Heating system for new build

lnos1

Hi,

I am hoping to get some advice about heating system for a new build. I have just got planning and I am considering having a cavity of 300mm with pumped bead insulation. As far as my understanding goes, it'll bring our U value down to about 0.12. The windows will have a U value of about 1.3. We'll also have a Heat Recovery System. I'll have a pre-cast first floor.
I have been considering putting in underfloor heating on the ground floor, using an air-to-water system to heat it. However, I would like radiators upstairs.
One of the rooms will have a stove in it, and the kitchen will have a range.
Does anyone know how long it takes to heat radiators using a stove (solid fuel)? Or would it be wiser to have an oil range that will heat radiators upstairs?
Any advice would be greatly appreciated.

Thanks,
Lar

sinnerboy

Before you go any further you need to check your design by having it assesed using the DEAP software.

This is the same software used by BER assessors to issue BER certs BUT it is ALSO the software used to check compliance with building regulations.

Don't underestimate how difficult this is. Find and pay for a good BER assessor i.e. one who was designing building long before the BER system . Ask for the DEAP assessment with a report ( not just the generic one generated by the software ) to inform your specification options for

1. U Values for floors/walls/roofs
2. U Value for glazing - to clearly show the impact of double vs triple glazing
3. Air Tightness - and how varying levels will impact regulation compliance
4. Ventilation - to clearly show impact of open fires vs room sealed appliances together with impact of natural ventilation vs heat recovery ventilation
5. Renewables - heat pump/solar panels/bio fuels ? What are the options?
6. heating system - heat pump/fossil fuel boiler ? What are the options?

Do not select your guy/girl on price alone . Pay €400/500 for a real service to point you towards the best house possible

fclauson

lnos1 wrote: »

Hi,
... I am considering having a cavity of 300mm with pumped bead insulation. As far as my understanding goes, it'll bring our U value down to about 0.12. The windows will have a U value of about 1.3. ...

with 300mm of insulation you will need very very little heating - so as well as a BER assesment I would suggest getting a PHPP passive house calculaiton done. You might never light the stove - and the range may burn away generating too much heat

On the windows with 1.3 U be wary of checking the FRSI calculaiton - this is where the surface of the window or frame may fall below the dew point in the house and attract condensaiton - with walls as well insulated as you have this problem gets exacerbated

JD6910

i have a similar query in the "heating and plumbing section". Would love for ye guys to give me ye're opinion. cheers.

engineermike

Hi,
I would always try and avoid having a heat pump with a solid fuel - back boiler, the solid fuel is an 'uncontrollable' heat source and there is a risk of damage to the pump. You can design a system to function properly together but its messy.

My 2 cents would be a heat pump with solar panels / evacuated tubes tied in - lowering your bills and the requirement for the pump to be in operation.
Correctly matched to the no. of hot water users in the property and U/F on ground floor and low temp. - high efficiency rads upstairs.
On the stove choice, just go for a room heating stove - giving you a feature, effective to heat the room.
The price of solar has come down markedly recently and its making perfect sense in the high cost fossil fuel environment today.
Solid fuel & oil - 1kw of fuel = 1 kw of heat
Heat pump - 1 kw of fuel = 3 or 4 kw of heat and hot water into the house
Solar - a couple of Kwh per year to run the circulating pump on the energy loop = a 3 sq metre system can provide some where in the region of 2000 Kwh of energy into your home annually( depending on where you are in the country / annual solar irradiation figures ).
mike f

fclauson

from a return of investment point of view I would drop the solar panels - they never pay for themselves and use PV insetad $ for $ they are better value

sinnerboy

To the OP I have to say again - you need a DEAP analysis before you can take on board so much of the technical input offered here.

Don't "fix" on anything yet but try to locate the type of person I mentioned who can intelligently mix together all the elements.

Having said that I think you are starting out with over-providing with the wall ( 300 cavity ) and under- providing with the windows spec. But my main point is - obtain the completed software analysis to SHOW you this.

kboc

as previously said you need a PHPP anal.

