@ragnaricedaine 

Hello and welcome to the forum. Two x 10kW sounds a lot but depends on the house.  If you want some detailed comments/advice, feel free to post a new thread with some details - house m2, MCS heat loss, etc.  The high ceilings will add to your heating requirement but having a neighbour above helps; if their house is the same temperature as yours you'll have no heat loss through your ceiling.  It's the other way around with the floor of course. 

I come from Edinburgh so I can picture the sort of property you're describing. 

EDIT - sorry, you have!!!

Post some more details here 🙂 

@Kev M, thanks for the welcome and for reaching out.

The house is about 125 sqm in size. After our renovation/structural works, we will have 3 bedrooms, one ensuite, one main bathroom, one large living room and one kitchen area. The kitchen is to be located in a shorter 2.7m high outbuilding on the south-facing rear of the house and the neighbour does not live above (so will insulate roof of this outbuilding).

Space heating is 23,873 kWh and hot water is 2,695 kWh. This however looks to have been copy and pasted from the original EPC of the house, not a detailed MCS breakdown accounting for U-values of walls, windows, future floors, future insulation etc. so need to question this (amongst other things).

We currently have a mix of suspended timber and concrete floors. We intend to remove the concrete and have insulation/a slab across the whole floor of the house. UFH then installed and likely tiles as the flooring option. My better half has her heart set on engineered wood, but trying to persuade her that tiles are better for the UFH efficiency. House also is draughty and so will seal these where we can and control ventilation.

We will have a woodburner in the living room - it is circa 30sqm in area and 3.7m high so expect the woodburner will top up the UFH when it gets chilly.

But now comes the question of heating and what source to use. We will miss the RHI deadline unfortunately but should still qualify for the Grants/loans from the Energy Saving Trust so an ASHP is still somewhat financially feasible. That being said, there are some horror stories on here about high bills etc. and so keen to learn and engineer out issues where I can. I do have a shared roof with neighbour that I could put solar panels on at a later date. But this is all more expenditure and so want to ensure I apply a logical thought process to the heating system.

 I do work in the renewables industry however and want to ensure that what I use minimizes carbon emissions where possible.

Happy to take any recommendations or advice. I am just starting on my project and aim to be in this house for the long run. 

@ragnaricedaine - If you want to test the affects of an ASHP I would suggest going to your boiler and turning down the temperature to 45/50 degrees. This way you can basically recreate what using one is like. See how comfortable the house is.

1. do your own heat loss. There is a calculator in my signature you can use.
2. Make sure the ASHP is installed in a suitable area where it can work efficiently - not down the side of the house pointing towards a fence
3. ask the installer to enable weather compensation  and show you how to tweak it (and what settings they are using). Get the codes
4. Make sure any filter they install is accessible to you INSIDE the house and its easy to clean - get them to show you
5. Put the controller in a main area (not in a cupboard)
6. Use high flow rate valves - not normal heating valves (which have higher temps but lower flow rates)
7. Try to remove any zoning you have - better to heat the whole envelope
8. Find a temperature you are comfortable with and use that
9. You probably don't need a low loss header for the radiators (the UFH will have its own one which you DO need) - LLH just add cost, complexity and wastes your money as you'll be the one buying it. The ASHP will be more than powerful enough to pump the water round your house.

@batalto

Thanks for the feedback. I should have noted in my original post that I have no heating at all in the house just now (we have a gas connection that supplied 4 small gas fires in 4 rooms but they were deemed unsafe when I moved in and were removed). The hot water electric immersion tank also gave up on life a few weeks ago, so not hot water either - using the gym at present.

The only area I have for placing an ASHP would actually be down the side of my house - though there is a 2.4m gap between the house and the neighbour's stone wall. The proposed ASHP installer has indicated this would be okay as it is still SSW facing, quite exposed and has a more than 1m of clearance - is this not in line with your thinking?

@ragnaricedaine thats not going to be ideal. You've got to leave at least 300-400mm behind the unit, then the unit itself (another 500mm probably). Now your clearance is only 1.5m (ish). 1m is really not suitable. The way the pumps work is by intaking ambient air and removing the heat from it. Your issue if the unit is too close to a wall is that the expelled cold air is captured again - now it contains less heat you need to work harder to extract it. You'll end up with a cold well and your COP will be terrible. You need to clear that cold air away. You said its exposed, is it quite windy down there? If so it might work as long as you are happy with the fact on a still day you might lose some performance. There must be another suitable area on the house for the pump?

