We have a static caravan on the little farm which we converted to use as our home office. This is great from a space point of view - our little wee house remains (relatively) uncluttered, and we get to have decent working space when working from home. Unfortunately, the old static caravan does not cope at all well with cold weather. It's about 10m x 4m, and the floor is a thin piece of chipboard - with the result that you can have a 2KW heater running full blast, with temperature in the mid 20Cs at ceiling level - but only marginally above freezing at floor level. This is not good for productivity in winter.

Consequently we spent some time thinking about insulation. The greatest weak point is the lack of thermal isolation at the floor, so that's what we decided to tackle first. I didn't like the idea of cutting pieces of isomil to fit - it seemed like an insensibly-large job. I didn't think fibreglass matting would handle being fitted to the underside of the van (too much water) and there isn't really clearance to raise the floor. We finally settled on a closed-cell polyurethane spray foam, which is available in a DIY kit . I finally got around to applying it this weekend. Donning a disposable paper boilersuit and a vapour filter mask, I felt I looked like an extra from a B-grade NBC disaster movie. Michelle took the obligatory silly photos, which I'll post here one of these days for giggles, and I set about it. I should point out that the spray foam kit includes to canisters containing some fairly nasty stuff which, when mixed, is fluffy, gets everywhere, is sticky, and sets hard really quickly. It is extremely hard to clean up - soap and water, spirits and petrol do nothing to shift it - the brochure says that once set it can only be removed using "mechanical means". In my case this involved a painful application of potscourer to hands. The paper boiler suit with silly hood is ABSOLUTELY indispensable, don't use this stuff without it. Lying on your back in 2ft of clearance under the caravan, rolling in gravel and nettles, is unpleasant enought on its own - getting the gravel irreversibly glued to you in the process is just delightful. The vapours produced are also quite an irritant - while the vapour filter initially seemed like overkill, I certainly recommend it. Stupidly I didn't where gloves - a pair of disposable latex gloves would have saved me a great deal of trouble.

In spite of all that, the foam is amazing stuff - you spray on a skinny layer of mousse, and it quickly expands to a few inches thick. Within a few minutes it's set hard, and can be cut with a saw. It's really easy to spray into awkward corners, where it will expand to provide good coverage. It's pretty much totally waterproof, and is one of the most effective commercially-available forms of insulation. The old van is already maintaining temperatures well above ambient with just the server and UPS running. I'm not sure if that will be enough - we may need to do the roof, and possibly the walls (they do a version which expands more slowly, suitable for injection into wall cavities), and maybe double-glazing - but just doing the floor has made a significant different already, to the point where the oil-filled radiator will hopefully be able to cope, even if it isn't very efficient. Also, I've always wondered about the wisdom of having chipboard more-or-less exposed to the elements - now it's nicely sealed off. The van is clearly quite old; hopefully this will help it last a few more years!