I am taking a very expensive punt.

Sorry to resurrect this thread but I am very interested in knowing from Viking House how the light weight aggregate has performed so far? I have been researching this method and no matter how I look at it, it seems a winner except for costs. I would love to know which aggregates you have used? I am at the moment looking at blown glass such as TECHNOpor but the costs are huge. Thank you.

Thanks for that Barney, very interesting to know. Did your dad use expanded clay?
I know that for technopor you need about 450mm for a u value of around 0.22 W/m2K, but for me the cost of that woks out to be about £5000...hell no way! So I'm trying to find a cheaper LWA and maybe fill some of the first layer with something else, then a LWA up to the floor joists and then wool between the floor joist laid on top of the LWA to get the best u value and to also stop the mice (of which I seem to have hundreds of) from eating any other insulation, which so far they have eaten all of the insulation from the heating pipes.

Thank you Barney...sorry I'm new to all this, I just have basic DIY knowledge and it's very basic! I'll keep looking but the prices are still coming in huge, probably due to needing about 450mm in depth and an area of 115 m2.

Hi Clare, we switched to EPS bonded bead under the floors because LWA was too expensive and we needed too much to achieve a good U-value.

I guess cavity wall people will do it? Plenty of them around

How often do fires start toned the ground floor in houses? Very rare I would think and even when it has caught fire if you are not out quicker than the fire reaches under the floor boards it could be too late to worry about the beads under there.

I don't seem to be able to find an EPS product that can be used to fill up the floor space. Can only find ones that you use to fill between the floor joists, leaving the ground open underneath.

I took on the risk myself, the supplier was Airpacks in Ireland. We did close to 50 houses, never any problems! My own house is even done, I just fitted a smoke alarm in the hallway.

I've just got Foamit foam glass from Lime Green. It only has 10% compaction as opposed to the 30% of Thermopor, and I need to compact it as it is going under a hempcrete slab. I looked into LECA too, but just felt I wanted the better non-wicking performance of the foam glass. Lime Green were the best price for the LECA too - I did initially find cheaper, but then discovered that it was the plain LECA not the silicone-coated, which I needed as it was to be a capillary break as much as insulation. In the calcs I needed either 170mm foam glass or 200mm LECA to combine with 100mm hempcrete slab to reach a min U-value of 0.25 (U value is a bit better than this for the foam glass option). Hope that helps a bit?

James,

These, perhaps?

http://www.lime-green.co.uk/

Slowbuilding...thank you so much for that info. It would be very interesting to know how much you paid for the Foamit from Lime green. I am currently chatting with the export manager at Foamit and waiting for quotes. I have two options at present 64 cubic meters delivered in a container from Germany or a truck from Yorkshire??
Doesn't help that I'm in Aberdeenshire...bloody hell....I'm gonna be poor!
I'm thinking now of using LWA as a base to act as a DPM, then EPS to fill up the gap a bit more, then more LWA (on top of the EPS) up to and surrounding the joist, to help with costs as my floor depth is about 450mm.

Quotes for Maxit LWA are coming in at £153.29-£164.81 for each bag which are 1.2 m3 the later based on needing 34.8m3 and Slivapor £142.10 - £154.33 for each bag which are 1.25m3 again the later based on buying baulk for 35.0m3.

Think I might have to sack this idea as it's going cost thousands.

I have no advise for you Victorianeco, I'm new to this myself. I really wanted to use LWA because my heating pipes run under the floor and bloody mice keep eating all the insulation. So once I insulate and put new flooring down my pipes will be beyond the thermal barrier and if fecking mice eat the insulation again I could end up with burst pipes. The prices for LWA are just so high and I could insulate using BDPM and wool (or something) for 1/3 of what the LWA is coming in at.

That would also be a big job...I have 3 foot thick Granite walls

Hi all, sorry I didn't reply, misunderstood how the forum worked (assumed notifications would be emailed).

So, for my project, some context might help. The first thing is I have a very small flat I'm doing this in - under 50sqm. I decided the best way to lower my 'footprint' would be to convert my 3-bed terrace into 2 flats, so did the upstairs with dabbed insulated plaster board, created an internal bathroom, and put a kitchen in the old bathroom. This is now let out. The ground floor will be my new, smaller, home.

I decided (due to rotten joists in many places thanks to previous owners raising ground levels, plus poor floorboards, plus limited wall space due to it being a small, open plan flat), to go for solid floors & underfloor heating. Because it is what I know the most, and have worked with the most, I always knew I'd be doing a hempcrete slab. Initially I was planning on silicone-coated LECA, but I uncovered enough concerns about the silicone coating not being guaranteed to have coated each clay ball fully etc. PLUS the fact I'd need 200mm of it rather than 170mm of foam glass, which would need digging out, that I decided to go with the foam glass. It's costing £135 per m3, and I will be using 9m3.