Advice on insulating a ground floor

Hi,

I'm looking for advice on my plan to insulate under my groundfloor floorboards. I've trawled the archives/search and some come to a similar conclusion as myself but I wanted to confirm it with the masses.

The groundfloor is all suspended flooring with a good sized crawl space (i can sit up in it!).. At somepoint in time the crawl space has been concreted and additional air bricks installed. Now at the moment we're slowly doing the house up (have been for the last 9yrs *sigh*) so pulling the floorboards won't be a problem, agro but not a problem.

So my question? What is the recommended solution for insulating under timber floors? I initially thought rockwool of some form with netting or something holding it close to the top the joists. But would kingspan/celotex or even the insulation slabs might be a better solution (eliminating the netting.. But perhaps needing another way to fix say battens fixed to the joists?)
Eventually when all is done some form of wood flooring will be being laid throughout the groundfloor..


Any advice/guidance very much appreciated.

Rob

Hi unseen, here are some links for you to peruse //www.diynot.com/forums/viewtopic.php?t=189697

Hi freddie,

Thanks for that. They were the only links I could find myself when searching previously.

I guess my main question should really have been which is better? Solid foam ala kingspan/celotex or rockwool (of some form)? Time to install/Cost although a factor, not a major one as I'd rather take my time and or spend a wee bit more for added benefit, unless the extra cost doesn't bring a major difference.

Out of interest which have you installed freddie? If you did one over another (ie rigid instead of roll) any particular reason?.. I can see the benefits of rigid boards, but I wonder if the extra cost is a proven benefit.

Thanks

Rob

Rigid is easier to install but will be more expensive. I've never specified mineral wool insulation for a floor, only advised people on here to do so as a cheaper (albeit more difficult) solution. With rigid you can be sure you're filling the space and not leaving any voids anywhere, if you're doing it from underneath its gonna be a pain to keep the mineral wool up there while you suspend some mesh off the joists to hold it there, probably a 2 man job too. If you're not bothered about time or hassle and want to save every last £ go with the mineral wool.

Thanks again for the reply freddie,

I'm basing this on an assumption here... If I go for the rigid solution in theory (assuming I can get it through the floor traps) it could be done without lifting the floorboards up right?

To be honest, I've thought about the wool solution before and I've always been in two minds about it.. I did wonder if This might work?

So if I go down the rigid route (ooer!) it's best practice to get it as close to the floorboard as possible fastening with either nails into the joist or battening to suspend it. Then as you mentioned any gaps foam filled and what perhaps duct tape joints between boards or is that just overkilling it slightly? (When I can find somewhere online thats selling the rigid reasonably priced any suggestions?)

Again thanks all the help is being taken in!

Rob

Yes, fit rigid from beneath and secure with battens or nails, fix it tight up against the boards. Seal any gaps with foam and as you're down there getting cramp you may as well tape the joints.

Like the rest of the sheds, Wickes are silly money for a lot of stuff and I'd be very suspicious of any insulation products where they don't specify its thermal resistance (or its heat loss values). You can get a decent make such as Kingspan TF70 or Celotex GA3000 for less and you can be sure it will do what is says, the exact thickness required depends on the perimeter and the area of your ground floor plan and what U value you intend to achieve. If you opt for Kingspan or Celotex post your area and the perimeter of your ground floor back on here and we'll tell you what you need, probably about 70mm.

There are places online such as here http://www.soundstop.co.uk/store/products.php (just google celotex prices or similar), or builders merchants, as ever a bit of haggling won't go amiss to get the best prices. http://www.enconinsulation.com/contact/ seem quite popular down here.