# Insulation Spec for UFH



## BMD (17 Aug 2010)

Can someone advise me on the following spec that my architect has spec'd for my UFH and insulation. I don't think it is sufficient

*Ground Floor*

Slab to be in-situ reinforced concrete slab in accordance with the Structural
Engineers details, incorporating insulation to achieve min 0.25 W/sq mK.
75mm Cement: sand screed to accommodate Under floor heating pipes on
100mm high density insulation on 150mm in situ Concrete floor slab.
Dpc to be lapped and bonded with “Monarflex RMB” 400 Radon membrane on
hardcore. Radon sumps to be fitted with pipes from same to terminate outside
building and be capped.
25 mm “Kingspan” Therma Floor TF70 insulation to perimeter of slab taken up
between wall and slab. Ground floor construction to achieve minimum of 0.25 W/sq. mK

*First Floor*

Concrete panel floor slabs
To be 150mm precast concrete panel floor slabs in accordance with IS and
structural engineers specifications with 75mm Cement: sand screed to
accommodate Under floor heating pipes


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## sman (17 Aug 2010)

see below link

[broken link removed]

page 16 is relevant to flooring . you need .15 on ground floor anyway for UF so you need at least 125 mm of the Warm-R or equivalent.


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## BMD (17 Aug 2010)

Do I need insulation below the UFH on the first floor? No insulation has been spec'd


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## onq (20 Aug 2010)

Assuming you're interested in keeping your house heating zones separated you might want to install some insulation, otherwise you'll be heating the floor below.

Worse though will be the lag in the system because heat isn't being reflected up into the room that its required to serve.

And think about what floor build up and finish you're using - 25mm timber or a thick carpet blunts the effectiveness of an UFH system - both are good insulators.

Talk to Kingspan or some other supplier about the U-Value you'll achieve in the ground floor - they will carry out a calculation for you and revert.

I seem to recall 1,5 u-value can be achieved with 75-80mm HD board below a 150mm slab, but make sure you consider all your penetrations and Radon Gas Membrane detailing fully,

ONQ.

[broken link removed]

All advice on AAM is remote from the situation and cannot be relied upon        as a defence or support - in and of itself - should legal action   be      taken.
Competent legal and building professionals should be asked to advise in        Real Life with rights to inspect and issue reports on the matters   at      hand.


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## boots (13 Sep 2010)

BMD,

We are putting 40mm insulation on the first floor, between the screed and the precast units.

I spoke to some people who said we are wrong to do this, including the owner / director of a regional construction firm, who has UFH. Their opinion was that with UFH you need to think about heating the whole house and that the heat in the precast units will be transferred to the rest of the house.
One flaw with this view, I think, is that you are expecting the heat to travel downwards through your plasterboard on the ceiling, as well as through the cavity between the battens and the plasterboard - 100mm or more if you have HRV ducts in this cavity.
UFH installer was in favour of the 40mm insulation and his points seemed to make sense.

We'll see I guess, good luck with it.
boots


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## RKQ (15 Sep 2010)

boots said:


> One flaw with this view, I think, is that you are expecting the heat to travel downwards through your plasterboard on the ceiling, as well as through the cavity between the battens and the plasterboard - 100mm or more if you have HRV ducts in this cavity.
> UFH installer was in favour of the 40mm insulation and his points seemed to make sense.


 
If you have HRV and an Airtigh house, then where will this heat escape too?
Underfloor is about using low temp water to heat up a slab. The slab becomes a radiator. The thicker the screed the longer it takes to heat up BUT the longer it radiates heat.

In reality you'll heat upstairs for an hour or two before bedtime.


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## build4less (15 Sep 2010)

I dont think that UFH is a good job. You have little control on the turning on and off the heating in hot and cold weather. It takes a long time for the slab to cool down in hot weather but with hot weather sometimes comes cool evenings and you cant turn on your heating as it takes hours for the floor slab to heat up, but it is too warm for the heating to be on during the day hense there is a waste of energy to keep heating up and cooling down the slab as the floor slab needs to be at a min temp at all times so your heating is never off.

I have it i my house and it is a disaster, complete waste of money I'd be better off with radiators or similiar. I'd never do it again. I have it fitted in a 4000 sqft house upstairs and down stairs. Never again.

Look for alternatives as there are plenty out there.

Build4less.ie


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