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Author Topic: Thermal bridging in a fireplace  (Read 5386 times)
Countrypaul
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« Reply #15 on: September 17, 2017, 11:39:00 AM »

that link seems to say that the height is from the hearth bed, have i read that correctly? if so depending on stove you can use existing floor, but it states it must be defined? we just have the stove (a big beast) on the tiled floor which is on the screed over the ufh, no issues.
have you chosen the stove an asked them?
i wished we had put more insulation in, not less, anywhere.

steve

The stove will be a Dunsley Yorkshire. There is no existing floor at present, it is concrete down at the Beam and Block level so we need to build it up by 190mm.  It seems to me putting in 120mm of non-combustable insulation and 70mm of screed meets the building regs requirements and also minimises cold bridging.

Steve, what is beneath you screed where the stove is?
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Countrypaul
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« Reply #16 on: September 21, 2017, 09:27:13 PM »

Following up various ideas and leads has been surprisingly disappointing.

Kingspan K103 phenolic boards were suggested but Kingspan technical said not suitable as not classed as non-combustable.
Rockfloor - Rockwool informed me that one of their producs were suitable without actually clearly explaining why not.
Knauf - Nothing suitable.
Vermiculite concrete -various conflicting pieces of information as to how well this performs. It appears to be rather subjective and rather full of opinions rather than facts.
Foamglass - technically good, but ridiculas cost for small amount (150 delivery).

Thermalite blocks - this is currently looking the most likely option.
Leca - another possibility but does not appear to offer much over the thermalite blocks.

Any other ideas?
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Nickel2
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« Reply #17 on: September 21, 2017, 10:10:01 PM »

How about investigating refractory cement? People regularly home-build crucible furnaces for melting metals at high temperatures, using refractory cement, silica sand, + whatever else. Once you have a spec, then it can be presented for inspection with the relevant figures.
YouTube <  diy refractory concrete  >; gives a few results that may steer you towards a suitable solution. People are always willing to give their recipes to the right query.
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1.140kW mono south-facing at 49*
EpEver 4210A at 24v
New (Old) 8S7P LiFe battery, 105Ah @ 26.4V
EpEver STI1000-24-230 pure sine inverter
Of course it'll work. (It hasn't caught fire yet).
Nissan micra Spirita   (Short range)
Countrypaul
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« Reply #18 on: September 21, 2017, 11:38:27 PM »

Having had a quick look at refactory cement, it certainly looks as though the temperature under a hearth would be no problem, it is diffcult to get any clear idea of its insulation properties, but refactory bricks seem to be around 0.9 W/mK compared to thermalite blocks at 0.11. I am looking for insulation that is not combustable rather than something to withstand the full heat of the fire.
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Warble
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« Reply #19 on: September 22, 2017, 10:45:23 AM »

Why not precast the hearth then mount it on thermalite with some rockwool fill under.
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Nickel2
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« Reply #20 on: September 22, 2017, 12:04:04 PM »

Here is another option:



They may have an agent in UK

Youtube  <https://www.youtube.com/watch?v=2urkcQUpwlo>
« Last Edit: September 22, 2017, 12:08:17 PM by Nickel2 » Logged

1.140kW mono south-facing at 49*
EpEver 4210A at 24v
New (Old) 8S7P LiFe battery, 105Ah @ 26.4V
EpEver STI1000-24-230 pure sine inverter
Of course it'll work. (It hasn't caught fire yet).
Nissan micra Spirita   (Short range)
eabadger
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« Reply #21 on: September 23, 2017, 12:11:34 PM »



The stove will be a Dunsley Yorkshire. There is no existing floor at present, it is concrete down at the Beam and Block level so we need to build it up by 190mm.  It seems to me putting in 120mm of non-combustable insulation and 70mm of screed meets the building regs requirements and also minimises cold bridging.

Steve, what is beneath you screed where the stove is?
[/quote]

an extruded t&g stuff 120mm then concrete then then ufh pipes then 60mm screed, in theory the ufh pipes are combustible, so where does that leave regs?? tiles dont burn neither does screed.
the extruded stuff does burn, i had a fire in the generator shed a few years back and i had insulted with kingspan type stuff, it was a nightmare after that refused to use in house, we have in roof multifoil with lambswool layer which self extinguishes i have tested it and rockwool layer.

my personal thought is if you insulate floor as you want then cover with screed/tiles it is fine.

steve


* IMG_0105.JPG (82.67 KB, 640x480 - viewed 248 times.)
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1600w PV main array at 24v, excide 2v 1000a forklift cells now x 2, 320w PV secondary array at 12v. Enfield 1944 ex RAF 5.6kw diesel genset (now in pieces, big ends gone), Petter AC1 28v diesel charging set at 2.8kw.
1kw wind turbine.
26kw wood stove back boiler to underfloor heating and dhw
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