GSHP for small house?

Renovationista

Hi, 
Looking for some advice on what might be the most energy efficient heating and hot water system to install in an old small (less than 90 sq mtr) bungalow/cottage in a  Midlands town with no Gas.  The house will be completely renovated and insulated to the highest standards. We like the idea of underfloor heating but worry about high oil consumption with oil fired boilers.  Ground Source Heat pumps seem a better fit but possibly too expensive an outlay for such a small house? My elderly mother will be living in the house so ensuring it is well heated and not too expensive to run is a massive priority.  Keen to hear any and all suggestions. Many thanks. 

MicktheMan

Renovationista wrote: »

Hi, 
Looking for some advice on what might be the most energy efficient heating and hot water system to install in an old small (less than 90 sq mtr) bungalow/cottage in a  Midlands town with no Gas.  The house will be completely renovated and insulated to the highest standards. We like the idea of underfloor heating but worry about high oil consumption with oil fired boilers.  Ground Source Heat pumps seem a better fit but possibly too expensive an outlay for such a small house? My elderly mother will be living in the house so ensuring it is well heated and not too expensive to run is a massive priority.  Keen to hear any and all suggestions. Many thanks. 

I'm not being smart here but what do you mean by "insulated to the highest standards"? Has anybody done any calcs on heat demand & heat load? What air tightness and ventilation strategies will be employed? These questions need to be addressed first before anybody can give any useful answers to your questions.

air

If it's a small poperty just go with a multi split air source heat pump. Will be a fraction of the cost to install.
As total heat demand reduces it gets harder to justify the additional cost of ground source. Also there's has been a lot of improvement in the COP of air source, Ireland is generally quite warm and winters are predicted to get warmer as a result of climate change.

Condenser

air wrote: »

If it's a small poperty just go with a multi split air source heat pump. Will be a fraction of the cost to install.
As total heat demand reduces it gets harder to justify the additional cost of ground source. Also there's has been a lot of improvement in the COP of air source, Ireland is generally quite warm and winters are predicted to get warmer as a result of climate change.

Which is why it's been close to zero for the last week and forecast to get colder? There's been virtually no improvement in the cop of ashps in the last 10yrs or more and wet weather below 8c leads to some of the worst efficiencies due to icing of the coil and high defrost requirements. Exactly the kind of weather we get here for 90% of the winter.

air

The lowest monthly mean temperature is 5-6C throughout Ireland.
In a small super insulated house it would still be more economical to use an ASHP with regular defrost or even resistive electrical heating to get through exceptional conditions than investing tens of thousands in a ground source system.
The annual heat demand needs to be compared with the COP benefit of a ground source system.
As properties become better insulated ground source heat of becomes increasingly difficult to justify.

As for recent weather, that doesn't contradict my assertion that winters are forecast to become milder overall due to climate change.
That's from the head of forecasting in Met Eireann speaking last week, but what would he know?

Condenser

air wrote: »

The lowest monthly mean temperature is 5-6C throughout Ireland.
In a small super insulated house it would still be more economical to use an ASHP with regular defrost or even resistive electrical heating to get through exceptional conditions than investing tens of thousands in a ground source system.
The annual heat demand needs to be compared with the COP benefit of a ground source system.
As properties become better insulated ground source heat of becomes increasingly difficult to justify.

As for recent weather, that doesn't contradict my assertion that winters are forecast to become milder overall due to climate change.
That's from the head of forecasting in Met Eireann speaking last week, but what would he know?

10s of thousands? Now you really are talking rubbish. You can install a gshp with ufh throughout in a property similar to the op for about 10k. Which is about 1k more than an ashp and will have 3 times the lifespan. But feel free to keep believing the propaganda.

air

We're talking about retrofitting to an existing house, a borehole could easily cost 6-7k alone and trenching would like mean reinstating lawns, driveways and all sorts on top of the actual trenching and pipe laying costs. None of that is required for an ASHP.

Also a GSHP will require either replacing all the radiators with larger ones or excavating the floors, insulating and relaying, all expense that could be avoided with a few wall mounted indoor units.

Condenser

air wrote: »

We're talking about retrofitting to an existing house, a borehole could easily cost 6-7k alone and trenching would like mean reinstating lawns, driveways and all sorts on top of the actual trenching and pipe laying costs. None of that is required for an ASHP.

Also a GSHP will require either replacing all the radiators with larger ones or excavating the floors, insulating and relaying, all expense that could be avoided with a few wall mounted indoor units.

6 to 7k for a borehole to satisfy a 90sqm house? Yes you're well abreast of all the figures. And of course fan coils can't be used on a gshp either.

You really need to talk to someone other than the salesman of your favourite Ashp.

air

I said "could", depends on the ground conditions obviously and if the house is an urban area there could even be access issues for a drilling rig. What's the minimum costs for a borehole then given mobilisation costs etc?

Of course fan coil units can be coupled to a GSHP but I've never seen it done in Ireland.

A multi split unit can be purchased off the shelf and installed by any air conditioning contractor. This forum is littered with threads from people with expensive GSHPs that they can't get anyone to service after the installer has gone out of business. At least multi splits are based on commodity units that are in widespread use commercially in Ireland and it would be no problem to find someone used to working on them.