From my own personal exp, a (good) heat pump will do the job. With an excellent plumber who will look after your hot tank you wont need Solar Panels either as the heat pump will look after that also. I get 500 litres of hot water (to 45 deg) every day at a cost of 24p. (the hp use 3 units of elec for 1 hour at 8p/unit).

it can become quite complicated with some plumbers (hp ,solar panels, etc., etc.) if you do your PHPP and get your data, you can exactly size your hp. If the house is airtight and well insul etc., a 5kw hp will more than do the job, which will use on average, 1.5 units of elec/hr. cheap heat.

good luck

lnos1

Thanks everyone for your replies.
What does PV mean?
Who would do a DEAP analysis? The same people who do BER certs? If the DEAP analysis is done, would that tell you how much heat you require to heat the house and then advise on what heating system to use?
The U value for windows is so high as they are slide/sash windows and is hard to get lower U values on them. Casement windows do give a lot lower U values but we have to use sliding sash. I thought if the wall cavity is well insulated, it would compensate for the poorer U-values with the windows. Do you think condensation would gather on the inside of the window? That would be serious if that happened. Would the heat recovery system correct that? I am afraid that whatever system I end up using will use a lot of electricity.
I was enquiring about Geotherm, and I was advised that the house wouldn't need as much heat as that would cost to install, so it wouldn't pay for itself. Thats why I was looking at air-to-water. Are solar panels out?
I am thinking about a stove for heating the rads upstairs because if the electricity was ever off, at least there would be still heat around the house from the solid fuel stove.
The whole thing is a muddle!

fclauson

lnos1 wrote: »

Thanks everyone for your replies.
What does PV mean?

Photo Voltaic -they generate electicity

Who would do a DEAP analysis? The same people who do BER certs? If the DEAP analysis is done, would that tell you how much heat you require to heat the house and then advise on what heating system to use?

DEAP is use by BER assesor to do their calcs - and Yes to second question

The U value for windows is so high as they are slide/sash windows and is hard to get lower U values on them. Casement windows do give a lot lower U values but we have to use sliding sash.

Why ?

I thought if the wall cavity is well insulated, it would compensate for the poorer U-values with the windows. Do you think condensation would gather on the inside of the window? That would be serious if that happened.

Might - you would need to do FRSI calcs - and yes the more you insulate one spot in a build the worse it makes it elswhere

think of it like this - if all the walls are at say 20 deg - then the area for condesation to form as a % of the internal surface gets smaller - and hence gets more concentrated

Would the heat recovery system correct that? I am afraid that whatever system I end up using will use a lot of electricity.

Partially - but not totally

I was enquiring about Geotherm, and I was advised that the house wouldn't need as much heat as that would cost to install, so it wouldn't pay for itself. Thats why I was looking at air-to-water. Are solar panels out?
I am thinking about a stove for heating the rads upstairs because if the electricity was ever off, at least there would be still heat around the house from the solid fuel stove.
The whole thing is a muddle!

Rads need a pump - a pump needs electricity :mad:

fclauson

lnos1 wrote: »

..The whole thing is a muddle!

Oh - and welcome to the world of building your own house

lnos1

Thanks fclauson for your reply.
I have to use sliding sash - planning regs. I haven't come across any company doing really good airtight sliding sash.
Is there any link in the forums to northern ireland window companies? Timber sash windows are very expensive.
Would many people find timber windows warping with cold/hot environment? I've heard that a lot of irish joinery companies don't treat the timber properly before making the windows. Has anyone any opinions on this?
I think once I have decided on the windows, I'll know my U-value for them and then can get a BER done.
Thanks again for all the replies

fclauson

got to question why the insit on sash

if you really canot find airtight ones go back to the council and propose that you will get a better energy rating if you use something else

beyondpassive

lnos1 wrote: »

I have to use sliding sash - planning regs.

