No Home Safe from Installation Mistakes with Fiberglass Batts

100% of fiberglass batt installations surveyed in New Zealand included mistakes likely to compromise thermal performance.

The audit, which was conducted for New Zealand’s Energy Efficiency and Conservation Authority, found that the most frequent mistakes were that the batts were folded, tucked, compressed, or had gaps—all of which lower overall R-values (see “Batt Insulation: Fiberglass, Mineral Wool, and Cotton”)—and in some places, batts were missing altogether. The survey, which used the New Zealand voluntary installation standard NZS 4246:2006 as a benchmark, also found that many homes lacked a 5mm gap to the underside of the roof overlay, potentially allowing moisture to be transferred to the insulation. The report was published in 2011 but came to EBN’s attention due to coverage at Treehugger.com.

The report concludes that education and training may help improve installer workmanship and guide subcontractors, like plumbers and electricians, whose work may inhibit proper installation; but responsibility also falls on the designer to ensure that an appropriate cavity is maintained, the authors argue. However, given fiberglass batts’ difficult installation and poor performance relative to that of blown-in materials, Lloyd Alter writes at Treehugger that experts should seriously be weighing other options. “There should be a designer or architect who decides what services go into insulated walls, how the wall is detailed, whether there is enough room, and what insulation is chosen.” In case there isn’t, he warns, “People get what they pay for.”