Navitron Renewable Energy and Sustainability Forum

HEAT PUMPS & Geothermal Energy => Heat Pumps => Topic started by: NugentS on June 05, 2019, 06:49:20 PM



Title: AHSP in Old House
Post by: NugentS on June 05, 2019, 06:49:20 PM
Hi all,

Background

My parents live out in the country in an old house (1700's part of it anyway we think).
Its not got cavity walls
Glazing is a mix of double and secondary

Current heating is a mix of Storage Heater and Radiators
Current boiler is a Oil boiler, about 30 years old. There is no Gas available
House has an EPC of F29

Oil use us about 175 litres / month (85.00 pcm) average over the last 74 months or so. Obviously more in Winter and less in summer
Electricity is (from latest bill) 230 pcm (I need to look into what rate they are paying)

I would suggest that energy usage is fairly normal for an older couple with one fairly active
A couple of moderate TV's, Cooker, 1 fridge-freezer, 1 freezer, 1 Washing machine, dishwasher, microwave and a dryer plus other ancillary stuff). The freezer and fridge freezer relatively new and reasonably efficient.
Mother runs a small business arranging and printing chamber music so has a significant computer, a large printer (mostly in standby) and a 24*7 NAS device. Dad also has a small computer which is only turned on for email.
2 Storage Heaters
1 Aircon unit in a bedroom, not used that much since the room was better insulated
House is a large 4 bedroom detached house

They have solar panels - about 2.4kWp which do naff all in Winter due to trees, but the sun clears the trees in the summer so they work then
Radiators are elderly and haven't been flushed since forever - but the heating is reasonably effective but I think relies on the storage heaters to keep the core warm with the rads filling in.

They have dual rate electricity of some kind for the 2 storage heaters

Questions
The boiler is 30 years old, works well but they realise it can't last for ever and are thinking of changing it either for a new oil boiler or a shiny new ASHP (cos its the new, renewable apparently)

According to my reading, ASHP's work best with a well insulated house (F29) and underfloor heating (forget it) or large radiators (would need changing (10-13 of them)) so as a minimum they would need the HP installing and the rads changing.
Can this work in an old, not well insulated house? Or should they forget it and look at a new oil boiler.

One possible supplier turned up, (described by Mother as an "Oily Salesman") had a brief poke around and said 10K for an 8.5kW Monobloc by Mitsubishi. Subject to an actual survey and after a 2K deposit is taken (refundable if you don't go ahead). I am not saying he is wrong as I just don't know but I am betting the survey adds several grand for new rads, a new larger tank and other stuff. Their quote never even mentions RHI

Parents would like to reduce their bills and Dad loves the idea of getting money back of the Government through the RHI. They would also love to get rid of the oil tank

Is this sort of house suitable in general for an ASHP. Can it actually work the way the advertising says or should they just go with a replacement, more efficient oil burner?

Any advice welcome

Regards

Sean


Title: Re: AHSP in Old House
Post by: Westie on June 05, 2019, 08:38:37 PM
Well, start with insulation, as much as you can possibly fit.

ASHP and GSHP produce large volumes of warm water which suits underfloor heating.   The problem with using those technologies in conjunction with a wet , rad based system is that the flow rates are low and your unable to get the rads hot enough.  This is even more of a problem if you have a wet system with the rads plumbed in microbore tubing which was 8 or 10mm diameter - which was the usual solution 30 yrs ago.   This is my problem.  One solution I've contemplated is a gas powered ASHP (Bulk LPG in my case).  This system produces water at around 70C which means the rads will get hot enough.  The product i've looked at is made by a company called Robur, its model no. is K18.  The cost is similar to the Mitsubishi ASHP you mentioned. 



Title: Re: AHSP in Old House
Post by: NugentS on June 05, 2019, 09:18:24 PM
Is this a hybrid?
A combo of ASHP and Gas boiler?

[In this case - gas not available and I don't think they will want to swap an oil tank for a gas tank]

Sean


Title: Re: AHSP in Old House
Post by: A.L. on June 05, 2019, 11:10:00 PM
hello,

According to my reading, ASHP's work best with a well insulated house (F29) and underfloor heating (forget it) or large radiators (would need changing (10-13 of them)) so as a minimum they would need the HP installing and the rads changing.
Can this work in an old, not well insulated house? Or should they forget it and look at a new oil boiler.

