofs, have minimal slopes, which create unique challenges:

Water drainage: Flat roofs do not naturally shed water as efficiently as pitched roofs, which can lead to water pooling. Therefore, roof insulation should be highly moisture-resistant and can support a waterproof membrane.
Thermal performance: Flat roofs are often exposed to direct sunlight and can absorb more heat, making thermal efficiency a critical consideration. Materials with higher R-values are preferred to reduce heat transfer and maintain consistent indoor temperatures.
Weight considerations: The weight of the insulation material used can impact the structural integrity of flat roofs. Lightweight materials are often favoured to avoid stressing the building structure excessively.

It is important to consider these factors when looking at flat roof insulation. Below we have provided the best roof insulation for flat roofs:

Polyisocyanurate (PIR) board

PIR boards are made from plastic foam, a popular choice because of its high R-value per inch, ranging from 5.6 to 7.0, providing excellent thermal resistance. Additionally, it produces less waste during production, making it an eco-friendly option for flat roofs.

These lightweight boards are easy to install and are compatible with a wide range of cladding and roofing materials, including metal roof insulation, brick, stone, wood, vinyl, and asphalt shingles. Securely attach PIR boards using adhesives or mechanical fasteners. Additionally, PIR offers fire-resistant properties and minimal environmental impact compared to other rigid board insulations.

It's important to note that while PIR boards can be relatively expensive, typically costing around £12.50 per square metre, they have lower resistance to water absorption. When exposed to wet conditions, these boards are likely to absorb up to 3% of their weight in water, which can reduce their R-value. This reduction in R-value can lead to mould growth and rot, especially in flat roofs where water can accumulate. Therefore, insulation needs to be water-resistant. Additionally, the R-value of PIR boards decreases in colder climates.

High R-value
Lightweight
Easy to install
Cost-effective
Produces less waste when made

Susceptible to water absorption
R-value decreases in colder climates
Mould and rot can occur

Extruded Polystyrene (XPS)

XPS is a durable thermoplastic foam produced by extruding polystyrene and a blowing agent through a die. It has a high R-value ranging from 5 to 6, depending on the product and environmental conditions, making it highly efficient for thermal insulation.

XPS has robust compressive strength and minimal water absorption&#;less than 1%&#;which preserves its structural integrity and thermal properties, even in damp climates. This makes it versatile for warm and cold decking insulation on flat roofs. XPS uses fossil fuels in its production and is non-biodegradable, making it less sustainable and eco-friendly than other insulation materials.

In addition, the cost of roof insulation with this material is much higher, at around £21.50 per square metre. It also offers less fire resistance than PIR, restricting its use with specific roofing materials such as asphalt shingles or those requiring torch-down techniques. When subjected to high temperatures, XPS can melt and drip, potentially spreading fire and emitting toxic fumes, which poses additional risks during fires.

Durable and strong
Moisture resistant
High R-value

High cost
Flammable
Not sustainable

Expanded Polystyrene (EPS)

EPS is the most cost-effective insulation material for flat roofs, averaging around £10 per metre. It's an excellent option for those seeking budget-friendly flat roof insulation. EPS is a thermoplastic foam with a consistent R-value of 4 to 4.5. It comes in various thicknesses, and you can cut it to fit your roof's dimensions, making installation easy.

EPS is not eco-friendly because it derives from petroleum, a non-renewable resource, and does not biodegrade, leading to long-term environmental accumulation. When burned, EPS can release harmful chemicals. Nevertheless, it is lightweight and has lower manufacturing energy requirements than other materials, providing some ecological benefits.

Additionally, EPS is incompatible with specific cladding and roofing materials, such as asphalt shingles, hot mop, or torch-down roofs, which can damage it due to high temperatures and solvents. An additional protective coat or layer is necessary to prevent damage. EPS is not as fire-resistant as PIR insulation and can melt and drip during extreme temperatures, potentially spreading fire and creating toxic fumes.

