When you read a Building Code, all major items are well defined – and they quite rightly grab the builder’s and building inspector’s attention. But recent studies have shown that the cumulative effects of the little allowances and exceptions can be very significant. The energy inefficient details in the building envelope fall under two headings: continuity of insulation and thermal bridging. A 2-to-5% allowance for a skylight, an ornamental window, or a door all add up. These percentage numbers are measured in area, not in thermal loss. It’s like having a bucket with a hole on the bottom that is only 2% of the bucket’s base: the bucket will not hold much water.

Same thing for buildings and heat – the heat will leak out like water from a bucket. Everything adds up. All balcony slab penetrations, pipes and ducts – even nails that penetrate insulation – contribute to heat loss. Homeowner Protection Office in British Columbia has developed a guide to thermal bridging, in which they provide techniques for measuring and compensating for heat loss.

The same goes for air leakages: new codes provide specific prescriptive instructions on how to minimise hot air leaving the building. The best bet for home owners is to get a blower-door test performed by a qualified Energy Advisor who knows how to locate the major leaks in your home and suggest how to address them.

Those details can double the building envelope heat losses. They really are devilish!