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Heating and cooling: Heating solution for straw bale hall - Radiators or IR?

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  1.  
    • CommentAuthorSandbank
    • CommentTimeOct 22nd 2016
     
    I need advice for affordable options to retrofit permanent heating in a new strawbale hall, 80m2 with a high sloping ceiling. Ceiling, floor and upper walls lined with sheep's wool, covered with plasterboard. Rationel windows and entry door. (We did not have enough money to put the heating in at time of construction, otherwise UFH would have been desirable). The hall is mainly used evenings for dining, also in the day for groups eg for yoga/meditation - so noise is a factor, also ease of use as its hired by outside groups. To date, we use 4 x 3kw oil-filled radiators, to establish the requirements. Left overnight they heat the room sufficiently for a weekend.
    One option (cheapest?) is to hardwire in electric radiators - there are limited fixing points on the walls, but it is possible. Maybe in conjunction with a heat curtain at the entrance door.
    Another option is Infra-red from the ceiling? Would this be more efficient in the long term? The hall is generally clear of furniture etc.
    There is an array of 64 solar panels on the roof, which feed into our general supply for other buildings. See www.kenchhill.co.uk
      IMG_20161007_130404.jpg
    •  
      CommentAuthorSteamyTea
    • CommentTimeOct 22nd 2016 edited
     
    Posted By: SandbankTo date, we use 4 x 3kw oil-filled radiators, to establish the requirements. Left overnight they heat the room sufficiently for a weekend.

    Right, so you need a peak load of 12 kW (kWp). When you say "sufficiently for a weekend", does that mean they are switched off for two days after a night's heating, or left on?
    Is there anyway you can work out how much of the time they are actually on i.e. 4 plug in energy meters to give you the actual loading.

    It may be worth you trying out some fan heaters, they distribute the temperature though the air quicker, again it may be worth getting some meters to read what is really happening.

    It is also worth correlating with outside temperature (usually easy enough to find a weather station nearby).

    I am not a fan of IR heating as it tends to be a 'point of view' system and only heats what is, in your case, below it. So tops of heads may be warm, feet cold.

    As you have a large solar array, somewhere in the region of 16 kWp, you may find that cheap Air to Air Heat Pumps are an affective method. You can get these types of units from about £300, they are easy to fit and can provide cooling if needed.

    The first thing is to work out the real energy usage first though.
    •  
      CommentAuthordjh
    • CommentTimeOct 22nd 2016
     
    What Steamy said about working out requirements. As well as getting a better understanding of exactly what the oil radiators have been doing, it would pay to work out whether you want to heat it intermittently, just when there's an event, or whether you want it warm all the time, or background heat most of the time, with a boost for events etc.

    Infrared or fan heating are best for intermittent heating; there are more options for the other strategies, but they cost more to buy and to run (because they are used more, whilst they may be more efficient).
    • CommentAuthortony
    • CommentTimeOct 22nd 2016
     
    ir 100% efficient

    ASHP 350% efficient

    You choose :)
    •  
      CommentAuthorSteamyTea
    • CommentTimeOct 22nd 2016
     
    And I would question the 100% efficiency of IR. If you have 10 m^2 of heater area to heat up 3 m^3 of people, it is not very efficient at all.
    •  
      CommentAuthorfostertom
    • CommentTimeOct 23rd 2016 edited
     
    Depends how well insulated it really is - whether continuous heat requirement to keep it permanently warm would be just a trickle, or substantial. Because it's poss that the overnight heat you're putting in to make the place warm for a day or w/e's use might just be a high startup input, which wd be followed by just a trickle to hold it there permanently.

    In other words, if highly insulated (and fairly massive) it would prob be best to keep the place warm permanently, rather than doing it intermittently, as you seem to be.

    Intermittent heating works best with a lightweight structure, which needn't be highly insulated - can make bodies feel comfortable while air remains cool, and the structure's inner surface soon warms up too.

