R-rated – is it as hot as it could be?

While Building Code changes and government subsidy schemes have focused on encouraging more insulation in new homes and retrofitting existing homes, there’s growing concern that poor installation is undermining the drive to improve housing performance.

Installing insulation incorrectly reduces its effectiveness at stopping heat loss. BRANZ fitted insulation to a wall panel and tested different-sized gaps. They found that R2.8 insulation with 16 mm gaps would only perform as well as R1.4 insulation. Even with gaps of just 4 mm, the R-value was reduced by 12-15%.

The danger is that if installation problems occur throughout the house, the cumulative effect on its thermal performance may mean it doesn’t meet the energy efficiency requirements of the Building Code, even if the correct R-value materials are used.

Typical problems

An audit of insulation fitted in new build homes, undertaken for the Energy Efficiency and Conservation Authority (EECA), provides worrying reading. None of the installations in the 58-house audit met the requirements of NZS 4246:2006 Energy Efficiency – Installing Insulation in Residential Buildings. This Standard provides a best practice guideline, in order to achieve good thermal performance.

Typical problems affecting the home’s thermal performance included:

• Folds
• Tucks
• Gaps
• Compressions
• Missing insulation
• Lack of insulation to the middle of the top plate

Other issues were the lack of a 25mm gap to the underside of the roof underlay, which has the potential to transfer condensation and moisture to the insulation, as well as significant safety faults through insulating over or around recessed downlights and electrical equipment.

The photographs (bottom left) show typical installation problems from a range of houses. Using a high-quality insulation product with a high R-value is important – but no matter which product you use, installation of that product is the key to good performance.

Ensuring good installation

The Insulation Association of New Zealand has been formed to encourage better performance in the supply and installation of residential insulation. The Association has developed a training programme offering industry-specific training in site safety and on the key requirements of NZS 4246:2006.

To get the best-quality installation for your clients, consider using a graduate of their training programme. You can find the names of graduates on the IAONZ website www.iaonz.co.nz

Alternatively, if you prefer to install insulation yourself, it could be worth taking the IAONZ training programme – you may be surprised how much you can learn about this important aspect of the builder’s craft.

After all, the better the installation, the warmer your clients will be in their new home and the lower their power bills, – all part of the ‘quality build’ process.

“Using a high-quality insulation product with a high R-value is important – but no matte which product you use, installation of that product is the key to good performance

Tips for good insulation

• Only insulate when moisture content of timber is less than 16%.
• Fit insulation closely to framing – there should be no gaps around the outer edges of the segments and framing, or between butted joins.
• Make sure there are no folds in the segments themselves.
• Make sure there is no tucking.
• Insulation material should not be compressed – it will not perform to its best.
• Insulation materials should be dry and undamaged.
• Leave a clear space of at least 25 mm between the insulation and roof or roof underlay.
• Leave clearances around recessed downlights, unless they have an IC (insulated contact) rating.
• Leave clearances around auxiliary control equipment, metal chimneys and flues.
• For wall insulation, check out the Guide for Retrofitting Wall Insulation by EECA and MBIE – download from www.eeca.govt.nz/resource/guide-retrofitting-wall-insulation

About Beacon Pathway

Beacon Pathway is a group committed to transforming New Zealand’s housing stock and neighbourhoods through research and demonstration projects, which show how to make homes more resource efficient, healthier to live in, adaptable, resilient and affordable.

For further information about Beacon Pathway visit www.beaconpathway.co.nz

 

Below: Typical installation problems