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Can concrete and masonry construction rival timber construction in terms of eco-friendliness?

In early 2017, the German Masonry and Housing Construction Association (Deutsche Gesellschaft für Mauerwerks- und Wohnungsbau e. V., or DGfM for short) published a paper asserting that the environmental footprint of houses built using conventional concrete frame, brick or blockwork methods, assuming a useful life of 50 to 80 years, is superior to that of timber frame homes. It also claimed that, according to extensive sustainability analyses, timber houses are more expensive to build.

Timber construction methods currently account for about 15% of all new detached, semi-detached and duplex houses built in Germany – and their share is rising. The attitudes of German self-builders have changed over the years. Sustainable, eco-friendly materials are growing in popularity, and so are those which are conducive to a healthy living environment. So the masonry lobby is naturally alarmed and trying to defend its chunk of the construction market, although at 75% it is still the lion’s share. This could explain why the DGfM commissioned the Polytechnic University of Darmstadt to carry out three studies. It was apparently hoping to slow the growth of the timber construction industry. Also involved in the studies were ARGE Kiel (Arbeitsgemeinschaft für zeitgemäßes Bauen e.V. ) and LCEE ¬ Life Cycle Engineering Experts GmbH in Darmstadt.

At SWISS KRONO, a globally active producer of environmentally friendly engineered wood products, we believe that some of the paper’s assertions are too sweeping. We would therefore like to set the record straight by reassessing them in a more differentiated manner and presenting the proven advantages of building with wood.

Turning Resources into Useful Materials

No other raw material spawns such a wide range of products as wood. It is timelessly beautiful and very strong despite its light weight and flexibility. It breathes and regulates moisture, and even the tiniest bits of scrap and production waste can be reused. Wood therefore meets the urgent need for a sustainable economic system in which materials are recycled and reused to the greatest possible extent. It is an ecologically valuable, green building material that charts the path into the future. It’s important to keep in mind that sustainable construction embraces all phases of a building’s lifecycle: from planning and building across use and renovation, all the way to eventual demolition and disposal.

At all times, it is paramount to use energy and natural resources frugally while minimising harm to the environment. SWISS KRONO has therefore defined extremely strict sustainability criteria that are adhered to at all of its plants. This is also why SWISS KRONO Germany manufactures its products using only wood from sustainably managed domestic forests. And it is the reason why our OSB and wood fibre insulation products bear the PEFCTM mark. SWISS KRONO expressly advocates cascading, or sequential, use of wood, which should not be burnt to extract its energy in the form of heat until it has been used in every other possible way, for example in the form of wood-based materials for erecting buildings.

We also go out of our way to minimise transport, use renewable energy sources and make sure that raw materials are completely utilised. What’s more, production of our wood-based materials is practically carbon-neutral, and to ensure that they are absolutely eco-friendly and conducive to healthy living, they are bonded using only completely formaldehyde-free binders.

Product Life Cycles

It all starts with wood, a raw material that is produced naturally by forests. According to the German Prefabricated Building Association (Bundesverband Deutscher Fertigbau), every 23 seconds enough new wood grows in Germany to build an entire single-family home. Wood is the only renewable resource that binds and stores climatically harmful carbon dioxide, which gives it an outstanding climate footprint. A cubic metre of wood extracts about a tonne of carbon from the atmosphere – which isn’t released again until the end of the product lifecycle, for example by burning it to create heat. The key point here is that, even then, no more CO2 is added to the environment than was originally stored.

Among other things, this means that wood and engineered wood have an excellent ecological footprint. So we’re talking about an absolutely sustainable building material. Wood-based materials deliver countless benefits throughout their lifecycle, including sustainability, wellbeing, a favourable indoor climate and many other major advantages that are explained in detail below.

Reduction and Storage of CO2

Forests are a natural carbon sink, and around 1.2 billion tonnes of carbon are currently sequestered in Germany’s forests alone. A hectare of forest entraps about 13 tonnes of CO2.annually by extracting it from the atmosphere by the natural process of photosynthesis. Each carbon dioxide molecule consists of a carbon atom and two oxygen atoms. Simplifying somewhat, light energy is used to pry apart each molecule, keeping the “bad” carbon atom by integrating it in organic compounds and releasing one of the two “good” oxygen atoms. The carbon is then lastingly stored in plants’ tissues.

Wood-based materials of all kinds – glulam, OSB, particleboard, solid wood and so on that are used to build houses, make furniture or produce parquet or laminate flooring – thus also contain carbon that trees once extracted from the atmosphere. From the perspective of what is good for the planet, it therefore makes sense to store as much carbon as possible for as long as possible in buildings. This helps guard against harmful climate change.

It follows that when we use wood to erect new buildings or refurbish existing ones, add annexes or extra storeys, or make floors or furniture, the carbon bound up in them remains stored throughout the products’ entire lifecycle.

On average, each cubic metre of wood that is substituted for other building materials reduces the amount of free CO2 in the atmosphere by a tonne.

Construction Times and Costs of Different Materials

The DGfM study claims that masonry is just as ecological as wood, and that a house built with timber is also more expensive.

