5 Jun 2007

On Dynamic Insulation

Ever heard of dynamic insulation? It’s an idea that’s been knocking around for a long time, always in the category of academic curiosity, but now at long last someone is coming forward with a marketable product called Energyflo which, they hope, will bring the concept to the masses and, just possibly, sell in great quantities.

So what is it and how does it differ from ordinary insulation? In conventional building models, heat leaks out gradually through the fabric, be it a wall or a roof. Dynamic insulation seeks to capture that leaking heat and feed it back into the building. It does this by making the insulation layer air permeable (by punching loads of holes in it) and then de-pressurising the house so that air is drawn into the house, heating up as it passes through the walls or roof. In theory, if you get it right, you can recapture all the leaking heat and you could produce a wall with a U value of near zero, without having to use more than about 90mm of insulation.

To get it to work, you have to get a fan sucking like hell inside the building to pull the air inside. What happens to the air being sucked through the fan? Well, here it starts to unravel a little because it gets dumped outside. But in fairness, warm air is going to get dumped outside in any event because you need to have some form of ventilation built into the house and you may just be able to get a second bite at that dissipating heat if you plug in a heat recovery unit.

Last Wednesday (May 30), I sat in on a presentation given by Mohammed Imbabi and Andrew Peacock of Environmental Building Partnership, a spin out from Aberdeen University, which is planning to market Energyflo as the basis of a low energy building solution. They reckon that with no airflow at all, the U value of the 95mm expanded polystyrene panels would be around 0.35, but with the airflow working as planned, the U value falls to around zero: i.e. there will be no heat loss at all.

Of course, it’s early days for this product. It’s still undergoing tests, most notably at a CALA homes site in Edinburgh where it’s been installed in the roofspace. There are also plans for it to be used on a big apartment site in Dubai.

I don’t think the presentation met with quite the level of appreciation the backers were hoping for. Many of the questions expressed a surprising level of scepticism. To work as designed, the Energyflo cells have an air filter embedded within them: someone suggested that this would rapidly clog up in Dubai where there are frequent dust storms. And there appeared to be a finite life to the cells as well, which was determined by the site characteristics (i.e. how much pollution) and the thickness of the filter. But if you are building the insulation into the fabric of the structure, how are you meant to replace it?

Perhaps its churlish to be too critical. As a product, it’s only just making its first tentative steps away from the research labs and there is doubtless much to be learned en route. To establish a foothold in the insulation market, it will have to be monitored on a number of different buildings over a lengthy time period, something we in the UK are not good at doing. So I wish them well, but don’t expect to be seeing a whole mass of dynamically insulated buildings tomorrow or in fact anytime soon.

1 comment:

  1. What a load or academic rubbish! Air will only heat up when being sucked into the house if energy is being put into it. If no energy is being put in then all one is doing is sucking in cold air. If you want the inside temperature to be the same as the outside then this is a great way to do it!