Floor Insulation Help

peterc14

I thought i would try and save money by laying the floor insulation myself before ufh is installed but have a few queries.

I am firstly fitting 25mm isulation to the perimiter wall (from slab to slightly above where screed will be) then I am laying floor insulation against perimiter insulation.

. The plasterer has skimmed right down to the floor so the insulation will sits out 25mm form the wall with the floor insulation abutting against it.... is this 25mm ok for fitting skirting and floors?
. The top of the perimiter insulation is sometimes slightly away from the wall (small 4/5mm gap)... should this be tight against wall... should i use grip fill to stick it to wall?
. When fitting the perimiter insulation, should i run it across internal door openings also? ie should each room be boxed with perimiter insulation or should the screed be able to flow from one room to the next unobstructed (sand cement screed).

Sorry for long post but would love some answers.

creedp

peterc14 wrote: »

I thought i would try and save money by laying the floor insulation myself before ufh is installed but have a few queries.

I am firstly fitting 25mm isulation to the perimiter wall (from slab to slightly above where screed will be) then I am laying floor insulation against perimiter insulation.

. The plasterer has skimmed right down to the floor so the insulation will sits out 25mm form the wall with the floor insulation abutting against it.... is this 25mm ok for fitting skirting and floors?
. The top of the perimiter insulation is sometimes slightly away from the wall (small 4/5mm gap)... should this be tight against wall... should i use grip fill to stick it to wall?
. When fitting the perimiter insulation, should i run it across internal door openings also? ie should each room be boxed with perimiter insulation or should the screed be able to flow from one room to the next unobstructed (sand cement screed).

Sorry for long post but would love some answers.

Im in same position myself and following different opinions from different sources have currently decided as follows:

I have 150mm of EPS on ground. Then Im placing a 150mm high x25mm thick PIR edge board againt wall and a further 100mm high by 25mm edge board outside this. Then I'm laying a 50mm PIR board against this edge board, i.e. on top of the eps giving a total floor insulation height of 200mm. As Im going with a 100mm screed (Im going with polished concrete finish) the 150mm board against wall will come to top of screed while the outer 100mm board will come 50mm way up the screed leaving a rebate of 25mm for the last 50mm of the screed. Im sorry if this is very complicated but I can't seem to simplify it any better.

On top I will have UFH and screed. I was originally going with 200mm of eps but the UFH suppliers said the eps didn't have mechanical strenght to hold UFH pipes in place so asked that I have a 50mm PIR board on top for this purpose.

In relation to the edge boards coming away from the wall, my builder did not want to have the outer 100mm edge board installed as he said that when the screed pushed against this the pressure would cause the top of the inner 150mm board to move away from wall. However, he seems to be happy to proceed as long as he ties the top of the inner board to wall with dabs of silicone.

Not sure if that is of any help and would welcome views from others on this issue.

peterc14

Thanks for taking time to reply...

does the perimiter insulation be to "external" walls only?

creedp

peterc14 wrote: »

Thanks for taking time to reply...

does the perimiter insulation be to "external" walls only?

No problem.

Im putting edge insulation around all walls as they are block and will create cold bridges to the subfloor. There is no difference between an external and internal wall in this context.

I will also be using edge insulation for wall upstairs even though the cold bridge to the subfloor is not an issue. However, with underfloor heating I'm of the view that the longer you can keep the heat in the screed the more will be emitted to the room space. May be a little uncessary but as I bought the edge insulation by the pack I have enough over to do upstairs - so nothing lost!

BryanF

did you guys consider quinlite or a similar material for the inner block-work leaf and internal walls at floor level to reduce thermal bridging?

peterc14

BryanF wrote: »

did you guys consider quinlite or a similar material for the inner block-work leaf and internal walls at floor level to reduce thermal bridging?

unfortunatley no... but it seems like a good idea.

peterc14

Another question related to this...

I am using Xtratherm 25mm at perimiter but I see you get more flexible edge insulation which comes in a roll... i would have thought the Xtratherm/Kingspan would have been better... though the roll probaby quicker to install?

creedp

BryanF wrote: »

did you guys consider quinlite or a similar material for the inner block-work leaf and internal walls at floor level to reduce thermal bridging?

Yes I did and built the inner leaf with 150mm quinlite blocks as I didn't want to have internal insulation board. In retrospect I would probably have liked to go with a wider cavity that the 150mm I did and build inner leaf with std blocks as did a number of contributors to this forum. However, 150mm was the limit of my engineer/builder! Horses for courses!