Cheapest flat roof material
Consistent R-value
Easy to install
Various thickness available

Low R-value compare to PIR and XPS boards
Flammable
Not eco-friendly
Not suitable to some cladding and roofing material

Best roof insulation for pitched roofs

For pitched roofs, the choice of insulation depends on factors such as thermal performance, ease of installation, and the specific use of the space under the roof, such as whether it will be a living area. The shape and structure of pitched roofs significantly influence the choice of insulation material. Pitched roofs, characterised by their sloping sides, present unique challenges and opportunities for insulation:

Complex structure: The angles and slopes of pitched roofs mean that not all insulation materials are suitable or easy to install. Materials need to conform to the roof's shape, limiting choices to flexible or easily customisable options like batts, blankets, or spray foam that can effectively fill irregular spaces, including eaves insulation.
Ventilation needs: Proper ventilation is crucial in pitched roofs to prevent moisture accumulation that can lead to mould and rot. Insulation materials and installation techniques must ensure air can flow adequately between the insulation and the roof surface.
Thermal bridging: The rafters in pitched roofs can often act as thermal bridges, allowing heat to bypass the insulation. Materials with higher R-values are preferred to combat this effect, as they provide better thermal resistance.
Space for insulation: Unlike flat roofs, pitched roofs often have an attic or loft space underneath, which can be used for either cold or warm insulation approaches. This space allows for thicker layers of insulation without compromising interior room headspace, which is beneficial for thermal efficiency.

Understanding the difference between cold and warm insulation types is crucial, as each method suits different requirements and affects the choice of material. Below, we will detail cold and warm roof insulation and the best roof insulation materials for these types of roofs.

Cold roof insulation for pitched roofs

Insulating sloped roofs with cold roof insulation is a cost-effective solution. It involves placing insulation between the ceiling joists, leaving the attic space unheated and cooler.

We recommend this method for attics used as storage rather than living spaces. It's also possible to add cold insulation between attic joists. While this approach is budget-friendly, it is crucial to maintain adequate ventilation in the attic space to prevent issues with condensation and dampness. Below are the best roof insulation for cold, pitched roofs:

Fibreglass

Fibreglass is a common and cost-effective insulation material for cold lofts, typically made of 40-60% recycled materials. Used for different applications, such as standard terrace homes, bungalows and even log cabin insulation, fibreglass is versatile and cheap and the best insulation material for cold roof insulation. It comes in rolls or batts and the cost of this insulation is around £10 per square metre. However, it can hold onto water and moisture, lowering its ability to block heat transfer and leading to mould and mildew growth. On average its R-value is between 3 to 4 per inch. Wear protective gear during installation to avoid skin and lung irritation from tiny glass fibres.

Non-combustible
Easy to install
Cheapest insulation material available
Eco-friendly

Can irritate skin and respiratory system during installation
Require protective gear for handling
Moisture sensitivity
Mould and mildew can grow

Cellulose

Cellulose insulation is made from recycled paper and easy to install using specialised equipment. It is eco-friendly, cost-effective, and fire-resistant. Its R-value is between 3.1 and 3.8 per inch. However, it can absorb moisture over time, reducing efficiency and requiring a vapour barrier. Installation can also generate dust, necessitating a protective mask, although it poses fewer health risks than fibreglass.

Cost-effective
Eco-friendly
Easy to install
Fire-resistant

Low R-value
Moisture sensitivity
Specialised equipment required
Dust generated during installation

Sheep wool

Sheep wool insulation is ideal for pitched roofs due to its excellent thermal and acoustic properties. It provides continuous insulation, has an R-value of 3.5 to 3.8 per inch, and can absorb up to 30% of its weight in water without compromising insulation. This is considered the most eco-friendly material available, however it is more expensive than other insulation costing around £19.75 per m2. Additionally it is fire-resistant and easy to install but susceptible to pests due to its organic nature.

Most eco-friendly insulation material available
Fire-resistant
Moisture regulation
Easy to install

Expensive
Lower R-value than other insulation materials
Susceptible to pests due to the organic material

Warm roof insulation for pitched roofs

When insulating a pitched roof using the warm roof method, the goal is to create a continuous thermal barrier directly under the roof, keeping the entire roof space warm. Warm insulation is applied under the roof covering, directly on the rafters, creating a warm, insulated envelope that includes the roof space. We recommend this method for attics used for living spaces. Below are the best roof insulation materials for the warm roof method.