You don't have to use sliding sash, this is a myth propigated by lazy design and ignorant planners (geography graduates) who have no design training and misinterpret the rural design guidelines. Most rural house designs submitted for planning seem to a have a symettrical neo-georgian front facade and a modern rear, which is just silly, houses in the landscape are always viewed from the side profile, never square-on. What's more important in sensitive rural design is the scale and proportion of the house, the siting in the landscape and the roof angle. Whether the windows are sliding or otherwise is irrellevent. Its always galling to see new mock georgians with very fussy front elevations, sliding saches and georgian fanlights, but no attention paid to the soffit or the gable. On the gable you usually have a clutter of pipes and a profusion of ill considered windows and doors which bear no relationship to the front facade. My view, if your going to do Georgian, then make it a good facsimile, if your doing modern, design modern but use the mannered proportions of the georgian style, this b@stardised hybrid just looks naff.

Sach windows, just arn't suited to MHRV and Passiv design concepts.

air

kboc wrote: »

From my own personal exp, a (good) heat pump will do the job. With an excellent plumber who will look after your hot tank you wont need Solar Panels either as the heat pump will look after that also. I get 500 litres of hot water (to 45 deg) every day at a cost of 24p. (the hp use 3 units of elec for 1 hour at 8p/unit).

Sorry to pull you up on this but the above is more or less impossible.
Assuming water is coming into your house at 10 degrees (likely less in winter), it will take approx 20kWh to heat 500L of water to 45degrees.
35degrees x 4185J/kg/K x 500kg = 73.2375MJ = 20.34kWh
Realistically your HP probably has a best case COP of 3 which means approx 7kWh of electricity will be required.
I pay about 20c/kWh for electricity including standing charges etc so the above would cost me around €1.50 per day or €550 per year.
Perhaps you use night rate electricity but then your COP would be reduced due to lower outside air temps assuming an air source HP.

When you add the capital cost of the heat pump, the annual maintenance required (a friend pays hundreds per year for his annual check on his GS pump) and the exposure to future electricity price increases, I fail to see the major attraction with heat pumps for domestic hot water.

Finally from an environmental perspective they're not much better than burning fossil fuels at home due to the current fuel mix in use for electricity generation in Ireland.

kboc

air wrote: »

Sorry to pull you up on this but the above is more or less impossible.

I have the NIE bills to prove this

Assuming water is coming into your house at 10 degrees (likely less in winter), it will take approx 20kWh to heat 500L of water to 45degrees.
35degrees x 4185J/kg/K x 500kg = 73.2375MJ = 20.34kWh
Realistically your HP probably has a best case COP of 3

it uses 2.97 units of elec per hour, this means a COP of 12/2.97 = 4.0404040404040

which means approx 7kWh of electricity will be required.
I pay about 20c/kWh

I pay 8p/unit night time and 15p/unit day time

for electricity including standing charges

10p per day

etc so the above would cost me around €1.50 per day or €550 per year.
Perhaps you use night rate electricity

yes i do

but then your COP would be reduced due to lower outside air temps

you are presuming that I use ASHP, I have GSHP, 800 linear metres buried 5 ft below the ground in 8 trenches 1 metres apart from one another, cold temp have no bearing at this depth

assuming an air source HP.

When you add the capital cost of the heat pump

greatly eased by this scheme

, the annual maintenance required

costs nothing so far, it is installed for nearly 2 years, the plumber has never being called back to any of these machines (he has installed tens if not over a hundred of them in recent times), he calls them the "ford transits" of heat pumps, they just go and go

a friend pays hundreds per year for his annual check on his GS pump) and the exposure to future electricity price increases

not near as bad as oil, gas or any other fossil fuel

, I fail to see the major attraction with heat pumps for domestic hot water.

I do, as my total elec bill is approx £900 for the year (420sq metres by the way), incl everything, tv, hot water, heat etc. etc. This is not me bumming them up, I will call a spade a spade, but I have the paper bills to back this up

Finally from an environmental perspective they're not much better than burning fossil fuels at home due to the current fuel mix in use for electricity generation in Ireland.

Did you tell the europeans and americans this, as they have been doing for years and they have obviously got it all wrong

air

Where are you getting 12 units from? Per my calculations it will take over 20kWh of energy to heat the water to that temperature. If I've made some error please let me know.
I suspect that you are not using the full 500L of water every day which would explain the "miraculous" figures.

