LPG + MHRV + PVs

Monfreid

Hello,

I've been granted planning permission and I'm willing to get LPG + MHRV + PVs. The house is a 1 and half storey house, north facing garden, 2200 spft with 4 people living in it.

This is option 2 from my Green Advisory report.

Option 1 is AWHP + UFH + MHRV + PV

My Energy consultant is trying to convince me to go for Option 1 but so far I find it hard to convince myself. The few people I talked to or feedbacks I've read on forums say that if it goes wrong, you could end up with huge electricity bills.

the cost of heating the house should be 1800 eur per year for LPG, compare to 900 eur with AWHP. I find it hard to believe that LPG would be so expensive. I currenlty live in a house (not new, roughly same size) that has an oil burner and it cost me 1000 eur per year and my neighbors have similar bills so I guess that LPG should be around the same price or less because the house will be well insulated and with MHRV

Do you have any feedback to give me on LPG heating on a recently built house? my house BER should be A3.

Am I insane to go for LPG?

Thank you very much for your feedback

Calahonda52

have you looked at the SEAI website where it has a chart somewhere of different fuel costs.?

you need to look at all the costs here of lpg, tank rental, monthly fixed charge etc as well as the price per kWh, not price per litre as fuel have different calorific values per unit of volume.
from memory,
lpg is 6.654 kWhs per litre
kerosene is 9.821
gas oil is 10.786

these then need to be reduced for the efficiency of the burner, before transmission losses which will be the same for a rad based system

I presume ur consultant has pointed out all of this.

The energy balance calculation for ur house will have an expected kWh per annum usage, or some other metric depending on how he does the math and this is what you plug in against the chosen fuel cost.

What is the life time cost analysis of both systems telling you?

Its not just as simple as upfront capital costs of a Heat pump: maybe 25k, versus a 2k lpg burner.

Put up as much detail as you want and w=ill have a cut at the math:)

Finally, I would look long and hard at A3 and ask why not A1 or better

Whats the airtightness expected value?

Keep well

Monfreid

Hi, thanks for your port

This is the info I have:

Air Tightness should be 3

Total Cost of Air to Water Heat Pump Heating Over 15 Year Period : €19,038.63 (4% annual rise in ESB prices)
Total Cost of LPG Heating over 15 Years : €38,533.62 (5% annual rise in oil prices)

Estimated Supply & Install Cost – LPG Heating System and PV Panels

Heat Recovery System
€7,754
Gas boiler and plant room fit out
€4,300
Radiator and Controls
€6,000
Hot water cylinder
€900
PV Panels
€3,200
Solid fuel stove / Fire insert
€1,600
Total (ex VAT)
€23,754


Estimated Supply & Install Cost – Air to Water Heap Pump
Heat Recovery System
€7,754
Air-to-water heat pump and plant room fitout
Underfloor heating & controls
Hot water cylinder
€11,578
Solid fuel stove / Fire insert
€1,600
Total (ex VAT)
€20,932

When you see all this, it sounds like AWHP is a winner but I'm just afraid if it goes wrong (based on what I've heard and read) and cost me a fortune, more than LPG in the end.

sydthebeat

factor in the replacement of the heat pump after 20 years .... so throw another 6-8k on the ASHP costings

Metric Tensor

In terms of the annual running costs does the calculation take into account the different style and behaviour of the UF vs (presumably) rads for the LPG.

I have found that homeowner behaviour with UF is very different to that of rads. Hard to quantify though for obvious reasons.

galwaytt

...I've had LPG in 2 different houses for 18 years. Bearing in mind that you are building a new, and therefore efficient house, I think you're LPG running costs are out.

I can quote a 363m2 house near me that spend €375 a year on LPG. UFH, MHRV, 3 x solar panels for DHW - NOT PV. It has UFH to GF and rads to FF.

Even my old 1990's house, at 220m2+ (still) doesn't use the amount you are quoting for your new build. Again, UFH to GF and rads to FF.

I did need a new boiler this year, and considered ASHP, but once I did the numbers, just bought a new boiler.

Fwiw I think you're airtightness figure is way too low. You should be aiming for 1.0m3/hr/m2 or better - makes a huge difference. I think (for now), that PV is pointless, unless you're at home all day consuming it.

Btw I like LPG for cleanliness, efficiency and a wide range of boilers and capacities - if the same existed in another fuel I'd look at that.