Rigid foam boards

Rigid foam boards such as PIR, XPS or EPS are one of the best roof insulation materials for this insulation method. They offer excellent thermal efficiency, warming the entire loft and are easy to install in difficult roof areas.. As mentioned above we have listed all pros and cons of PIR, XPS and EPS insulation material.

Spray foam insulation

Spray foam insulation is an excellent option for insulating warm rooms in pitched roofs. When applied as a liquid, it fills an entire cavity, creating an airtight seal that is particularly effective for irregular or hard-to-reach spaces. However, it requires specialised equipment and protective gear, as the foam can irritate the skin and respiratory system. The insulation costs are relatively high, ranging from £55 to £70 per square metre depending on the open or closed-cell foam chosen. Additionally, the R-value ranges from 3.6 to 7 per inch, depending on the type of spray foam used.

If you are looking for more details, kindly visit Langfang Clear Chemical.

It's important to note that spray foam insulation is not environmentally friendly due to the chemicals used in its production. Despite its high cost, spray foam can last up to 100 years, saving future costs and reducing waste.

Can have a high R-value depending on type of spray foam chosen
Airtight
Easy to install with irregular roof shape and structure
Long lifespan

Expensive
Not eco-friendly
Harmful to skin and respiratory system
Specialised equipment required for installation

Best roof insulation for roof rafters

Place insulation material between or over the sloped structural beams (rafters) to insulate the roof. Creating a thermal barrier, roof rafter insulation keeps interiors warm in winter and cool in summer, benefiting living spaces. Below are the top three best roof insulations for roof rafters:

Rigid foam boards: These boards, including polyisocyanurate (PIR) and extruded polystyrene (XPS), offer high R-values, providing excellent thermal resistance. They can range between £10 to £21.50 per m2 depending on the type of rigid foam boards you choose. It is perfect for roof rafter insulation as they are durable, meaning they can withstand heavy weight without cracking. Additionally, cut them into shapes to fit between the roof rafters for easy installation.
Fibreglass: This is the best roof insulation material for the budget-conscious. It is affordable and will cost around £10 per m2. Its lightweight batts or rolls are ideal for roof rafter insulation and can be cut to fit between the rafters.
Sheep wool insulation: This material is perfect for those of you looking to further reduce your carbon footprint. People consider it the most eco-friendly and sustainable roof insulation material available. Due to its flexibility and resilience, it is particularly suitable for roof rafters and is easy to install. Additionally, it has natural thermal performance, moisture regulation, acoustic insulation, and fire resistance. These attributes make it an excellent choice for eco-conscious homeowners looking for an effective and sustainable insulation solution for their roofs.

Collaborating with an expert is crucial to ensuring you choose the perfect insulation for your roof. Professional guidance is indispensable for prioritising eco-friendly, cost-effective, or high-thermal performance options.

Complete our 30-second form to connect with local, trusted roof insulation installers. You'll receive up to four free, non-binding quotes without hidden costs or obligations.

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Describe your needs
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Choose the best offer

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FAQ

The best insulation for a roof depends on various factors such as the roof type, budget, and desired thermal performance.

The best insulation for roof rafters in the UK includes rigid foam boards like PIR or XPS, known for their high thermal efficiency and moisture resistance. Fibreglass is the best insulation due to its affordability and ease of installation. Additionally, sheep wool insulation is highly regarded for its excellent thermal and acoustic properties, eco-friendliness, and ability to fit snugly between rafters.

The best insulation for a cold roof typically includes fibreglass batts or rolls, which are cost-effective and easy to install.

8 Common Types Of Roof Insulation & Their Features ...

Making sure your roof is adequately insulated is essential for creating a cozy and energy-efficient home. But choosing the best insulation material can be overwhelming given the variety of options available.

In order to make things easier, in this blog post, we will take a look at eight popular types of roof insulation. We&#;ll explore their qualities, benefits, and crucial elements to take into account, helping you to make an informed choice that improves your home&#;s efficiency and comfort.

