What would you do if you could start your ASHP process again?

[Bovril]

Hi all

 

Just to introduce myself here (after being a long-time lurker), after a couple of awful years (wife was diagnosed with the big C) and living with the in-laws, we're now thankfully in a position to take (baby) steps back to living more independently. 

 

We're in the end-stages of buying a victorian mid-terrace house in the north-east. There are many renovations we need to do but one priority is what we do about heating. The property is currently serviced by a back-boiler. I am giving serious consideration to replacing the system with an ASHP given that we are starting with, essentially, a blank canvas.

 

Do you think it is possible to utilise an ASHP and have a reliably warm house, especially in the north-east?

 

Using your learning and experience, what would you say would be the steps involved in getting a system that is both effective and reliable? 

 

The. big issues I see (but please, please, please add to them if you think necessary) are:

 

1. Insulation. We are mid-terrace. Have no issue hacking back plaster and putting in insulated plasterboard (what thickness would you recommend?). Head height is good so no issues putting down 4 or 6 inches of kingspan floor insulation. What insulation is needed between floors? Anything special? What about air ventilation and what do we need to do to avoid mould/damp patches?

2. Output. Thinking UFH for the downstairs and then radiators for the 3 bedrooms. What about the upstairs bathroom? Would you UFH that or just radiator? What do you use for showers? Electric showers, or hot water cylinder?

3. House (when finished) will be about 1000 sq feet with a roof conversion. What size ASHP is needed? I don't mind paying extra to get something oversized if it means more reliability / less stress on the system. What brands and models would you recommend?

4. Windows - what windows (is double glazed upvc OK?) and what insulation around windows is recommended? Doors - planning to get Solidoor composite door.

 

The property's EPC doesn't make any recommendations on cavity wall or roof insulation (both were satisfactory) so I think we're eligible for the government grant.

 

The final (big) question is how do I locate a competent specialist to install in the north-east? I've called a couple of businesses checkatrade says are ASHP specialists but they both are clearly conventional plumbers who are are just starting out with ASHPs. Neither of them seemed to think re-insulating the house was a good idea which was a little worrying to me.

 

The key drivers for us are warm and reliable heating - once we move in I'd like to be able to largely set and forget as we try and build our lives again. The driver isn't so much the cost.

 

Be grateful for any thoughts or even an action plan of the order of things we need to consider.

 

Thanks

[SteamyTea]

Welcome.

 

2 things first.

Wait until you own it.

Then sketch up the place and take daily meter readings for gas and electricity.

 

Then we can all chip in with conflicting advice and ideas.

 

 

[Bovril]

Thanks Steamy Tea. The house isn't capable of habitation on day 1 of completion so it'll be a full renovation from day 1. (We won't be living in there until all the works are done).

[JamesPa]

I think @SteamyTeais basically right but, if you post the epc (feel free to redact the address and other details you dont want to disclose), that will give us some info to make some general comments on.

 

Edited April 3, 2023 by JamesPa

[SteamyTea]

Right.  Then just some accurate sketches.

From them, heat losses can be calculated.

 

Houses are basic things really.  Insulated and airtight boxes, then control the ventilation and thermal inputs.

I have had 5 terraced places, two which are end terraces.  Was not until I moved to this place that I took much notice of energy usage, though I did appreciate the advantages of a better built place.

 

But all that can wait until you own it.  But in the meantime, read up about the physics of buildings on here, there is a lot of stuff.

[Bovril]

Thanks James. I'm not sure how to get a PDF of the EPC, but below is a copy and paste of most of it:

 

Energy Rating D

 

Property type

Mid-terrace house

Total floor area

85 square metres

Breakdown of property’s energy performance

This section shows the energy performance for features of this property. The assessment does not consider the condition of a feature and how well it is working.

Each feature is assessed as one of the following:

• very good (most efficient)
• good
• average
• poor
• very poor (least efficient)

When the description says “assumed”, it means that the feature could not be inspected and an assumption has been made based on the property’s age and type.

