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To insulate our solid concrete floors to Waldi's minimal thickness I'd have to chop six inches off the bottom of the doors !

Can UFH-type tubes be embedded on top of retrofitted wall insulation ? without getting air-locking !

Peter

 

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On 1/15/2021 at 5:41 AM, Waldi said:

Hi Richard,

I’m considering that too, we call it a “dry system” . Part of the living room does not have UFH. My goal is to have a bit more capacity to reduce the water temperature. UFH is very comfortable by the way.

There are several systems available over here, some only 20 mm thick; with 10 mm flexible tubes. Whatever you decide, ensure the bottom of the floor is properly insulated. I applied 80 mm rhesol foam to the underside of my floor (in the basement), that was 10 years ago. I would increase that if I had to do it today.

Cheers,

Waldi

Hi Waldi. Over here, a "dry" system is resistive electrical heating mats - which is an expensive way of heating as you're limited to 100% efficiency and electricity is about 3x more expensive than mains gas per kW.hr. But I think you're talking about a retro-fit wet system, which when combined with gas, or a well-designed heat pump with COP about 3 to 4 in typical conditions gives 300% to 400% efficiency, levels the gas-electric playing field.

I went to a club AGM at a cold village hall a few years ago. Except now the hall has an extension and UFH - it was sooooo comfortable! But the idea of leaving the heating on 24/7 seems totally wrong, especially when someone opening a door or the sun coming out can change things so quickly. In contrast my niece's kitchen extension with UFH is badly designed. I measured the floor temperature at over 30'C - the kids love it but it's uncomfortable for everyone else.

When you bury the heating pipes in the concrete slab, you slow down the response time in two ways. 1) it takes time to heat up the slab, or for it to cool down, because of its heat capacity. 2) Heat doesn't travel through things very quickly. It takes hours for heat to travel through these materials and achieve equilibrium.

But in a retro-fit the situation can be different. Put the pipes in channels cut into insulation panels, laid on top of the (concrete in my case) floor and lay the thinnest reasonable laminate on top. This gives a low thermal mass system so it's much more responsive. It also gives pretty much the lowest thermal resistance between the pipes and the floor surface, so you can use the lowest water temperature and have the heat pump running at its most efficient - a gas boiler would be condensing so it too would be at highest efficiency. The lower water temperature means less insulation is required below the pipes to keep losses to a reasonable figure. This also keeps build-up height to a minimum - 25mm in my case if my model is correct.

So, it all boils down to whether a low thermal mass UFH system can give the sort of responsiveness that's needed for a comfortable home. (The sun's just come out here in Reading!) Our hot air heating system, an original feature of the house, is VERY responsive. So much so that I've had to hack the control system to slow it down when it first comes on - my wife loves it but I break into a sweat. And later when it's been on a while, you feel colder because it only heats the air, not walls etc. But UFH is (almost) the reverse - you get a very large surface heated up (and it's by your feet which gives most benefit) but it takes a long time for the air to heat up.

Cheers, Richard

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21 hours ago, Peter Cobbold said:

To insulate our solid concrete floors to Waldi's minimal thickness I'd have to chop six inches off the bottom of the doors !

Can UFH-type tubes be embedded on top of retrofitted wall insulation ? without getting air-locking !

Build up height varies from house to house, but my model says it's only 25mm in our case - concrete slabs on dry London clay. The regs admit that you only need a 10th of the loss downwards compared to heat coming upwards. And in any case, there's a get out clause for retro-fits, though plainly no one wants the on-going costs of a badly designed heating system.

UFH heating panels on walls? Yes, someone does those, and with tiny bore tubing any air bubbles will be cleared. Larger bore you would zig-zag from side to side with overall flow upwards.

Cheers, Richard

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8 minutes ago, Spit_2.5PI said:

Build up height varies from house to house, but my model says it's only 25mm in our case - concrete slabs on dry London clay. The regs admit that you only need a 10th of the loss downwards compared to heat coming upwards. And in any case, there's a get out clause for retro-fits, though plainly no one wants the on-going costs of a badly designed heating system.

