Does a GSHP make sense in a Grade 2 listed building in need of complete renovation

Reed_Richards

A good thing about UFH is that you can typically run it at a lower temperature than radiators, allowing you to run your heat pump more economically.  A bad thing is that inevitably some of the heat goes into the ground rather than into your house.  Hopefully the former beats the latter but it will depend on how good the insulation beneath your UFH is.

fizio

FreeBear said:
If you are ripping up floors, float the idea of wet UFH with the CO. It would also pay to get someone on board early on to advise on plumbing & radiator sizing so that you can get pipes in as the renovations progress.

Yes, the kitchen and bathroom are concrete floors so will rip up and put in insulation and UFH (assuming CO gives the nod) - the ugly side extension, which is the bathroom, was added much later so I am attempting to get permission to demolish and rebuild it with better insulation etc (looks like it was a botch job joining kitchen to an outbuilding (coal shed?) and a cheap felt flat roof. 
The other 2 rooms downstairs are heavily damaged and rotted wooden floors (nothing special and have been carpeted over) so I would really like to insulate and concrete with UFH but that may not be allowed so alternative is to insulate as much as poss and replace the floorboards - I don't think I have a UFH option with this? 
In terms of pipework the current pipes and wiring was all surface mounted and stolen while the place was empty and derelict for many years so I will chase in new pipes and wiring then insulate and re-lime-plaster - this has largely been approved.

Reed_Richards

There may not be any economic benefit in having a mixture of UFH and radiators compared to just radiators. 

FreeBear

fizio said:

FreeBear said:
If you are ripping up floors, float the idea of wet UFH with the CO. It would also pay to get someone on board early on to advise on plumbing & radiator sizing so that you can get pipes in as the renovations progress.

Yes, the kitchen and bathroom are concrete floors so will rip up and put in insulation and UFH (assuming CO gives the nod) - the ugly side extension, which is the bathroom, was added much later so I am attempting to get permission to demolish and rebuild it with better insulation etc (looks like it was a botch job joining kitchen to an outbuilding (coal shed?) and a cheap felt flat roof. 
The other 2 rooms downstairs are heavily damaged and rotted wooden floors (nothing special and have been carpeted over) so I would really like to insulate and concrete with UFH but that may not be allowed so alternative is to insulate as much as poss and replace the floorboards - I don't think I have a UFH option with this? 
In terms of pipework the current pipes and wiring was all surface mounted and stolen while the place was empty and derelict for many years so I will chase in new pipes and wiring then insulate and re-lime-plaster - this has largely been approved.

If you are digging out concrete, do have a look at foamed glass to replace any hardcore/MOT1 used in the sub-base - It will provide some valuable insulation and reduce the amount of moisture wicking up from the soil.

You can install wet UFH with a suspended timber floor, but insulation may be an issue. To achieve Building Regs compliance, you'd need ~150mm of Celotex type insulation under the floor. Joist thickness may limit you to just 50mm.. But being a listed building, the CO can overrule BR, and there is a cop out in the regs that state "where practical" and "no worse than original".

If you are burying pipes in plaster (or concrete), 15mm copper is a nice sliding fit inside 20mm plastic conduit. The plastic will prevent plaster/cement from making contact with metal and minimise any corrosion.

QrizB

FreeBear said:

If you are burying pipes in plaster (or concrete), 15mm copper is a nice sliding fit inside 20mm plastic conduit. The plastic will prevent plaster/cement from making contact with metal and minimise any corrosion.

Is plastic-coated copper pipe still a thing? It was what we used when building my uncle's house almost 40 years ago. (I was labouring for him as a summer holiday job!)

fizio

Reed_Richards said:

There may not be any economic benefit in having a mixture of UFH and radiators compared to just radiators. 

You may be right.. Though I would pay the extra if it meant having a more effective heating system - I'm assuming that UFH means less humongous radiators at the very least.. Everything I have read seems to say that ASHP combined with UFH is the 'best' combination..

Reed_Richards

ASHP combined with just UFH is indeed the "best" combination in many respects.  And where you have UFH you don't need radiators, although where you do need them they may not be as humungous as you fear.  But with a mix of radiators and UFH you have to supply water that is hot enough for the radiators, which is liable to be hotter than the UFH needs.  In which case you don't get the economic benefit that you would get if you had only UFH and could reduce the water supply temperature.

If you had radiators big enough that you could run them at the same temperature as your UFH then radiators would be more "effective" because they don't lose heat into the ground.

fizio

Reed_Richards said:

ASHP combined with just UFH is indeed the "best" combination in many respects.  And where you have UFH you don't need radiators, although where you do need them they may not be as humungous as you fear.  But with a mix of radiators and UFH you have to supply water that is hot enough for the radiators, which is liable to be hotter than the UFH needs.  In which case you don't get the economic benefit that you would get if you had only UFH and could reduce the water supply temperature.

If you had radiators big enough that you could run them at the same temperature as your UFH then radiators would be more "effective" because they don't lose heat into the ground.

Thanks, that makes sense when you explain it so I will factor it in to my thinking. I will plan for both and see what gets through the LBC process as my main focus now is to get approvals to make the significant building changes needed to support the ASHP. 

fizio

Spoke to my architect and he reckons I have a good chance to get all the downstairs lime-creted with UFH - due to both the floor being riddled with woodworm and half missing with little original content but also I can say that I will not need 'big ugly radiators' on the walls so the property will keep a nicer historic look. As the downstairs rooms have chimneys I can but electric stoves as a backup heat source. Thats what we are going for with the LBC together with all round internal wall insulation to the max.