Feature	Description	Rating
Wall	Cavity wall, filled cavity	Average
Roof	Pitched, 250 mm loft insulation	Good
Window	Fully double glazed	Average
Main heating	Boiler and radiators, mains gas	Good
Main heating control	Programmer, TRVs and bypass	Average
Hot water	From main system, no cylinder thermostat	Poor
Lighting	Low energy lighting in 86% of fixed outlets	Very good
Floor	Suspended, no insulation (assumed)	N/A
Secondary heating	Room heaters, mains gas	N/A

Primary energy use

The primary energy use for this property per year is 267 kilowatt hours per square metre (kWh/m2).

 

Environmental impact of this property

This property’s current environmental impact rating is D. It has the potential to be B.

Properties get a rating from A (best) to G (worst) on how much carbon dioxide (CO2) they produce each year. CO2 harms the environment.

An average household produces

6 tonnes of CO2

This property produces

4.0 tonnes of CO2

This property’s potential production

1.4 tonnes of CO2

You could improve this property’s CO2 emissions by making the suggested changes. This will help to protect the environment.

Environmental impact ratings are based on assumptions about average occupancy and energy use. They may not reflect how energy is consumed by the people living at the property.

 

Improve this property’s energy rating

Do I need to follow these steps in order?

 

 

---

Step 1: Floor insulation (suspended floor)

Typical installation cost

£800 - £1,200

Typical yearly saving

£111

Potential rating after completing step 1

65 | D65 D

Step 2: Hot water cylinder thermostat

Typical installation cost

£200 - £400

Typical yearly saving

£71

Potential rating after completing steps 1 and 2

66 | D66 D

Step 3: Heating controls (room thermostat)

Typical installation cost

£350 - £450

Typical yearly saving

£122

Potential rating after completing steps 1 to 3

68 | D68 D

Step 4: Replace boiler with new condensing boiler

Typical installation cost

£2,200 - £3,000

Typical yearly saving

£360

Potential rating after completing steps 1 to 4

74 | C74 C

Step 5: Solar water heating

Typical installation cost

£4,000 - £6,000

Typical yearly saving

£99

Potential rating after completing steps 1 to 5

76 | C76 C

Step 6: Solar photovoltaic panels, 2.5 kWp

Typical installation cost

£3,500 - £5,500

Typical yearly saving

£629

Potential rating after completing steps 1 to 6

86 | B86 B

 

 

Estimated energy use and potential savings

Based on average energy costs when this EPC was created:

Estimated yearly energy cost for this property

£1983

Potential saving if you complete every step in order

£763

The estimated cost shows how much the average household would spend in this property for heating, lighting and hot water. It is not based on how energy is used by the people living at the property.

Heating use in this property

Heating a property usually makes up the majority of energy costs.

Estimated energy used to heat this property

Type of heating	Estimated energy used
Space heating	6615 kWh per year
Water heating	3518 kWh per year

Potential energy savings by installing insulation

The assessor did not find any opportunities to save energy by installing insulation in this property.

[Bovril]

Just to add, it is currently a 2 bed property but as part of the works we will be putting in a roof conversion. We will be in control of that and so will specify the highest levels of insulation available.

[Bovril]

8 minutes ago, SteamyTea said:

Right.  Then just some accurate sketches.

From them, heat losses can be calculated.

 

Houses are basic things really.  Insulated and airtight boxes, then control the ventilation and thermal inputs.

I have had 5 terraced places, two which are end terraces.  Was not until I moved to this place that I took much notice of energy usage, though I did appreciate the advantages of a better built place.

 

But all that can wait until you own it.  But in the meantime, read up about the physics of buildings on here, there is a lot of stuff.

 

Really appreciate this, thank you.

 

By sketches do you mean floorplans? Thanks again for the input.

[SteamyTea]

1 minute ago, Bovril said:

By sketches do you mean floorplans? Thanks again for the input.

Floors, walls, ceilings, rooms, roofs.

 

With UFH, power delivery is a function of surface area and temperature.

Eternal walls the heat losses are a function of area and temperature difference, same with windows and doors.

Ceilings and roofs are a little difference a it depends on construction.  But basically the same.

Some rooms may be at a lower temperature than others, hence knowing the physical sizes helps with the heat emitter sizing.

