RODERICK WILES explains how American hardwoods help minimise a building’s impact on the environment

In embracing sustainability, designers are not simply responding to a new fashion. Nor are they only seeking to minimise the direct impact of their own creations on the environment. They are promoting desirable visions that compel people to want to live sustainably. And, by doing so, designers are becoming a key part of the process to move towards a more sustainable future.

The choice of materials is a key component of sustainable design. By using American hardwoods, designers are assured that they are minimising their impact on the environment throughout all the stages of the product life cycle, from extraction, through processing, use, reuse and final disposal. At the same time, through their choice of particular species and grades of American hardwoods, designers have a central role to play to reduce waste and maximise utilisation of this valuable natural resource.

Copenhagen Opera House: American hardwoods contribute to sustainable design

American hardwoods contribute to sustainable design in many ways. They have a low impact on the environment at all stages of their life cycle right from the point of extraction. Forest management in the sector is not intensive, as most American hardwood forests are owned and managed by individuals, families, or small companies rather than large timber corporations. Forest holdings are relatively small, mostly under 10 hectares, limiting the size of harvesting operations.

The primary motivation for owning the land is usually not timber production or economics, but simply the enjoyment of forest ownership. As a result the owners tend to manage less aggressively and grow their forests on longer rotations. Selection harvesting is typical, involving removal of only a few trees per hectare, rather than clear-felling. After harvesting, forest owners usually rely on natural regeneration. There is little need or incentive for addition of chemical fertilisers. No non-native ‘exotic’ or genetically modified species are used.

EXPANDING RESOURCE

Regular forest inventories undertaken by the US federal government every 10 years demonstrate that American hardwoods are not only renewable, but are an expanding resource. The latest data from the United States Department of Agriculture (USDA) shows that between 1953 and 2007, the volume of US hardwood growing stock more than doubled from 5 billion cu m to 11.4 billion cu m. The survey also shows that forests are aging and more trees are being allowed to grow to size before being harvested. The volume of hardwood trees with diameters 48 cm or greater has tripled from 731 million cum to 2.3 billion cu m since 1953.

While other industries like steel, concrete and plastic often emphasise efforts to reduce their negative environmental impact, American hardwoods are one of the very few materials that make a positive environmental impact.

Long-term management of US hardwood forests for sustainable timber production makes a significant contribution to carbon storage. Each year for the last 50 years American hardwood forests stored around the equivalent of 165 million tonnes of carbon dioxide (CO2), excluding all harvested material. This direct contribution of America’s hardwood forests to carbon sequestration excludes the carbon held in long-term storage as a component of American hardwood products. With useful lives spanning generations, furniture, flooring, cabinetry and trim crafted of American hardwoods act as an additional carbon store for many decades.

The process of converting wood into usable building products requires considerably less energy than most other materials. Furthermore, much of the energy needed to produce American hardwood products is bio-energy. A 2007 study of 20 hardwood sawmills revealed that 75 per cent of the energy required to manufacture kiln dried lumber derived from biomass (such as tree bark, saw dust and wood off-cuts). As a result, even less carbon dioxide is emitted when producing American hardwood lumber than when producing many recycled materials.

Embracing sustainability: American white oak was used on the new multi-function hall in Bury St Edmunds in England, UK

Assessment of the carbon footprint of American hardwoods from forest to European distributor indicates that carbon sequestration during forest growth of the tree more than offsets the total carbon emissions resulting from harvesting, processing and transport. In fact, transport is a relatively minor factor in the overall carbon footprint. This is particularly true of ocean transport. Transporting American hardwoods by ship across the Atlantic, a journey of over 6,000 km requires little more energy than an overland journey of 500 km. In fact, even a complete circumnavigation of the world by sea (40,000 km) would be readily offset by the carbon sequestered in the wood product.

The health risks associated with a natural material like American hardwood, which requires no glues or other chemical treatment during processing, are minimal. Where needed, a wide range of low-VOC (volatile organic content) finishes can be used to protect the aesthetic appearance and performance of American hardwoods.

American hardwoods are easy to maintain with non-toxic cleaners and they don’t trap dust, dirt and other allergens. Simple regular maintenance such as dust mopping, sweeping and vacuuming keeps the environment allergen-free. For this reason, they are recommended for chemically sensitive individuals, or those who suffer from allergies or asthma.

RECYCLABLE AND BIODEGRADABLE

A key principle of sustainable design is that products, processes, and systems should be designed for performance in a commercial ‘afterlife’. This is allied to a new trend towards biomimicry, involving the redesign of industrial systems on biological lines and enabling the constant reuse of materials in continuous closed cycles. The most direct way to achieve biomimicry is through use of natural organic renewable materials like American hardwoods. Because they are untarnished by mixing with other materials and chemicals, American hardwoods are readily reusable and recyclable at the end of a building’s life span. Those American hardwood components needing to be disposed of are biodegradable and non-toxic. They may also be safely incinerated, providing a carbon-neutral source of energy.

Longer-lasting and better-functioning products have to be replaced less frequently, reducing the impacts of producing replacements. American hardwood products are naturally durable and tend to outlast their synthetic counterparts. For example hardwood floors can last 50 years or more. Broadloom and tile carpeting, on the other hand, has a four to six years life-span. After 15 or 20 years of use, hardwood flooring can gain a fresh, new appearance with refinishing for roughly half the cost of replacing carpet or other flooring options.

ETHICALLY SOURCED

Sustainable design must be based on ethically sourced materials, extracted and manufactured in a way that supports human rights and basic needs like sufficient pay, healthcare and benefits. These issues are comprehensively dealt with through a fully-enforced regulatory framework in the US.

While other materials can be made to look like American hardwoods, they can’t convey the same inspiring story about sustainable living. This is the story of a natural organic product that enables the redesign of lifestyles and industrial systems on sustainable lines. And it’s the story of a natural carbon store that, through increased use, helps to prevent potentially catastrophic climate change.