Scientists at ARGE I Kiel determined that building a new single-family home of stone costs over four percent less on average than an equivalent timber house.

It’s a fact that the materials required for timber construction are dearer. Quality has its price, and more and more self-builders are willing to pay it. But taking all factors into account across a house’s planning, building and living phases, the slightly greater investment definitely pays off.

Unlike masonry or concrete frame approaches, timber frame construction is a mainly dry method in which a house can be assembled from prefabricated modules and sealed against the weather in just a few days. Extensive prefabrication makes it possible to systematically avoid weaknesses such as joints, interfaces between different kinds of materials, trapped moisture and long construction times. Plus, no extra space is needed for storing building materials, as the prefabricated modules can be delivered on schedule straight to the construction site and immediately assembled there.

Here the emphasis is on the time that can be saved compared to conventional construction techniques. The fast pace of construction reduces expenditures for follow-on trades, and the house is also ready to be occupied sooner, which lets the owners avoid paying rent while waiting for their new home to be completed. And wood has yet another major advantage: despite its much lower weight, it is extremely strong. An existing building can be vertically extended by adding up to several more storeys on top of its roof using joists, boards and panels. This is especially attractive in densely settled urban areas where few empty lots are available for developing.

Energy Efficiency: the Right Insulation Material

Besides wood’s structural advantages, it also insulates very effectively. Alternative energy efficiency approaches like zero energy and passive houses can be built using timber frame, brick, blockwork or concrete frame methods. But those who take conventional approaches rarely bother to install ecological insulation materials. Masonry is typically combined with very low-cost but environmentally damaging materials such as expanded clay, calcium silicate, perlite, foam glass or mineral wool. This may save money in the short term, but the production and disposal of these materials are far from climate-friendly. In timber frame construction, by contrast, sustainable insulation materials such as flax, hemp, wood fibre, wood wool or cellulose are typically installed; many communities also provide monetary incentives to promote their use.

The DGfM has also taken aim at the latter, criticising the practice of unfairly “forcing” owners to rely on renewable energy sources.

It claims that, although heat pumps, solar heating, heat recovery from exhaust air in ventilation systems etc. may improve energy efficiency, these technologies incur unacceptably high costs for owners who aren’t privileged to benefit from government subsidies. It is therefore calling for the German federal and state governments to also subsidise concrete and masonry construction projects (which are supposedly just as eco-friendly) in order to make these approaches more attractive.

Living Space and Healthy Living

Wood makes for healthy living! And we’re happy to explain why. Apart from the other benefits of building with wood – faster construction and the possibility of self-builders doing much of the interior finishing work themselves if they want – structures can also be easily and flexibly altered later if their needs should change. What’s more, wood and engineered wood are extremely healthy, low-emission materials that let people with allergies breathe easy. The important thing is for consumers to look carefully and choose certified, high-quality products. Wood-based products from SWISS KRONO are especially eco-friendly and absolutely healthy – among other reasons, because they contain no harmful binders and the wood used to make them comes from sustainably managed domestic forests.

Besides being extremely aesthetic, wood creates comfortable, healthy living spaces. Wood has always affected people in a special way; it is perceived as warm and comfortable. It been demonstrated to improve the indoor climate of buildings, and unlike other building materials even has a proven antibacterial effect that can help alleviate health problems.

Regarding sustainability and eco-friendliness, the positive impact of wood on indoor climates deserves special mention. It creates a very favourable “bioclimate” that significantly improves occupants’ health and wellbeing. A study by the firm of Holzcluster Steiermark in cooperation with the Human Research Institute in Austria has shown that children learn better, have a reduced pulse rate and feel better in classrooms that contain wood.

Wood also has moisture-regulating properties: it absorbs moisture from the ambient air and releases it again when the relative humidity drops. Open-pored wood can even filter the air by binding pollutants, thus additionally improving the indoor climate. Yet another advantage of wood is that it can’t acquire an electrostatic charge and therefore doesn’t attract dust, making it especially suitable for people with allergies. In terms of its look & feel, antistatic properties, odour, natural moisture regulation and much more, wood is a convincing material across the board (no pun intended!).

Even if you aren’t convinced by all of these advantages, at the very least you can look forward to a more spacious home with timber frame construction. The exterior walls can be considerably thinner than with conventional building systems such as concrete frame and masonry, yielding 10% more floor space without sacrificing energy efficiency.

Fire Protection

The masonry construction industry loves to advertise with the slogan “stone doesn’t burn!”

It also likes to claim that home owner insurance costs more when building with wood, despite the fact that many insurers treat stone and wood equally. It is widely, but incorrectly, believed that wooden houses burn faster than conventional buildings. In fact, interior finishings, furniture etc. start burning before the actual structure ignites.

Apart from this, wood actually inhibits combustion! It does this by charring on the surface and forming an insulating layer that protects the core. These properties make wood predictable in the event of a fire. We now know that wood also performs very well in this regard. There’s no question that wood is combustible, but structural wood members actually have advantages: timber joists and studs often resist fire longer than steel, which quickly loses its load-bearing ability and fails when exposed to intense heat.