 

If the roof is suitable i.e. facing the right way, then PV is worth considering, especially if it needs reroofing.  Put in PV modules rather than slates/tiles.

[JamesPa]

Again I agree with @SteamyTea 

 

Having said that the EPC is not so bad as it stands!  You have insulated cavity walls, 250mm loft insulation and double glazing.  And of course, because its a terrace, two walls have approx zero loss.  7MWh/year space heating is quite low in absolute terms, albeit quite high in relation to floor area.  Probably means you need max 8kW ASHP, possibly less.  Its at least possible that a lot of this insulation was put in after the current CH system, so your many of your radiators may even be large enough, but without doing the calcs we cant tell.

 

So it really depends on how far you want to go and what sort of approach you want to take.

 

I think I would probably start the approach like this:

 

New build additions - as good as you can make them

 

Additional wall insulation (to existing) - unless all the plaster/skirting is coming off anyway possibly not worthwhile if you genuinely have insulated cavities (I didnt think Victorian houses were built with cavities but apparently Im wrong).  It would be good to know the actual wall construction - is there somewhere that the cavity can be exposed?

 

Floor insulation - if the floors are coming up anyway or you are going for UFH then definitely do it, else only a maybe if you really want the absolute best.  But consider also ventilation

 

Windows - perhaps consider replacing them with more modern units, they will have better u values (I replaced my panes only and it made a noticeable difference!)

 

Ventilation - if mould is already a problem then you definitely need more.  If you insulate the floors or block up vents then you will probably need more.  The fundamental problem is that old houses were designed to be leaky and modern innovations seal the leaks.  You ideally want whole house MVHR  but this may be too much hassle/not practical, in which case consider localised 'dMVHR' - distributed MVHR.  Basically fans with heat exchangers which can be fitted in individual rooms or in pairs.

 

Solar PV - as @SteamyTea says.  Wouldn't bother with solar water heating, just max out on the PV.  E/W facing also works.

 

Heating (DHW/Space) - Most of the recommendations in the EPC amount to 'swap out the heating system', so it sounds like its old.  A well designed ASHP system should be capable of doing this quite easily.  Is there an obvious location for the outdoor unit?

 

If you are doing a complete strip out anyway Id go for UFH (I don't have it, and I'm envious of those who do).  If you are not doing a complete strip out and most of your existing rads are large enough for 45C or less flow temp (they might be - see above) then consider retaining them.  If most arent large enough and you arent doing a complete strip out anyway then the cheapest route will probably be to replace rads with larger, but UFH will ultimately be more satisfactory.

 

I would be tempted to ask several of the ASHP brigade round to quote just to see what they say.  Its their time not yours!  Unless you are happy doing heat loss calcs yourself (they are actually very easy if you know the construction) I would also consider paying pay one to do a full survey (will cost about £300), unless your architect, if you have one, can recommend someone to do the calcs or is doing that as part of the job.  Don't believe the sales pitch that the survey is transferable - it isn't in practice, so just regard it as the price for getting some information.  The BUS wont actually save you any money, because the MCS brigade just up the price by the same amount (or more).  But it may be what is needed to get them involved, unless local plumbers will do it.

 

That's my starter for 10, but the process is iterative, some decisions need to be made before others can be easily finalised.

 

 

 

Edited April 3, 2023 by JamesPa

[SteamyTea]

12 minutes ago, JamesPa said:

I replaced my panes only and it made a noticeable difference

I did the same 17 years ago. Went from 4-8-4 (mm) to 4-16-4 (mm). Just had to make a new bit of trim.

Some have now blown so will replace them in due course. No hurry as I don't sit looking out the windows. Shall do it next time I paint the frames. A quick job now I have my own scaffold tower.

[nod]

Just to add that the EPC is a really tough guide 

Most will do the whole street the same rating 

We’ve a chap that does the EPC for our rentals and he charges £38 per property 

He normally gets between 5-10 done pare day Then types them up at home 

[ReedRichards]

16 hours ago, Bovril said:

Do you think it is possible to utilise an ASHP and have a reliably warm house, especially in the north-east?

