Hive ~ that heating app thing ~ a few questions

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  • Hive ~ that heating app thing ~ a few questions
  • trail_rat
    Member

    those doubting it have never lived in a house with 3ft thick stone walls without interior cladding. Its cheaper to keep heat in those walls than heat the air space every time as that stone can pull the heat quicker thn the rads can put it in(rental house so couldnt dry line it)

    for standard cardboard box houses the above does not apply.

    Its cheaper to keep heat in those walls than heat the air space every time

    Bare stone walls are simply crap insulators.

    trail_rat
    Member

    and your point is ? they are there , and they were there to stay and not mine to change….

    there for when your house is stone walled its cheaper to keep them heated if you occupy it as a family home and not just a doss pit

    In theory, the smart thermostat of choice will work out what is the most energy efficient way to heat said stone wall house.

    Premier Icon molgrips
    Subscriber

    for standard cardboard box houses the above does not apply.

    You mean well insulated ones? 🙂

    Premier Icon gray
    Subscriber

    Maybe I’m being thick, but I simply don’t get why people think that it can be cheaper to keep a house constantly heated than to only heat it when you need to.

    While a house is hot inside, it is leaking energy out to the outside. This is true in any real house unless it’s hotter outside than in. The effectiveness of your insulation affects how much heat you loss. The thermal mass in the structure of your building affects how long (for a given heat source) or how much energy it takes to heat it up. But, SURELY, the hotter your house is inside, the greater the thermal gradient to outside, so the higher the (absolute) heat loss is.

    If I turn my heating off while I’m out for the day, then I will lose less heat energy during that day than if I left it on. The only way that it can possibly end up costing me more, is if my heat source works less efficiently when delivering a high rate of heat input (whilst warming the house up from cold) than in a state of “keeping it warm”. Modern condensing boilers DO work a bit more efficiently at lower revs, so to speak, but not by THAT much. And anyway a cleverer system would be to figure out that if you’re home from work at 7, then it’s better for the heating to come on at 6 with a flow temp of, say, 40C, rather than at 6:30 with a flow temp of 60C. Or equivalently, for a clever operator to simply turn down the temperature setting on his dumb system and wait longer for the house to warm up.

    I’m thinking of getting a Honeywell Evohome setup (wireless programmable TRVs, centrally / remotely programmed and controlled) so that I can also only heat the rooms that I want to heat, for both comfort and economy benefits. E.g. I can set it so that little kids’ rooms won’t drop below 17C overnight in winter, without the kitchen being heated at 3am, I can set it so that bedrooms are free to get chilly during the day, and with one press I can set it to all switch to economy mode if I’m off out for the day / weekend whatever. That’s the plan, anyway. Not cheap though, so not sure if it’ll pay for itself in its lifetime (current set-up already fairly efficient).

    and your point is ?

    Oh yes, I did omit that.

    Without meaning to sound rude, my point is that you’re wrong, it is cheaper to only heat the house for when you need it heated, instead of heating it all the time, regardless of the wall construction.

    trail_rat
    Member

    ok , enjoy being cold.

    I don’t.

    None of which has anything to do with heat flow and home heating cost.

    sharkbait
    Member

    Maybe I’m being thick, but I simply don’t get why people think that it can be cheaper to keep a house constantly heated than to only heat it when you need to.

    Has anyone mentioned this being better (I can’t be bothered going back and reading)?
    The issue being discussed is whether these systems will ever repay their cost compared to a standard 7 day programmable thermostat? Or have they been produced by companies making money off some people’s believe that all technology is for the better?

    nealglover
    Member

    Has anyone mentioned this being better (I can’t be bothered going back and reading)?

    Yes.

    Most of this page so you won’t need to read back all that far 😉

    Premier Icon gray
    Subscriber

    Maybe I’m being thick, but I simply don’t get why people think that it can be cheaper to keep a house constantly heated than to only heat it when you need to.

    Has anyone mentioned this being better (I can’t be bothered going back and reading)?
    The issue being discussed is whether these systems will ever repay their cost compared to a standard 7 day programmable thermostat? Or have they been produced by companies making money off some people’s believe that all technology is for the better?[/quote]

    I think that’s what trail_rat was saying, though am not entirely sure:

    those doubting it have never lived in a house with 3ft thick stone walls without interior cladding. Its cheaper to keep heat in those walls than heat the air space every time as that stone can pull the heat quicker thn the rads can put it in(rental house so couldnt dry line it)
    for standard cardboard box houses the above does not apply.

    And someone else:

    Plus, a house that’s allowed to cool down will just use more fuel heating back up.

    (I can’t be bothered to go back up and read to see who, if you can’t.)

    Some of these systems are really not expensive. I don’t know the exact costs of Hive / Nest, but I think that they’re in the ~£200 ballpark. Given that some people seem to spend more than a grand a year on gas (never mind those on more expensive fuels), it really wouldn’t take much of an efficiency boost to pay for themselves in a year or two.