Calahonda52

Lets see the lpg numbers in more detail as well as whats the spec on the heat pump (11k all in suggests maybe the engine is too small) as well as more on the MHRV seem as 8k seems a lot unless its a Paul or similar.
As tt says the A/T value is critical; more important than insulation so if this my my project I would give serious consideration to redoing the budget so as u get the fabric of the house as good as possible: e.g.: u can always trash the 5k ikea kitchen in 5 years instead of spending the 25k in the current budget and use the 20k to get the building fabric as good as possible: u will never retro it.

Oil is 40 usd a barrel now, not long ago it was 150 so nice inflation rates of 4 and 5 % just don't do it in my book.

Re PV vs Solar panels: I think PV a better long term and much simpler option: look at using it in an element in the HC cylinder until we get feeding tariffs or u buy an electric car: u wont always have 4 in house, Solar thermal is designed on current usage so bad process in my view.

Monfreid

Thanks for that.

I was thinking of getting rads GF and FF because I'm not a big fan of UFH.
My energy consultant says that solar panels for DHW are not good (I will never get my money back) but I've heard people saying that they are very happy with it.
So I asked for DHW with solar panels but he said that PVs would be a better option but on the other hand he says that PV are useless because they don't bring that much electricity and you can't sell it either.
Hard to know, I feel more confident getting LPG because I know what I'm getting but he wants me to get AWHP like most of the new build nowadays ... but I know a guy who is building a house at the moment with Oil Central heating so sounds like Heat Pumps are not so widely installed. I want LPG but the Energy consultant says something else and he is trying to convince me so now I'm confused, still want LPG but why is he insisting on this, because he does not want me to make a mistake or for another reason?

Monfreid

Calahonda52 wrote: »

Lets see the lpg numbers in more detail as well as whats the spec on the heat pump (11k all in suggests maybe the engine is too small) as well as more on the MHRV seem as 8k seems a lot unless its a Paul or similar.

the recommended HP is Danfoss DHP-AQ 10.7kW Air-to-Water heat pump (SPF= 4.13)
the recommeneded MHRV is Vent Axia Kinetic Plus E

Calahonda52

How is the air intake for the stove going to work with the MHRV?
is is wood burning or multi-fuel because if the latter u may have Part L issues

I prefer this one from the vent-axia range
http://www.vent-axia.com/range/lo-carbon-sentinel-kinetic.html
it has a summer by pass and has more controls.
One concern is what the design flows are and if you are close to the max for normal design then it will be noisier than if a lower fan/airflow speed, especially at night.
Also smaller diameter ducts lead to higher airflow and thus noise.

Look fwd to the lpg calcs:)

galwaytt

Calahonda52 wrote: »

As tt says the A/T value is critical; more important than insulation so if this my my project I would give serious consideration to redoing the budget so as u get the fabric of the house as good as possible: e.g.: u can always trash the 5k ikea kitchen in 5 years instead of spending the 25k in the current budget and use the 20k to get the building fabric as good as possible: u will never retro it.

That's it in a nutshell. My own take on it is that once you hit u-values of 0.20 or below that airtightness is far more important, and delivers measurable returns. Insulation not necessarily.

Calahonda52 wrote: »

Re PV vs Solar panels: I think PV a better long term and much simpler option: look at using it in an element in the HC cylinder until we get feeding tariffs or u buy an electric car: u wont always have 4 in house, Solar thermal is designed on current usage so bad process in my view.

I can only go on my own experience, but I have a 1000L buffer tank to drive my UFH heated by solar, and topped up by LPG. From March/April until Oct this year my boiler was off completely, and all my DHW needs were met in their entirety by the panels.
I don't discount PV completely: all I think is that in the absence of a feed in tariff there's no merit in doing right now. As soon as that changes, or you're allowed nett-metering, then that changes everything. In the meantime, PV panels will improve in quality & efficiency.

Monfreid wrote: »

Thanks for that.

I was thinking of getting rads GF and FF because I'm not a big fan of UFH.
My energy consultant says that solar panels for DHW are not good (I will never get my money back) but I've heard people saying that they are very happy with it.
So I asked for DHW with solar panels but he said that PVs would be a better option but on the other hand he says that PV are useless because they don't bring that much electricity and you can't sell it either.
Hard to know, I feel more confident getting LPG because I know what I'm getting but he wants me to get AWHP like most of the new build nowadays ... but I know a guy who is building a house at the moment with Oil Central heating so sounds like Heat Pumps are not so widely installed. I want LPG but the Energy consultant says something else and he is trying to convince me so now I'm confused, still want LPG but why is he insisting on this, because he does not want me to make a mistake or for another reason?