Without a doubt it is possible.  If your house is badly insulated it will be expensive to heat whatever heat source you use.  With either a low temperature gas boiler or an ASHP you would need radiators with a large surface area, increasingly large as the rate of heat loss from your house is increasingly large.  At today's prices an ASHP achieving a SCOP of 3 (which it should) would have about the same running costs as a gas boiler.

 

My heat pump installer is based in Blythe, is that north-east enough for you?  He installed my heat pump in December 2020, seemed to know what he was doing then and has over 2 years more experience now.  Or you could try one of the installers that have paid HeatGeek for some sort of certification/verification https://www.heatgeek.com/find-a-heat-geek/ (althoug personally I think HeatGeek tends to be a bit OTT, you might not get the set-and-forget that you want).

 

You need to be careful mixing UFH and radiators.  UFH can typically be run at a lower water temperature than radiators need but responds much more slowly.  Get the control wrong and you lose any economic benefits that UFH might bring you (because you have to make the flow water hot enough to satisfy the requirements of the radiators).  

[JohnMo]

A well installed and designed heat pump system should cost less to run than gas.

 

If you go heat pump route find the CoP tables for your chosen heat pump, you will see the dramatic effect flow temp has on running costs.  For our heat pump at -2 deg, I get the following 

 

A flow temp of 30 will give a CoP of 3.6, while at 45 deg, you get a CoP of 2.6.

 

So if you used a 100 units of heat, your energy usage would be either 27kWh for the low flow temp or 38kWh for the higher temperature. An increase of around 30% in running costs.

 

So do what is required to have low flow temps, huge radiators and / or well insulated floor with UFH. Run the system on Weather compensation long and low.

[Dave Jones]

your end goal needs to be an airtight, highly insulated box containing all your rooms ventilated by an mvhr system.

 

Aim to meet new build U values for insulation as the refurb ones are crap.

 

 

[sharpener]

2 hours ago, JohnMo said:

A well installed and designed heat pump system should cost less to run than gas.

 

If you go heat pump route find the CoP tables for your chosen heat pump, you will see the dramatic effect flow temp has on running costs.  For our heat pump at -2 deg, I get the following 

 

A flow temp of 30 will give a CoP of 3.6, while at 45 deg, you get a CoP of 2.6.

 

 

 

I am struggling with the running cost comparison at the moment.

 

Our oil costs 66p/litre plus VAT which is around 8.5 p/kWh. So even with a CoP of 3.6 the HP would need an average electricity price of 30p/unit to break even. On E7 we pay 15 and 45p/unit and there is quite a lot of surplus PV as well, however we will also need to run at a higher temp some of the time for water heating and rads so it doesn't look promising. (We already have MVHR upstairs and there is not much more scope for insulation.)

 

PS I am surprised the OP has cavity walls in Victorian terrace, they are common enough where we live but AFAIK all have solid walls. However one  advantage of a terraced house can be that "central heating" means you are central and they provide the heating.

[JamesPa]

1 hour ago, sharpener said:

am struggling with the running cost comparison at the moment.

 

Our oil costs 66p/litre plus VAT which is around 8.5 p/kWh. So even with a CoP of 3.6 the HP would need an average electricity price of 30p/unit to break even. On E7 we pay 15 and 45p/unit and there is quite a lot of surplus PV as well, however we will also need to run at a higher temp some of the time for water heating and rads so it doesn't look promising. (We already have MVHR upstairs and there is not much more scope for insulation.)

Oil prices are currently quite low (it is currently and, unusually, cheaper to heat with oil than with gas) and electricity prices at an all time high, so at present that's hardly surprising.  However oil is most likely going up and electricity  certainly coming down, so the balance is more or less certain to change.

 

The reality of life is that the prices of all three fluctuate a lot, are manipulated by governments, not necessarily logically and are therefore at least in part artificial.  Electricity is almost completely devoid of logic - the price is tied to gas prices for historic and now largely irrelevant reasons, but much of the production is very cheap renewables.  This being the case the only absolute guaranteed cost comparison is that a heat pump will be cheaper than another form of electric heating.   

