Insulation installation

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Installing insulation in a new dwelling or adding insulation to an existing one can make a significant difference to the comfort and energy performance of the home, but it is vital that the insulation is put in correctly. Read the article in conjunction with Insulation to find out how to install insulation in various types of construction and useful tips for achieving the results you want.

Under the Building Code of Australia (BCA), the resistance of a building fabric to heat flow, expressed as ‘total R-value’, varies depending on climate zone and the building site’s height above the Australian Height Datum. Ensure you comply with the BCA requirements for energy efficiency of building fabric.

Installation tips

To install insulation without compromising its effectiveness, you need to consider a range of issues: thermal bridging, vapour barriers, ventilation, air gaps, and physical handling of the different types of insulation.

Thermal bridging

The building frame can act as a thermal bridge, particularly in cold climates, conducting heat and allowing it to bypass otherwise effective insulation. Metal framing is a particular problem because of its high conductivity. The presence of the frame reduces the overall insulation value, as the frame can constitute up to 15% of the wall, ceiling or floor surface. To help overcome the effect of thermal bridging:

• install polystyrene isolating strips between the metal frame and cladding, which must be at least 12mm thick with an R-value of 0.2
  
• fix bulk insulation, such as polystyrene boards, over the external or internal surface of the frame.
  

Vapour barriers

Vapour barriers include polythene sheeting, reflective foil, foil backed plasterboard and well maintained water-resistant painted surfaces. Water-resistant insulation, such as polystyrene, can also act as a vapour barrier. Tape or glue all joints in vapour barriers to keep out moisture.

Use vapour barriers to protect from condensation:

• in high humid (tropical) climates
  
• in cool climates where the difference between indoor and outdoor temperature is significant
  
• in roof spaces with a low ventilation rate (e.g. cathedral or raked ceilings)
  
• in situations where high amounts of vapour are generated and not exhausted
  
• on the underside of metal roofing, to minimise the likelihood of condensation and corrosion.
  

Install vapour barriers on the warm side of the insulation:

• in cold climates, on the inside of the insulation (directly above the ceiling lining and next to the internal wall lining)
  
• in warm climates, on the outside of the insulation.
  

Roof ventilation

Ventilate the roof space where possible to allow built-up heat to dissipate. Even in cooler climates a minimal amount of ventilation is desirable to allow built-up moisture to escape. Air gaps along the ridgeline or between tiles often provide sufficient ventilation. Gable or eaves vents may also be used.

Ventilated roof spaces in high humid (tropical) climates under metal roofing can result in excessive condensation within the roof space at night. You can prevent condensation dripping off the underside of metal roofing onto the ceiling by installing reflective foil sarking similar to that used under roof tiles, or using a foil-backed building blanket (anti-condensation blanket) under the metal roof, or closing the vents at night to prevent night air from entering the roof space.

In bushfire prone areas, cover any openings with fine stainless steel mesh to prevent cinders from entering the roof space. Keep roof spaces weather-tight and vermin proof.

Gaps

Avoid gaps in all types of insulation. Even a small gap can greatly reduce the insulating value. Fit batts snugly and don’t leave gaps around ducts and pipes. Tape up holes and joins in reflective insulation. Make sure the ends of multi-cell and concertina foils are well sealed, and ensure that corners of walls, ceilings and floors are properly insulated as these are areas where heat leaks most often occur.

For safety reasons, minimum clearances must be left around hot objects, such as flues from fires, recessed downlights and their transformers

Health and safety tips

Wear protective clothing, gloves and a face mask when installing glass wool, mineral wool or cellulose fibre insulation. These materials can cause short term irritation to skin, eyes and the upper respiratory tract. It is good practice to always wear protective equipment when working in dusty roof spaces.

Wear adequate eye protection when installing reflective insulation, as it can give off a painful glare, and be aware of the increased risk of sunburn.

Insulation materials containing reflective foil must be kept clear of electrical wiring and fittings, and should not be secured using metal staples.

Electrical wiring must be appropriately sized or it may overheat when covered by insulation. Have it inspected by a licensed electrician.

Allow clearance around hot flues, exhaust fans, appliances and fittings that penetrate the ceiling to the manufacturer’s installation instructions.