Does anyone have experience of pumping insulation into underfloor voids. My in laws house has an expensive finish on suspended timber floors which they don't want to damage. The crawl space is about 400mm vented, but with no access. Could pump something in though. i noticed Viking House mentioned this on previous discussions, but not much detail given.

Hi piersadler,

there is a thread about this here:

http://www.greenbuildingforum.co.uk/forum114/comments.php?DiscussionID=6150

Peter

Tom, any idea of a m3 cost for that?

Bagged leca prices:
http://www.mikewye.co.uk/naturalproducts.htm#leca


Blown LECA - no prices.
http://www.leca.co.uk/33736

Look at the menu on the left for within ’ Flooring Insulation’.
‘For deeper foundations, the Leca® LWA can be blown directly from a vehicle into the void from a distance of up to 50 metres. Once the old floor has been excavated, the blowing vehicle pulls up outside the building and discharges the material at around 50m3 per hour’

Jeez, rules it out for this place then.

Posted By: piersadlerDoes anyone have experience of pumping insulation into underfloor voids. My in laws house has an expensive finish on suspended timber floors which they don't want to damage. The crawl space is about 400mm vented, but with no access. Could pump something in though. i noticed Viking House mentioned this on previous discussions, but not much detail given.

I've pumped EPS bead under the floors of over 20 houses with good sucess. I imported a few loads of Leca back in the day but found it as expensive as EPS. Remove or re-route electric cables if you can.

The choice (if acceptable to Bldg Control) is between Leca, and EPS bead. Can we list the pros and cons?
Cost, delivered
Insulation value (tho not as impoertant as it seems, because large thicknesses involved, which makes Leca's insulation plenty gd enough)
Behaviour with water - absorbtion, effect of absorbtion on insulation value, wicking

Also something trying to take form in my mind - EPS wd be a total insulation, isolating the interior from the subsoil. Leca, being much denser (tho still v lightweight as an aggregate) and having less fierce insulation value, could be seen as a thermal continuity with the subsoil, if doing the other things necessary to do the thermal storage tricks that subsoil can provide.

On my forthcoming newbuild project, Leca is blown in (or placed in bags + loose) to enclose the floor joists soild and to come tight (in thermal contact) up to the 25mm CPB (cement particle board) deck and tile flooring thereon. Below, the Leca is on DPM direct on the subsoil (and the CPB is an inboard VCL). Towards the centre of the floorplan, the Leca is as thin as can be, just under the joist soffit. Going outboard, it thickens, just enough so the DPM will drain outward any water or condensation that might get into the void. Further outboard, the joists bear on railway sleepers (up to 6m long 'crossing (points) sleepers') on edge as ground beams and the dpm dips to go under them. So outboard of the ground beams, the Leca is in considerable thickness, around the floorplan perimeter. Then at the perimeter the wall EWI is continued down about 1m in narrow-bucket trench (i.e. 'free-floating', not attached to any wall) and the Leca comes out to the inner face of that.

So the block of subsoil under the floorplan is enclosed in 200 EPS downstanding 1m, and that subsoil block is in thermal contact with the interior, via Leca of varying thickness under the CPB and tiled finish. This is an attempt to make an effectively heavy solar-absorbing floor (because tall wide glass area to SE) in contact with its subsoil (protected from edge-loss) but with a modicum of insulation to ensure that floor surface keeps cosy.

This is the sort of thinking that makes me favour Leca over EPS.

I can't wait to get to grips with Therm. Did AECB/Peter Warm course on it but my borrowed laptop played up and I hardly got beyond sq 1, not even concentrating on the info given. Am promised a re-run at reduced cost.

Thanks everyone. So much input in the short time since I started this.

Having heard about the Viking solution and read all the above am thinking about pumped insulation under the suspended timber floor in my own house as well as in laws.

My back wall is fairly damp due to having leaky cement render on the outside, so i am taking off the render and using a wood fibre board and lime render external wall insulation system (Diffutherm? not sure yet). As far as I know there is no effective dpc and the ground level outside is similar to that in. It is a little damp under the floor already. I think if I extend the EWI below ground level with EPS plinth board and use EPS/Leca under the floor, I have a reasonable chance of keeping joist ends warm.

I thought of thinning the insulation, say 0.5m in from the joist ends to allow a gap between joists and top of EPS (as per Peter Clark suggestion on previous thread) to allow any moisture to evaporate.

I favour EPS for the better insulation properties, although price will be a factor. Not really interested in thermal mass in my house as have plenty in walls. I have also done the THERM course and am reasonably competent with it-my advice Fostertom is have a go with THERM it's pretty straight forward. Perhaps I will model a simplified version and put on my website.

Any comments welcome.

Posted By: fostertomYr damp situation sounds dodgy, to be filling the cavity - shd sort it out fundamentally first. An external french drain might do it. What is EPS plinth board?

Thanks fostertom

I think the damp is related to the leaky render and poor back to front ventilation. The leaky render will be addressed with EWI. The back to front ventilation will no longer be required as condensation will occur only below the insulation (as per Viking comments). The External french drain is included in the design. Plinth board is board designed to be used at and below dpc ground level - this is the term used in the Diffutherm brochure and by other insulation manufacturers for similar applications.

Posted By: fostertomI don't understand the next para?

Next para - the idea is that in the middle of the room, away fro joist ends the insulation can come up to the underside of the floor boards, whilst at the edges, close to joist ends, the insulation is filled to a level just below the joists to allow them to dry if needed.

Indeed, if such a dodgy bodgy idea as CWI is found to work, why not this kind of under-suspended-timber-floor fill?

What acronym shall we give to this procedure? - making history here! (like AFAIK I was first to use 2G/3G for double and triple glazing!)

Posted By: piersadlerPlinth board

I'm just using standard EPS board.

That cd describe many extg. practices - something more distinctive?

Regarding pumping polystyrene beads under a floor please read http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=7526&page=1 so that you are aware of the potential risks.

There are quite a few other threads on the forum where people have proposed this but so far I haven't read of anyone getting it by Building Control.

I don't beleive they will either as it contravenes several other requirements in Approved Document C - namely prevention of moisture ingress and ensuring adequate sub-floor ventilation.

Don't do it

Hi Pmagowan. You would want to ventilate the floor to avoid condensation building up within the void and subsequently causing rot. I disagree with your interpretation of 'warm zone' (see the thread I linked to above)

It is required by Building regulations Part C for this reason and makes no difference whether the floor is timber or any other construction.

It is required in suspended concrete floos because of the risk of steel corrosion within concrete beams which can cause subsequent spalling and failure

I read the whole thread and all I see is that the traditional method is rubbish. Lots of pictures of ventilated floors rotting even one where the timber is right next to the vent. It seems this old fashioned way of doing things is not very good. I appreciate that inappropriate use of UFI would be worse than sticking with the old method much the same as insulating your loft badly would but that is no reason for not doing it properly.

If you EWI the house, have a french drain of Leca around the founds and use blown bead UFI I can not see how this would do anything other than protect the entire structure of the building. Under the house will be dry, the founds will be drained and thus dry, no rising damp (if such a thing exists), the walls will be warm, the floor will be warm. How, in this situation, will the wood get damp enough to cause rot. I am not really interested in the regs because I think they are likely to be designed for old fashioned, inefficient and poor building methods. I am more interested in what would work best.