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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
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    • CommentAuthorJeff B
    • CommentTimeSep 11th 2020
     
    Does anyone have any experience of this system for UFH? Looks like a neat solution for UFH retrofit (no need to dig up floors!).
    • CommentAuthorjfb
    • CommentTimeSep 11th 2020
     
    No experience of it but this can't be right........

    "Concrete sub-floors provide a much better thermal barrier to downward heat loss than suspended
    timber. "

    Assuming there is no insulation in a concrete floor then it is going to be very inefficient and costly to run.
    •  
      CommentAuthordjh
    • CommentTimeSep 11th 2020
     
    The only thing I can see that is special about this system is that it uses 10 mm pipe, whereas most of the other similar systems use 15-16 mm pipe, although I've found one that uses 12 mm. So I suppose the question is how important a few mm height difference is?
    • CommentAuthorowlman
    • CommentTimeSep 13th 2020
     
    Digging up, presumably uninsulated concrete? floors to install UFH?
    If you're determined to put in UFH and you are seriously looking at something that has a 25mm build up plus whatever finished floor you install on top of that then I'd go for a thick layer of rigid insulation and electric resistive cables; much better than a wet system IMO.
    In fact having lived with a ducted A2A heat pump system in my own home for over a year now I 'd go so far as to say that ALL wet CH systems are outdated including UFH.
    • CommentAuthorJeff B
    • CommentTimeSep 13th 2020
     
    <blockquote><cite>Posted By: jfb</cite>No experience of it but this can't be right........

    "Concrete sub-floors provide a much better thermal barrier to downward heat loss than suspended
    timber. "

    Assuming there is no insulation in a concrete floor then it is going to be very inefficient and costly to run.</blockquote>

    I suppose they mean that a concrete slab is relatively better as a thermal barrier than a suspended wooden floor? As you say, unless there is sufficient insulation under the slab, well.....
    • CommentAuthorJeff B
    • CommentTimeSep 13th 2020
     
    <blockquote><cite>Posted By: djh</cite>The only thing I can see that is special about this system is that it uses 10 mm pipe, whereas most of the other similar systems use 15-16 mm pipe, although I've found one that uses 12 mm. So I suppose the question is how important a few mm height difference is?</blockquote>

    Maybe means that you could squeeze in a thin-ish layer of insulation under the UFH system whilst keeping the overall thickness of the floor covering reasonable?
    • CommentAuthorJeff B
    • CommentTimeSep 13th 2020
     
    <blockquote><cite>Posted By: owlman</cite>Digging up, presumably uninsulated concrete? floors to install UFH?
    If you're determined to put in UFH and you are seriously looking at something that has a 25mm build up plus whatever finished floor you install on top of that then I'd go for a thick layer of rigid insulation and electric resistive cables; much better than a wet system IMO.
    In fact having lived with a ducted A2A heat pump system in my own home for over a year now I 'd go so far as to say that ALL wet CH systems are outdated including UFH.</blockquote>

    A relative of ours is looking at this system as a possibility for use in a new extension to the house. He already has a conventional gas fired C/H system. so this could be tapped into that (with the necessary manifold, valve, thermostat etc). Seems to be DIY-able too which appeals!
    • CommentAuthorRobL
    • CommentTimeSep 13th 2020
     
    Hi Owlman - can you explain more about your comments about A2A, and why are wet systems outdated?

    My context: we have gas CH (1960’s radiators still) and DHW, but are expecting a significant heating reduction due to 150mm Ewi this year. I’d like to get rid of all gas use, and am undecided about what to do.
    •  
      CommentAuthordjh
    • CommentTimeSep 13th 2020
     
    Posted By: Jeff BA relative of ours is looking at this system as a possibility for use in a new extension to the house. He already has a conventional gas fired C/H system. so this could be tapped into that (with the necessary manifold, valve, thermostat etc). Seems to be DIY-able too which appeals!

    If it's a new extension then I don't see how/why the thickness of the new floor construction is relevant?