If you're not having UFH, then I see no point in ASHP at all. It is a producer of volumes of low-grade heat (which is what UFH consumes), whereas rads require higher temps (and lower volumes).

If your 'advisor' is saying PV's are better but are useless in the same sentence then I'm not surprised you're confused.

As I said above, all I know is that thermal solar works for us - I see no reason why we shouldn't take advantage of every gain (sic) going - solar included. I never even looked a payback or otherwise when I put them in. I just like having DHW on tap (sic) all the time, and leveraging the sun where I can.

Calahonda52

tt: can't and wont argue with you re the PV versus thermal.

Just wonder can you post what your lpg is costing per kWh: the multiplier is c 6.654 khw per litre.

More points on oil vs lpg
+
lpg harder to steal.
tank has much longer lifespan
no sludge/water etc
can get a bbq connected up so no more undercooked steaks!
-
lpg deliveries in frostily snowy weather are much more restricted than oil deliveries in the same weather.

MicktheMan

Monfreid wrote: »

Air Tightness should be 3

Reiterating what others have said, reconsider a tighter target (<1m3/hr/m2 @50Pa).

Monfreid

galwaytt wrote: »

If you're not having UFH, then I see no point in ASHP at all. It is a producer of volumes of low-grade heat (which is what UFH consumes), whereas rads require higher temps (and lower volumes).

yes, I agree. The advisor told me that the HP will be less efficient and will cost more with the rads and the difference in its yearly cost estimation between LPG and HP with rads was then not as big as with UFH, therefore not a good deal.

So I'd say I should come back to him and say that I want LPG+MHRV and focus more on the insulation/air tightness (ideally 1) so that heating the house should not cost me much.

Monfreid

Calahonda52 wrote: »

How is the air intake for the stove going to work with the MHRV?
is is wood burning or multi-fuel because if the latter u may have Part L issues

2 options for the stove:

Option 1: Install a solid multi-fuel stove with an independently certified efficiency of 75% or greater.
Option 2: Install a Wood Log stove with an independently certified efficiency of 75% or greater.

External Ducted Air to Solid Fuel Stove has to be installed

Calahonda52 wrote: »

Look fwd to the lpg calcs:)

Looking at the Advisory report, I don't see information regarding how the maths were done, no indication on space heating vs water heating, ... So I'm afraid I can't give you too much info on that

Monfreid

Calahonda52 wrote: »

Re PV vs Solar panels: I think PV a better long term and much simpler option: look at using it in an element in the HC cylinder until we get feeding tariffs or u buy an electric car: u wont always have 4 in house, Solar thermal is designed on current usage so bad process in my view.

7 no. 0.25 kWp Photovoltaic Solar Panels (PV)

is that good enough to provide any king of electricity savings?

Calahonda52

Monfreid wrote: »

...


Looking at the Advisory report, I don't see information regarding how the maths were done, no indication on space heating vs water heating, ... So I'm afraid I can't give you too much info on that

If I was being asked to spend 38k I would need this detail: you have to know what the cost be KWh for LPG is

galwaytt

Calahonda52 wrote: »

Re PV vs Solar panels: I think PV a better long term and much simpler option: look at using it in an element in the HC cylinder until we get feeding tariffs or u buy an electric car: u wont always have 4 in house, Solar thermal is designed on current usage so bad process in my view.

....just be aware if OP were to do that as part of his BER, his BER would plummet through the floor........once you heat the water with electricity, even if self-generated (indeed, even if you were off-grid completely), SEAI consider that the same as a mains-connected immersion for BER calc purposes......

....just to throw the cat amongst the pigeons OP, did you do the numbers for an oil burner ?

Monfreid

galwaytt wrote: »

....just to throw the cat amongst the pigeons OP, did you do the numbers for an oil burner ?

I can't have oil apparenlty because, in order to be compliant with part L, I would need a large number of PVs and I don't have enough space for them on my roof.

sydthebeat

Monfreid wrote: »

I can't have oil apparenlty because, in order to be compliant with part L, I would need a large number of PVs and I don't have enough space for them on my roof.

