At the heart of every green building project are the materials, as you will see in the following section, taking care over the materials we use in construction can make a significant difference on the quality of life in our world – not just for now but for future generations. The Green Building Council says that the UK construction industry is the nation’s largest consumer of natural resources, using “more than 400 million tonnes of material every year.” So we in the industry need to make sure this material is environmentally friendly, and construction processes produce as little waste as possible. In the following pages you can find practical advice to help you contribute to making a better, more sustainable industry.
Recycling and Reusable Materials
The most recent report by the Department for Environment, Food and Rural Affairs estimated that out of a total 200 million tonnes of total waste in generated by the UK in 2012, half of this was generated by construction.
Having the right information about environmentally-friendly practices and materials in the building sector can help make us make better decisions. Given the percentage of waste generated by construction it means we can have a significant impact.
Consider using recycled, salvaged or renewable materials and if that isn’t possible look for materials whose production have had a low impact on the environment such as stone, earth, clay, timber and natural fibre products.
It’s surprising how small changes in construction methods can make an environmental difference all along the lifetime of a structure. When disassembling a house, it will be easier to re-use undamaged material so consider using screw fixings rather than nails in wood (easier to remove) and likewise when it comes to bricks use soft lime mortars rather than harder modern equivalents which are less easy to remove. Bricks, particularly facing bricks have to be fired at high temperatures, using a lot of energy so. By using reclaimed bricks production energy is saved.
Reclamation and Paving
When it comes to paving, reclaimed stone is not only more environmentally friendly, it can be considerably cheaper than new stone. But you need to keep an eye on how different quality reclaimed stone can actually be used. It’s best to buy from a reputable supplier who can advise and try to buy by area not by weight.
Stones thinner than 20-25mm were probably originally roof tiles, they may be used for paving but must be laid on a bed of mortar for added strength. They should not be laid in areas likely to have too much load imposed on them.
Slabs 25 – 60mm thick can be used for paths and patios but are best not used for vehicle access. Slabs 50-75 may be used for paving in pedestrianised public spaces.
Slabs 70-150mm thick can be used for residential driveways and other areas which may experience occasional use by low speed vehicle traffic.
There is a great difference in the quality of reclaimed paving. Avoid paving that looks friable. Chipped paving can be tidied up and oil, paint and mortar stains can be removed but at a cost. Flags from old woollen mills are likely to contain high levels of undesirable chemicals.
Unfired Clay products have low energy embodiment in production. Clay surfaces are warm in winter & cool in summer, Clay’s ability to absorb & diffuse water vapour & heat helps offset swings in humidity & temperature thus providing high levels of comfort. They are highly recyclable and provide thermal mass and acoustic insulation.
Timber is a material generally considered to have excellent environmental credentials, it’s partly why architects and builders are rediscovering it in the age of climate change. High profile news stories around timber skyscrapers such as Vancouver architect Michael Green’s proposal for a 35-storey timber building in Paris have given this age-old construction material a contemporary glamour.
Timber building materials have low carbon emissions in their manufacturing production, are a renewable resource which reduces the amount of CO2 in the atmosphere and is easily worked. It is a renewable, reusable and biodegradable material and is also inexpensive compared with other materials. And if you source locally, or in the UK in general, it will have a low carbon footprint.
Choosing the correct source
When timber is becoming so popular as a building material there are consequences such as deforestation and the destruction of habitats. This is why it’s important to make sure you buy timber certified that it’s form a sustainable source. The Forest Stewardship Council is one of the best-known operators.
Think local, choosing timber for UK construction that is grown in far away forests, in places like Canada and USA reduces the ecological value of the choice because of the high transport costs incurred. Most tropical hardwoods are not replanted so avoid them if you want to be ecologically responsible.
European & Scandinavian timbers are mostly from well managed/ replanted forests. Where possible, buy locally grown timber from associated sawmills. Douglas fir, sweet chestnut & oak are excellent for building load-bearing constructions.
Other ecological issues
Bear in mind other processes or treatments for the timber may make it less environmentally-friendly. Avoid using softwood externally as this timber requires regular treatment throughout its useful life to prevent rotting. Many of these treatments are highly toxic. If possible use a durable timber which can be used externally without treatment.
The other consideration when building with timber is its lack of thermal mass which has to be compensated by using large amounts of insulation material to inhibit solar gain in the summer and heat loss in the winter.
Recycled Concrete / Aggregates
A study by researchers at the University of Notre Dame revealed that over half of the concrete that has ever been produced has been produced in the last 20 years. It’s why recycled aggregates – crushed and graded materials, such as concrete, cement and brick retrieved from demolition sites – is increasingly important. Much of it is used as foundation hardcore and course low grade aggregate.
Recycled concrete aggregate (RCA) has a masonry content of not more than 5%. This ensures the quality for reuse in the manufacture of precast/ prestressed concrete products. Standards for RCA and its use are given in BS 8500-2 & BS EN 206-2 Part-2.
The use of recycled aggregates in concrete construction offers a valuable outlet for this otherwise bulky-to-dispose-of waste material. The production of aggregates, from mining to processing and transportation expends a lot of energy so recycling aggregates can be economically viable and environmentally beneficial.
If wood has the lowest embodied energy of building materials, plastics are six times as much by weight. Its basic material is petroleum and natural gas. It’s partly why the embodied energy of plastics is extremely high and the industry is responsible for over half of all toxic emissions in the environment. However, because plastics are waste products from the petroleum industry, using recycled plastics reduces the accumulation of waste products from that industry.
Plastics are non Bio-degradable and are therefore not desirable in landfill sites – they can take up to 400 years to break down. Plastic is low maintenance, it is rot, corrosion, crack and splinter proof. It is resistant to water, chemical, insect & fungal attack and does not require painting or preserving. These unique characteristics redeem it slightly as a material as they reduce the amount of embodied energy in use.
The good news about industrial steel is that that because of its high value most industrial waste metal is recycled back into the manufacturing industry – its quality is known and often uncoated so can be melted down with little preparation.
Steel, Stainless Steel & Aluminium have high-embodied energy and are expensive to produce. Not only does the smelting process require large amounts of energy, the process generates toxic dioxin emissions because of the chlorine present in most metals.
The good news about industrial steel is that that because of its high value most industrial waste metal is recycled back into the manufacturing industry – its quality is known and is often uncoated so can be melted down with little preparation.
Using recycled aluminium in preference to virgin aluminium significantly reduces CO2 emissions.