What are the different types of roof insulation?

It’s easy to get lost in a shop when you don’t know what you’re looking for and there are too many options. Luckily, we’re here to help make things a little less complicated and to help you choose which roof insulation product is right for your home. Firstly, there is a large variety of roof insulation products manufactured today. These products vary in material type, for example glasswool, polyester, and rockwool, and product form, such as roof insulation batts, rolls, loose fill, and rigid foam boards. Each roof insulation product has its pros and cons, so make sure you do a little research beforehand, to ensure you are choosing the best insulation for your home.

Glasswool insulation

Glasswool insulation is a popular thermal roof insulation material that has been around for many years. In the last 10 years, manufacturing processes have drastically improved the durability and reduced the itchiness of the glasswool material. Increasingly, glasswool products are now claiming to be low-itch, robust and durable, lasting for the lifetime of your home.

Pros

• Cost-effective
• Non-combustible
• Made from recycled glass material
• Low-itch factor and easy to install

Cons

• Protective gear should be worn whilst installing
• Compression of the fibreglass material reduces its performance

Polyester insulation

Polyester insulation is a man-made synthetic product which is made from recycled PET plastic such as drink bottles. It is a strong and durable product that does not degrade over time. It is available in blankets, rolls and batts. The following polyester cheap roof insulation products available at Pricewise insulation include; Autex GreenStuf, and Bradford Polymax.

Pros

• Durable product
• Non-allergenic, non-irritant, non-toxic
• Environmentally friendly

Cons

• More expensive than glasswool
• Will melt when exposed to open flame

Cellulose Insulation

Today, cellulose insulation is made from up to 85% recycled paper. It is heavily treated with chemicals such as boric acid, borax and ammonium sulphate. Cellulose roof insulation can be installed during the construction phase of your home or retrofitted to existing homes. If you are choosing to install cellulose roof insulation, it is recommended to achieve a minimum of R4.0 in the ceiling. Cellulose insulation can be blown in, wet or dry.  As cellulose insulation is treated with boric acid, this increases the fire resistance of the insulation, and reduces mould growth and increases insect resistance.

Pros`

• Reduces amount of wasted paper and cardboard being dumped into landfills
• Generally cheaper than glasswool / fibreglass insulation
• Less itchy than traditional fibreglass material

Cons

• Installation costs can be more expensive as it requires machine hire and basic training for installation.
• Dry-blown cellulose tends to sag and settle over time, which gradually reduces its R-value.
• Absorbs moisture more easily than other insulation material types.

Rockwool Insulation

Due to its minimal organic content, rockwool insulation is non-combustible and does not produce significant toxic smoke. Additionally, rockwool is made from natural basalt rock and chalk, and can withstand temperatures of above 1,000°C. It is most commonly used in fire-rated walls but can also be used as roof insulation.

Pros

• Soundproofing capabilities
• Great fire ratings
• Fire resistant
• Moisture resistant
• Acoustic performance is high

Cons

• Can irritate skin when installing
• PPE is recommended to be worn when installing this material
• Generally, more expensive than other bulk insulation materials

Sheep’s wool insulation

Sheep’s wool works in the same way as other insulation products, by trapping air between fibres within the wool. Wool is a poor conductor of heat, even more so than other insulation materials such as fibreglass and rockwool. Naturally crimped fibres help the wool batts to maintain shape and stability over time. Sheep’s wool insulation is said to have a similar R-value, when compared to other insulation products of the same thicknesses. It is a great roof insulation product that can last for the lifetime of your home.

Pros

• Naturally fire-resistant
• Biodegradable
• Sound absorption – reduces airborne noise, transmission sound and surface vibrations.
• Does not itch, and is easy to work with

Cons

• More expensive
• Sheep’s wool is either bonded together mechanically or with a polyester adhesive

Summary of Roof Insulation Materials:  (Low = L, Medium = M, High = H)

Different Forms of Roof Insulation

Insulation can come in a variety of forms to suit your specific needs. Below are a few of the most common roof insulation material forms used in both commercial and residential settings.

Blanket Roll Insulation

Insulation rolls are a commonly used form for roof insulation as they are most suited to installing large areas. Insulation rolls can also be used as a top-up layer in the roof area. Start by rolling out the insulation from the outer corner to the middle of the roof and manhole access. Use any offcuts to insulate the smaller, harder-to-reach places in your roof area.

Batt Insulation

The most common form of insulation is batt insulation. Usually available in 430mm or 580mm width and are pre-cut to fit between joists and studs. Remember when installing roof insulation batts, don’t leave any gaps which will compromise the effectiveness of the insulation. Roof insulation batts are easy to install as they are pre-cut, however if further cutting is required you can use any offcuts in small spaces that are hard to reach.

Rigid Board Insulation

Insulation boards are able to achieve high R-values with narrow thickness, whilst others have a foil outer layer that reflects heat. Insulation boards are rigid and durable and can be installed in the roof and ceiling area, including cathedral ceilings. All insulation boards reduce winter heat losses and summer heat gains, enabling comfortable indoor temperatures year-round.

Spray foam insulation

Polyurethane spray foam is the most commonly used material. As it has air-sealing ability, it minimises the risk of condensation, dampness, mould or corrosion. The polyurethane foam expands to fit perfectly into the space in which it is being installed, making it a great roof insulation product. It is available in both open and closed-cell sprays to suit your home’s needs.

Loose-fill insulation

Loose-fill insulation is material such as fibreglass, cellulose, and rockwool that is kept in a loose form and blown into the desired area. These areas include wall cavity, roof area, underfloor area, etc. Loose-fill insulation can be installed into almost any area and space, it is great for those hard to reach places. Installing loose-fill insulation requires special equipment so the overall installation cost may be higher, especially if an experienced installer is involved.  

Structural Insulated Panels (SIPs)

SIPs are designed for residential and light commercial applications. They are made of an insulating core such as expanded polystyrene EPS or polyisocyanurate PIR and on either side a structural facing such as oriented strand board OSB. They can form roof, walls and floor areas, as they are available in varying thicknesses. SIPs can be constructed to meet most building designs, can save you construction time, reduce overall project costs as well as reduce labour costs.