Yes it can work, the whole system just has to be designed to meet the heating demand of the house. Current heat input in the coldest months looks like averaging more than 150kWh/day with the worst days at twice that. An 8kW heat pump for 24hrs/day is 192kWh/day, so not big enough. When heat pump output rises above 14kW DNO's usually require you to use 3 phase electricity (s). Loft insulation will be required for RHI payments and should bring heat demand down by 20% if none at present. Mitsubishi do an 11kW ecodan which might just manage. Are the current radiators sized to provide 100% of heating demand, radiators at 40C give out about 1/3rd that of rads at 70C but this can be partly compensated by long (>16hr) runtimes. RHI may assume higher demand temperatures, and thus greater demand than your parents currently use.


Title: Re: AHSP in Old House
Post by: A.L. on June 05, 2019, 11:15:19 PM
hello,

Is this a hybrid?
A combo of ASHP and Gas boiler?

no, this an example of the gas absorption cycle rather than the vapour compression cycle. COPs around 2 wrt to energy in the natural gas used to power it


Title: Re: AHSP in Old House
Post by: rogeriko on June 05, 2019, 11:16:44 PM
An ASHP will not work in your situation, you will be freezing cold in the winter and wishing you had not wasted your money. Buy a new condensing oil boiler and everyone will be happy. The RHI now is not worth bothering with.


Title: Re: AHSP in Old House
Post by: Countrypaul on June 05, 2019, 11:36:27 PM
As has been mentioned recently on another thread, you may also want to look at a hybrid system.   You should be able to get some figures for degree days for the location, then relate than to the proportion of heat required giving a fairly good approximation to the heat load required. This might be easier than trying to have heat load calculation done based on Uvalues for the walls, ceilings, floors etc. and likely to be more accurate.

If you ignore the RHI and the extra restrictions that imposes, you might find that using an ASHP will cover the majority of autumn and spring as well as milder periods during winter. The oil boiler should be able to handle the more severe weather during winter. Having 3 sources of heat (storage heaters) means that even if one such as the ASHP or oil boiler were to fail should mean that the house won't get absolutely freezing but may be colder than prefered until the failure can be remidied. As your parents get older this may be more important.

Around 2000L of oil per year doesn't actually sound that much given the description of the property. Can you tell how much electricity is used for heating presumably E7 or similar, as that might be a significant amount that can also be reduced by using the heat pump.


Title: Re: AHSP in Old House
Post by: todthedog on June 06, 2019, 06:36:39 AM
Rogeriko +1

As much insulation as you can manage. We have a 70's bungalow with modern'ish condensing oil boiler. We went through the same thoughts but decided against, that the cost and disruption, new underfloor or at least oversized rads, and no guarantee of being warm in winter. If it ain't broke don't fix it. From personal experience we swapped an old oil boiler for a modern one and saw our oil consumption half!  Different house some years back.
At one point in time we had an lpg boiler modern supplying rads and hot water pre going green in France, it would have been cheaper burning notes as fuel.

Could they get a grant for new boiler in Wales continual cold calls offering this ?
Like Mart we have a ashp air/air in the lounge kitchen combined with PV which I hope will provide heating for most of the year we don't like hot bedrooms.
Good luck




Title: Re: AHSP in Old House
Post by: brackwell on June 06, 2019, 07:05:04 AM
Rogeriko + 1

There is no chance of RHI as the cost to comply with the qualifications would be huge.

I suspect your parents are of that age where they should be seeking a more modern cosy place nearer to civilisation and support that we need in really old age.  Of course they will not move but for me it highlights all the future problems stacking up.  People need to think about the end game earlier and not leave it till it is to late.


Title: Re: AHSP in Old House
Post by: gnarly on June 06, 2019, 09:02:29 AM
For a hybrid system with an average ASHP (maybe 5-8kW), surely you could still get RHI at a reasonable rate with the existing rads.  For this output power the rads won't need to be oversized and they will still get good SPF as the flow temp won't need to be that hot.

