What are the different types of roof insulation?

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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 itchiness of the glasswool material. Many glasswool products are now claiming to be itch-free, 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. Cellulose insulation can be blown in, wet or dry. If you are choosing to install cellulose roof insulation, it is recommended to achieve a minimum of R3.0 in this area. 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 other 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 settles over time, which gradually reduces its R-value.
  • Absorbs moisture more easily that other insulation material types.

Rockwool Insulation

Due to its minimal organic properties, Rockwool insulation is non-combustible and does not produce toxic smoke. Additionally, Rockwool is made from natural Basalt rock and Chalk, and can withstand temperatures of above 1000 degrees. Most commonly used as a firestop wall but can also be used as roof insulation.

Pros

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

Cons

  • Can irritate skin when installing
  • PPE is recommended to be worm 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 higher 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

  • Non-combustible
  • 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)

Material Application Itch Factor Thermal Resistance Acoustic Properties Fire-Resistance
Glasswool Residential; walls (external & internal), ceilings, underfloor M H H M
Polyester Walls (external & internal), ceilings, underfloor L H H M
Cellulose Residential and commercial applications M M M M
Rockwool Residential and commercial applications M M M H
Sheep’s Wool Insulation Residential; walls (external & internal), ceilings, underfloor L M M H

Different Forms of Roof Insulation

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

Batt Insulation

Most common form of insulation is batt insulation. Usually available in 420mm 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 it is pre-cut, however if further cutting is required you can use any off-cuts in small spaces that are hard to reach.

Rigid Board Insulation

Insulation boards can achieve high R-values with narrow thickness, whilst others have a foil outer layer that deflects 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 minimizes risk of condensation, dampness, mould or corrosion. The polyurethane foam expands to fir perfectly the space in which is it being installed, it makes a great roof insulation product. Can be available in both open and closed cell sprays to suite your homes need.

Loose-fill insulation

Loose-fill insulation is material such as fibreglass, cellulose, and rockwool that is kept in a loose form and blown in to the desired area. These areas include; wall cavity, roof area, underfloor area, etc. Loose fill insulation can be installed into 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 a qualified 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 it is available in varying thickness. SIPs can be constructed to meet most buildings designs, can save you construction time, reduce overall project costs as well as reduce labour costs.

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