Timber buildings naturally also have to comply with strict fire protection requirements, but a modern timber house meets them just as easily as a building constructed using conventional concrete frame or masonry approaches, even with multiple storeys. Wood structures also have a long and time-honoured history: many of the world’s oldest intact buildings are made of wood.

The Accusation of Forest Depletion

Dr Sebastian Pohl of LCEE-Beratungsinstitut, a consultancy, sees an “ecological threat” in the current levels of wood consumption for energy, furniture, papermaking, furniture and construction. He warns of “forest depletion”, writing that “the situation of the coniferous woods that play key roles in construction – especially spruce – is problematic. The last German forest inventory revealed that consumption exceeds the natural regrowth rate by 15%.”

These figures have provoked consternation in the timber construction industry. According to Denny Ohnesorge, managing director of the German Timber Council (Deutscher Holzwirtschaftsrat), more than 120 million cubic metres of new wood grow each year in German forests. It would be possible to use 100 million cubic metres sustainably, i.e. without diminishing standing stocks, but in fact only about 80 million are harvested annually. The German Prefabricated Building Association has worked out how much wood is needed to build a prefabricated house: “It takes no more than 23 seconds for it to grow back in Germany’s forests,” says its speaker, Christoph Windscheif. “What’s more, the market share of prefabricated timber houses varies considerably within Germany. And it’s no coincidence that the figures are especially large in areas where there is a lot of forest.”

Spruce is a real classic amongst coniferous tree species. It is the most widespread variety in Germany, accounting for a quarter of the country’s forests. Its wood is especially lightweight, strong and elastic at the same time, and excellently suited for making furniture and houses. It is also used in the papermaking industry. And the spruce population really is shrinking. But not because trees are being wastefully and indiscriminately felled, but rather because German foresters are gradually, sustainably and systematically converting fast-growing coniferous forests into mixed stands that will avoid the risks of monocultures.

The Holz-Zentralblatt wrote: “Competing association shoots itself in the foot: the DGfM [German Association for Masonry and Housing Construction] is trying to disparage the use of wood for building.” Copyright / source: Holz-Zentralblatt no. 7 of 17 February 2017, p. 171

The Holz-Zentralblatt wrote: “Competing association shoots itself in the foot: the DGfM [German Association for Masonry and Housing Construction] is trying to disparage the use of wood for building.”
Copyright / source: Holz-Zentralblatt no. 7 of 17 February 2017, p. 171

Just recently, spruce was voted “tree of the year” for the first time. It is mainly concentrated in Southern Germany, is a major component of many or most German forests, and it’s safe to say that it will never disappear entirely. This has also been confirmed by Michael Höcker of ProHolz Bayern: “Spruce will never vanish completely because it is vital to agriculture. Quite a lot of research is being done on deciduous trees, and in a few years beech trees will also become established as a source of construction wood.”

SWISS KRONO mainly uses pinewood to make its wood-based products. Pine trees are hardy and even thrive in very dry and low-nutrient soils. They are therefore an outstanding source of raw materials and will continue to provide a steady supply on a long-term basis.

The Potential of Substituting Wood for Mineral-Based Building Materials

The potential of the world’s oldest building material is substantial, especially with a view to protecting the earth’s climate. This was recently confirmed by a comprehensive scientific study carried out at the University of Bochum within the scope of the Forest Climate Fund of Germany’s Federal Ministry of the Environment, Nature Conservation, Construction, Building and Nuclear Safety.

The study contains comprehensive greenhouse gas balances for wooden houses and substitution factors that confirm the enormous potential of building with wood.

One of the conclusions drawn is that the market share of timber construction must keep growing in order to fully tap this potential. It is also essential to immediately begin substituting timber for mineral-based buildings in order to meet the commitments of the Kyoto Protocol.

Conclusions

Wood is the only renewable raw material that emits far less CO2 than conventional building materials such as steel, concrete, plastics, brick and aluminium when used in its natural form or as engineered wood products. It is also the only one that binds and stores carbon dioxide, a dangerous greenhouse gas.

Wooden houses possess major advantages over conventional mineral-based structures in respect of carbon storage, construction, indoor climate and the use of sustainable, environmentally compatible building materials. Wood lets us breathe more easily, as it has been shown to create a healthy, balanced indoor climate. Wood is timelessly beautiful, versatile and future-proof. Choices in favour of wood aren’t always motivated by price; far more often, they reflect an attitude.

By way of conclusion, here is a very to-the-point statement by Melanie Wollenweber, the speaker of the German Timber Council (DHWR): “The unique advantages of wood for saving the earth’s climate and enabling prefabricated housing are undisputed. Those who question them are neither in tune with the times nor thinking of the future. It goes without saying that we don’t have to dogmatically insist on using wood as the only permitted building material. There is also great potential in hybrid approaches, for example, in which materials are combined depending on their suitability on a case-to-case basis.” From the standpoint of the DHWR, it is indispensable for the industry to join forces to master the challenges of the future.

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