Please help - not enough room for floor insulation

boarduser01

We are in the middle of building our house and have now found that there is not enough room for sufficient insulation under the floor. Please can anyone suggest what we should do. We have 105mm from the top of the base to the dampproofing under the timberframe. Because we are having underfloor heating we should be having 70mm insulation and 75mm screed minimum, but obviously this is 145mm, 40mm too high without the finished flooring. Now we don't know what to do.

We are obviously reluctant to reduce the floor insulation, but what are the alternatives?

What are the sizes of different types of finished flooring? I have been told that we should be leaving 15mm for wooden floors, 10mm for tiles - are these correct and what other options are open to us?

I hope you can help, thanks

Qwerty?

one option is to used the 'easyscreed', which can be poured to a thickness of about 30mm i think. It's dear thou. It's a self leveling screed supplied by some company in dublin. Can't remember there name.

Viking House

Qwerty? wrote:

one option is to used the 'easyscreed', which can be poured to a thickness of about 30mm i think. It's dear thou. It's a self leveling screed supplied by some company in dublin. Can't remember there name.

Gerry Beades Concrete

Pataman

Contact Dynamic Packaging Solutions in Rathcoole. They have an insulation roll: 5mm gives the same insulation as 25mm standard and 10mm the same as 50mm. i have just put it down under my pipes and then had 50mm of concrete on top.

ardara1

Pataman wrote:

Contact Dynamic Packaging Solutions in Rathcoole. They have an insulation roll: 5mm gives the same insulation as 25mm standard and 10mm the same as 50mm. i have just put it down under my pipes and then had 50mm of concrete on top.

Ask the christmas fairy to sprinkle fairy dust on the floor it will have the effect - is it a foil?. Can they substantiate their claims?

If its a multifoil, then it wont work without a 25mm gap either side of it.
Even so there is a lot of controversy about it's effectivness.

What is your room height? can you affort to lose a bit here and set your doors higher??

boarduser01

Thanks for all the suggestions so far, in answer to some of the questions:

We could easily raise all internal doors and we have at least 10mm extra height for the external doors as we can go over the pvc a bit. But the problem is the timberframe- can we just tack dpc up the side of it and not have a problem? What overlap of the timberframe could we safely go?

We were already considering easy-screed, but the problem is that I think we need the depth of screed to act as a "thermal store" for the heat from the underfloor heating pipes - is this correct?

Pataman

Deleted User wrote:

If its a multifoil, then it wont work without a 25mm gap either side of it.

What gap is this? A friend has being using this since last year without any complaints.

ardara1

Pataman wrote:

What gap is this? A friend has being using this since last year without any complaints.

The gaps ARE the insulation - we all know air is an insulant when trapped - by facing one side of an air gap with foil we actually increase the thermal performance of that air gap - but only to the value of about 10mm of fibre glass.
On a wall say - put timber batten on wall (cavity No 1) then the foil, then the counter batten (cavity no2) and you'll end up with a U-value of around 0.40.

On a floor you cover your BACOFOIL with something, concrete or timber flooring - no cavities - no insulation. - Big Con.

boarduser01

So which is better 3" insulation with 2" screed containing underfloor heating pipes or 2" insulation with 3" screed containing underfloor heating pipes?

ardara1

boarduser01 wrote:

So which is better 3" insulation with 2" screed containing underfloor heating pipes or 2" insulation with 3" screed containing underfloor heating pipes?

If you don't have enough insulation - the heat goes the wrong direction - bad idea.

The minimum sand cement screed (over pipes) is 65mm any way.

So you're stuck - with 50mm Kingspan/Xtratherm (Should be around 75mm minimum.

My suggestion - don't put UFH in anyway - it's just not suitable (Responsive enough) for Irish climate.

Is your house Timber Frame per chance?

ardara1

Sorry - just seen earlier post -

Do you know that the BRE recommends that because of the high response time of TF that the slow response time of UFH is unsuitable - your heating time should be more responsive - radiators?

