A gap in the market

You want your home to be energy efficient. But you don’t want it to resemble the Teletubby HQ in la-la land. You’d rather it was modern, stylish, perhaps a trendy composition in concrete, steel and glass. So what do you do? Learn from your fridge, of course.

Fridges keep things cool by using VIPs - vacuum insulated panels. But VIPs keep things warm too. So why not use them in a building’s envelope? It’s a question architect Ian Abley is posing as he embarks on a doctorate programme at the Centre for Collaborative Engineering at Loughborough University.

Abley will be sandwiching VIPS within reinforced concrete panels. The aim is a U value so low – 0.1W/m2 K – it will make the Building Reg targets look hugely unambitious. To achieve that performance with fibre or foam concrete panels would require around 300mm, but a VIP can do it in just 25mm, claims Abley.

Whereas standard insulation traps gases to reduce heat transfer, VIPs work by removing those same heat-transferring gases to create a vacuum. Thermos flasks operate under the same principle, and they’ve been around since 1904. Now, a century on, the construction industry has decided to take note.

Abley says: “It’s not a new idea. We’re going back to first principles with this. It’s about getting more performance out of less thickness.

“In trying to push foam insulations to ever higher performances you’re fighting a losing battle: cavities get wider, wall ties are turning into big bits of metal and becoming thermal bridges themselves. It’s not a logical process. And, of course, there’s a big commercial advantage in developing a wall panel that’s thin and liberates more floor area.”

The downside is that VIPs are a pain to handle because of their fragility. The core filler material is encapsulated in a plasticised metal foil barrier film, which is evacuated to a vacuum and sealed. But a pin prick is enough to render it useless. That means fixings have to be co-ordinated with VIP dimensions.

Another challenge is that the barrier foil forms a vapour barrier which must be made continuous at VIP joints. So even though storey-sized VIPs are now cost effective, their vulnerability and technical trickiness have dented their appeal to specifiers.

Abley’s project aims to design out their inherent fragility. With Darren Williams, national specification manager at Lafarge Readymix, Abley will use Agilia, Lafarge’s self-compacting concrete, to tackle concrete sandwich panel design – with VIPs as the in-between filling. They will also be looking at using plastic synthetic fibres to keep the panel thin.

The next stage is pulling a team together to develop a prototype – with a width of around 225mm – for commercial application in early 2007. Abley and Williams are talking to a precast concrete panel producer, an in-the-mix filament reinforcement company, an FRP wall tie manufacturer (to further reduce heat transfer), and most important, a VIP manufacturer.

Abley sees his product as perfect for a number of construction sectors and cites two examples, Latitude House, a recently completed housing development in Camden, and the as yet unbuilt Dyson School of Design Innovation in Bath, as being the kind of designs that vacuum-insulated RC would be suitable for.

And if interest grows, other cladding surfaces can be developed for the product. Why not ceramic tiles, cast stone or brick facing?

Abley will still have to conquer the industry’s reluctance to consider new technologies, but he remains positive: “This isn’t science fiction. This is just a way of pushing a conventional form of construction, but improving the component parts of it. It’s an incremental improvement but with a large performance leap.”