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Heating and cooling: Set temperatures

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  1.  
    • CommentAuthortony
    • CommentTimeMay 17th 2022
     
    I am sure that we have discussed this before but with the price hike we should now revisit it

    What temperature should a lounge be , during the day? During the evening, During the night, during the morning?

    Ditto other areas?
    • CommentAuthorMike1
    • CommentTimeMay 17th 2022 edited
     
    In the 18 - 21°C range when occupied, depending on the occupant's age & health:
    https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/776497/Min_temp_threshold_for_homes_in_winter.pdf

    At other times a lot depends on the reaction time of the heating source - lower if well insulated with rads, higher of necessity if well insulated and UFCH. But not more than a few degrees lower if condensation is likely.
  3.  
    Every room has a time constant*, which is the time it takes it to cool down** when the heating is turned off and then warm up again when you turn it on.

    Could be an hour for a very thermally-responsive construction, or several days for an insulated building with a lot of concrete in it.

    If the room is to be unoccupied for less than that time constant, then leave the heating on steady all the time, makes no difference.

    If the room is to be unoccupied much longer than that then turn the heating off (or to setback), any heating you provide will have been lost and replaced before you come back.


    If I am sitting still all day WFH over a laptop I need the living room warmer (19-20⁰C) than if I'm moving about (17-18⁰C). If the walls have cooled down (become cold radiators) then I need the air to be warmer.

    Bedrooms should be cooler than living rooms, the cooler environment overnight helps regulate the circadian rhythm along with light/darkness. 16-18⁰C recommended:
    https://thesleepcharity.org.uk/information-support/adults/sleep-environment/

    Edit to add: people do acclimatise according to where they live. When I visit the place where I grew up in southern UK, I now find it uncomfortably hot. A colleague always keeps their house heated and has got adapted to warmer temperatures than me.

    Another edit: air movement has a big effect, as does feet/floor temperature. Cool draughts or cold feet make people turn up the thermostat.


    *Actually several time "constants" (or not) for heat from different parts of the construction, lost to ground and to outside air, and more constants for reheating, solar gain, heatpump vs combi, rads vs UFH, etc etc, making it more complicated doesn't help
    ** Actually by 1-1/e = 63% of the way to "steady" state, ditto
    •  
      CommentAuthordjh
    • CommentTimeMay 17th 2022
     
    •  
      CommentAuthorfostertom
    • CommentTimeMay 17th 2022 edited
     
    Posted By: Mike1higher of necessity if well insulated and UFCH
    I've thought lower, not higher, for two reasons:

    1. UFH's output has much greater radiant component (vs convective) than any radiator system. When radiant component is high, the body subjectively feels comfortable when air temp is several degrees lower than with rads, let alone with warm air heating.

    2. UFH's time constant is high compared to any rad system, let alone warm air heating. If someone leaves window open, stored heat in the screed, maybe slab as well, is multi x capable of re-heating the room air and any cooling of walls etc, and can replenish that stored heat at leisure.

    Lower room air temp (which translates as fabric heat loss) is the prime reason why UFH uses less energy than any rad system , let alone warm air heating (again!).

    We did a scheme of radiant wall heating (more radiant area hence yet greater radiant component than UFH); the occupants run air temp at 17C in full comfort.
    • CommentAuthorborpin
    • CommentTimeMay 17th 2022 edited
     
    Posted By: tonyWhat temperature should a lounge be
    What temperature is the Lounge really at?

    I currently have 4 sources of temperature measurement (largely collocated) in my open area with UFH (although it is off) and the temperature varies by 4°between the 4 sensors. No drafts, no sun to affect the readings, just a variation in how the sensors are calibrated, sensitivity and rate of change. I have even moved the recent Govee sensor around the room and it read with the same offset wherever I place it.

    Just about to change my source of the information for my HA thermostat and I will have to change the settings by 0.5°.

    The right temperature is the one you are comfortable at and can afford!
  7.  
    radiant wall heating


    Could you tell us more Tom? How was this done, any particular system/product?

    The ground floors and external walls lie on the heat loss paths from the room, so underfloor heating increases potential heat loss through the floor, counteracted by adding extra insulation. Same with the walls, or just heating internal walls?
    •  
      CommentAuthorfostertom
    • CommentTimeMay 19th 2022 edited
     
    Trust you to pick up on that Will! I thought I'd written the definitive descrip on GBF but can't find it. Just bits n pieces, in:
    http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9743
    http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=14256

    The pic shows 12mm UFH pipes zigzag'd over the walls, parge coat being applied for thermal contact, before 200 EPS EWIing. Ea loop of pipe, down wall and back up, connected to a UFH manifold in roof space, so circuits cd be balanced. Was designed to be supplied by home-made whole-roof solar collector, but has been running on client's wood-pellet boiler/accumulator. The paint dots were to make abs sure where the pipes were, as the EWI had to be mechanically fixed thro, in this case!

    Nowadays, input by electric trace-heater tapes wd be a lot easier than pipes/manifolds, but wd then run off PV rather than wet panel collectors, needing a lot of to be sufficient right thro Dec/Jan, whereas wet panels running at v low (23C) flow temp are fantastically efficient (%age of (intermittent) incident radiation captured, hence Dec/Jan weekly output per m2), given precautions against standing and start-up losses every time sun went behind cloud. We reckoned that the walls would store useful heat for 7-10 days, so could accept extremely peaky heat input, stored one midwinter clear day to the next.
      IMG00265-20101210-1441smaller.jpg
    • CommentAuthortony
    • CommentTimeMay 20th 2022
     
    Window reveal losses worry me but I like 200mm EPS

    The philosophy of not putting rads under the window just went up the wall
    •  
      CommentAuthorfostertom
    • CommentTimeMay 20th 2022 edited
     
    Posted By: tonyWindow reveal losses worry me but I like 200mm EPS
    you mean if extg windows are kept, thus 300 dp reveals thinly covered? Luckily this project got new Russell 3G windows, outboard within the 200 EPS zone.

    Posted By: tonyThe philosophy of not putting rads under the window just went up the wall
    Er- is that a joke? quite a good one!

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