The only cost is an additional heat meter (temperature sensors and flow meter)

Somehow there does need to be a solution for this kind of house - there are plenty of them around!



Title: Re: AHSP in Old House
Post by: brackwell on June 06, 2019, 09:17:11 AM
Sell them to someone who has the money to knock them down and start again.

Everything in life we throw out and replace after a few yrs with more modern up to date tech but when it comes to houses our attitude changes. Remember these houses would be prohibited to be built today.


Title: Re: AHSP in Old House
Post by: NugentS on June 06, 2019, 09:33:24 AM
The move conversation just isn't worth it. They have been in the house for the last 50+ years and have no intention of moving

Sean


Title: Re: AHSP in Old House
Post by: NugentS on June 06, 2019, 09:36:03 AM
The last bill (estimated) was for 3 months
1420 Units of unrestricted
3468 Units of E7

Ouch

Also they appear to be paying 11.94 / 16.97 per unit as they don't know what switching means - needless to say that will be fixed shortly. Just not sure what with.

Sean


Title: Re: AHSP in Old House
Post by: brackwell on June 06, 2019, 11:24:08 AM
Those power consumptions do not look unreasonable but as you say need to shop around for prices.

I would suspect that they may have not have done enough to reduce drafts and air leakage (of hot air).  Visit when it is strong winds and put your hand around windows and doors looking for draughts.  Any unused chimneys need to be blocked up to prevent draughts -this is a huge 24/7 heat loss. How much insulation have they actually got in the loft -thier definition may not be up to date -if non or little they maybe able to get a grant for it.


Title: Re: AHSP in Old House
Post by: GarethC on June 06, 2019, 11:34:00 AM
How about a few air conditioners, supported by existing heating system if really really cold? No RHI, but far cheaper and easier to buy and install, higher COPs, more controllability. Selfish aspect to asking this question as I'm considering doing this.


Title: Re: AHSP in Old House
Post by: todthedog on June 06, 2019, 12:22:12 PM
We installed 3.5 kW Mitsubshi ASHP  COP of 4.26 about 1100 installed.

Should be plenty to warm the lounge /kitchen.


Title: Re: AHSP in Old House
Post by: TT on June 06, 2019, 12:28:32 PM
Whats the house construction?
Single storey, 2 storey,   detached ?
Access to loft space?
Access to void under ground floor?
do they go away for holidays?- My parents had new heating installed 10 years ago, they  seemed to worry about things.....


Title: Re: AHSP in Old House
Post by: NugentS on June 06, 2019, 08:06:28 PM
Well the existing heating system has to change a bit at the very least. The boiler is 30 years old and the rads are likely to need flushing - but that's all quite simple.

I honestly don't see the parenting team being able to adjust to using aircon machines. Whats more is (and maybe someone here can correct me) putting aircon in a bunch of rooms is going to end up more expensive than running an efficient oil boiler

Sean



Title: Re: AHSP in Old House
Post by: NugentS on June 06, 2019, 08:09:24 PM
Those power consumptions do not look unreasonable but as you say need to shop around for prices.

I would suspect that they may have not have done enough to reduce drafts and air leakage (of hot air).  Visit when it is strong winds and put your hand around windows and doors looking for draughts.  Any unused chimneys need to be blocked up to prevent draughts -this is a huge 24/7 heat loss. How much insulation have they actually got in the loft -thier definition may not be up to date -if non or little they maybe able to get a grant for it.

Its not a drafty house.
There are two chimneys, one is used occasionally as a log / coal fire. The other is blocked up.

Loft insulation - they had some put in a while ago (a few years) which apparently helped. But sections of the roof are "difficult" to get into and may not have any. Difficult is an understatement


Title: Re: AHSP in Old House
Post by: ecogeorge on June 06, 2019, 11:05:41 PM

[/quote]

Its not a drafty house.
There are two chimneys, one is used occasionally as a log / coal fire. The other is blocked up.