What Are Some Different Types Of Roof Insulation?

1. Fiberglass Batt Insulation

Fiberglass Batt Insulation

Cost: $1 to $1.50 per square foot

R-Value: R-2.9 to R-3.8 per inch

Fiberglass insulation, whether in batt or roll form, is a popular choice for insulating both the residential and commercial spaces. It is made from tightly woven glass fibers and offers effective thermal and acoustic insulation. It is ideal for framed cavities and is easy to handle and install in various areas such as in between rafters, joists, and studs. It often comes in pre-cut pieces for convenience.

Alongside being relatively inexpensive, fiberglass insulation is fire-resistant, easily recyclable, and known for its moisture resistance, making it suitable for roofs, attics, and walls. Despite its benefits, precautions are needed during installation due to potential eye or skin irritation from released fibers.

Nevertheless, its ability to block sound, resist fire, and adapt to different needs makes it a practical as well as a cost-effective solution for improving energy efficiency and soundproofing in buildings.

2. Polyisocyanurate (Polyiso) Insulation

Cost: $0.65 to $0.85 per square foot

R-Value: R-6.5 to R-8 per inch

Polyisocyanurate insulation boards are highly efficient thermal materials used in construction. They come in different thicknesses and are designed to eliminate thermal bridges, making them adaptable for various applications. These rigid boards, often faced with foil for enhanced performance, resist air infiltration and moisture, ensuring durability and ease of handling during installation.

This material is commonly used in attics, roofing, and flooring due to its excellent compressive strength and resistance to rot. Available in different types tailored for specific needs, polyiso insulation is valued for its slim profile and thermal properties.

Its high R-values and moisture resistance make it ideal for use in various roofing systems, including flat roofs, and it&#;s particularly useful for buildings with limited insulation space.

3. Expanded Polystyrene (EPS) Insulation

Expanded Polystyrene (EPS) Insulation

Cost: $0.40 to $1.20 per square foot

R-Value: R-3.9 to R-4.4 per inch

Expanded polystyrene (EPS) is a lightweight, rigid foam material commonly used in construction and packaging. Made from solid polystyrene beads, it&#;s 98% air and recyclable. With low thermal conductivity and moisture absorption, EPS offers great insulation properties.

It can be modified with additives like flame retardants for improved fire resistance. EPS is used in construction due to its thermal insulation, compressive strength, and long lifespan. It&#;s budget-friendly, easy to install, and available in various forms. Compared to other insulation, EPS has slightly lower compressive strength and is more permeable to air and moisture.

It&#;s commonly used in floor, wall, and roof insulation, offering durability, corrosion-resistance, and a cost-effective solution.

4. Spray Foam Insulation

Spray Foam Insulation

Cost: $1 to $2 per square foot

R-Value: R-3.6 to R-3.9 per inch

There are two options of spray foam insulation: closed-cell and open-cell. While closed-cell foam is denser and has higher R-values, open-cell foam is more flexible and less dense. Both varieties stick to surfaces, offering superior air sealing and guarding against water infiltration.

Spray foam insulation is usually applied as a liquid and expands into solid foam. It can be sprayed onto any surface, making it suitable for various spaces. While open-cell foam is ideal for sound insulation, closed-cell foam is better at preventing heat transfer and water damage.

Spray foam insulation is appropriate for both home and commercial use. It can be applied in almost any area of a building, including the attic, walls, basement, and under floors, making it an excellent choice for oddly shaped spaces or hard to reach areas.

5. Reflective Foil Insulation

Reflective Foil Insulation

Cost: $0.25 to $2 per square foot

R-Value: R-3 to R-17 per inch

Reflective foil insulation utilizes reflective materials to create a barrier against radiant heat. It typically comprises layers of reflective aluminum foil, thermo-foam, and polypropylene, which reflect heat and trap air to prevent heat loss.

Lightweight, thin, and easy to install, it can be found in walls, floors, and roofs. This insulation offers high thermal performance, acting as a radiant barrier to maintain comfortable temperatures year-round.

