Wall Mounted Air Source Heat Pumps & Village Hall.

Then a lot of heat will be lost downwards presumably with no under insulation.

There will always be some loss downwards, but most overlay systems include a bit of thermal insulation. For large solid floor areas it's sometimes less of an issue anyway as it's much harder for the heat to reach the perimeter in order to escape "outside" - not so long ago building regs allowed thermal insulation to be reduced or omitted entirely if the floor was over a certain size and shape (i.e. not long and thin) - in effect the ground under floor was regarded as being inside the thermal envelope. Less effective if the building is allowed to cool down completely between uses though.

   - Andy.

Then a lot of heat will be lost downwards presumably with no under insulation.

There will always be some loss downwards, but most overlay systems include a bit of thermal insulation. For large solid floor areas it's sometimes less of an issue anyway as it's much harder for the heat to reach the perimeter in order to escape "outside" - not so long ago building regs allowed thermal insulation to be reduced or omitted entirely if the floor was over a certain size and shape (i.e. not long and thin) - in effect the ground under floor was regarded as being inside the thermal envelope. Less effective if the building is allowed to cool down completely between uses though.

   - Andy.

I assume that the hall heat loss was calculated before the heat pump installation. Many of these units only provide a couple of kW of heat unless it is warm outdoors, A heat pump with a 20C differential might have a COP as small as 3, so that might give 12 kW of heat. That is not a lot for a hall with a stage, which is presumably at least 1000 sq ft in size and high too, so maybe 20,000 cu ft. Even with good insulation, I would expect it to take a couple of hours to really feel warm. SW IR heaters are very good for this kind of place, but quite a lot are needed, probably about 30kW for my guess at the size of the hall. Still only a few pounds per hour though!

The installation would have been approved by the "Hall Committee" ( a bunch of amateurs) with  local Council Approved. The units were installed by a "specialist" contractor based in Norwich I believe.

The hall is chilly!

But, new double glazing has been ordered. The existing seems o.k. apart from a few broken hinges and handles. These village halls get so much public funding with grants etc. It is frightening.

Z.