Ideally you want the below image - nice and clear front and back. Realistically the back is less of a problem than the front. 

@batalto - great info, thanks.

FYI, this is where the ASHPs are planned to go - the SSW side of the house where the "shed" currently is (you'll have to excuse the mess). The shed will be replaced with a smaller one but one of the 10kW ASHPs was proposed to be placed between the two black metal pipes and another adjacent to it.

The Southern side of the house (where the table of apples is) is more exposed but this is the nicest external area of the house to sit out and have a beer, so don't really want an ASHP here. I may also build an extension in this area later, so think placing an ASHP here is not so feasible.

It is quite windy down there (as prevailing winds in UK/Scotland are from a SW direction and so hit the corner of the S/SSW side) but cannot say how good it will be for helping cold air disperse.

@ragnaricedaine it doesn't look like a great location as its quite sheltered and boxed in. 

I'd consider where the table is frankly. In the summer the ASHP wont be running, but as you alluded to, its not great to look at. Can I ask, why do you need 2x10kW units? I have a 260m2 house and we just have a 12kw unit. When you come to do the renovations, have you considered insulated plasterboard? It would be a very easy way to lower your heat loss - especially on the ceilings. Why spend your money heating the flat above!!

@batalto - appreciate your candid feedback. Certainly allows for a more informed decision.

Well, the house has 3.6m high ceilings and comprises of a small amount of rather big rooms (so lots of volume). Lath and plaster interior walls with no insulation. Architect not keen to touch walls due to desire to maintain breathability and integrity of the house (as it has stood strong for 130 years in it's current form - insulation on/in internal walls may compromise this). I also have very nice cornicing on the ceiling and quite high windows so plasterboard on walls and ceiling not really an option.

Also agreed that 2 x10kW seems a lot, hence why I have been questioning the MCS calculations done to date. Also as with electricity going up to circa 23/24p per kWh this needs to be reflected in the MCS calculations. 

@ragnaricedaine I've got a heat loss calculator used by MCS installers in my signature. Its from Freedom heat pumps. Feel free to use that, just make a copy, or download and fill it in. Its pretty straightforward.

Honestly though, without insulation its going to be expensive to run.

Hey all - been a while since I posted. My house renovation was delayed due to planning but looks like it may kick off in next few months.

With all the energy pricing activity going on, I am still on the fence with my heating decision. Options are a gas system boiler or ASHP (likely a 12-14 kW). I plan to put in UFH everywhere and have low-temp radiators and insulate where I can regardless. My concerns are on reliability and performance (I know gas systems work). 

Given everything that has gone on recently with pricing and with more to come, would the members here still advocate for an ASHP or would any recommend gas? My gas doubled in price in April so ASHP starts to make a bit more sense (and could be more flexible with day/night tariffs, future solar etc.).

It would be rather brash of me to try recommending anything over a gas system when I have never had mains gas at this property and so have no reference point to compare to. I would certainly recommend the ASHP over the oil system we had since the unregulated oil price fluctuations mean we've certainly saved significantly on our heating bill.

I would, however, go so far as to absolutely advocate the ASHP and solar PV/battery combination. If one can switch to an efficient electricity-based heating system whilst at the same time generating one's own electricity, the odds suddenly stack far more heavily in your favour. I can only guess, but I imagine one could potentially see similar marked savings if one had a gas heating system combined with (for instance) one of the new pyrolitic waste --> gas converters that are being tested at the moment. Either way, it's not so much which energy you pick as the ability to generate your own power in the form the heating system will use.

To put some figures to that, I have (courtesy of a trawl through the forum) got a table of the expected heating demand and solar production broken down by month so can extrapolate the stats I already have. Basically, this year the prediction is that the ASHP will consume 4155 kWh heating the house and water, and that we will end up having generated 5529 kWh from the solar panels. The battery means we've been so far able to maximise the amount of what we generate going towards servicing our own needs, but where we can't match directly we're at least earning from the Octopus agile export tariff. In fairness, I'd put those stats up against any purely consuming heating system.

As for reliability, it's too early to say; one would expect any system that's less than a year old to be glittering reliability-wise. However, whilst you say you know gas systems work, you also know how reliable your 'fridge is and that's exactly the same technology as the ASHP. The stories I'm hearing again and again rather strengthen my basic belief that a heating system's reliability is based on how well it has been designed overall to fit in with a particular family's/property's needs rather than the reliability of any of the constituent parts.

Not sure that precisely answers your question, but I hope I've covered some important related points.