??? that sounds very dodgy on behalf of the assessor

as far as Part L is concerned there is NO difference between oil and LPG (well a very slight CO2 difference, but thats negible)

it would make no difference to your amount of renewables whether your boiler is lpg or oil fueled

Calahonda52

galwaytt wrote: »

....just be aware if OP were to do that as part of his BER, his BER would plummet through the floor........once you heat the water with electricity, even if self-generated (indeed, even if you were off-grid completely), SEAI consider that the same as a mains-connected immersion for BER calc purposes......

....just to throw the cat amongst the pigeons OP, did you do the numbers for an oil burner ?

Agreed, I should have added that in suits not done that way to start with, likewise the stove, are there not issue with multiple vs wood only?

OP, just a quick look at the sea website show an A rated house costing 800 euro pa for water and heating:

Monfreid

sydthebeat wrote: »

??? that sounds very dodgy on behalf of the assessor

as far as Part L is concerned there is NO difference between oil and LPG (well a very slight CO2 difference, but thats negible)

it would make no difference to your amount of renewables whether your boiler is lpg or oil fueled

that's because of the planning, you can't have more than 20% of the total surface of your roof covered with Solar panels or so many panels or something like that.

sydthebeat

Monfreid wrote: »

that's because of the planning, you can't have more than 20% of the total surface of your roof covered with Solar panels or so many panels or something like that.

but as i said, whether your fuel is LPG or oil makes NO difference to the amount of renewables you have to install

Monfreid

sydthebeat wrote: »

but as i said, whether your fuel is LPG or oil makes NO difference to the amount of renewables you have to install

the more I read comments on this blog, the more my Advisory report makes no sense ... It is supposed to give me options, sounds like it's written in a way to force me to go for HP ... and if I say I want to go for LPG, there is still a will to make me change my mind ... is it because he wants me to avoid a big mistake or is it for other reasons ...

galwaytt

Monfreid wrote: »

the more I read comments on this blog, the more my Advisory report makes no sense ... It is supposed to give me options, sounds like it's written in a way to force me to go for HP ... and if I say I want to go for LPG, there is still a will to make me change my mind ... is it because he wants me to avoid a big mistake or is it for other reasons ...

....tbh, like most of the BER's I've read, there is so much cut & paste going on it does make you wonder............

Monfreid

galwaytt wrote: »

....tbh, like most of the BER's I've read, there is so much cut & paste going on it does make you wonder............

exactly, it sounds pretty much like a template where they just change a few things here and there ... for that price it's a sort of scam ...

sydthebeat

Monfreid wrote: »

exactly, it sounds pretty much like a template where they just change a few things here and there ... for that price it's a sort of scam ...

what price? if i may be so bold

Monfreid

sydthebeat wrote: »

what price? if i may be so bold

around 900 eur inc VAT ...

Monfreid

just a quick question, I believe that installing LPG boiler + rads should be cheaper than AWHP + UFH but the advisory report says the opposite ... €23,754 vs €20,932 ... another source of confusion. My current house is a bit smaller than the new one but I'm only spending 1000 eur per year on oil so how come a new house could cost 1800 eur per year with LPG with a much more efficient boiler and good insulation + heat recovery? it doesn't add up ...

Calahonda52

Monfreid wrote: »

just a quick question, I believe that installing LPG boiler + rads should be cheaper than AWHP + UFH but the advisory report says the opposite ... €23,754 vs €20,932 ... another source of confusion. My current house is a bit smaller than the new one but I'm only spending 1000 eur per year on oil so how come a new house could cost 1800 eur per year with LPG with a much more efficient boiler and good insulation + heat recovery? it doesn't add up ...

This might help re pv vs thermal
http://www.boards.ie/vbulletin/showthread.php?t=2057400774

Monfreid

Calahonda52 wrote: »

This might help re pv vs thermal
http://www.boards.ie/vbulletin/showthread.php?t=2057400774

thanks, very interesting

Monfreid

How can I estimate the running cost of heating my 220 m2 house with either system?

I came accross this figure: space heating demand of 55kWh/m2/yr

So if I do the maths using the seai fuel comparison report

space heating: 220 * 55 = 12100 kWh / year
DHW: 4000 kWh / year (4 people)

so that's 16100 kWh per year

So now the cost (c/kWh):

LPG (90% efficient) = 11.04 c/kWh ==> 16100*11.04= 1777 eur
AWHP (COP 4) = 6.06 c/kWh ==> 16000/4=4000 kWh ==> 4000*6.06= 242 eur but the HP will not work at COP 4 all the time so this 242 eur / year is only in theory ...

