Insulation made easy

The placement of batts in internal and external walls usually happens during a build or renovation, as once the internal lining is fixed in position there is no access to the wall cavities.

Begin by measuring the surface area in square metres to calculate the number of packs required for the job, then purchase batts with the required R-value and width.

Batts come in 430 and 580mm widths to match 450 and 600mm stud spacings.

Check the stud depth to ensure the specified R-value batts fit snugly in the cavity. Before commencing installation, check whether any electrical wiring is connected to the meter box.

Also, make sure the power is turned off and any safety hazards are identified.

At external stud walls, the batts must be kept within the frame and not touch the brickwork or mortar.

To keep the batts contained, staple one vertical strap or stringline in position or two horizontal straps or stringlines for each noggin opening.

When all the batts are in position inside the stud framework, the wall linings can be secured.

The two main types of insulation, bulk and reflective, are ideally used together to maximise benefits.

REFLECTIVE FOIL insulation is laminated to a base.

Positioned next to an air space, it resists heat transferred by radiation and is used to wrap wall and roof framing.

BULK INSULATION products such as fibreglass, rockwool and cellulose fibre are used in ceilings, floors and walls.

They inhibit the transfer of heat and the higher their R-value, or level of thermal resistance, the more effective the insulation.

FIBREGLASS BATTS are made of up to 80 per cent recycled glass that is melted and spun into fibres to form matting of different R-values to suit various climates.

The most commonly used bulk product, they’re affordable and easy to cut and install DIY.

It’s important to protect your skin, eyes and lungs when working with fibreglass batts.

The handling of this type of material may result in temporary itching, so consider wearing disposable coveralls, about $4 each, from hardware stores, plus a hat, mask, goggles and work gloves.

Do seal around window and door jambs with expanding spray foam.

The purpose of the foam is to seal the space to prevent air infiltration.

Use an expanding foam suitable for window and door insulating, as these minimal expanding types reduce the chance of warping the jamb.

If there’s still space after the foam has cured, lightly stuff the gaps with strips of fibreglass insulation.

Don’t split the batts apart to fit around and totally enclose electrical cables, as thermal insulation prevents the dissipation of the natural heat rise of cables carrying electrical current.

As cable operating temperatures rise, their ability to carry current is reduced.

This phenomenon is called ‘cable derating’.

Fit the batts snugly between the wall studs, ensuring they‘re not thicker than the stud width.

Cut to length by compressing the insulation, placing a scrap of plywood under and cutting with a sharp utility knife.

Don’t tuck full-thickness batts behind any pipes or ducting.

Compressing the fibreglass decreases its insulating value and creates voids between the insulation and plasterboard.