New guide helps designers cut energy use before they build

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Get your free copy of the Building Envelope Thermal Bridging Guide

If you're planning to build new facilities and want them to be energy efficient, start with two things: a tight building envelope, and a new guide that explains how to minimize its energy leakage.

The Building Envelope Thermal Bridging (BETB) Guide is the result of more than four years of work by engineering firm Morrison Hershfield in collaboration with BC Hydro Power Smart and other partners.

The guide focuses on "thermal bridging," a critical area of heat loss that has, until now, been hard to measure and mitigate. The term refers to the pathways of high heat flow through walls, roofs and other insulated building envelope components that allow heat to bypass the insulating layer, effectively defeating the purpose of the insulation.

Thermal bridging guide helps designers cut building operating costs

The BETB Guide provides easy-to-use methods for understanding and mitigating thermal bridging in the design phase. Since heat loss and air leakage across the exterior envelope can account for more than 50 per cent of the total energy load, addressing thermal bridging can mean reduced significant energy savings over the lifetime of the structure.

Reducing thermal bridging also delivers better thermal comfort and air quality inside a building, and can lead to a longer life for the building envelope.

"The BETB Guide illustrates that, depending upon the building type and the insulated envelope assembly, actual building heat loss can be up to four times greater than is generally accounted for in conventional design practice," says BC Hydro Power Smart engineer Gordon Monk, project manager for the guide.

Guide will save time, reduce guesswork, and improve energy performance estimates

The guide is broken into three stand-alone parts. Part 1 is a catalogue of the thermal performance (effective R-values) of more than 230 envelope assembly details commonly used in B.C., with ideas about how to minimize thermal bridging.

In the past, building energy modelers often used nominal R-values, leading to faulty estimates of heat loss. By contrast, the Guide's thermal analysis is exact and reliable.

Part 2 supports a cost/benefit analysis of the costs associated with improving thermal performance against forecasted energy savings. Part 3 discusses how design practitioners, as well as government and utilities, might use thermal bridging information in both design and in new building codes and bylaws.

The guide will make life easier for anyone involved in new building design, says Greg McCall, energy policy specialist for the City of Vancouver.

"It used to take me two whole weeks to calculate the performance of a building envelope, with plans all over the floor, colour crayons everywhere," says McCall. "Now practitioners can access the latest in modern technology to calculate energy performance in far less time and with far greater accuracy."

"This supports Power Smart's goal to help transform the B.C. marketplace to the point where all new buildings are designed and built to the highest standards of energy efficiency," says Oscar Ceron, manager of BC Hydro's Power Smart New Construction Program.

The guide was officially launched last fall. Workshops continue to help practitioners become familiar with this latest tool. Use of the guide will become a mandatory element in applying for the New Construction Program effective April 1, 2015. It is highly encouraged for new construction within the City of Vancouver, too.

Monk believes the guide is one of the most significant energy-efficiency initiatives he's been involved with throughout his career. "There has been a North America-wide gap of information about thermal bridging," he says. "And ultimately, [the Guide] will benefit the people who buy and live and work in the units the construction industry builds."

Get a free copy of the Building Envelope Thermal Bridging (BETB) Guide.