Stone cottage renovation - ASHP worth thinking about??

[gdal]

We have just bought a Grade 2 listed stone cottage. Two storeys, tiled roof. Needs a complete renovation - new windows, systems, internal replaster, new bathrooms, kitchen. the works. We will dig out and insulate the existing solid ground floor, using limecrete. The walls are 400-500mm thick limestone. Current heating is an old gas combi fed by a cluster of propane bottles.

 No mains gas, no room for LPG tank, no room for GSHP.  We do have room for an oil tank. The house is in Oxfordshire, elevation 95m, reasonably sheltered. Internal floor area about 150 sq metres.

We will install slimline double glazed softwood windows, and insulate the cold loft as well as we can. We will not insulate the walls.

I'd like to put UF heating on the ground floor, radiators upstairs, towel rails in the 2 bathrooms.

There is a central chimney/inglenook fireplace and we will have a 8-10kw wood burner.

I dislike the concept of oil heating, but I really don't want to spend all of our money and be cold.

Is an ASHP worth considering? Or shall I go straight for oil. Cheaper, easier, hotter.....

[markc]

Beautiful place but You are never going to get that air-tight or enough insulation to make ASHP work

[PeterW]

Oil every day of the week .. even consider an Aga if it hasn’t got one to do core background heat. 
 

Why have you gone for limecrete in the floor..? As you’re removing the whole floor, as a thermal element you’ll need to meet minimum building regulations values so just go for decent insulation and concrete and be done with it. 

[ProDave]

Yes go with oil.  Much cheaper than bottled LPG and you will have enough heat.

 

And do the best you can with insulation and upgrades but it is always going to be an expensive house to heat.

 

P.S which village?  looks familliar to me.

[gdal]

29 minutes ago, markc said:

Beautiful place but You are never going to get that air-tight or enough insulation to make ASHP work

Yes that is pretty much what I  think

[gdal]

3 minutes ago, PeterW said:

Oil every day of the week .. even consider an Aga if it hasn’t got one to do core background heat. 
 

Why have you gone for limecrete in the floor..? As you’re removing the whole floor, as a thermal element you’ll need to meet minimum building regulations values so just go for decent insulation and concrete and be done with it. 

Floor needs to be breathable, I think, in order to reduce the risk of damp migrating out to the edges and in to the solid stone walls. I think we can get a good amount of insulation in, and achieve this. But I guess when the digging starts we will find out.

I kind of like the Aga idea, but I think that just burns even more oil, and I'm already a bit ashamed of that. I really think a simple oil fired system boiler with a nice big cylinder will keep us warm, cost us less. Sorry planet, I will make it up in some other way

[pdf27]

3 minutes ago, gdal said:

Yes that is pretty much what I  think

It's worth noting that there is a difference  between work (as in provide the desired comfort levels) and work efficiently (i.e. provide the lowest cost means of giving the desired comfort levels). ASHP can be designed to give good comfort levels even in an old building with mediocre insulation, but may be quite an expensive way of doing it.

Major issues to address with ASHP would be:

1. Heat emitters that work with reasonably low flow temperatures. If you're digging out and insulating the floor and fitting a new heating system, this might not actually be that hard and you probably want to do this with oil if you can as well because it should help with efficiency no matter what you do.
2. Capital cost - a big ASHP will always be more expensive than a big oil boiler. Running cost is likely to be cheaper for oil at the moment, but that's very dependent on how oil and electricity prices vary over the life of the system so you need to take your own view on what fuel prices will be over the life of the equipment.
3. Power supply - a big ASHP is probably going to need a 3-phase supply, which can be hard to get in a rural property. This may actually be a showstopper for an ASHP, so it's well worth working out what your total heat demand will be and whether you can do that on a single phase. If not and you can't get 3-phase at a sensible price then an ASHP is a non-starter.

[gdal]

7 minutes ago, pdf27 said:

It's worth noting that there is a difference  between work (as in provide the desired comfort levels) and work efficiently (i.e. provide the lowest cost means of giving the desired comfort levels). ASHP can be designed to give good comfort levels even in an old building with mediocre insulation, but may be quite an expensive way of doing it.

Major issues to address with ASHP would be:

1. Heat emitters that work with reasonably low flow temperatures. If you're digging out and insulating the floor and fitting a new heating system, this might not actually be that hard and you probably want to do this with oil if you can as well because it should help with efficiency no matter what you do.
2. Capital cost - a big ASHP will always be more expensive than a big oil boiler. Running cost is likely to be cheaper for oil at the moment, but that's very dependent on how oil and electricity prices vary over the life of the system so you need to take your own view on what fuel prices will be over the life of the equipment.
3. Power supply - a big ASHP is probably going to need a 3-phase supply, which can be hard to get in a rural property. This may actually be a showstopper for an ASHP, so it's well worth working out what your total heat demand will be and whether you can do that on a single phase. If not and you can't get 3-phase at a sensible price then an ASHP is a non-starter.