    So on that basis I would judge this system against all the other UFH systems and judge them largely on the basis of cost.
    • CommentAuthorJeff B
    • CommentTimeSep 13th 2020
     
    Posted By: djh
    Posted By: Jeff BA relative of ours is looking at this system as a possibility for use in a new extension to the house. He already has a conventional gas fired C/H system. so this could be tapped into that (with the necessary manifold, valve, thermostat etc). Seems to be DIY-able too which appeals!

    If it's a new extension then I don't see how/why the thickness of the new floor construction is relevant?

    So on that basis I would judge this system against all the other UFH systems and judge them largely on the basis of cost.


    It wouldn't be relevant except that he is thinking of installing UFH in the room in the existing house leading to the new extension at the same time and where the thickness is definitely relevant. I have advised to go for a wet system because in the long run it may be cheaper to use gas than electricity but that situation could change dramatically over the next 10 - 20 years anyway and I don't have a crystal ball!
    •  
      CommentAuthorfostertom
    • CommentTimeSep 14th 2020 edited
     
    Posted By: owlmanI 'd go so far as to say that ALL wet CH systems are outdated including UFH
    This is the revolution we need to get used to! But not to substitute warm air heating, as per owlman's experience - it's because PH doesn't (or near-PH nearly doesn't) need a heating system; radiant is always superior to convection; and electricity's carbon-content is dropping so fast it'll very soon beat even gas.
    • CommentAuthorowlman
    • CommentTimeSep 14th 2020
     
    I would agree Tom that going down the PH road, ( or near ), is the way forward for new build, or serious property remodelling. However, that's not going to happen to any great degree, for all sorts of reasons.
    For the more numerous, average, smaller scale refurbishments, or additions like the OP, then there are alternatives, and IMO better ones than following the, wet CH route. Additionally, if new properties are constructed to a PH (light), standard and still requiring some degree of space heating, then putting in a wet system is a backward step.
    •  
      CommentAuthorfostertom
    • CommentTimeSep 14th 2020
     
    Agreed, PH (or near) is going to be a minority pursuit, perhaps forever, as autonomous or local-network renewable (mainly solar) electricity gets ever cheaper and ever more abundant (as distinct from renewable sourced grid electricity, which is going to be saddled with the govt-guaranteed exorbitant-cost nuclear electricity for a long foreseeable). Cheap abundant renewable electricity undermines the 2010-style case for PH - why attempt superhuman insulation/airtightness when you can burn a fair bit of the 'free' electricity instead? But not too much!

    So PH-lite (NZEB in EU-speak) will be increasingly with us, as owlman says, just good enough to make direct electric heating feasible. But still, radiant heat is much superior, and far cheaper, than warm-air/convected. That means lo-temp electric radiant floors or walls, not wall-mounted electric 'radiators' which are really convectors.

    For the rest, the great bulk of lightly-uprated existing stock, it's going to be ASHP, and for that, wet heating will remain the anamalous, expensive solution that will take a long time dying.
    • CommentAuthorowlman
    • CommentTimeSep 14th 2020
     
    Posted By: RobLHi Owlman - can you explain more about your comments about A2A, and why are wet systems outdated?

    My context: we have gas CH (1960’s radiators still) and DHW, but are expecting a significant heating reduction due to 150mm Ewi this year. I’d like to get rid of all gas use, and am undecided about what to do.


    Often the reason people stick to wet systems is the DHW spin off, often more DHW than is actually needed, and is hence stored all the time going cold and constantly being topped up. Showering for e.g. actually uses comparatively little water, this plus a bit for washing up and those needs can be adequately met by a simple tank with a couple of immersions especially if linked to Solar PV and a power diverter. Same goes for selective underfloor resistive cable heating e.g. wet rooms.
    Space heating supplied by a complex system of circulating hot water, taking up wall space in the bargain or a similarly complex grid of underfloor pipes and manifolds just seems to me to be too many links in the chain.
    All that can be achieved by directly heating or cooling ( a great summer bonus BTW) the air, again with the added bonus of precise switched controllability that electricity gives. If you have Solar PV all the better as the power you're generating runs any Summer cooling for free. The response time for either is much, much faster too.
    Admittedly my (half house) system is ducted rather than wall hung indoor units, so my opinions may be slanted because of it. Ducted is a bit onerous to fit into an existing property, but is the better system if interior aesthetics are an issue.
    Over the years I've lived with all sorts of CH systems and my current one is an ageing biomass wet system for which I have a virtually free supply of wood. I decided to fit the A2A heatpump system on a suck it and see basis, for when my biomass gives up, and it's exceeded all expectation. I fitted quality kit which I spent about 9 months researching and I have no regrets.
    • CommentAuthorJeff B
    • CommentTimeSep 14th 2020 edited
     
    So it seems we should be leaning towards electric UFH then.

