Wall insulation retrofits on trial

Thermal image post wall insulation

A recent series of trials by Sustainability Victoria has investigated the viability and cost-effectiveness of energy efficiency retrofits. Eva Matthews summarises the overall study and the results from one trial, retrofitting wall insulation.

WHILE residential development (new housing and renovations) continues apace throughout urban Australia and mandatory building standards have been introduced over the last couple of decades to improve energy efficiency and reduce greenhouse gas emissions, there remains a huge pool of older existing housing stock that hasn’t benefitted from these improvements. There have also been few studies to determine the extent of inefficiency in this existing housing, how it might be practically upgraded and how cost-effective it would be to do so. Step in Sustainability Victoria (SV), who commenced a study in 2009 to investigate these information gaps.

Their On-Ground Assessment (OGA) compiled data, based on modelling, from a “reasonably representative” sample of 60 pre-2005 homes in Victoria, with the results published in December 2015 (The Energy Efficiency Upgrade Potential of Existing Victorian Houses; www.bit.ly/2cTP6eJ). The second phase of the study was to implement energy efficiency upgrades in a selection of houses and to assess costs and savings, householder perceptions and any implementation issues. The results of these trials are also at the above link.

Here we outline the results of the OGA as it relates to wall insulation, focusing on the Cavity Wall Insulation Retrofit Trial, conducted with 15 homes in 2012 and 2013, with results published by SV in January 2016.

Why the focus on wall insulation? Simply, because it is a significant factor in the energy performance of buildings, and millions of older homes don’t have it. Those that do, benefit from a home that is warmer in winter and cooler in summer with reduced need for supplementary heating/cooling due to greater retention of the heat and coolth, fewer draughts, less noise pollution and less condensation on internal walls in winter—the latter inhibiting mould growth which can be a significant health hazard.

Why consider pumped-in wall insulation as the most feasible retrofit option? Unless you’re undertaking a renovation that includes the removal of internal wall linings or one in which weatherboards are to be removed to allow access to the wall cavities from the outside, pumping in wall insulation is the only practical option for existing housing stock.

The OGA found that 95% of the 60 homes in the study had no wall insulation. With 15% to 25% of heat gain/loss being attributed to uninsulated walls, this helps clarify why the average house energy rating of these pre-2005 houses was just 1.81 Stars (significantly lower than the requirement of 5 Stars for post-2005 and 6 Stars for post-2011 homes).

Read the full article in ReNew 140.