Available in various thicknesses and sizes, it can fit between rafters and joists or be installed continuously. Reflective foil insulation is cost-effective and sustainable, meeting building regulations and standards for performance and quality.

6. Perlite Cover Boards

Cost: $1.20 to $9.60

R-Value: R-2 to R-3 per inch

Perlite cover boards are specialized insulating materials used in roofing systems. Made from expanded perlite ore, cellulose fibers, and other materials, it is an effective type of roof insulation. These boards offer fire and moisture resistance while regulating temperature and shielding buildings from extreme thermal fluctuations.

Lightweight, durable, and environmentally friendly, this material improves energy efficiency and is ideal for low slope or flat roof constructions. Known for their non-combustible nature and ability to withstand high temperatures, perlite cover boards boast excellent thermal insulation properties due to their porous structure.

Additionally, they can be used as a base for various roofing membranes, offering superior strength and insulation.

7. Blown-In Insulation

Blown-In Insulation

Cost: $0.50 to $2.50 per square foot

R-Value: R-3.2 to R-4 per inch

Blown-in insulation, or loose-fill insulation, is versatile for insulating buildings. It is applied by blowing or pouring loose material into enclosed spaces like in between framing boards or attics. It is commonly used to fill existing cavities or add insulation to hard to reach areas. It&#;s a practical, cost-effective solution suitable for various building types, improving thermal and acoustic performance.

Whether made from fiberglass, cellulose, or recycled materials, blown-in insulation is ideal for filling large attics or crawl spaces. Fiberglass insulation is non-flammable and is less suited to cold climates, while cellulose insulation, though flammable, is better for colder regions and is more durable than fiberglass.

It can be efficiently blown into any space using a flexible tube. With control over the total amount of insulation installed, it&#;s adaptable to different climates.

8. Structural Insulated Panels

Cost: $10 to $18 per square foot

R-Value: R-5 to R-7 per inch

Structural insulated panels (SIPs) are innovative building materials used in walls, roofs, and floors. They feature a piece of foam insulation between two boards, typically oriented strand board (OSB). SIPs offer exceptional thermal performance, airtightness, and strength, contributing to an energy-efficient and durable building.

Available in various thicknesses and customizable to fit project needs, SIPs facilitate fast installation times. It is used in residential, commercial, and industrial construction, and SIPs are recognized for their sustainability and cost-effectiveness.

The foam core, often closed-cell rigid polyurethane or expanded polystyrene, provides excellent thermal resistance and structural integrity. With dimensions of up to 4-feet in width and 24-feet in length, SIPs offer versatility in design and construction.

Why Is Roof Insulation Important?

Now that you know the different types of roof insulation, it is also essential that you understand its importance. Let&#;s delve in to get a better understanding:

Saves Energy and Money: Keeping your roof well insulated helps you save on energy bills by trapping heat in winter and blocking out excess heat in summer.
Prevents Damage: Proper attic insulation stops issues like uneven snow melt, ice dams, and condensation buildup, which can harm your building over time.
Supports Sustainability: Insulating your roof reduces your reliance on heating and cooling systems, contributing to a healthier environment and fighting air pollution.
Controls Temperature: It maintains a comfortable indoor temperature year-round by minimizing the loss of air through the roof.
Reduces Noise: Insulation acts as a sound barrier, making your indoor space quieter by blocking outside noise.

Conclusion

Picking and knowing which type of roof insulation is best for your roof depends on a few things that have been mentioned above in this blog post. Now that you have an understanding of the different kinds of insulation available, you can choose the best one for your needs and budget. It&#;s also a good idea to talk to an expert to get advice on what&#;s right for your building before making a final decision.

All Around Roofing, Siding & Gutters is here to help! If you have any questions or need help choosing insulation for your home, just get in touch with us. And if you&#;re looking for top-notch insulation installation services, remember All Around Roofing, Sidings & Gutters is here to serve you in the Dayton area. For the best roofing services get in touch with us at (937) 902-.

Contact us to discuss your requirements of Roof Insulation Supplier. Our experienced sales team can help you identify the options that best suit your needs.

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