I stated above that I wasn't sure whether you were air or ground sourced, regardless I doubt you are achieving a COP over 3. Even a GSHP is going to have reduced efficiency in winter due to lower ground temperatures, even 5ft down - admittedly it should perform better than an air source pump.

As stated a friend of mine told me that his system has cost him 2-300 euro / year on maintenance since it was commissioned. This is merely anecdotal evidence of course.

Any technology can be made viable with a grant scheme. Personally I don't feel grants should be made available for heat pumps as there is limited gains to be had through further R&D. I suspect that the argument made in favour of heat pumps from an environmental perspective is based on us reaching a point in the future where the percentage of renewables in electricity is much higher. However I believe that any installations completed today will be due for replacement before that comes to pass.

As for what the Europeans and Americans do, I'm not too interested to be honest, have you got anything to suggest what I've said on overall energy usage is incorrect?

However I would suggest that the reason that they have come to use air source heat pumps is that they traditionally use them for summer cooling and nowadays run them in reverse during the winter as heat pumps. Energy efficiency was not the driver behind this development.

As I alluded to above, at the moment our electricity is primarily generated from fossil fuels and delivered to our homes at probably circa 40% efficiency in terms of the ratio of the fuel's chemical energy delivered to our homes in electrical format.
The COP of a heat pump hopefully makes up for this loss of efficiency.

However you're still no better off than if you had burned the fossil fuel in your home. On the downside though, using a heat pump necessitates the use of capital equipment in terms of a power station, transmission network and heat pump itself vs the alternative of a simple gas or oil boiler in the home.
Furthermore, using electricity for any form of heating - resistive or heat pump based, increases the magnitude of seasonal peak demands on our electricity network and generating plant.
This contributes to increased electricity costs for everyone as it means that more generating plant needs to be kept on standby and transmission networks need to be built with ever greater capacity.

Do you mind mentioning how much your heat pump install cost and what the expected lifetime of the equipment is?

kboc

air wrote: »

Where are you getting 12 units from? Per my calculations it will take over 20kWh of energy to heat the water to that temperature. If I've made some error please let me know.
I suspect that you are not using the full 500L of water every day which would explain the "miraculous" figures.

Of course I don't use 500L everyday, I am not sure what fraction I use of this capacity, and it does take more time the more it is used, in fact if memory serves me correctly, when the HP first heated the tank it took 2-3 hours. All I know is that every day our house has ample water available all day at 45 deg. Costing 3 units of night time elec, and thats what I want.

I stated above that I wasn't sure whether you were air or ground sourced, regardless I doubt you are achieving a COP over 3. Even a GSHP is going to have reduced efficiency in winter due to lower ground temperatures, even 5ft down - admittedly it should perform better than an air source pump.

As stated a friend of mine told me that his system has cost him 2-300 euro / year on maintenance since it was commissioned. This is merely anecdotal evidence of course.

Any technology can be made viable with a grant scheme. Personally I don't feel grants should be made available for heat pumps as there is limited gains to be had through further R&D. I suspect that the argument made in favour of heat pumps from an environmental perspective is based on us reaching a point in the future where the percentage of renewables in electricity is much higher. However I believe that any installations completed today will be due for replacement before that comes to pass.

I feel you and I are looking at this from different view points. You are analyising this proces right through the energy supply chain. I rather ignorantly analyise this with my pocket's point of veiw

As for what the Europeans and Americans do, I'm not too interested to be honest, have you got anything to suggest what I've said on overall energy usage is incorrect?

However I would suggest that the reason that they have come to use air source heat pumps is that they traditionally use them for summer cooling and nowadays run them in reverse during the winter as heat pumps. Energy efficiency was not the driver behind this development.

As I alluded to above, at the moment our electricity is primarily generated from fossil fuels and delivered to our homes at probably circa 40% efficiency in terms of the ratio of the fuel's chemical energy delivered to our homes in electrical format.
The COP of a heat pump hopefully makes up for this loss of efficiency.

However you're still no better off than if you had burned the fossil fuel in your home.

