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Author Topic: FoilType UFH insulation  (Read 1108 times)
Bikerzz
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« on: January 21, 2019, 06:28:55 AM »

Oki after much time and posting on here...........
I have finally dug up most of my screed on my block and beam floors and ready for the major work to begin (UFH and a wall out, new kitchen, etc...)

The contractor I propose to use is happy that I only have 50mm space for insulation ontop of my block and beam (Its a retrofit so best I can get), however he has suggested I use a multi foil insulation as well as celotex type insulation such as:

https://www.thermal-economics.co.uk/thermal_sys_sel/floortherm-mp/

Any advice?
I know this will add cost but I'm all for doing this right first time as its a house I intend to live in for 30 years.

Cheers

« Last Edit: January 21, 2019, 06:47:49 AM by Bikerzz » Logged

Triple Glazing.50mm CWI.
JohnS
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« Reply #1 on: January 21, 2019, 07:25:54 AM »

My understanding is that foil insulation works by a combination of trapped air slowing conduction and 'silver' foils reducing radiation.  The foil needs an air gap on both sides to reduce radiation.

Surely the screed willncompress the foil, rendering it useless?
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Bikerzz
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« Reply #2 on: January 21, 2019, 07:38:07 AM »

That "was" my impression. However it seems that might be old fashioned view as you can see the link, that stuff is designed for this job of compressed under screed. Just wondering if anyone has actually done it or if its just marketing bull and better with extra 10mm of Celotex
« Last Edit: January 21, 2019, 09:39:36 AM by Bikerzz » Logged

Triple Glazing.50mm CWI.
JohnS
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« Reply #3 on: January 21, 2019, 01:23:54 PM »

Looking at the website there are two products.

First.  The foil.
All the photos etc of it being used, in the brochure, show a cavity next to it.  Eg when it is laid over joists or there are battens between it and the flooring.  For block and beam floors, it is in under the block and beams. Can you get under your beams?

Second. TE Premium.
This is basically a deluxe polystyrene board with added graphite.  Generally EPS when extra thickness does not matter as it is cheap.  It does not sound as though you have room for extra thickness on top of the block and beam.  As far as I can make out, only this product is suitable for under a screed.

It looks to me as though your contractor is proposing the wrong product for the application.

 
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marshman
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« Reply #4 on: January 21, 2019, 01:26:53 PM »

Back in the late 1980's I installed UFH in a bungalow we were building. We used 2 layers of 2L2 - a triple sandwich of foil - bubble wrap - foil - bubble wrap - foil.  Can't remember what the R value was. This was laid on top of the concrete oversite, then the pipes were laid on top tied to reinforcing mesh. The whole lot was then covered in a 50mm thick screed.

As far as I know this was the method recommended by Wirsbo (now Uponor) at the time.  We lived in the bungalow for 15 years and it was always nice and warm - and our gas bills were half of anyone elses in the area. Only down side was a relatively slow response time.

There didn't seem to be an issue with compaction of the 2L2 insulation.



* 2l2-1.jpg (75.82 KB, 816x568 - viewed 176 times.)

* 2l2-2.jpg (221.11 KB, 1556x1120 - viewed 184 times.)
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3.15kWpk (15xSharp ND210)/SB3000. & 3.675kWpk (15 x Suntech 245WD)/SB4000TL, 10kW GSHP driving Wirsbo underfloor heating from 1200m ground loops. 10' x 7' solar wall (experimental). Clearview 650 Wood Burning Stove. MHRV - diy retrofit. Triple glazing.
A.L.
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« Reply #5 on: January 21, 2019, 02:18:52 PM »

hello,

The website claims a thermal resistance of 1.32m2K/W for a 50mm horizontal cavity with foil on one side. 50mm of Celotex or similar will have a thermal resistance of around 2.17m2K/W. So Celotex has a higher thermal resistance and I expect it to be cheaper. 
Presumably the floor load is transmitted through batons at regular intervals?
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Bikerzz
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« Reply #6 on: January 21, 2019, 02:32:17 PM »

Thanks Marshman, I remember your post from another thread stating similar which is good news for me with limited space.
Guys this is 50mm celotex AND the Foil on top of a block and beam floor. 
Sounds like it could be worth it but making sure they use  TE Premium.
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Triple Glazing.50mm CWI.
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