The Materials

Everything there is to know about Insulation for a self-build

01 Materials Customising your self-build

02 Product guides Choosing your materials

The ultimate guide to insulation

The role of insulation in any property is more important than ever. With rising fuel costs and the need to lower CO2 emissions a top priority, you need to carefully consider the kind of insulation you are going use inside your self-build home.

Insulation is used in all of the external envelope along with most internal walls and floors.

Ensuring you choose the correct insulation and where to place it can, for example, reduce the risk of interstitial and surface condensation. Placing thermal insulation to the outside of a steel frame wall creates a warm frame construction and reduces the risk of condensation forming on the steel studs. It is advisable to use a correctly specified air and vapour control layer (AVCL) product to minimise the risk of condensation while maximising thermal performance.

Glass mineral wool insulation

This is a common form of insulation in the UK. Available in a range of densities, glass mineral wool offers excellent thermal and acoustic properties as well as enhanced fire safety. The production of glass wool uses far less energy than the amount of energy it saves once installed within the building.

Glass mineral wool is made by melting sand, soda ash, limestone and recycled glass in a furnace at a temperature in excess of 1400°C. The molten glass is taken from the furnace and fed into spinning discs where it is spun to form fibres that are in turn directed through the application of a binding agent onto a moving conveyor to form a mat of glass mineral wool. This mat is subjected to further forming processes including curing within an oven before undergoing cutting/shaping into rolls or slabs.

Sheep’s wool insulation

With excellent thermal and acoustic properties, sheep's wool makes the perfect alternative to man-made insulation.

Sheep's wool is breathable too, therefore it can rapidly absorb and release water vapour, reducing condensation and helping to keep buildings cool in the summer and warm in the winter. This makes it suitable for timber frame constructions.

As you'd expect, sheep's wool is a renewable and a continuous resource - which makes it reusable, recyclable and biodegradable.

PIR (polyisocyanurate) insulation

This thermoset material is made by combining facing materials and a formulated blend of MDI, Polyol and additives to produce a rigid foam product. The heat generated during the reaction allows the generation of gases which become encapsulated within foam cell structure delivering premium thermal performance features.

Celotex PIR insulation, for example, would be an ideal solution when trying to meet the requirements of energy assessments. With a low thermal conductivity, it can be used to create some of the thinnest and most thermally efficient constructions. However, within any new build there will generally be a requirement for several types of insulation to ensure that both thermal and acoustic specifications can be achieved.

Which type of insulation should I use?

Cavity walls, timber frame constructions and solid walls

Rigid foam boards are ideal insulation materials to be installed into cavity walls, timber frame constructions and solid walls as well as roof and floor constructions. Celotex manufactures general purpose boards (TB4000, GA4000 and XR4000), which can be cut to fit between timber framing in walls and roofs and laid over solid slab or beam and block flooring.

Celotex’s cavity wall boards (CW4000) are designed to fit between wall ties to partially fill the cavity of a masonry construction. The insulated plasterboards PL4000, can be used to upgrade solid walls or line other wall and roof constructions as a method of preventing thermal bridging.

Masonry cavity walls/attics and loft spaces

For masonry cavity walls one of Isover’s CWS range of cavity slabs should be used, and for masonry separating (Party) walls RD Party Wall Roll should be used.

For attic and loft spaces Isover’s Spacesaver/Spacesaver Plus can be used between the joists. If you are looking to create a room in your loft then Metac should be used to insulate between the rafters.

If you are insulating external timber stud walls then Isover’s Timber Frame Roll or Timber Frame Batt should be used, and for timber separating (Party) walls then Timber Frame Party Wall Roll should be used. Internal partition walls should be insulated with Isover’s Acoustic Partition Roll (APR1200), as should internal floors. APR1200 can also be used for insulating separating floors.

For ventilated facades or for the overcladding of framed walls, Isover’s Polterm Max Plus could be used.

It is worth speaking directly to manufacturers regarding your project to obtain the best solution. Always consult building control to ensure your project complies with building regulations.

Which insulation is best for soundproofing?

For acoustic products, a combination of mineral wool insulation and sound reduction plasterboards such as those manufactured by Isover and British Gypsum, could be the right fit. Glass mineral wool has excellent sound absorption qualities so would be suitable for all soundproofing requirements within walls and floors; APR1200 would be the ideal product to use here.

What kind of insulation is used on air ducts?

This would depend upon where the air duct is situated and how the insulation is to be detailed. In some instances, a flexible insulation product may be required and in some applications the duct may form part of the wall construction at height. In these situations, a mineral wool product may be required. If the ducting is within a roof void, then a rigid type of insulation could be used to form a box type of construction around the duct.

Climcover Roll and Climcover Slab are the best solution for insulating circular or rectangular ductwork for thermal or acoustic reasons. If, however, you require a specific period of fire resistance for your ductwork then the U Protect system should be specified.

What kind of insulation is used when replacing windows?

When replacing windows, Celotex PL4000 can be included at the side reveal to prevent a cold bridge. PL4015 has been designed specifically for this application and with an overall thickness of 27.5mm won’t encroach too much over window frames. The construction of the surrounding wall would have a consideration on what insulation is added around the windows.

Can insulation be recycled?

Although the technology exists to recycle PIR insulation, the vast majority of recycling centres would not have the facility to perform this. The foam core is not widely recyclable. Insulated plasterboards must have the plasterboard separated from the insulation component before disposal as the plasterboards are gypsum based and cannot be sent to landfill. Off-cuts of PIR and glass mineral wool can be disposed at normal household waste centres.

When does insulation need to be replaced?

Typically, if correctly installed, insulation should last the lifetime of the building (around 60 years) and shouldn’t require replacement unless damage occurs, such as flooding or structural problems. If a construction, such as a roof or wall is being upgraded, then it may be easier to remove existing insulation but often this can just be added to, in order to meet current Building Regulatory requirements.

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