Loft insulation - they had some put in a while ago (a few years) which apparently helped. But sections of the roof are "difficult" to get into and may not have any. Difficult is an understatement
[/quote]
315 a month on heating ................WTF...........
are the windows missing ?.................
My 3 bed semie 46/mth -log burner and 2kw solar...........(no gas)
Check your energy tarrifs , and INSULATE..............


Title: Re: AHSP in Old House
Post by: todthedog on June 07, 2019, 06:24:41 AM
I'm with George on this one.

The used chimney sealed with log burner and tubed or large hole?

Dodgy roof insulation. Look at possible blown insulation if difficult to reach.

Have you stood near the windows on a windy day?

If they were installed a while back chances are they had old style seals. Ours certainly had, could feel my wig move on a gusty day. I found replacement seals online easily, and simple to take out the old and replace with new. Negligible cost.

Certainly investigate a modern condensing boiler if the old is ancient and non efficient. Flush out the rads and properly balance the system. Check available grants.

A modern aircon system is a remote control set the temperature and switch on and off. 

The forum mantra insulate, insulate, insulate holds true.  Money saving expert MSE have a good comparison site easy to switch and will auto email if cheaper prices found.

A much lower cost option.

Good luck




Title: Re: AHSP in Old House
Post by: brackwell on June 07, 2019, 07:18:40 AM
"occasionally as a log / coal fire."

Unless nearly used continually open fires are a net loss of heat due to the fact that hot air is rising up the chimney 24/7. On a cold winters day if you put your hand just a little way up the chimney when there is not a fire, you will feel the flow of air and this is not helped if the chimney is long and cold (even worse if on a outside wall) ie good conditions as intended for a fire.

Not sure what your parents have against oil other than cost - would they be interested in a wood pellet stove (as well as a new oil boiler)


Title: Re: AHSP in Old House
Post by: Iain on June 07, 2019, 07:53:32 AM
Hi

Quote
.Well the existing heating system has to change a bit at the very least. The boiler is 30 years old and the rads are likely to need flushing - but that's all quite simple

My parents have a boiler installed in 1985 and is still running very well.
One plumber suggested a new boiler would be a lot more efficient so we looked into it.

The problem is that my dad wants the house nice and warm with the radiators "hot" and that means the boiler is kicking out water over 75 degrees, I have tried turning it down but he notices.
I think a lot of the older generation like "hot" radiators and a condensing boiler will struggle whist staying in condensing mode.
All the trv's are set to 6 so don't actually do anything. The system is basically running on the room stat in the hall.
If I turn a TRV down a bit, I get the comment " there is something wrong with the system, that radiator isn't hot."
If a new condensing boiler was fitted the boiler would never run in condensing mode so most of the efficiency benefits of a new boiler would actually be lost.

For a non condensing system the boiler is still quite efficient.
Obviously when the boiler fails it will be changed but depending on temperatures needed might not be as efficient as advertised.

The biggest improvement is insulation, once the heat losses are reduced the boiler could be addressed.

Iain


Title: Re: AHSP in Old House
Post by: kristen on June 07, 2019, 09:10:07 AM
What a fantastic collection of comments, particularly related to "getting ready for being old".

We spent money (in our 50's) so that we were Spending Capital then, whilst earning, so that in our retirement we a) won't need to spend [much] capital and b) running costs will be tiny and c) we will be able to afford to maintain our living standards.

Best solution (but not Eco ...) is knock-down rebuild.  Trouble is you wind up with the same house. Maybe it will be worth 20% more, but cost of knock-down-rebuild isn't 20% ...

So you are left with trying to improve it.  I am of the opinion that is "impossible" for 99% of UK housing stock.  OK ... overstatement ... but it is blinking hard.

The other thing I see people do, repeatedly, is to "improve it a bit". After you've done that half a dozen times, as the price of oil goes up and makes the payback of each change worthwhile, you look back and wish you'd done it once and right-first-time.

Regulations for Insulation have doubled; every decade; for the last 50 years.  So they will double again in the next decade. So at the very least fit twice whatever the regulations currently are. Yup ... doubling-it is a law of diminishing returns, and twice the price (well, maybe not twice the labour/effort). Tough I'm afraid.

Here's my 2p-worth on Insulation.