100% I am better off. My neighbours have built houses 2/3's the size of mine and cost over £2000/year on oil. As stated previously my total energy bills for 420 sq m is approx £900/year

On the downside though, using a heat pump necessitates the use of capital equipment in terms of a power station, transmission network and heat pump itself vs the alternative of a simple gas or oil boiler in the home.
Furthermore, using electricity for any form of heating - resistive or heat pump based, increases the magnitude of seasonal peak demands on our electricity network and generating plant.
This contributes to increased electricity costs for everyone as it means that more generating plant needs to be kept on standby and transmission networks need to be built with ever greater capacity.

again, I look after my house, others in ESB etc look after these issues.

Do you mind mentioning how much your heat pump install cost and what the expected lifetime of the equipment is?

12Kw GSHP + 800m 32mm MDPE piping + associated pumps + fittings + data therm controls = £8,500, No VAT for Self Builds in NI.
Separate price was 500L DHW tank and fittings

air

That's fair enough and as I expected, I think your original post was misleading due to the reference to 500L which has no bearing on your actual usage.

I don't dispute your running costs at all but I think you're comparing apples to oranges, I had a look through your older posts and it sounds like you did a great job insulating your house to a high standard. Perhaps if your neighbours had done the same they wouldn't be spending so much on fuel. IE I believe it is likely that it is differing levels of insulation and not the heat source as such that is the greatest factor leading to the disparity in running costs.

Incidentally you refer to your house as being 420sqm in this thread (4250sq ft) while in other threads you mention it variously as being 3500sq ft and 3800 sq ft, a bit of ambiguity there.

On the broader points, I accept that the figures are working out for you in terms of ongoing costs. However they are reliant on grant aid and government policy to a large extent. When making a decision with long term repercussions I feel it's best to base it on things that can be controlled in so far as possible.

On the ESB side, I agree this isn't something that you have to worry about at the moment. However in time the ESB / NIE may come to realise that they need to learn from operations in other countries and restrict the maximum import capacity of domestic users and / or charge more for large import capacities. Being reliant on a heat pump exposes you to this policy risk and may lead to increased running costs in the future.

Finally the capital cost you quote for that heat pump doesn't include for substantial installation and commissioning costs. I saw you spent £20k overall on your system. When one includes the cost of credit for this capital install it further diminishes the case for heat pump based heating systems in my opinion.

just do it

Thanks lads for a good debate;).

Lots of info here and good to get costings on your system kboc. I must have a look back at your level of insulation, windows etc, unless of course you want to give a brief synopsis here.

kboc

air wrote: »

That's fair enough and as I expected, I think your original post was misleading due to the reference to 500L which has no bearing on your actual usage.

Of course it does, my average daily usage of hot water is met by 1 hour of night time elec heating a 500L tank. How much is used dpends on many factors which change on a daily, weekly and monthly occurance. The 500L allow the flexibility of this

I don't dispute your running costs at all but I think you're comparing apples to oranges, I had a look through your older posts and it sounds like you did a great job insulating your house to a high standard. Perhaps if your neighbours had done the same they wouldn't be spending so much on fuel. IE I believe it is likely that it is differing levels of insulation and not the heat source as such that is the greatest factor leading to the disparity in running costs.

I would look at this from a different point of view. That is one in which I researched this to within an inch of it's life and appreciated that heat pumps are only really successfull and justifable when the house is relatively airtight and really well insulated, which mine is, and as you rightly assume my neighbours isn't. I think that is a ridiculously negative view from that particular point that I made.

Incidentally you refer to your house as being 420sqm in this thread (4250sq ft) while in other threads you mention it variously as being 3500sq ft and 3800 sq ft, a bit of ambiguity there.

May mistake, the house is 320 sq m, i apologise.

On the broader points, I accept that the figures are working out for you in terms of ongoing costs. However they are reliant on grant aid and government policy to a large extent. When making a decision with long term repercussions I feel it's best to base it on things that can be controlled in so far as possible.

My HP was bought before this scheme and regardless of any possibility of a scheme. The scheme allows retrospective claiming on HP systems. This is how my plumber is organising this grant, follow by the 17 years of an annual payment, with guesstamations around the £500 or £600 per annum. This will nearly leave my house (energy) bill free.

