New build Poroton clay floor put down insulation or not for Underfloor heating

CaraK

We are building using a poroton clay block and have got to first floor level. We opted to use the manufacturers Ziegeldecken for the floor which is essentially a block and beam floor with 195mm block plus concrete.

I am Looking for advise on whether or not I need to put insulation on top of poroton clay block floor at first floor, We haven't put UFH in downstairs yet. We are building to passive standards and it's debatable whether we need it so it's a backstop option 😀



My own thinking is that the clay block should be sufficient insulation. I can put a strip of insulation on top of the blocks trimmed to the width of the blocks if needs be

Any advise or recommendations greatly appreciated

BryanF

Confirm w/m2k of build-up under proposed ufh?

Looking at picture you certainly do need insulation

CaraK

thanks for replying

w/m2k 0.5 clay block 195mm
not sure what w/m2k is for the concrete (75mm)
ceiling 20mm lime or clay plaster

on the ceiling side their is still an option of creating a warm sandwich( radiant ceiling) by putting ufh on the ceiling rather than the ground floor and spray plastering a lime or clay based renðer on it

Metric Tensor

I personally see no huge benefit in insulation between first and ground floor, even with UFH. Any heat escape is still into the envelope of the building and thus contributing to the overall house temperature.

Plus the difference in temperature between upstairs and downstairs will only ever be a few degrees at most so the "Delta T" is not there to push high rates of heat transfer. Also the overall floor structure will be brought up to temperature once ever and remain at roughly the same temperature for the entire time the house is occupied.

The structure of the floor (poroton or any other) shouldn't matter in this case.

*All of the above is personal opinion of course. Happy to hear explanations to the contrary. The main one I know is that the layer of insulation gives a handy base to which the plumber can fix the underfloor pipes.

sydthebeat

its a first floor....

the poroton blocks themselves should be good enough insulation between zones.
like MT above i dont see any particular need to add any extra insulation here.


to the OP, im interested to know what your target wall U value was, and what poroton block are you using, and do you need additional wall insulation applied?

CaraK

Metric Tensor wrote: »

I personally see no huge benefit in insulation between first and ground floor, even with UFH. Any heat escape is still into the envelope of the building and thus contributing to the overall house temperature.

Plus the difference in temperature between upstairs and downstairs will only ever be a few degrees at most so the "Delta T" is not there to push high rates of heat transfer. Also the overall floor structure will be brought up to temperature once ever and remain at roughly the same temperature for the entire time the house is occupied.

The structure of the floor (poroton or any other) shouldn't matter in this case.

*All of the above is personal opinion of course. Happy to hear explanations to the contrary. The main one I know is that the layer of insulation gives a handy base to which the plumber can fix the underfloor pipes.

Thanks for replying much apreciated

I agree and as the poroton block will be externally insulated all the heat will be contaned within the building. I think my main worry will be overheating hence the UFH system we choose can also be switched to cooling function.

The plumber did raise concern about how he was gong to get a fixing for the clips

I contacted the UFH manufacturers in Austria and they did agree that from heating perspective that poroton block was sufficent inslation in itself however they raise the issue of the need for sound insulation given that the poroton blocks are hollow

BryanF

Sorry missed the ‘first floor’ bit, assumed ground floor

CaraK

sydthebeat wrote: »

its a first floor....

the poroton blocks themselves should be good enough insulation between zones.
like MT above i dont see any particular need to add any extra insulation here.


to the OP, im interested to know what your target wall U value was, and what poroton block are you using, and do you need additional wall insulation applied?

Thanks for your input

We are using the poroton 300 block( thermal conductivity 0.10) externally insulated and lime rendering for a u value of 0.15. All internal walls will be poroton also using a 115mm block. We brought them in direct from the manufacturers in three 45 foot containers.We did look at getting the 495 insulated block which would of given us a u value of 0.15 but we would of spent more on shipping them here then they actually cost because of the size of the pallet they are stacked on.

The floor blocks was another container and we had spare capacity so we got 6 pallets of the insulation filled ones which we will use on the first few courses after floor is poured. it will be interesting to see f t shows up on the thermal images

sydthebeat

Lime rendering on top of polystyrene EWI??

Do you advisors predict the wall will need to be breathable, and if so, what impact will the polystyrene have on that?

CaraK

sydthebeat wrote: »

Lime rendering on top of polystyrene EWI??

Do you advisors predict the wall will need to be breathable, and if so, what impact will the polystyrene have on that?

I never said we were using polystrene for EWI. Still looking at options for EWI but whatever we choose it will be breathable. We are looking at Rockwool/Cork/wood fibre

CaraK

sydthebeat wrote: »

Lime rendering on top of polystyrene EWI??

Do you advisors predict the wall will need to be breathable, and if so, what impact will the polystyrene have on that?

wufi analysis for 120mm rockwool option

housetypeb

Well done on going for passive house standard.

How is the rockwool attached to the poroton blocks? I presume there's special fixings as the blocks themselves can be brittle enough.

Will be doing some building myself towards the end of the year subject to planning approval, was planning on standard block on flat with 200mm external insulation on an insulated slab, but will look at poroton again i think.

CaraK

housetypeb wrote: »

Well done on going for passive house standard.

How is the rockwool attached to the poroton blocks? I presume there's special fixings as the blocks themselves can be brittle enough.

Will be doing some building myself towards the end of the year subject to planning approval, was planning on standard block on flat with 200mm external insulation on an insulated slab, but will look at poroton again i think.

Good question we are currently testing various fixing options. I am leaning towards an Italian based EWI system (natural insulation and 100% breathable ( poroton is widely used on the continent) which has 20 year guarantee and they dont use any dowels/ mushroom insulation type fixings they use their own adhesive to attach the panels to the wall (brick etc) it needs to be completely attached to the surface that will hold it in place. Im not convinced by systems that just bolt a panel onto the brick with 5 bolts and 5 points of contact or ones that combine it with dobs of adhesive

Best of luck with your planning,the key reason we opted for Poroton was 100% breathabilty and not having to worry about trapped moisture behind insulation boards/ airtight membranes etc.

BryanF

When you say ‘we are’ testing - are the new euro codes affecting this with the poroton blocks? What’s you Engineer saying?

Thanks

CaraK

BryanF wrote: »

When you say ‘we are’ testing - are the new euro codes affecting this with the poroton blocks? What’s you Engineer saying?

Thanks

Thanks for replying

I am not an engineer so not familar with the euro code you are referring to if you could post it ,i will check with the manufacturer and my engineer.

My Engineer who is familar with poroton builds ( he is German) recommended that i look at european systems and that i get the EWI installers to do pull out test on the various options that we are looking at. The testing is basically building test wall and testing the products for pull out resistance anchors with glue/without glue, 3 anchors, 5 anchors, boards applied blobs of glue plus anchors with 3/5 anchors, glue fully applied with/ without anchors / 3/5 anchors etc. The EWI systems we are testing are all certified ( presumably in compliance with the most recent euro cods you are referring to) but I would much rather test them myself with poroton and be satisfied.

The Italian EWI system i referred to above is composed of natural material it is applied without mechanical anchors (dowels) and is CE marked (ETA 11/0263).

BryanF

if eng is doing pull out tests he’s on top of it.