Fibreglass Insulation Batts

Fibreglass insulation batts (also known as Glasswool batts) are the most used thermal insulation material in house building / home construction in Australia.

Fibreglass insulation batts are precut, whereas blankets are available in continuous rolls. Compressing the material reduces its effectiveness. Cutting it to accommodate electrical boxes and other obstructions allows air a free path to cross through the wall cavity.

One can install batts in two layers across an unfinished attic floor, perpendicular to each other, for increased effectiveness at preventing heat bridging.

Batts can be challenging and unpleasant to hang under floors between joists; straps, or staple cloth or wire mesh across joists, can hold it up.

Gaps between batts (bypasses) can become sites of air infiltration or condensation (both of which reduce the effectiveness of the insulation) and requires strict attention during the installation. By the same token careful weatherization and installation of vapour barriers is required to ensure that the batts perform optimally.

 
Thermographic image of a vulture in the winter.
He uses a layer of trapped air as insulation.

• Fiberglass Made from molten glass (silicate), usually with 20% to 30% recycled industrial waste and post-consumer content. Non-flammable. Most fiberglass is unfaced, but some are supplied paper-faced with a thin layer of asphalt, and some is foil-faced. Paper-faced batts are vapor retarders, not vapor barriers. Foil-faced batts are vapor barriers. The vapor barrier must face the proper direction.
• Rockwool (CSR Bradford Insulation) made from rock (basalt) or iron ore blast furnace slag. Some rock wool contains recycled glass. Non-flammable.
• High-density fiberglass is used to create fibreglass insulation batts with higher sound attenuative properties - offering soundproofing properties as well as thermal insulation.

Fibreglass Insulation Batt sizes

They are sold in in batts designed to fit in the gaps between wall studs and ceiling joists (or the bottom chord of roof trusses). Wall studs and roof trusses are designed at 450mm or 600 centres (meaning they will be 450mm or 600mm apart). As a general rule, the space between external wall studs (load bearing walls) is approximately 430mm and internal non load bearing walls wall studs is 580mm while the space between ceiling joists is mostly 580mm in modern homes (older trusses may still be at the 450mm centres).

The universal length of insulation batts is 1160mm (2 x times 580mm)

Are Fibreglass Batts hazardous to my health?

Fibreglass batts are manufactured from spun mineral fibres - silicate or basalt, as such, it is hazardous to inhale or ingest the fibres in to the body. It is very important to wear both protective clothing and appropriate breathing apparatus when installing fibreglass / glasswool insulation batts.

Once the batts are installed either in to the walls before lining them with plasterboard, or in to the ceiling cavity, they effectively are contained within the walls or ceiling space and are no longer harmful to you or your family's health in any way.