On the ESB side, I agree this isn't something that you have to worry about at the moment. However in time the ESB / NIE may come to realise that they need to learn from operations in other countries and restrict the maximum import capacity of domestic users and / or charge more for large import capacities. Being reliant on a heat pump exposes you to this policy risk and may lead to increased running costs in the future.

I will deal with that when it happens

Finally the capital cost you quote for that heat pump doesn't include for
substantial installation and commissioning costs.

How can you say this? Do you know me or my plumber?
It does. That is the cost for my GSHP as I said, everything, a perfectly working system.

I saw you spent £20k overall on your system.

You have far too much time to trawl through Boards,
GSHP = £8500
UFH + Manifolds = £8000
500L DHW = £1800

There you go!

When one includes the cost of credit for this capital install it further diminishes the case for heat pump based heating systems in my opinion.

You are just spitting hairs at this point.
Actually, I have split these hairs, as i was my own project and this project was micro-managed. I rsearched this also and my figures still add up, before grant. My pay back (before grant) on this GSHP is estimated at 5 or 6 years.

I can't help but feeling you are grinding an axe against HP.

I am not taking this personally, because if my cow's shiite would heat my house efficiently and effectively I would be using it instead. I have no attraction to GSHP or any HP other than my pocket!

kboc

just do it wrote: »

Thanks lads for a good debate;).

Lots of info here and good to get costings on your system kboc. I must have a look back at your level of insulation, windows etc, unless of course you want to give a brief synopsis here.

Walls 150mm cavity bonded bead blown in

Floors 150 PIR sheets (50mm then 100mm) with all joints taped and all gaps filled with expansion foam

slope ceilings 150mm between rafters of quality wool product and 100mm PIR sheet below rafters

flat ceilings in loft space 550mm of quality wool insulation

All of this is irrelevant without a HRV and airtight tapes around windows, doors and junction where rising walls meet floor insulation

double glazed windowsI missed out on some detail around bison slab/walls and wall plate that some people are putting in now, but the level of knowledge and experience was just not there at that time.

oh, I have to add, I have a run of glass 5m east/south facing and immediately perpendicular to this 9m of south/west facing glass which contributes huge solar gain to the house. My heat goes off mid march and does not come back on until early/mid oct. apart from some very few exceptions.


good luck

air

I accept everything you've said above, albeit there are still some minor misunderstandings.

In conclusion I would say that your house has an admirably low heat requirement which you are meeting amply by means of a heat pump. In my opinion heat pumps make no sense in Ireland at the present time for the reasons I have stated (primarily end to end efficiency, complexity, capital costs & maintenance). The average COP is 3-4. From a purely cost perspective the COP is cancelled out, personally I pay about 5c/kwH for natural gas and 20c/kwH for electricity which would negate a COP of 4 for a HP. If I was running oil fired ch this would favour the HP slightly more.
Incidentally what you spent on your heat pump would pay my home heating bills for approx 40 years (poorly insulated but half the size).

I'm delighted for you that a grant scheme looks likely to subsidise the cost of your installation for the next 17 years. Unfortunately this doesn't make heat pumps any more viable in the long term for the masses (grants are unsustainable long term).

For the record I've no vested interests in heat pumps or any other technology, I'm just sharing (hopefully) objective information that may be of use to others.

fclauson

here is a spread sheet you might find useful

Solar is just not worth doing - you can tweek the numbers of the sheet to increase inflation (I have used 5%,8% and 12% fuel) - but the fact remains that a HP is cheaper than Oil + Solar by a long way

I have asumed no maint on the HP (it should need none) and no cost of electricity to run the Oil + Solar systems

I have also assumed a COP of 400% for heating and 300% for hot water

I have assumed electricty at 16c/unit being a bit of a hybrid of the 8c from cheap overnight and 18c of expensive daytime (I have ignored standing charges I pay these any way for my other electricity)

AntrimGlens

. In my opinion heat pumps make no sense in Ireland

So would you say they make no sense in Ireland if i were running it off my own hydro system, generating my own electricity to run it, in a highly insulated house? Or do your following issues still make it unfeasible - end to end efficiency, complexity, capital costs & maintenance).

air

No of course not, but that situation is hardly typical of the average home owner in Ireland or anywhere else!

just do it

Air

What's your suggestion for the OP?

air

My suggestion would be the same as for anyone else:
1. Calculate the projected energy demand for the house per year in kWh
2. Compare the locally available fuel options in terms of cost per kWh
3. Assess the capital costs of equipment associated with each fuel type and look at it's cost over it's expected lifetime.
4. Make a judgement call on any likely fluctuations between various fuel sources.

