Old grade 2 farmhouse space heating options.

[renewablejohn]

Ok assistance required. Just found out I may be eligible for a heating refurb grant as not heated by gas. Present system uses all wood with primary central heating being a Dunsley Yorkshire woodstove heating conventional radiators. Supplemented in the snug with a Dunsley Highland woodstove and in the kitchen an Esse range cooker which also heats the hot water.
Farmhouse dares back to about 1650 but date stone when house was extended is 1721. 2ft thick solid stone walls with triple glazing and 600 mm in roof ie 400mm ceiling 200mm rafters.
Being listed we had to get listed building consent so we have permission for triple glazing throughout, ufh throughout both pipe and electric. Insulation of solid floors with foamed glass but stone floors have to be retained and on show. Partel MVHR system to "maintain" the fabric of the building, Scandinavian type insulated outward opening doors.
Currently installing PV which looks like its going to be 3 x 5kw hybrid Sun Synk systems one for farmhouse one for barn and one for workshop with option in workshop to combine all 3 to enable 3 phase in workshop for industrial motors.
The refurb grant has heat pump options but which would be the best as I could install water,ground, or air and I do still have free biomass

[marshman]

"Upgraded" to a GSHP a few years ago. Should have done it sooner, best thing we ever did. Heatpump is left to "do it's own thing", has external weather compensation.
If it were me and you have the ground for the collection loops a GSHP would be a no brainer - middle of winter, -6 deg C outside air temp, incoming "brine" temperature still 9 deg C. If we ever move, UFH and GSHP would be a must have in the next house.

[Thebeeman]

I didn't want the added complication of a pump to increase pressure/flow.

We're off a borehole which fills an over ground tank and then a pressure vessel and pump set to normal mains pressure. You would only need the pressure vessel and pump to boost output. our pumps need changing about every 6 years when they get noisy, a "fairly" cheap DIY job and once in 25 years the pressure switch failed, we have a good mains pressure around the farm. No tanks in the loft to freeze/leak.

[renewablejohn]

You could be describing our house! Bits dating back to late 1600's, 2 ft thick walls, triple glazed, wet UFH throughout, MHRV, insulation etc. Used to be heated by a wood stove with back boiler driving the UFH. "Upgraded" to a GSHP 7 1/2 years ago. Should have done it sooner, best thing we ever did. House is detached, approx 240 sq m. Heatpump is left to "do it's own thing", has external weather compensation - we are very exposed near the coast with zero shelter from the wind. 12 month electricity consumption for the heat pump is around 1150kWh for the whole year including DHW in the winter. Heats the whole house 24/7, I don't bother shutting off unused rooms. We do have "oversized" ground loops due to the fact we are on shingle with patches of clay and there were concerns about the heat conductivity of the shingle - so we ended up with 4 x 300m long loops for a 10kW heatpump. We did replace the old wood stove with a cleaner burning Clearview 650, but it is used more for effect in the darker winter evenings - no more worries about finding wood as we now use so little.

We have a 300 litre DHW tank which is unvented and fed from the old cold water tank in the loft - mains pressure is not enough here to do everything off the mains and I didn't want the added complication of a pump to increase pressure/flow. Its heated by immersion via a solar diverter when there is excess PV, otherwise the GSHP heats it and gets it to a useable 55 deg C in next to no time. Max draw of the heatpump is 3kW so runs nicely from the 6kW inverter and batteries. As it is an older design I am sure there are more efficient ones out there with compressors that "modulate" rather than straight "on/off" like ours is.

If it were me and you have the ground for the collection loops a GSHP would be a no brainer - middle of winter, -6 deg C outside air temp, incoming "brine" temperature still 9 deg C. If we ever move, UFH and GSHP would be a must have in the next house.

What size solar do you have to keep the batteries topped up in the winter to enable the max 3kw draw ro keep working. Sorry had not spotted your system listing. So next question given the amount of solar you have do you still have enough for the 3kw draw in the depths of winter.

[Andy]

Even with 18kW of panels I won't make much more than 400kWh in the depths of winter. I am in the north of Scotland and the panels are at an average of 25º. However even at an optimum pitch doesn't dramatically increase the production.

With 15kW installed, PVGis forecasts about 700kWh for the south of England. Remember though that it will be production will be concentrated in a few good days.

https://re.jrc.ec.europa.eu/pvg_tools/en/

[renewablejohn]

Even with 18kW of panels I won't make much more than 400kWh in the depths of winter. I am in the north of Scotland and the panels are at an average of 25º. However even at an optimum pitch doesn't dramatically increase the production.

With 15kW installed, PVGis forecasts about 700kWh for the south of England. Remember though that it will be production will be concentrated in a few good days.

https://re.jrc.ec.europa.eu/pvg_tools/en/

I thought that would be the case with solar. I do have 700w hydro for the winter which will contribute to the battery bank but it still looks like the Dunsley Yorkshire central heating boiler needs to be plumbed in for backup.

[marshman]

What Andy said ! I have PV, not at ideal/optimal angles for winter generatio. Even at an ideal angle it wouldn't make much difference, it may double the yield but double not a lot is still ........ not a lot!


PV will not cover you use in the short dull winter days of Dec/Jan, no matter how much you have - not in the UK. Your 700W hydro will make a significant contribution, as would a small (ish) wind turbine - but they are maintenance "heavy".


Not sure you need to keep the woodstove "hooked" in to the central heating, heat from a wood stove will convect through a lot of the building if needed, especially with MHRV system helping to circulate the air.

[renewablejohn]

Was really thinking if the woodstove boiler was still hooked into the UFH then when electric is in short supply a circulation pump on the woodstove would use a lot less energy then the water source heat pump. Bare in mind logs are free of charge apart from my time and cut with electric saw in summer when there will be plenty of solar.