AWHP (COP 3) = 8.09 c/kWh ==> 16000/3=5333 kWh ==> 5333*8.09= 431 eur
AWHP (COP 2.5) = 8.16 c/kWh ==> 16000/2.5=6400 kWh ==> 6400*8.16= 522 eur

so let's say your HP runs at COP 2.8 on average all year long, that should be 480 eur /year

my advisory report says 1800 for LPG and 900 for AWHP so my maths look ok for LPG but a bit off for AWHP

so 900 eur difference per year, if AWHP is 25 K and LPG boiler 2K (as per one of the first post in this thread), you will get your money back in ... 23 years or so ... that can't be right ...

Please let me know if you think my maths are wrong there. thanks

galwaytt

Monfreid wrote: »

How can I estimate the running cost of heating my 220 m2 house with either system?

I came accross this figure: space heating demand of 55kWh/m2/yr

So if I do the maths using the seai fuel comparison report

space heating: 220 * 55 = 12100 kWh / year
DHW: 4000 kWh / year (4 people)

so that's 16100 kWh per year

So now the cost (c/kWh):

LPG (90% efficient) = 11.04 c/kWh ==> 16100*11.04= 1777 eur
AWHP (COP 4) = 6.06 c/kWh ==> 16000/4=4000 kWh ==> 4000*6.06= 242 eur but the HP will not work at COP 4 all the time so this 242 eur / year is only in theory ...

AWHP (COP 3) = 8.09 c/kWh ==> 16000/3=5333 kWh ==> 5333*8.09= 431 eur
AWHP (COP 2.5) = 8.16 c/kWh ==> 16000/2.5=6400 kWh ==> 6400*8.16= 522 eur

so let's say your HP runs at COP 2.8 on average all year long, that should be 480 eur /year

my advisory report says 1800 for LPG and 900 for AWHP so my maths look ok for LPG but a bit off for AWHP

so 900 eur difference per year, if AWHP is 25 K and LPG boiler 2K (as per one of the first post in this thread), you will get your money back in ... 23 years or so ... that can't be right ...

Please let me know if you think my maths are wrong there. thanks

I think your estimated LPG cost is too high, and your ASHP cost too low. I think the report you're working off is fundamentally flawed somehow.

The difference in payback for ASHP and the LPG, whilst maybe not entirely accurate, isn't that far out. Payback on a lot of things, (including say building to Passive spec), does take decades. And you have to finance that premium at the start, for the duration of the mortgage......

And you haven't allowed for a compressor rebuild in that period either....

sydthebeat

Also remember that your heat pump will not be offering you your DHW requirements at full COP performances.

in reality, heat pumps providing DHW at 65-70 deg will only be running at about 40% efficiency, so a COP of 4 will drop to about a COP of 1.5ish

and also realise that, once a heat pumps COP goes below 2.37 it is no longer an efficient system.... because electricity comes from the grid at a rate where 2.37 kwhr of primary energy is needed to create 1 kwhr of electricity.

Calahonda52

sydthebeat wrote: »

Also remember that your heat pump will not be offering you your DHW requirements at full COP performances.

in reality, heat pumps providing DHW at 65-70 deg will only be running at about 40% efficiency, so a COP of 4 will drop to about a COP of 1.5ish

and also realise that, once a heat pumps COP goes below 2.37 it is no longer an efficient system.... because electricity comes from the grid at a rate where 2.37 kwhr of primary energy is needed to create 1 kwhr of electricity.

Well said. [ the 2.37 AFAIK is to get you from the primary fuel to the customer meter.]
The kit in question has a max temp of 60C output.

tt: the c/kWh figure for LPG looks okay
Flogas charge, before any volume discounts or other rinky-dink stuff, 64c a litre
which is 6.6kWh so 6.6/64/.9 is near enough 11 cents a kWh

Monfreid

galwaytt wrote: »

The difference in payback for ASHP and the LPG, whilst maybe not entirely accurate, isn't that far out. Payback on a lot of things, (including say building to Passive spec), does take decades. And you have to finance that premium at the start, for the duration of the mortgage......

That's exactly what I was afraid of ... I can't have/don't want a big mortgage so invest a lot of money in a system that will take so long to payback does not make sense, I prefer to put this money in other things in the house. The house should be well insulated and with MHRV so LPG will do a good job heating the house and water at a reasonable price