Yes, insulate-insulate-insulate

But ... once you have done that, you can have comfort. It becomes trivially easy to have the house 1C warmer, and negligible in cost.  Without insulation getting the house 1C warmed is expensive, and you probably have to flog your boiler to death.  As we get older that affordable-comfort becomes more important.

Along with insulation address air-tightness

Its not a drafty house.

I bet it is :) in terms of air-changes-per-hour (i.e. done as a pressurised test). Most UK housing stock is around 10 ach, good housing is down around 5 ach (mine was a 1960 build, concrete raft, first floor is concrete, flat roof was concrete, pitched roof and insulation added on top since, as such it is extremely good and that (after I blocked up the open fire chimney) was 3 ach.  I've since built a Passive House extension and that is 0.3 ach ... and that is night-and-day in terms of energy requirement for heating/cooling (I think it is something like 1 kW to heat a 3 bedroom Passive-house when it is -10C outside). So there, at least, is a target.

Trouble with improving air-tightness is that you also reduce air-flow Natch! and then you get some moulds (not necessarily mushrooms-growing-on-ceiling, but enough to perhaps get more winter infections :( ).  People from earlier generations typically open windows to vent the room - which of course chucks all the heat away (including making any thermal mass radiate its heat away too ...).

If the house has good air tightness you can fit mechanical ventilation (ideally with heat recovery - "MVHR"). Along with wall insulation that too is a nightmare of a retro fit. Hence why I think upgrading existing housing stock is "impossible".

My advice:

Fit max loft insulation. Aim for twice the current Regs. If it is hard-to-do then find a solution (harder / more expense ...)

Have the expectation/aim of improving comfort

Change all open chimneys to stove, and ideally stoves with external air supply (so you do not have to have an always-open air-brick in the room for Regs :( )

Consider having an Air Tightness test done, but if not do the "windy day" test with back of hand, or a smoking joss-stick to see where draughts are. Consider having existing Double Glazing "serviced" (might be all windows out, and reseated), or having replacement windows - in which case triple glazed is a consideration - if you can get the internal pane surface to be no more than 4C colder than room you will not get falling-convection-air, and you won't have that circulation/draught-feeling in the room, and then you can turn the heating down (or just be more comfortable).

Consider the wall insulation. That's also in my "impossible" category. typical best solution is to wrap the outside of the building, which is fine if it is currently rendered, probably a non-starter for a nice brick/stone exterior, and hideously expensive. Internal wall insulation can be done room-by-room (e.g. as you redecorate) but the external walls then no longer contribute to thermal mass of the room.

Putting these things together is why I think retro-improving existing housing stock is neigh-on-impossible.

Yeah, replace the boiler. 30 years old presumably means its on last-legs, and also that a modern replacement would be more efficient ans save money/fuel.  Interesting point about Parents "wanting to feel that the radiators are hot", which might rule out a condensing boiler. My acid test would be "Can I sit in any room in Winter in my shirt sleeves" and also not feel that the air is stuffy.

I think that ASHP is only any good with UFH in a well insulated house (sweeping statement), so I wouldn't got aht route to upgrade existing wet system.


Title: Re: AHSP in Old House
Post by: Philip R on June 07, 2019, 10:19:25 AM
Are the radiators hot because they give off little heat, I.e. Plain old rad panels or are they convector rads blocked up with hair cobwebs and dust. I have many customers complaining of this. If the latter I clean rads with my basil brush down each flute and hoover out. One customer had two rads that filled my henry hoover. Check the rads and maybe fit convectors rads if not already fitted. Then the boiler flow temperatures could be reduced and still get the room warm.

A condensing boiler will be better as the flue gas temperatures will be much reduced from over 200 deg C to say 85 deg c, even if the rads are scolding hot.
Westies advice on the Robur K28 absorbtion heat pump is sound. I do not understand why they are not used more, their COP performance is superp. LPG is dearer than natural gas and oil per gross kwh.

What state is the oil tank in? Plastic tanks don't like sunlight, and shading them breeches regs pn safety clearances to buildings boundaries hedges etc.

