UFH insulation

[seasickstevie]

I'm taking up the screed on our kitchen floor and putting under floor heating pipe in.

The heating pipe will be sat on 25mm of Kingspan.

Does 25mm sound sufficient?

I'd like to put thicker in but there isn't the space. The screed will be about 70mm thick above the top of the pipes. I'm told this is a minimum depth required.

Am I going to be paying for heat transferred through the 25mm insulation into the concrete base?

 

[DevilDamo]

Does 25mm achieve the required u-values in accordance with the building regulations? I'm thinking maybe not. You could look at an alternative product of similar thickness, which may achieve the necessary u-value's. Or look at putting a thicker insulation below the slab... if possible?

I was always led to believe the "absolute" minimum thickness for a screed with underfloor heating is 65mm for domestic situations and 75mm elsewhere.

 

[mointainwalker]

25 mm is rather little. I would steal 10 mm - or more - from the screed ( don't believe 70 mm is necessary ) and add it to insulation layer.

Self-levelling screeds can be down to 50 mm

It will help a little if you put a layer of silver foil under the insualtion as well ( single sheet, not this multi-foil stuff)

Suggest you don't put pipe directly on insulation as this will not allow screed to fully surround it and hinder heat=transfer. Wedge it 5 mm (approx) above for self-levelling, 10 mm for concrete screed.

 

[SmithyXL]

http://www.screwfix.com/prods/50913/Building/Roofing-Insulation/Airtec-Double-Insulation-1-5m-x-25m

Have a look at this product from Srewfix, it would give you an equivalent of 110mm polystyrene for ony 5mm.
Not sure if will help but worth looking at.

 

[mointainwalker]

And if you believe the cobblers posted above, would you also like to buy a very nice magic ring, guaranteed to make you win the lottery.

Only 250,000 pounds !!

 

[SmithyXL]

And if you believe the cobblers posted above, would you also like to buy a very nice magic ring, guaranteed to make you win the lottery.

Only 250,000 pounds !!

"self leveling screeds can be down to 50mm"
Thats as long as you want the heat to break it up and relay your floor within a year or two. 65-70mm minimum ask any real builder, at least 45-50mm over the pipe is the minimum standard.
Maybe the French do it a bit 'differently' to us.

 

[mointainwalker]

smithXL

As well as being a shill for a piece of nonsensical foil crap, you come back to show us you know nothing about screeds either.

The info below comes from the first company that came up on a search for free-flow screed UFH. ( www.undefloorheatingscreed.co.uk )

Liquid Underfloor Heating Floor Screed - Flo Screed
Flo-screed is a liquid underfloor heating floor screed designed to compliment and complete your underfloor heating system with significant advantages over traditional sand and cement floor screeds. Flo-screed is a liquid screed/flowing screed produced to a flowable consistency to fully encompass the underfloor heating pipes producing a void free screed which is virtually impossible to achieve with sand and cement. Flo-screed is ideal for commercial, domestic and self build projects of all sizes including renovation as well as new build.



Generally 50mm of liquid screed
(i.e. giving a 35mm cover over a 15mm pipe)
can be used instead of 75mm of sand and cement screed.


Seems to contradict rather emphatically both your total depth and pipe coverage, wouldn't you say ?

Got any other fairy tales you want to tell us today ?

 

[SmithyXL]

Tried your link to upgrade my poor knowledge, it says website not found.
Are you sure its not a fairytale?

 

[mointainwalker]

It's not a link, i just typed it in afterwards. Just input it as is ..

and come back afterwards and tell us if it's a fairy-tale.

 

[SmithyXL]

It's not a link, i just typed it in afterwards. Just input it as is ..

and come back afterwards and tell us if it's a fairy-tale.

I have a quick look and would have to bow to your supieror knowledge of screeds, I hope it takes you a long way, I'm sure it will.

I tried to offer the fella a cheap option the might of got him out of a hole.
(even said it may be of no use to him)
Where as as you sir, have behaved in the manner of an iternet Penis.
Good luck with your screeding, as on your hands and knees seems to be your destiny in life.

 

[mointainwalker]

" tried to offer the fella a cheap option the might of got him out of a hole. "

What a load of crap.

If there was a product that replaced 110 mm of polystyrene by 5 mm of foil costing only pnds 3 per m2, why has it not captured 100% of the insulation market world-wide and been trumpeted from the roof-tops by governments ?

Your attempt at mitigation fails.

edit

P.S. The advantage of free-flow is that no-one has to go down on their knees

 

[alittlerespect]

Hi

25mm thickness of insulation will reduce heat loss by around 50% but the U value would not comply with current standards. To meet these you would need a minimum thickness of 75mm, but as you do not have sufficient headroom then 25mm is better than nothing.

I would steer clear of the foil insulation mentioned it is unlikely to be suitable for the purpose that you wish to put it too, check the detailed specification for the product. Again, same principle applies to the floor screed, technology has moved on significantly since the days of sharp sand and cement screeds, you just need to ensure the product is suitable for laying over your chosen insulation material.

Regards

 

[mointainwalker]

@ALR

Between which screeds and insulants do you envisage any incompaibilities ?

 

[seasickstevie]

incompaibilities ?

I am told I need a PVC sheet above the PIR - not necessarily to DPM standard - just to prevent the moisture draining from the sand & cement too quickly.

Not sure what you mean. What is there to be incompatible? (presume that's what you're saying m'walker).

I'm taking what alittlerespect is saying seriously. Don't want to spend all winter heating a 3" slab of concrete below the insulation. Over the years, this could cost a few £££.

Going to enquire with someone today about a pour-in product. Not sure if this is something available to the DIYer or is it something that requires specialist mixing gear.

Thanks for all contributions so far.

 

[mointainwalker]

The sheeting is correct.

Don't forget to put a flexible component ( polystyrene or foam) around the walls and any other fixed object to allow for expansion and prevent cold-bridging into the walls. Should be min 8 mm but around the walls i would use thicker polystyrene/insualtion material to minimise heat-loss.