Summary
¦ Light House is a sustainable building centre in Vancouver.
¦ A Light House study analysed 11 green building rating systems.
¦ Life cycle impact of materials is largely ignored by rating systems.
¦ Adoption of wood as a low carbon building product must be driven by the design community.

Around the world, rating systems have been successful in communicating the elements of green building design to consumers, in concentrating designers’ efforts to move the green agenda forward and in stimulating innovation within technology and product companies. Programmes such as LEED in the US, Canada’s Built Green and the UK’s BREEAM are easy to understand and offer brand value, which has resulted in rapid uptake and adoption by regulators as a means to deliver on green building policy initiatives.

Given the fact that wood from replenished sources is renewable, is recyclable, can offset climate change and, strength for strength, uses far less energy to produce than concrete or steel, one might think of it as a major credit earner in green building rating systems. However, there are gaps in some of the most commonly used rating systems and how they relate to wood.

Embodied carbon

According to a 2010 study by Light House, a sustainable building market catalyst based in Canada, many rating systems are falling short of delivering low carbon buildings, particularly in terms of the embodied carbon of the building materials employed.

Of concern to the forestry industry, most rating systems currently undervalue (even, in some cases, ignore) the life cycle benefits of low carbon materials, such as wood.

The Light House study analysed 11 green building rating systems, which comprised a total of 18 separate applications. To be included in the study, rating systems needed to be holistic in scope and administered independently.

Overall, rating systems are more similar than they are different. To a greater or lesser degree, wood is recognised as follows: certified wood; local sourcing of materials; recycled/reused/salvaged materials; building techniques (for example, advanced framing); waste minimisation; life cycle impacts; and indoor air quality.

The study concluded that, on average, only 20% of credits in US-based rating systems relate to wood. In UK systems, less than 10% of credits were applicable.

Light House used each rating system to compare two hypothetical building projects – one that maximised wood use, the other with low-intensity wood use – to assess how wood earns points compared to non-wood building products, such as concrete, steel and plastic.

While rating systems for homes generally favour wood, in non-residential systems it is slightly easier to gain points by using other building materials, such as concrete and carpet.

Life cycle assessments

The study also examined the prevalence of life cycle assessment (LCA) among rating systems. LCA is an objective methodology for comparing materials or even entire structures over the course of their service life. Findings show that the life cycle impacts of materials are not widely considered: only six of the 18 rating systems surveyed quantitatively and holistically recognise LCA and, of those, there is little follow-through from the calculation to the building project itself.

Around the world, work is under way to develop robust LCA data and, so far, studies overwhelmingly confirm that wood buildings produce less air and water pollution, require less energy across their life cycle, and generate fewer CO2 emissions than alternative materials. (To find out more about LCA, visit www.athenasmi.org).

Research by the US-based Consortium for Research on Renewable Industrial Materials (www.corrim.com) found wood to outperform alternative materials in studies using LCA to compare homes framed with wood and steel in Minneapolis and homes framed with wood and concrete in Atlanta. Research indicates that homes framed in steel and concrete required 16% and 17% more energy respectively (from extraction through maintenance) than the timber frame homes. The global warming footprint of the steel frame house was also 26% higher and the concrete house 31% higher than the timber frame homes.

Environmental Product Declarations

The advent of [international] Environmental Product Declarations (EPDs) is facilitating the adoption of LCA. EPDs disclose a product’s environmental impacts in such a way that the consumer can make side-by-side comparisons, much like a nutrition label on food products. While the preparation of EPDs requires investment by manufacturers, EPDs can position wood products ahead of the competition, while educating specifiers about the environmental benefits of wood.

While EPDs will become part of design parlance in the near future, suppliers need to provide information to designers today about how to achieve specific credits for wood-based products. Environmental Information Sheets (EIS), easy-to-use design guides, structural sizing charts, code interpretations, credit application “cheat-sheets” can all help building professionals negotiate their way through the tangle of rating systems and earn credits for the use of wood in residential and non-residential applications.

Working together

For their part, designers need to work with clients to quantify sustainability goals and to set building performance targets. Clients need to be educated about the value of wood irrespective of the rating system to be employed.

The full potential of wood as a genuine green building material with the capability to get to carbon neutrality may well be under-recognised by the rating systems. Moreover, current pricing structures do not include the true external costs of products in terms of transport, raw materials, and the like, and the industry is also constrained by liability issues and risks inherent in innovation. Adoption of wood as a low-carbon building product must therefore, for the short term at least, be driven by the design community. This can best be accomplished with rating-system targeted support from wood product manufacturers.

Light House provides professional services to businesses and governments to implement sustainable building solutions; for details click here. For more information on green building, or a copy of the Light House report click here