You will quickly figure out that a house with a low heat demand favours an energy source with lower capital costs. Any advantage that a higher capital cost option has in cost / unit is realised in fewer units output. There will be a crossover point where if you're using enough energy it will be worth investing in the expensive option.

Capital Expenditure Comparison:
Compare oil vs gshp as follows - nominal figures used.
OFCH boiler etc - cost 4k - over 20yrs @ 4% = €5817
GSHP etc - cost - 20k - over 20yrs @ 4% = €29087

This means you need to gain €1167 / year by choosing the GSHP just to break even.
This neglects maintenance / replacement costs completely.

Running Cost Comparison
Again nominal figures, insert your own accurate ones
Heating Oil - 10c/kWh (€1/litre - 10kWh/litre)
Heat Pump - 3c/kWh (Night Rate Elec 10c / kWh - COP of 3)

This implies a cost saving of 7c/kWh for the heat pump option.
In this case, the heat pump makes sense if you use more than (1167/.07)=16,671 kWh of heat energy per year.
As an example, if your house performs 3 times worse than the passive standard - ie 45kWh/m2/year, then the above would be enough to heat a 370 square metre home.

If it's likely that only the heat pump itself needs replacement after 20 years, you could amortise the cost of the other elements of the installation over a longer period, reducing the energy consumption at which the heat pump makes sense slightly.

This type of analysis is the reason why many passive houses just have resistive heating elements in their MHRV units or whatever.
The cost per unit is high, but the home is likely to use so few units per year that the high unit cost is completely outweighed by the super cheap cpaital cost of the heating element.

cuculainn

air wrote: »

Capital Expenditure Comparison:
Compare oil vs gshp as follows - nominal figures used.
OFCH boiler etc - cost 4k - over 20yrs @ 4% = €5817
GSHP etc - cost - 20k - over 20yrs @ 4% = €29087

Think your numbers are a bit off here......Are you telling me you would get a OFCH system installed for 4k including burner, UFH (you have to compare like with like, so underfloor instead of rads) DHW tank, oil tank?

Also you have to include a renewable source of energy per the building regs, therefore you need to include the cost of solar panels or whatever

air

I think the most important word in my last post was NOMINAL!.

As I stated above, you need to research your own figures, however the methodology above is sound - although I stand to be corrected if anyone has spotted errors.

I would suggest excluding the UFH element, domestic hot water tank and anything else that is common to both systems, so perhaps compare the cost of oil burner + tank + install to the cost of GSHP + install + related ancilliaries + cost of coils and their installation.

I take your point on solar, however I think it's added cost is often overstated and / or people are often ripped off.
You need a hot water cylinder anyway so the additional cost should just be for the extra cylinder coil, panels, pump station, ancillaries and install. 4k should more than cover this including installation..

Including hot water complicated the figures somewhat.
You'll need to add the projected yield from the solar panels into the calculation.
Personally I don't think heat pumps should be allowed to count as a renewable energy source for reasons I have already outlined.

As I keep repeating, everyone needs to do the calculations for themselves using an objective methodology such as the one I have detailed above.

Too many people listen to things like "John has a massive house and it's only costing him X per year to heat with a heat pump" and say therefore I will install a heat pump.
One needs to look at one's own heat demand, local fuel costs and the costs of the equipment needed to use that fuel.

fclauson

Remember into this mix you have to add Part L compliance

so if you go oil - you will need solar or something to provide your Part L - so the calc has to take this into account too

That's why its not always as easy -
oil = €x
GSHp = €Y

as to "x" you would have to add your renewable souce 10kwh/M2 where as your "y" might (or might not) give it to you