 

My personal take therefore on the running cost comparison is that a heat pump (with my 45C design flow temp) will be around the same as gas at current prices.  Very probably it will be cheaper in the long term, once electricity prices are more closely tied to the actual cost of production, and the fact that can power a HP with solar PV in the shoulder season also helps.  For me this is good enough.   I'm not fitting one because it saves money, Im fitting one because I have an aging gas boiler which needs replacing anyway, its the right choice socially and environmentally, and it is (to the best approximation reasonably possible) no more expensive to run.  As a bonus the 'slow and low' approach to heating is actually more comfortable to live in (I grant that can also be done with gas/oil, however the cost equation tips a bit more towards HP if slow and low is your chosen approach)

 

The only way absolutely to guarantee that you always have the cheapest heating is to have the ability to burn oil, gas, wood and electricity (the latter with a heat pump of course).  

 

 

 

 

Edited April 4, 2023 by JamesPa

[sharpener]

1 hour ago, JamesPa said:

Oil prices are currently quite low (it is currently and, unusually, cheaper to heat with oil than with gas) and electricity prices at an all time high, so at present that's hardly surprising.  However oil is most likely going up and electricity  certainly coming down, so the balance is more or less certain to change...

 

Very probably it will be cheaper in the long term, once electricity prices are more closely tied to the actual cost of production, and the fact that can power a HP with solar PV in the shoulder season also helps.  For me this is good enough.   I'm not fitting one because it saves money, Im fitting one because I have an aging gas boiler which needs replacing anyway...

 

The only way absolutely to guarantee that you always have the cheapest heating is to have the ability to burn oil, gas, wood and electricity (the latter with a heat pump of course).  

 

 

Yes to all of that. The oil boiler installed by our predecessors is now 28 years old and Kidd have gone out of business so I want to replace it at a time of my own choosing i.e. this summer not Christmas Eve.

 

No mains gas here but you will doubtless understand why I also do not want to dispense with the Aga and WB stove. However the MCS rules only allow account to be taken if they can be "fully and correctly integrated into a single control system" (which I cannot achieve with any known HA product) hence leading to MCS over-specifying the HP.

[JohnMo]

17 minutes ago, sharpener said:

MCS over-specifying the HP

Don't go MCS route, do it yourself. Or specify and get electrician to hook up and plumber to plumb.

[Luke1]

1 hour ago, sharpener said:

 

Yes to all of that. The oil boiler installed by our predecessors is now 28 years old and Kidd have gone out of business so I want to replace it at a time of my own choosing i.e. this summer not Christmas Eve.

 

No mains gas here but you will doubtless understand why I also do not want to dispense with the Aga and WB stove. However the MCS rules only allow account to be taken if they can be "fully and correctly integrated into a single control system" (which I cannot achieve with any known HA product) hence leading to MCS over-specifying the HP.

 

Are you saying there are no HP systems that can intergrate a WB or Aga into the control system? 

[sharpener]

2 hours ago, JohnMo said:

Don't go MCS route, do it yourself. Or specify and get electrician to hook up and plumber to plumb.

 

That's always been the idea. Actually since I can do my own plumbing and wiring I intend to do most of it myself under a Building Notice, with the possible exception of G3 and F-Gas work (if any). @JamesPa has a cautionary tale regarding the planning implications of DIY though

 

1 hour ago, Luke1 said:

 

Are you saying there are no HP systems that can intergrate a WB or Aga into the control system? 

 

My reading is that the "single control system" would have to control the Aga and WB, which although techically possible would require remotely-operated air/fuel controls on both appliances. There is a Toby controller made for the Aga but it is a bang-bang servo and not well regarded amongst Aga owners; there was a better one, now discontinued. I haven't looked into the WB but it would need to be wireless in addition, as it is at the other end of the house. Both are IMO a complication too far even if there were an MCS contractor willing to integrate them.

[Radian]

On 03/04/2023 at 15:30, Bovril said:

Head height is good so no issues putting down 4 or 6 inches of kingspan floor insulation.

If you go to all the trouble, a minimum of 150mm would be advisable. However, while the ceilings may be a long way up, what about the door heads? To raise the floor level almost certainly means raising the door lintels and this is a bit more involved for supporting walls.

An alternative method that works very well is to lift the floorboards and suspend insulation between the joists (a membrane can be draped over the joists to serve as a 'hammock' for the insulation).