Grand - Air-Tight - Designs

The episode of Grand Designs that went to air on ABC 1 last night featured a new home "built using the latest avant garde eco technologies." On top of its eco-concrete foundations sit a series of timber frame boxes, heavily insulated with recycled newspaper and clad in English cedar. Large, triple glazed windows to the south help to heat the house using the power of the sun to warm the heavy concrete slab. To conserve heat the whole building was: enveloped in a special membrane to make it super-airtight; tested using the same air leakage assessment technology that Energy Imaging use; and then fitted with a ventilation system to recover heat from the air.

The UK building codes of 2006 introduced mandatory air leakage testing of new houses. Best practice for building air leakage is considered to be between 3 and 7 m3 of air, per hour, per m2 of permeable surafce area at a 50 Pascal (Pa) pressure difference between inside and out. Once a building gets below 3 at 50 Pa, mechanical ventilation is required to maintain indoor air quality. The home featured on Grand Designs achieved an impressive score of just 1.2. To put this into perspective, most houses we test in Canberra are between 15 and 25 at 50 Pa!

Australia is yet to introduce a maximum air leakage standard for new buildings despite it being the most cost effective way to achieve direct energy savings, reduce GHG emissions and improve comfort levels. It is also the simplest and most cost-effective way to retrofit an existing building.

NB: there is a difference between insulation and air leakage. Insulation does not prevent air leakage. Both insulation and air leakage must be addressed to achieve energy efficeincy. Your insulation cannot do its job if your precious heated air can escape directly through holes in the buidling envelope. If you are serious about improving the energy efficiency of your home: 1. seal the air leaks + 2. insulate thoroughly and evenly... 1 + 2 = 3 x more efficient heating in your average Canberra home.