UFH heating panels on walls? Yes, someone does those, and with tiny bore tubing any air bubbles will be cleared. Larger bore you would zig-zag from side to side with overall flow upwards.

Cheers, Richard

Tks Richard,  25 mm floor insulation is feasible. I clearly need to find Wales' building regs for  retrofit. Peter

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Hi Peter and Richard,

yes, I means the systems with tubes embedded in a 20 or 25 mm thick layer of dense EPS. For proper reduction of heat loss to the soil below (if you have no basement where you can install insulation like I did), thicker is better, Peter, there are Rhesol plates with very good heat resistance, better than EPS, that can be installed below the slitted (pre-formed) sheets for the tubes.

Tube size 16x2 mm will result in a thickness of 25 mm. Thinner diameter tubes will add 20 mm only.

My basement temperature dropped from 27 to 15 C when I applied insulation there. And then  0,23 mm thick PE foil on the bottom to lower the relative humidity in the basement(from 90-95%) to 60-65%. Yes, I like to measure what I’m doing:)

The COP also depends on where you live, I live close to sea to warmer than in the eastern part of Holland.

Jippy, it’s snowing here currently, 1st time since over a year, will go out now.

Cheers,

Waldi

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36 minutes ago, Peter Cobbold said:

Tks Richard,  25 mm floor insulation is feasible. I clearly need to find Wales' building regs for  retrofit. Peter

I should have said Peter, that's 18mm insulation with 12mm pipes, plus 7mm or 8mm laminate. Total 25mm or 26mm.

 

28 minutes ago, Waldi said:

(if you have no basement where you can install insulation like I did), thicker is better, Peter

Waldi, you've got a basement - you lucky thing! Without that, installing more insulation adds to build-up height which means you have to cut down your doors and your room starts to look too low. The Rhesol you mention, that's phenolic insulation, right? I did wonder why nobody does phenolic or similar panels with UFH grooves cut in, it seems such an obvious thing to do.

Cheers, Richard

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Absolutely! If you can't add enough insulation without an unacceptable build-up height, simply dig a trench around your house and put the insulation in there. The heat loss path is to the surface of the ground in the vicinity of your house, not the centre of the earth!

Cheers, Richard

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Anyone know about water-sourced heat pumps?  We ahve a stream flowing close to the cottage (5 metres!) thats flows most winters and will be warmer than air. Seems to me to be cheaper than boreholes and will ensure, unlike solid ground, the "coolth" is flushed away.

Peter

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4 minutes ago, Spit_2.5PI said:

Absolutely! If you can't add enough insulation without an unacceptable build-up height, simply dig a trench around your house and put the insulation in there. The heat loss path is to the surface of the ground in the vicinity of your house, not the centre of the earth!

Cheers, Richard

With 18 inch thick solid stone 18century walls would that work?  Maybe avoid putting ufh within 1 metre (?) of perimeter to minimse gradient into wall ?

Peter

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14 minutes ago, Peter Cobbold said:

Anyone know about water-sourced heat pumps?  We ahve a stream flowing close to the cottage (5 metres!) thats flows most winters and will be warmer than air. Seems to me to be cheaper than boreholes and will ensure, unlike solid ground, the "coolth" is flushed away.

Peter

It depends on the flow temperature all year round 

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It's not really related to heat pumps and ufh, but I found a modern thermostat Honeywell CM900 with a solid state temperature sensor and a P&I control scheme made a significant improvement to my heating system.

Its predecessor was a bimetallic strip thermostat with a 3 or 4 degree dead band and a simple on-off control scheme, and the time lags in the system added significant overshoots and undershoots to the dead band, so you really noticed the high and low points in the temperature cycles. 

 

Edited by acaie
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17 minutes ago, Peter Cobbold said:

With 18 inch thick solid stone 18century walls would that work?  Maybe avoid putting ufh within 1 metre (?) of perimeter to minimse gradient into wall ?