    My personal guess is that it depends hugely on what system / way of using it they are replacing. Some people are really crap at using their systems efficiently, because either it’s too much hassle or they just have no interest in it. Any cunning system that helps them might well give them a 20% reduction I reckon, but clearly it depends, for some people the boiler would end up doing damn near exactly the same thing as it does with a standard timer / stat setup. The marketing material for the Evohome system that I mentioned talks about a 40% reduction. I can believe that that’s theoretically possible if moving from a crappy system being used crappily, to using a posh system really effectively, but I’d be amazed if I achieved more than a 5 or 10% reduction with it (meaning a 6-12 year payback time, so the main benefit would be convenience – which is why I’m not convinced that it’s a good idea, but that’s because we’re talking ~£600).

    I would be surprised if the people making them weren’t hoping to make money, and for that to be partly attributable to people upgrading for the technofun of it, but it’s hard to argue against the notion that simple systems aren’t perfect, so it’s no bad thing to make them better. Personally I think the auto-learning (i.e. when you tend to come home etc.) magic is the slightly daft aspect of it – I’m not convinced that people are consistent enough for that to be very useful..

    sharkbait
    Member

    Yes.

    Most of this page so you won’t need to read back all that far
    Oh right. Well I think they’re wrong 🙂

    Premier Icon ourmaninthenorth
    Subscriber

    I don’t know the exact costs of Hive / Nest, but I think that they’re in the ~£200 ballpark. Given that some people seem to spend more than a grand a year on gas (never mind those on more expensive fuels), it really wouldn’t take much of an efficiency boost to pay for themselves in a year or two.

    A grand! I should be so lucky….

    Nest was £180 fitted. On bottled LPG, I reckon it will pay back within a year.

    Premier Icon gray
    Subscriber

    A grand! I should be so lucky….

    Nest was £180 fitted. On bottled LPG, I reckon it will pay back within a year.

    When we were on coal and got through just over a grand in a winter, we thought “crikey, this is nuts”, and got gas installed. Our last (different house now, not that that’s terribly relevant) gas bill was about £250 for Jan-Mar, so we’ll probably be paying around £700 this year. I know that’s not much compared with some, but it still could be better. We’re in a 50s 3 bed semi, fairly well insulated but nothing unusual. It has been a very mild winter though, and I’m guessing that in ten years, fuel prices will be a touch higher (hence my guestimate that we’ll pay an average of nearer a grand per year over the next decade).

    It’s only a few years ago that our gas bills were more like £80 per quarter, but I’ve a hunch that’s at least partly because we were out all day in the week, and just put up with it being pretty cold. Now that there are people here almost every day, some in the range 0-2 years old, we’re using a lot more gas. That might change a bit over the next decade too though, I guess.

    We can’t really use a Hive or Nest with our system – we don’t actually have an internal thermostat, just an external one, hence looking at a TRV-based system (which also gives the option to control rooms / zones separately).

    Premier Icon ourmaninthenorth
    Subscriber

    We can’t really use a Hive or Nest with our system – we don’t actually have an internal thermostat, just an external one, hence looking at a TRV-based system (which also gives the option to control rooms / zones separately).

    Nest itself is the controller and thermostat. It then speaks wirelessly to switch that’s wired into the boiler. I suspect you could make it work.

    I think the full TRV-based system is probably the best way (along with heaps of insulation), though for me the Nest is a neat way into some more accurate control over our heating (and gas usage).

    And these days the stove is used throughout the winter.

    Premier Icon molgrips
    Subscriber

    What our house needs is a heat recirculation system – sucks hot air from the top floor and blows it in at the bottom.

    OR underfloor heating in the downstairs hallway.

    Premier Icon gray
    Subscriber

    Nest itself is the controller and thermostat. It then speaks wirelessly to switch that’s wired into the boiler. I suspect you could make it work.

    Technically I could indeed do that, but would need to bypass the controller that’s built in to my boiler along with the external temperature sensor. That would mean ditching the weather compensation and reverting my system to an old-skool on-off set-up that would almost certainly cancel out any economy benefits of the Nest set-up.

    My current system monitors outside temperature and not only gets a head start on what the house is likely to do (e.g. temperature outside dropping -> start pumping some heat into the house to avoid temperature drop inside) for comfort, but also modulates the radiator circuit temperature according to the difference between the outside actual and inside desired temperatures (for efficiency). This way it will actually run with a lowish temperature (and hence in max. boiler efficiency domain) most of the time rather than going through a rads cold, rads cold, rads HOT, rads HOT cycle. It’s a very good system for a “what I want is all rooms comfortable all of the time, achieved in the most efficient way” scenario, but doesn’t have very convenient controls for the situations where you want to only heat the house (or indeed individual rooms) when you need it heated.

    I reckon that in 10 years, the best aspects of all of these systems will be combined and commonplace. Currently it would take lots of geekery and money to get the ideal set-up, but not for any good reason.

    Premier Icon ourmaninthenorth
    Subscriber

    gray – that’s really interesting. And I agree, that combining all this stuff will soon become obvious. By which time we’ll all be debating the merits of payback on those future systems!

    One thing – my Nest knows what my outside temp is (not through external thermostat, but the blunter instrument of available weather data for the area). It also knows internal temp where it is sited, and also internal humidity. In theory, it ought to follow a similar principle to your system for when it switches the heat on/off, but without the benefit of specific local external temps and room specific monitoring.

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