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Efficiency of an electric heater is a ratio of the heat up time to the run time. So if a heater needs to be on one hour before the hall is used and it is used for one hour then it is 50% efficient.
The radiant heater often used in churches would seem the most efficient, but it has a huge problem, as soon as it is turned off, the occupants feel cold, so the only way to control is to have multi-bars and switch between one or four bars to adjust heat output. even then it has a problem, normal thermostats are useless, they measure air temperature, and the radiant heater does not heat the air, like the sun it heats directly on the body, it will in the end heat the air by warming every item in its path which in turn heats the air. So in the main the radiant heater needs a manual control. But for less than one hour still likely the best option.
Once we leave radiant heater we then must look at the mass of the heater, the less heat the heater absorbs the more heat goes into the hall, the fan heater must be the best, with the storage radiator or maybe under floor heating the worst.
Although fan heaters work well, they do produce noise, I know with the camera club we left one venue because when the heating cut in those at the back could not hear the speaker, so it may need a PA system if using fan heaters.
Next is down to if permanent seats or not, tube heaters under the seats in churches works well, again the occupants feel the heat before the room has got warm, light panel heaters tend to emit so radiant heat, but here safety is a problem. Often radiators need covering with boxes to allow heat to get out with convection but occupants can't touch the hot parts, so any heat from radiation is converted to convection so the part radiation idea is lost.
So question one is if noise of fan heaters is a problem or not? If not than likely the best.
One option is a combination of radiant heaters and other heating, the radiant heaters being on a timer which switches them off after first 1/2 hour by which time the other heaters take over.
How well the hall retains heat is another consideration, with a well insulated hall you can consider back ground heat which is boosted when in use, the church we now use with the camera club uses this idea, as we arrive the PIR's boost the heat, at around 8 pm back ground heat is reduced to anti-frost, I am not sure when the heat increases again, but if occupied then does not matter, with church halls the verger will often put the heating on before an event, with the village hall not so easy, if the back ground temperature went from frost to say 12°C at 10 am that would likely cover most use. PIR's lift it to 18°C when occupants arrive, with only 6°C to raise this will not take long, with no back ground heat raising from 4°C (anti-frost) to 18°C a raise of 14°C it is a problem, users need to have some one switch it up an hour before the event.
There is clearly a difference between a hall used for 30 hours a week to one used 5 hours per week even if the events are the same time. Also between a hall only used in the evening to one used during the day.
I am sure with enough solar panels and wind generators the hall could be heated for free, but the installation cost would be silly, so some compromise is called for.
The radiant heater often used in churches would seem the most efficient, but it has a huge problem, as soon as it is turned off, the occupants feel cold, so the only way to control is to have multi-bars and switch between one or four bars to adjust heat output. even then it has a problem, normal thermostats are useless, they measure air temperature, and the radiant heater does not heat the air, like the sun it heats directly on the body, it will in the end heat the air by warming every item in its path which in turn heats the air. So in the main the radiant heater needs a manual control. But for less than one hour still likely the best option.
Once we leave radiant heater we then must look at the mass of the heater, the less heat the heater absorbs the more heat goes into the hall, the fan heater must be the best, with the storage radiator or maybe under floor heating the worst.
Although fan heaters work well, they do produce noise, I know with the camera club we left one venue because when the heating cut in those at the back could not hear the speaker, so it may need a PA system if using fan heaters.
Next is down to if permanent seats or not, tube heaters under the seats in churches works well, again the occupants feel the heat before the room has got warm, light panel heaters tend to emit so radiant heat, but here safety is a problem. Often radiators need covering with boxes to allow heat to get out with convection but occupants can't touch the hot parts, so any heat from radiation is converted to convection so the part radiation idea is lost.
So question one is if noise of fan heaters is a problem or not? If not than likely the best.
One option is a combination of radiant heaters and other heating, the radiant heaters being on a timer which switches them off after first 1/2 hour by which time the other heaters take over.
How well the hall retains heat is another consideration, with a well insulated hall you can consider back ground heat which is boosted when in use, the church we now use with the camera club uses this idea, as we arrive the PIR's boost the heat, at around 8 pm back ground heat is reduced to anti-frost, I am not sure when the heat increases again, but if occupied then does not matter, with church halls the verger will often put the heating on before an event, with the village hall not so easy, if the back ground temperature went from frost to say 12°C at 10 am that would likely cover most use. PIR's lift it to 18°C when occupants arrive, with only 6°C to raise this will not take long, with no back ground heat raising from 4°C (anti-frost) to 18°C a raise of 14°C it is a problem, users need to have some one switch it up an hour before the event.
There is clearly a difference between a hall used for 30 hours a week to one used 5 hours per week even if the events are the same time. Also between a hall only used in the evening to one used during the day.
I am sure with enough solar panels and wind generators the hall could be heated for free, but the installation cost would be silly, so some compromise is called for.