If you go for oil condensing boiler, get something decent from the likes of Grant.
Philip R


Title: Re: AHSP in Old House
Post by: GarethC on June 07, 2019, 10:24:52 AM
I really, really, really don't understand the insulate, insulate, insulate mantra. If everyone did that, they'd reduce their emissions and costs a lot, but still be stuck with a fossil fuel boiler for the remaining heat and hot water. But now the financial cost and hassle of replacing that fossil fuel system would be horrendous relative to the financial benefit, so no one would do it and we'd be stuck with that fossil fuel use for ages.

Surely the mantra should be, insulate and draught proof to the extent sensible (so as a minimum, good draught proofing, good loft insulation and a few other cost effective measures), then look at other tech. At that point, installing an ASHP might well be the best option. Will reduce emissions as more insulation would AND reduce hot water emissions, but, unlike with more insulation, would continue to become greener as grid carbon emissions fall, to zero eventually.


Title: Re: AHSP in Old House
Post by: kristen on June 07, 2019, 11:25:22 AM
still be stuck with a fossil fuel boiler for the remaining heat and hot water

I'll have a go ... I'll be interested in other peoples' view too

More insulation / old boiler = now have 50% less, maybe 90% less?, boiler-on-time, with resulting fuel saving, and reduced emissions.

If you reduce your fuel cost simply by replacing knackered, inefficient, old boiler with brand Spanking new one then the payback sums work ... but you still have the same draughty, inefficient, house and you may not be able to easily achieve "comfortable" (depending on the output of Rads being able to combat Draughts). You are still losing/leaking just as much heat as you did before and thus there is NO saving there (although your new boiler might be able to make that heat more cheaply than your old boiler could)

If you insulate and reduce the need-for-heat you need less, and your existing knackered boiler will do, and you can be more comfortable (much easier to achieve +1C if that is what you want). You might still choose to change your boiler of course - more savings and less emissions because new-boiler is more efficient.

Quote
Surely the mantra should be, insulate and draught proof to the extent sensible (so as a minimum, good draught proofing, good loft insulation and a few other cost effective measures), then look at other tech

The problem I perceive with this is that is what people have done, and then repeated 10 years later as the economics of "yet more insulation / higher price of oil" make it affordable.  Overall they would have been better off to have done it once, right-first-time. Plus all they have achieved is some fuel-cost saving, but no extra comfort. Its still a draughty, inefficient [to heat] house.

Quote
. At that point, installing an ASHP might well be the best option. Will reduce emissions as more insulation would AND reduce hot water emissions, but, unlike with more insulation, would continue to become greener as grid carbon emissions fall, to zero eventually.

My view on this is that the ASHP output (I am assuming a greatly lower temperature than your current boiler) is not going to heat your house at all UNTIL it is way better insulated (and it probably needs to be more airtight too) so that the heat requirement is drastically less, and then can be easily satisfied by a "relatively low temperature" heat source - such as ASHP + UFH.

You could fit larger rads, but if you fall short on Comfort you will not be able to just "turn it up" to get Comfort.

If you Insulate then a (relatively) tiny heat source will do.  And that heat source will be capable of outputting more - if we get a week of -10C at night then just run it 24 / 7, whereas in conventional draughty house your leakage / heat loss to -10C outside will feel cold until the weather improves.

In mid Winter if I go away for 24 hours and turn everything off (including heating) then the house will lose 1C in 24 hours. If the heating was bust I could get it back up again by inviting a dozen friends around for a party ... In the 2017/18 winter we had a cold snap for a week and I kept meaning to increase the hours the UFH was on to compensate. I never got around to it, and when I checked the logged data the lowest overnight room temperature was 0.5C lower than "normal winter night low".


Title: Re: AHSP in Old House
Post by: GarethC on June 07, 2019, 12:00:17 PM
All good points thanks kristen.

I don't understand the suggestion that an ASHP can't heat a draughty, badly insulated house just as well as anything else can. If it can't, it just means that the pump or emitters are undersized.

The only problem I can see is that necessary radiators can become unfeasibly large, and there is perhaps even a limit to UFH heat transference. Which might be a fair point. It's why I would choose a low wall fan coil based emitter instead as a much better way to transmit heat, while also being cheaper and easier to install than other options.