    Any thoughts on the on-going running costs of electric UFH as opposed to tapping into an existing conventional gas C/H system? Also regarding safety - is there any inherent danger of localised overheating of an electric system e.g.directly underneath heavy furniture?

    Finally does anyone have electric UFH and could recommend a particular brand? The total floor area is 33 sq.m.

    (Sorry, seems to be all questions!).
    • CommentAuthorMike1
    • CommentTimeSep 14th 2020
     
    Posted By: Jeff BSo it seems we should be leaning towards electric UFH then.

    I wouldn't do that. Electric heating elements can burn out and are then difficult to replace - and can't be used for cooling.

    'Traditional' piped UFCH should have a long life, and can be matched with various heating and cooling sources, which can be changed over time.

    Unless you're heading towards Passivhaus, when air-based heating / cooling may well be all you need.
    • CommentAuthorJeff B
    • CommentTime6 days ago
     
    Update: the quote for my son's UFH scheme has come in at £2500. The floor area is 40 sq.m. This does not include fitting but he will be able to DIY-it.

    For that sort of money wouldn't a two-way split air-to-air ASHP system be a better choice? (One internal unit in the extension and one in the existing lounge).
    • CommentAuthornick1c
    • CommentTime6 days ago
     
    Not strictly relevant to the OP, but we have gone for wet UFH, a Sunamp, ASHP & PV in our “almost passsive” house.
    We have yet to move in, but the rationale was:
    In a well insulated house overheating, particularly from solar gain can be as much of a problem as keeping warm. One of the main ways that can occur is the floor being heated from the sun & re-radiating the heat into the house. The ASHP can run in cooling mode to help stop the floor overheating, as this, by definition will only happen when the sun is out it will be powered by the PV & therefore free.
    Standing heat losses from the Sunamp are (supposedly) low which will help.
    The cost of installing the UFH was minimal & its life expectancy long - assuming the framers missed the pipes!

    We are looking forward to finally moving in & discovering if the theory matches reality.
    • CommentAuthorJeff B
    • CommentTime6 days ago
     
    Nick1c: air-to-air would also provide cooling in the summer if necessary. The extension will be south facing with a vaulted ceiling and roof windows so could get pretty hot I guess.
    • CommentAuthornick1c
    • CommentTime6 days ago
     
    A2A won’t affect the heating of the floors by the sun, which then is pushed into the house. The closer the floor temperature is to your desired ambient temperature the better. We will need to ensure the flow temperatures are above the dew point to avoid condensation problems.
    •  
      CommentAuthordjh
    • CommentTime6 days ago
     
    Posted By: nick1cA2A won’t affect the heating of the floors by the sun, which then is pushed into the house.

    This is true, but shading the windows so they don't get too much sun in the summer is a better answer then either form of heat pump. It's also true that it doesn't matter all that much how the heat is taken out of the house, as long as the energy balance is the same the results will be largely the same. There will be some differences of course.
    • CommentAuthornick1c
    • CommentTime5 days ago
     
    Our house wasn’t designed with large eaves, which doesn’t help. We went for external Venetian blinds on the south & east elevations instead for this reason. This will hopefully help in spring and autumn when the sun is lower, but still has a fair bit of power. They can also give privacy as the road is to the south of the house.
    • CommentAuthorJeff B
    • CommentTime5 days ago
     
    <blockquote><cite>Posted By: nick1c</cite>A2A won’t affect the heating of the floors by the sun, which then is pushed into the house. The closer the floor temperature is to your desired ambient temperature the better. We will need to ensure the flow temperatures are above the dew point to avoid condensation problems.</blockquote>

    So if my son goes for a wet UFH system powered by an ASHP, cooling the floor will reduce the room temperature more effectively than an air-to-air heat pump system? I find that hard to understand! I notice you say that you are looking forward to finally moving in & discovering if the theory matches reality - from this I take it you haven't actually found this to be true in practice? Or maybe there is a useful reference you could point me to gen up on this?