Peter

No it would be a cold spot and defeat the object 

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Peter,

Brick, stone, has a very low resistance, and even massive wood is low, compared to insulation materials.

I use a simple program (and free), to make heat loss calcs, it also includes dew point calcs. For those interested, follow the tutorial first:

https://www.ubakus.com/nl/rc-waarde-calculator/

Wether the near-by stream works better depends on the average temperature of it, compared to the avg. outside air temperature.

The Rhesol I referred to is a vacuum type PIR, with extremely low conductivity: Lambda 0,007 W/(m.K). 

25 mm will pride an Rd of 3,55!

https://www.kingspan.com/nl/nl-nl/producten/isolatie/vacuum-resol-pir-isolatie/isolatieplaten/optim-r/optim-r-vacuum-isolatieplaat

So the flow will be going up 50 mm (45 if you want) with acceptable insulation below it (for renovation).

Indeed, avoid installing the hoses close to the wall, but with this system less of an issue compared to hoses burried in cement.

It is not cheap, here around 50-70 eu/m2 (add insulation and laminate to that) for a DIY project

Waldi

Cheers,

Waldi

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My new kitchen extension had 100mm PIR on the structural slab and 25mm round the perimeter, 20mm water pipes clipped to the insulation, then a 70mm screed, adhesive and porcelain tiles. It has a independent control system for that room with the air temp set at 21C, with 0.5C hysteresis and a control logic to stop overshoots. The water temperature is set to 32C. The floor surface temperature is typically 28C. Comfortable yet controllable. I have set up stand alone temperature monitoring for air and floor temperature. The kitchen has large patio doors facing South and East. It responds well if and when the sun comes out. Very happy with it, so far.

Mick

 

 

Edited by Mick Forey
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That looks good Mick. If you can operate with 32 C water you must have a well insulated house. I tested how far I could reduce, but still need 60 C at the moment, largely due to insufficient capacity of radiator/UFH. My UFH was meant as “additional” with the hoses at a pitch of 200-250 mm. 100 mm is specified here if used as main heating source. And not the entire living is fitted with UFH (yet). So I have an additional Jaga convector with 6 quit fans that kick in once water temperature is above 45C.  

My energy bill is low already, so not much financial gain in spending more on this.

An important note for everyone with a fired “high efficiency” boiler (“107% efficiency” is what is the max number over here):
This higher efficiency is only achieved if the combustion gas is able to condensate and give this heat back to the heating water. It is the heat from the condensation which brings the additional efficiency. A maximum water return temperature of 55-60 C is what is needed for this, lower is better.

So if your return water temperature is higher “for more comfort” you increase your gas/oil bill by up to 15%.
Note the set-temperature (water to radiators) can be higher, this is about the return temperature.

To further reduce consumption, reduce the water temperature in fall and autumn even a bit further. The result is the boiler will run more hrs/day, at a lower temperature, and modulate back. 

Cheers,

Waldi

 

Edited by Waldi
Tried to attach graph, sorry no luck.
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Hi Waldi, sadly the original part of the 17th century house has very poor insulation and loads of drafts. The new two story extension has excellent insulation. The water temperature for the UFH is controlled by its own re-circulating pump and thermostatic valve. It is fed from the normal gas central heating water at 70C, which the rest of the house needs. The house system is split into a number of zones, each with their own thermostat and 2 port valve. The only way to keep the bills down. I still get through 35,000 kWh of gas every year. The joy of an old house.

Mick

UFH manifolds.jpg

Edited by Mick Forey
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Hi Mick,

I have a similar set-up.

My house was built in 1975, at which time insulation requirements were minimal (50 mm rock wool in walls and roof for example).

Over the years I was able to reduce our monthly bill to less than 150 euro, that is for natural gas and electricity.

Some improvements bring a large financial return (based on DIY work) others less so. But comfort increases, which gets more important as we get a bit older. The Ubakus tool can help you prioritise what to do first. 

Cheers,

Waldi

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