Full disclosure I'm nothing but an 'Internet expert' here...


Title: Re: AHSP in Old House
Post by: kristen on June 07, 2019, 01:09:33 PM
I don't understand the suggestion that an ASHP can't heat a draughty, badly insulated house just as well as anything else can. If it can't, it just means that the pump or emitters are undersized.

Undersized = yes.

Very broad brush numbers here, just to illustrate the point - Someone else will be able to give you some better / realistic numbers.

ASHP (or ground source) produces water at, say, 40C. Boiler produces water at say 70C. So you need, say, 2x as much to get the same heat.  (By the by, you still have to solve getting DHW up to 60C if you have ASHP, that issue is avoided by using a Boiler. ASHP won't give you a COP of 4 making 60C DHW :( )

If your existing pipes are narrow bore that's a problem - bigger pump is fine, but you won't realistically be able to get enough/fast enough around the system ... I suppose the heat losses (from boiler to rads) may also be a problem.  Start at 70C arrive at 65C is one thing, start at 40C arrive at 36C is another ...

Your radiators need to be, say, 2x the surface area. That's fine, but IME the lady of the household will complain about wall space consumption competing / interfering with furnishings :) In that regard UFH is fantastic - NO wall space intrusion at all (plus having the heat low down is more comfortable than Rads which inherently cause convection air currents ... and draughts (within the room, even if not external) which still have the effect of making you feel cold.

And you have the cost of replacing all the Rads with bigger ones (which a new, high temperature, boiler avoids). That said you might choose to replace old fashioned panel radiators with newer convector rads, so maybe you are going to incur that replacement cost anyway.

Your whole pipework might be shot and due for renewal ... rather than just needing flushing through. Huge expense, but becomes an unavoidable change at that point ... and at THAT point you might consider UFH replacement rather than "pipes and rads like last time"

In a well insulated house, with good thermal mass, you have the "balance" of that. You can produce less heat, over longer, to get the same result because the insulated thermal mass buffers it. But in a draughty / inefficient / poorly insulated house you must combat the heat loss in real time, and you may not be able to achieve that [with a lower temperature heating media]


Title: Re: AHSP in Old House
Post by: kristen on June 07, 2019, 01:17:19 PM
the insulated thermal mass buffers [the heat]

meant to say: In our house we run the UFH for about 12 hours a day in winter.  The temperature of the UFH is only a few degrees above ambient, so the amount of heat is small, but running it for long periods delivers the heat at the rate that the building needs it.  Thermostat is useless (in my case).  The temperature in the room doesn't vary by more than about 0.5C, and if I had a thermostat which turned the UFH off when it went 1C over the inherent stored heat already pumped into the the floor, by then, would carry on radiating for hours and raise the temperature of the room by several degrees more ... and by the time the room cooled back to 1C below threshold it would be hours before the UFH could bring it back up to ideal temperature again ...

So very different way of "managing heat" in a very well insulated house.  I don't really need to do anything at all (even in prolonged extreme winter cold), but if I did it would be either pump-more-hours when the weather is cold, or increase-water-temperature-by-1C.


Title: Re: AHSP in Old House
Post by: Warble on June 07, 2019, 02:17:45 PM
"SmartRad"s are an alternative to UFH at lower water temperatures.


Title: Re: AHSP in Old House
Post by: TT on June 07, 2019, 02:38:03 PM
what about updating insulation, improving window  and door draught proofing
going all electric, less hassle to install, easy to operate, supplement with more PV  to offset costs.
PV with diverter for immersion for heating hot water, ditch oil, tank etc
depend is the folks can deal with the hassle with all this, some people cope better than others with having carpets lifted, floorboards up, trades, in, disruption etc.


Title: Re: AHSP in Old House
Post by: NugentS on June 07, 2019, 10:42:45 PM
Thank you to all who commented.
The project has been shelved. Parents are not going to live long enough for this sort of work to be worth doing (their words)

We had several companies turn up and look around. Some of which just wanted to sell an ASHP with no consideration as to whether it would work well or not. Our last visitor was brutally honest about everything and came across extremely well, knowledgeable and skilled and her advice matched what people from this forum were saying and my own inexpert opinion - that it just wasn't gonna work - not without spending a bucket load of money on insulation and other stuff as well.