    Permanent heating works best for heavyweight structure, but only if heavily insulated. Structure up to temp in-depth, and air too, continuous heat demand low thanks to the insulation.

    'Straw bale' sounds highly insulated but then we have 'upper walls' and roof with - what thickness of? - sheep wool. And the floor - how much insulation there?

    If only moderately insulated plus fairly massive (straw bales and floor) then you've got a problem - not ideal for either intermittent (radiant based - comfortable while allowing air and structure to remain a bit cool) nor permanent (air and structure fully up to temp).

    The lads above say 'measure the heat demand'. That shd mean the continuous dedmand, after several days of xs consumption needed to get it fully up to temp.
    • CommentAuthorSandbank
    • CommentTimeOct 23rd 2016 edited
     
    Thank you. Up to now we have only heated it intermittently. The base temperature is usually 10C whatever the external temp. With the rads on overnight at 2kW it rises to 18 C and retains the heat all weekend. It is highly insulated and massive, so it does seem sensible to keep it warm permanently ie approx 15 C. I will look at ASHP option but installation could be impractical through the straw walls now.
    •  
      CommentAuthorfostertom
    • CommentTimeOct 23rd 2016
     
    Posted By: Sandbankretains the heat all weekend
    Does that mean with heating off, or still pumping it out? Do yr heaters have an input wattage selector e.g. 1kW element or 2kW element, or both together for 3kW? You cd try turning it down to 1kW and see if it still copes. Or turn off 2 or 3 of the 4 heaters.

    BTW, anything that increases air speed (like fan heaters) is going to make it feel hotter if air temp is a bit high, or more to the point colder if air temp is a bit low. Whereas radiant heat (providing you're within range) makes the body feel more comfortable even with low air temp.
    • CommentAuthorringi
    • CommentTimeOct 23rd 2016
     
    Be careful with slow response heating, as you may have a group of 30 people in a keep fit class that wants it cool, then a group of 10 old people that want it hot, with only 10 minutes change over between the groups.

    I expect that the insulation is more than is worthwhile, however this money has already been spent.

    I have seen IR heating work well in village halls, as it makes people feel like they are warm and response quickly to the requirements.

    I would consider some ceiling mounted fans to push heat back down to the people. If you have mains gas, then fans assisted radiators would be a good option as they give a quick response.

    AirToAir heat pumps can be a good option, as they can give a fast heat up, and also let you cool without opening the windows. Being able to keep the windows closes can help keep the noise in when the hall is being used for a late night church service or party.
    • CommentAuthorgyrogear
    • CommentTimeOct 23rd 2016
     
    Posted By: ringiI would consider some ceiling mounted fans to push heat back down to the people.


    +1
    reversible and multi-speed, into the bargain !

    gg
    •  
      CommentAuthordjh
    • CommentTimeOct 23rd 2016
     
    Posted By: SandbankThank you. Up to now we have only heated it intermittently. The base temperature is usually 10C whatever the external temp. With the rads on overnight at 2kW it rises to 18 C and retains the heat all weekend. It is highly insulated and massive, so it does seem sensible to keep it warm permanently ie approx 15 C. I will look at ASHP option but installation could be impractical through the straw walls now.

    How many hours is the heating used on average (per day or better per week). Intermittent heating is definitely best for things like churches that are used one day a week and rarely heated otherwise. If you're using it quite regularly then continual background heating begins to make more sense.

    Are plans of your building available somewhere? You haven't given a lot of detail about what the floor structure is or how much insulation apart from the bales, or how much attention was paid to airtightness, or how much window area there is. I live in a straw bale house and that quite clearly tracks the outside temperature and sunshine, albeit in a very filtered way. A constant 10°C sounds more like an underground building.

    It's quite easy to drill through straw walls if required, by the way. You just need to be careful to avoid too much damage to the render.

    PS +1 to ringi's comments.
  12.  
    What about smart storage heaters fed from the PV? Topped up with E7 when needs must. I vaguely remember seeing something like that which is produced by Dimplex

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