AJL

Built a kingspan TEK house similar to a TF but with the insualtion. Put in a air heating system with an air to air heat pump at the side of the house. Is this an option for you? It is easy to install and is a product well suited to a TF house. Just need to cut holes to blow heat into the rooms and when fitting plasterboard the vents are attached to the stud so the plasterer just custs out the holes for the vents.

I have 130 mm of gap so putting 60 mm insulation and the rest screed. If you put in the above system you would have no pipes in the floor so no issue.
If you want more info give me a shout. maybe you have put in your heating system already.

qazxsw

don't know about the dpc membrane issue, but assuming that could be got around...

Depending on your ceiling heights, would it be possible to bolt and glue on a secondary base plate of say 2" and get the timber frame company to raise the heads of all the doors by a corresponding 2" either on-site or, if not too late, in the factory.

If you have ceiling heights of over 8ft sacrificing the 2" shouldn't be a prob, if you don't it still shouldn't be a Major prob ??, but that's a matter of opinion of course. . It might mean having to take 2" off all the plaster slabs before slabbing begins but this would be a days work at the most for an experienced slabbing crew.

Of course you'd have to check with your engineer - coz they'll be the ones signing off, though in my experience they are pretty reasonable w.r.t. bending the rules a small bit (i.e. 2")

boarduser01

Thanks for all the comments, just a few more questions.

ardara1:

The minimum sand cement screed (over pipes) is 65mm any way.

The minimum we have been told is 35mm for the screed, that is what we were intending to get upstairs. So this should not be a problem and

Do you know that the BRE recommends that because of the high response time of TF that the slow response time of UFH is unsuitable - your heating time should be more responsive - radiators?

if this is true then having a thinner screed would be more of an advantage! I could not find the BRE information that you mentioned - do you have a link for where I could find it? Thanks

qazxsw:

If you have ceiling heights of over 8ft sacrificing the 2" shouldn't be a prob, if you don't it still shouldn't be a Major prob ??, but that's a matter of opinion of course. . It might mean having to take 2" off all the plaster slabs before slabbing begins but this would be a days work at the most for an experienced slabbing crew.

We just have 8ft but I think that we will have to sacrifice the couple of inches where we can, unfortunately the tf is already erected so we cannot add to the base under the frame!


AJL:

Put in a air heating system with an air to air heat pump at the side of the house. Is this an option for you? It is easy to install and is a product well suited to a TF house. Just need to cut holes to blow heat into the rooms and when fitting plasterboard the vents are attached to the stud so the plasterer just custs out the holes for the vents.

This may be a possibilty but we were recommended against it due to the Irish weather!!!! Does the house need to be air-tight, because ours is not!

AJL

Dont know why they would say the irish weather the canadian weather is more severe.
It probably is best that it is air tight for this system otherwise you are wasting energy. The beauty of it is you do not need vents cause it controls the flow of air. the motto is "seal tight ventilate right" I think! If you want the name of the company that supplied the product pm me.

boarduser01

AJL - thanks again for your reply. We just put in windows with normal vents - so it would not be possible to use this system surely? Also I was told it was the dampness in the air, not the cold that made the system less efficient here in Ireland, am I being misled?

Do-more

boarduser01 wrote:

Also I was told it was the dampness in the air, not the cold that made the system less efficient here in Ireland, am I being misled?

From what I understand of air-to-air heat pumps it is the higher humidity here that causes problems. As heat is stripped from the air condensate can freeze on the evaporator which then needs to be defrosted, different manufacturers use different methods to do this, but the nett effect is that they all consume energy in doing it. The Scandinavian and Canadian climates are much less humid so perversly despite having lower ambient temperatures they are more suited to air-to-air heatpumps.

That is my understanding of it anyway, if I am talking horse$hit, I am sure that someone will correct me!:D