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Out of this world

Ultra-light, highly insulative, Nanogel began life as part of the space race but is now being used in construction

What's called 'solid smoke', looks like a cross between Martian jelly and a hologram, is the world's lightest material and constitutes the most insulating, translucent building material ever?

Aerogel - or, to be exact, Nanogel aerogel. Aerogel, discovered in the 1930s, is a highly insulative material with the lowest density of any known solid; one form is actually 99.9 per cent air and a mere 0.1 per cent silica dioxide by volume. It is one thousand times less dense than glass and holds six world records for physical properties.

Nanogel began life in aerospace.

NASA developed it to capture cometary dust particles without altering them, which it can do by virtue of its super-low density. NASA's Stardust mission was launched in 1999 and will use aerogel to capture material from a comet's dust cloud and bring it to Earth in 2006. According to NASA, a block of aerogel as large as a human may weigh less than 0.5kg yet be able to support a subcompact car, about 454kg. NASA's Jet Propulsion Laboratory has developed an enhanced form of aerogel for 'several space-related applications', but it is now being applied to construction.

Boston-based Cabot Corporation has developed a range of products, called Nanogel aerogels. Putting sodium silicate in water to 'grow' Nanogel makes the molecules line up to form a hydroporous structure.

Cabot has perfected a commercially viable method of safely extracting the liquid from the pores in the gel without losing its volume, leaving behind Nanogel - a bit like an extremely lowmass honeycomb. The pores measure 20 nanometres (billionths of a meter).

'What makes Nanogel so effective is that the porous structure does not allow air molecules to touch one another, so they can't transfer energy to one another, ' says Jim Satterwhite, Cabot's global business manager for the construction industry. 'And it's hydrophobic - you can't get water to permeate particles - a big benefit in fenestration products.'

Nanogel is the ultimate in sustainability. 'Unlike most insulating materials, ' which get damp or have the air forced out of them by gravity, ' says Satterwhite, 'Nanogel's insulation performance has no lifespan.' In theory, you could take the Nanogel component out of any aerogel-containing product after 50 years and reuse it.

Insulating light Nanogel is currently being paired with Kalwall, a light-transmitting, structural, composite cladding panel that diffuses natural daylight for museumquality interiors without glare, shadows or hotspots. Sandwiching aerogel inside Kalwall - imaginatively called Kalwall+Nanogel - dramatically raises its insulating value: Kalwall+ rooflights from Stoakes Systems have a panel U-value of 0.28W/m 2K and light transmission of 13 per cent.

Architect Christopher Sykes describes it as 'using light as a building product - a glazed wall with the same insulating value as a brick wall'.

'The weak link for building envelopes has always been fenestration, ' says Satterwhite, 'which are high in heat loss and heat gain. Nanogel moves products such as Kalwall into a new performance dimension.

'There are long-documented ergonomic and functionality benefits to natural daylight but building regulations say you have to drive up the Uvalue of the building envelope.

Nanogel products give architects a new tool for letting daylight in while lowering U-values. Kalwall+ is by a very large margin the most energy efficient product on the market today.'

A Kalwall+ rooflight was specified for one domestic job in the UK, and in a first UK commercial application, Atkins has just specified Kalwall+ for a regeneration project near Wakefield due to begin in mid-August. Atkins will use Kalwall+ for a single-storey managed office centre in Hemsworth commissioned by the local council.

The site, which slopes 6m from back to front, was previously derelict.

'The building has a long elevation, ' says Natalie Sarabia, senior architect for Atkins' Leeds office, lead consultant on the project, 'so we looked at how to break it up. The Kalwall+ used for part of the front and side elevation makes it look quite different, providing natural light which gives a pleasant atmosphere inside the building.

'It helps with security, as well.

Unlike a glass window, which would need roller shutters in this area, it's a form of cladding - a deterrent to break-ins. And Kalwall+ also has a 0.28 U-value, making the building perform better for the end users.'

Cabot is researching and developing an almost limitless range of applications for Nanogel. There will be more light-transmissive building materials: multiwall polycarbonates, U-profile glass, insulated glass lights.

Nanogel could appear in highperformance, breathable-yet-waterproof clothing, pharmaceuticals, cosmetics, matting agents in paint finishes, aerospace insulation, automotive heat shields, etc. It may even be used for cryogenics and to insulate sub-sea oil piping.

Satterwhite says the price of Nanogel products should fall within about five years, as Cabot ramps up its scale of production in Frankfurt. It aims to make Nanogel 'daylighting technologies' available to 'a wide palette', everything from expensive, high-spec products to cheaper, lowerspec ones.

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