Regards

Sean



Title: Re: AHSP in Old House
Post by: gnarly on June 09, 2019, 08:32:06 AM
Really interesting thread, thanks for asking NugentS !

I came across this Radio 4 'Costing the earth' podcast about gas boilers - there's a bit on hybrid heat pump / boilers starting at 17:00 in

https://www.bbc.co.uk/programmes/m0003qy0



Title: Re: AHSP in Old House
Post by: Home Farm on July 19, 2019, 07:50:05 AM
A well insulated house is key to the efficiency of ASHPs. If your house leaks heat, ASHPs, from our initial experience, will not be effective. We installed our ASHP in a farm house built in the 1800s, but we have double glazing throughout and heavy wall insulation. So far, the pump has been very effective.


Title: Re: AHSP in Old House
Post by: Home Farm on July 19, 2019, 03:21:51 PM
Further to my previous, for those that are interested, you can see an overview of our air source heat pump, which will helpfully answer questions:

 https:// youtu.be/P2tnW4rZl68

More info is available here: http://myhomefarm.co.uk/moving-from-oil-to-air-source-central-heating


Title: Re: AHSP in Old House
Post by: gnarly on July 19, 2019, 06:12:10 PM
Home farm: YouTube links should have a space inserted in the URL otherwise  a quirk of the bulletin board software means it disappears !  Looking forward to watching it !!!


Title: Re: AHSP in Old House
Post by: Home Farm on July 19, 2019, 09:29:18 PM
Thanks gnarly. Not really sure if I understand what you meant. Should it be http:// space then link? Ie. Http:// YouTubelink.



Title: Re: AHSP in Old House
Post by: GarethC on July 22, 2019, 09:49:44 AM
"SmartRad"s are an alternative to UFH at lower water temperatures.

I take it you mean essentially radiators with fan coils, and decent control systems? This appears the logical answer. UFH is expensive and disruptive to install. Conventional radiators need to be unfeasibly large to operate at low enough temps (high enough COPs) - often it's not doubling, but quadrupling the size, or more, of current rads to get sufficient heat transfer.

Smart rads should provide much higher heat transfer in compact sizes. I'd like to look into these. Can anyone suggest suppliers?

The ability to simply swap existing 'dumb' radiators for these when installing a heat pump should save cost, time and hassle. Is it doable? If you use existing pipework, though, can pipes always circulate the low temperature (say 45 degrees) water fast enough to deliver sufficient heat? That's the main issue I can think of.


Title: Re: AHSP in Old House
Post by: JonG on July 22, 2019, 03:13:40 PM
Smith's ecovectors and Jaga DBE's are most common I would say, but they are costly, can get noisy as they age and dust is sometimes an issue depending on dwelling cleanliness!


Title: Re: AHSP in Old House
Post by: GarethC on July 23, 2019, 08:38:13 AM
Thanks Jon. Also found dimplex units. Surely not expensive compared to installing UFH?

What about pipework? Think existing stuff will tend to do?


Title: Re: AHSP in Old House
Post by: Countrypaul on July 23, 2019, 09:31:25 AM
If you central heating radiators work on normal 22/15mm pipe there is a chance that will suffice, if they are plumbed in microbore 8/10mm you could be dissapointed as the flow rate with the much lower tempreture water needs to be much higher to get the same amount of heat out the radiators.


Title: Re: AHSP in Old House
Post by: GarethC on July 23, 2019, 02:12:58 PM
Yes, do heat pumps even 'accept' microbore I wonder? I think the flow rate would have to be several times that used with a conventional boiler.

I suppose another positive, if existing pipes do work, is that only a fraction as much heat is wasted/lost 'en route' from the pump given the lower flow temp compared to conventional boilers (perhaps three quarters less?).


Title: Re: AHSP in Old House
Post by: Countrypaul on July 23, 2019, 02:46:12 PM
But assuming it is all within the thermal envelope, then it is all useful heat. If the pipes go outside the thermal envelope then the heat will be presumably completely wasted.