    As cold air "falls" wouldn't the internal fan unit of an air-to-air heat pump be circulating cool air down the wall and across the floor? Intuitively this seems to be a better proposition but I stand to be corrected!
    •  
      CommentAuthordjh
    • CommentTime5 days ago
     
    Posted By: Jeff BAs cold air "falls" wouldn't the internal fan unit of an air-to-air heat pump be circulating cool air down the wall and across the floor?

    They're usually designed and mounted to blow air across the ceiling, or at face level, depending how you set the louvres. But I don't know what's the best mounting for a device intended to both heat and cool.
    • CommentAuthorowlman
    • CommentTime5 days ago
     
    Distribution of hot and cold air certainly seem at odds to one another, from one supply system, and in an ideal world you'd have two different sets of distribution registers or e.g. on a ducted system I guess you could throw a diverter switch and have supply and return flows reversed, but not without a bit of difficulty.
    In practice my experience has been that on my domestic interior both warm and cool work fine from the same ceiling mounted supply and return ducting grilles.
    With wall hung, or ceiling cassette, interior units motorised louvers are available I believe, so again not really a problem. I can't speak for using underfloor pipework for cooling but I can't imagine it being very effective.
  1.  
    Think there was a thread not long ago and Goodevans had found cooling by ashp/ufh was more energy-efficient than by running MHRV fans.
    http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16687&page=1

    Edit: even better if some windows can tilt/turn and be left securely open overnight for free cooling!
    • CommentAuthornick1c
    • CommentTime4 days ago
     
    I am in west Cornwall, the sun can be strong, but the air temperature is rarely oppressive outside. I expect the UFH in cooling mode to prevent the slab from overheating & re-radiating that heat into the building rather than reduce the internal temperature significantly below the average daily temperature.
    • CommentAuthorEd Davies
    • CommentTime4 days ago
     
    Some people use UFH to re-distribute solar heat from the floor areas in sunlight to the rest of the house by running the circulation pump without any heating or cooling as such. This will improve the efficiency of solar heat gain as well as the comfort in the house.

    Posted By: Jeff BAs cold air "falls"…
    Why the scare quotes? It does fall, that's what convection is: denser (usually cooler) fluid falling and displacing less dense fluid upwards.
  2.  
    >>> Some people use UFH to re-distribute solar heat from the floor areas in sunlight to the rest of the house by running the circulation pump without any heating or cooling as such

    I'd heard that too, but for it to transfer a worthwhile amount of heat, the floor in the sunny area would have to be many degC warmer than the floor in the cool rooms, which would mean the room air would be too. Does that actually happen in a new house?
    •  
      CommentAuthordjh
    • CommentTime3 days ago
     
    Posted By: WillInAberdeenI'd heard that too, but for it to transfer a worthwhile amount of heat, the floor in the sunny area would have to be many degC warmer than the floor in the cool rooms, which would mean the room air would be too. Does that actually happen in a new house?

    I'll be impressed if anybody measures air temperature and floor temperature* with the required accuracy.

    * what is 'the floor temperature' anyway? The temperature of a concrete slab or a screed, or the surface temperature of a carpet, or maybe a timber floor or what?

    Sorry, not trying to be difficult. Just saying that it's difficult to be sure about what is being measured.

    What I can say is that our south-facing rooms get noticeably warmer than our north-facing ones. As felt by the Mk1 human and as measured by thermometers. And both extra ventilation and shading can make a difference. Since we don't have any UFH plumbing I can't say whether or not such circulation is effective; you'd have to ask someone who does have the system, and I gather they say it does work.

    And what do you mean by 'many degC' anyway?
   
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