 

Thank you that is useful - I hadn't considered that 3 phase might not be easily available.Then you are into 3 phase converters and all sorts of complex considerations.

My plan is to fit wet UF heating if we possibly can. I expect to do this.

The relative prices of different fuel supplies is a facer isn't it? At the moment gas and oil are so much cheaper than electricity, but if any government were to really get behind a serious carbon reduction strategy, then that must change. I guess if the cost per unit of energy for gas/oil/electricity starts to move in favour of electricity (and I would support that) then at that stage perhaps we all swap our fossil fuel boilers for electric boilers? Or install big heat pumps.

 

Thank you everybody

[J1mbo]

R290 heat pump, 35°C flow (would that be enough?) SCOP approaches 5. Electricity 15p so effective cost a bit over 3p. Oil 11 kWhr per litre so break-even is about 30-35p per litre assuming 90% efficiency.

 

Although single phase, cost of oil boiler I was considering was £6k with no RHI obviously. Heat pump £14k with £12k RHI payments. RHI would pay more with UFL due to higher SCOP, but there is a cap. Look at the EPC, it will tell you estimated annual heating demand in kWhr, then you can ascertain the heat pump size from that as a starting point and associated heating energy cost.

 

Supply upgrades: What do you need to upgrade | UK Power Networks IIRC cost for me was about £10k, it wasn't needed in the end.

 

With stone walls it will need a lot of energy. Maybe it will need multiple heat sources, some nice log burners around the place in addition to UFL. Quick calc suggests 150m2 would need 55°C flow to provide 16kW, for example.

Edited March 25, 2021 by J1mbo

[gdal]

4 hours ago, J1mbo said:

R290 heat pump, 35°C flow (would that be enough?) SCOP approaches 5. Electricity 15p so effective cost a bit over 3p. Oil 11 kWhr per litre so break-even is about 30-35p per litre assuming 90% efficiency.

 

Although single phase, cost of oil boiler I was considering was £6k with no RHI obviously. Heat pump £14k with £12k RHI payments. RHI would pay more with UFL due to higher SCOP, but there is a cap. Look at the EPC, it will tell you estimated annual heating demand in kWhr, then you can ascertain the heat pump size from that as a starting point and associated heating energy cost.

 

Supply upgrades: What do you need to upgrade | UK Power Networks IIRC cost for me was about £10k, it wasn't needed in the end.

 

With stone walls it will need a lot of energy. Maybe it will need multiple heat sources, some nice log burners around the place in addition to UFL. Quick calc suggests 150m2 would need 55°C flow to provide 16kW, for example.

Interesting, but....

No current EPC owing to the house being pretty derelict, and it's  a listed building as well. We can specify the improvements, and we'll do our best to make it draught proof and have decent windows ..... but we are not going to turn it into an efficient, highly insulated modern building.  So I think that the combination of poor efficiency in the house, the higher capital  cost of ASHP, potential extra cost and complexity of getting 3 phase connected, and the distinct possibility of ending up with a chilly home even after all that, makes me think we'll go for oil.

 

Now how to choose an oil fired boiler? I'll do some thread searches unless a kind person can point me in the right direction

 

Thank you 

[Balou]

GDAL, if its of any use, we live in a house the majority of which was built in 1760's, so thick solid walls, no wall insulation, no under floor insulation, 2 large inglenook fireplaces with wood stoves, about 3300ft2 in size . Luckily, its not listed. 10 years ago we carried out a fairly big renovation, so some of the older part has minimal insulation, new parts were insulated to the standard of the time, loft has lots of insulation, double glazing fitted etc..At the time we also fitted solar panels to the rear south facing roof and for heat/hot water we have been using a Daikin 16KW ASHP. The Daikin has been working fine, especially if its just left ticking over and particularly if youre going to use a woodstove as well. All our heating/hot water/cooking is electric (except the woodstove which is handy when the village has its powercuts) for which  we are currently paying around £800 per annum. Hope thats of use.

[Balou]

ps- ours uses  single phase electrics

[gdal]

On 27/03/2021 at 18:51, Balou said:

ps- ours uses  single phase electrics

Thank you Balfour, interesting. Do you use radiators, or underfloor heating?

[Balou]

On 04/04/2021 at 22:29, gdal said:

Thank you Balfour, interesting. Do you use radiators, or underfloor heating?

Hi gdal, sorry only just seen this. Upstairs is all rads, downstairs is a mix of rads and underfloor heating (in the new part). The rads get warm enouth to cope, although in the winter it is boosted by the woodburner.