Insulating a raised floor ??

There's usually access to the under floor area. Mine's via a few loose boards inside a cupboard. I've yet to insulate my ground floor area. My immediate neighbour went down to look at his the other day and found that there was rockwool between the joists, held in place by a covering of chicken wire.

I went under mine and used 1 of 2 techniques

I would use kingspan if I did it again.

Rick

That's what's deterring me. Maybe measure up and put the rockwool into polythene tubes, then seal the ends before fitting. That would reduce most of the unpleasant effects.

Lot's of potential for ill fitting and pipework obstructions here.

Looks good, haven't made a price comparison.

i would seriously consider kingspan, all you have to do is put lats over(under in actual fact) to hold it up and if you need to it can easily be removed and put back for maintainance on the floor/pipework!

Kingspan / polystyering have similar mechanical properties. Kingspan insulates twice as well per mm of thickness, so you use half as much or get it twice as good. B&Q prices were 50mm thick 17.05 100mm 32.54 for an 8x4 sheet inc VAT, these were competative when I last checked.

You can use sprayfaom to fill in any gaps you leave.

The rockwall solution is massivly unplesant, not only to fit, but to do any work on pipes/wires in the future. Rockwayy themselves do some floor insulation slabs which expand to tightly fit beween joists, I have not used these yet, but they may work out well for you.

Rick

Thanks for the useful info, I'll go and check the price of Rockwool polythene tubing and chicken wire or plastic mesh now.

At ebay prices:

Equivalent area of Kingspan insulation (which would tend to produce more waste) at B&Q prices £875.00

I'll go for the Rockwool in a polythene tube option.

Yeh but I do not want to lift the floor, even a small inspection hatch.

I was thinking about drilling thru an air brick, and then injecting the void with cavity wall expanding foam ??? Or getting an insualtion company to inject it.

Sure, what you want and don't want to do is a most valid consideration. Personally I'd tend to try to be flexible on a effectiveness/convenience/cost basis.

that's a lot of foam if I understand you right and wouldn't the foam object formed breach the damp proof course by capillary action?

Floor cost me £700 to get put in, so any heat savings and cost of ripping part of it up, and putting it back down, has got to out way the cost of doing it.

If costs are too much I may as well brick up the air bricks, and accept that in 20 years time or so, the joists will have rotted, and replace the lot with a concrete floor.

Doesn't cavity wall foam have the same problem of breaching the damp proof course ??

I would describe making an access hatch as "ripping part of it up". It could be done much more subtley than that. Even better if it can be done from inside a fitted cupboard or similar.

I get the impression that you really want a concrete floor.:-)

It would tend to but a large monolithic block of foam would have a much greater area to draw moisture from.

OTOH, foam insulation might be the answer to my 1st floor draught problem, so thanks for bringing it up.

Knauf do an 100mm thick "itch free" fibre glass type material already wrapped in a polythene tube. I've been thinking about it for this use for some time.

How did you seal gaps around the edges of the Kingspan to keep the warm air above the insulation?

Sounds like a very useful product. I don't mind taking standard fibre glass and wrapping it myself if it saves me the price of a few bottles of vinous, but I'll definitely do a price comparison there.