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Feature Eco materials for 2015


8 Passive ventilation with heat recovery by Ventive


9 LEDs


LED lighting isn’t new, but it is continually evolving. The latest products have seen such improvements in efficiency that the economics are almost comparable with conventional fittings, says Jesse Putzel, senior sustainability manager at BAM. “Developers have been specifying LEDs for a long time, but not for the entirety of a building. They might use it for downlighting or high circulation areas, but not for linear lighting in an office. It’s now reaching the point where the efficiency has improved so much that it makes sense from a cost perspective.” BAM has just specified


LEDs throughout one of its own speculative commercial developments in Glasgow: “This is a step change for us,” says Putzel. “Energy efficiency and sustainability have always been a priority but up to a certain point. Cost can still be a barrier but with major innovations coming in controls technologies, I think LEDs will be specified as standard in the near future.”


This passive ventilation with heat recovery system was developed in response to the problem of poor air quality in retrofitted properties, but can be installed in new homes. Increasing air-tightness reduces heating but leads to higher levels of toxic chemicals, CO2 and moisture in the air. Ventive fits either within a chimney


stack or duct, and uses the buoyancy of warm air to create a continuous flow. With Ventive S, the chimney pot is replaced with a cowl and cassette containing a heat exchanger. With Ventive S+, the same unit is installed between the rafters and sealed through the roof. Stale warm air rises up through the system, passing through the heat exchanger and warming the fresh air as it enters the house. This air is drawn down and dispersed through the room.


“Ventilation and energy


efficiency is a very difficult balancing act,” says Tom Lipinski, Ventive’s technical director. “You can’t just put a hole in a wall because the insulation won’t work, but the fan in a mechanical ventilation and heat recovery unit can use as much energy as three fridges running 24/7. We were trying to design an effective ventilation solution for insulated homes and we realised we couldn’t defeat air buoyancy and gravity. Then we thought if that if these forces are so strong that they won’t let us force air around the house, why don’t we use them to drive air through the heat exchanger? We did feel like the early flight pioneers realising that gravity always gets the better of you...” It took several years to develop the product and test it, including


designing a completely new heat exchanger to fit within the space along with the omnidirectional cowl, which works with wind blowing in any direction. The first prototype was released 18 months ago and Ventive is now installed in around 200 homes, half of which are social housing. A whole-house version of the system is due to be launched at Ecobuild in March, with a larger heat exchanger that can serve many ducts.


www.ventive.co.uk


10 Wood


Okay, so wood isn’t a new material. But there are several technological advances that are enabling it to be specified for a greater range of uses. Cross-laminated timber (CLT), is an engineered panel made from layers of spruce arranged crosswise and glued. It has high strength, dimensional stability and offers the speed and cost benefits of offsite construction. It even performs well when exposed to fire – the charring on the outer layer acts as an intumescent coating. In the UK, CLT has so far been used for a small but steadily rising number of projects, including the nine-storey Stadthaus apartment block in Hackney, briefly the tallest such structure in the world. Lend Lease is also using CLT to build half the 3,000 homes planned for the Elephant & Castle. There are a growing number of


acetylated products available in the UK, where wood is chemically treated with acetic acid to reduce its ability to absorb water, making it more dimensionally stable and less susceptible to decay. Thermal modified wood, meanwhile, is heated to around 200°C in the absence of oxygen, which changes its chemical structure and increases its durability. Most timber used in the UK is imported – the UK is the world’s third largest net importer behind China and Japan – which increases its embodied carbon. This is what the Grown in Britain campaign, established in 2013, is hoping to change. Britain has the same species as mainland Europe, but trees grow faster here so the timber is not as strong in its untreated state. However,


22 | JANUARY 2015 | CONSTRUCTION MANAGER


7 Porotherm bricks by Wienerberger


Sussex House by Wilkinson King Architects. CLT supplied by KLH (UK) Ltd.


with thermal modification, hardwoods such as ash and sycamore can become suitable for a wider variety of uses, potentially creating a new market for the trees cut down due to ash dieback. A study by Napier University also found that C16 Scottish Sitka spruce manufactured into 130mm CLT panels performed as well as 120mm panels made from C24 Austrian spruce. British CLT was also trialled in the podiums for the Commonwealth Games in Glasgow, and is the subject of considerable interest. “This year is likely to be the year when we see a whole project built out of British CLT,” says Steve Cook, principal sustainable development manager at Willmott Dixon and co-chair of the campaign. “At the moment, all CLT is imported from mainland Europe, but if the concept can be proven it could pave the way for investment in a British manufacturing plant.” www.growninbritain.org


These hollow clay bricks have been used for decades in Europe, but they’ve only been promoted in the UK market in the last few years. They have many small pores and a honeycomb structure, which makes them breathable and thermally efficient. They are also strong, light, use less water to make and have a low embodied energy. A growing number of developers are building with Porotherm, including McCarthy & Stone, BAM and Barratt, which intends to use the bricks for 10% of its buildings in 2015. Architect Gale &


Snowden is considering using the bricks on several developments: “In the right circumstances you don’t need insulation in the walls when using these bricks because the air pockets provide enough, as long as the rest of the building is compact, well-insulated and airtight,” says director David Gale. “It is possible to build a Passivhaus block of flats with just clay brick walls – rendered each side and that’s it. We need to move away from cavity wall construction.”


porothermuk.co.uk


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