Renovationista

Thanks to you all for your [font=Open Sans, Arial, Helvetica, sans-serif]replies.  Just to clarify the house has been derelict for the past 15 years and one of the first jobs on the build will be to tear down everything but the 4 exterior walls.  So no Micktheman we have not done any calculations on heat demand and heat load at this time.  My intention when posting this question was to find out [/font]

[font=Open Sans, Arial, Helvetica, sans-serif]Is fitting a GSHP a good return on investment in a house this size?[/font]

[font=Open Sans, Arial, Helvetica, sans-serif]or is[/font]

[font=Open Sans, Arial, Helvetica, sans-serif]A small house, well insulated with the correct air tightness and ventilation better served by an Oil Burner, traditional radiators and possibly a solar heat collector.  [/font]

[font=Open Sans, Arial, Helvetica, sans-serif]My contractor has advised the latter and suggested including the provision to add ATW in time.  However like Condenser I have read that the humidity in Ireland plays havoc with ATW and that they are being fazed out of the Nordic countries. [/font]

[font=Open Sans, Arial, Helvetica, sans-serif]Again, all thoughts and advise gratefully received.[/font]

Dardania

Renovationista wrote: »

Thanks to you all for your [font=Open Sans, Arial, Helvetica, sans-serif]replies.  Just to clarify the house has been derelict for the past 15 years and one of the first jobs on the build will be to tear down everything but the 4 exterior walls.  So no Micktheman we have not done any calculations on heat demand and heat load at this time.  My intention when posting this question was to find out [/font]

[font=Open Sans, Arial, Helvetica, sans-serif]Is fitting a GSHP a good return on investment in a house this size?[/font]

[font=Open Sans, Arial, Helvetica, sans-serif]or is[/font]

[font=Open Sans, Arial, Helvetica, sans-serif]A small house, well insulated with the correct air tightness and ventilation better served by an Oil Burner, traditional radiators and possibly a solar heat collector.  [/font]

[font=Open Sans, Arial, Helvetica, sans-serif]My contractor has advised the latter and suggested including the provision to add ATW in time.  However like Condenser I have read that the humidity in Ireland plays havoc with ATW and that they are being fazed out of the Nordic countries. [/font]

[font=Open Sans, Arial, Helvetica, sans-serif]Again, all thoughts and advise gratefully received.[/font]

What you could do is choose the radiators (or underfloor) to suit the temps of a future ATW heat pump, but also to suit a current oil boiler. So temps like flow 50C, return 40C. Will mean bigger rads than you would normally see, but good future proofing. Controls can be very simple (particularly considering it's an older person) - TRVs on all the rads with straightforward programmable thermostat so they can set & forget.
Also, consider trying to functionally separate the domestic hot water from the space heating - so have a DHW cylinder, with solar inputs and electric element also. And only if you can temporarily boost your boiler to output 65C flow should you have a coil from the oil boiler. It'll make it easier to switch the space heating to ATW in future if you're accustomed to using solar with electric backup for domestic hot water.

Condenser

Dardania wrote: »

What you could do is choose the radiators (or underfloor) to suit the temps of a future ATW heat pump, but also to suit a current oil boiler. So temps like flow 50C, return 40C. Will mean bigger rads than you would normally see, but good future proofing. Controls can be very simple (particularly considering it's an older person) - TRVs on all the rads with straightforward programmable thermostat so they can set & forget.
Also, consider trying to functionally separate the domestic hot water from the space heating - so have a DHW cylinder, with solar inputs and electric element also. And only if you can temporarily boost your boiler to output 65C flow should you have a coil from the oil boiler. It'll make it easier to switch the space heating to ATW in future if you're accustomed to using solar with electric backup for domestic hot water.

Are you seriously suggesting a flow temperature of 50c on a heat pump? Do you have any idea how a heat pump works?

Dudda

If it was a larger house I’d go with underfloor heating at 30-35 degrees powered by an air to water heat pump however in this case you’ve better options available.
At only 90sqm it’s a small house and as you’re removing everything except the four external walls it’s going to give you a great opportunity to create a super efficient home. I’d strongly consider building to passive house standards. In a house that small you could use a Nilan Compact P.
This is an all in one device that contains MVHR, heats hot water and heats the house with it's built in heat pump. Its used on a passive housing estate in Wexford that’s getting a lot of coverage on Nationwide TV show, passive house forums and magazines which is where I’ve heard about it. I’m not connected in any way.
On a small passive house you need so little heat that you can just heat the air that goes through the MVHR and this heats the whole house. It provides a huge saving as you don’t need radiators or underfloor heating and all the associated plumbing that goes with them. In addition as it has a built in heat pump it meets you're part L building regulations requirements so you don't need solar panels (more savings). It’s only suitable for small super insulated houses which why it’s not for everyone but something I’d strongly consider in your case. As just one unit its easier for an old person to use so great for your mother and a lot cheaper to install and run. They had an 80 year old woman on Nationwide who purchased one of the houses showing how it worked.

Renovationista wrote: »

My contractor has advised....

You’re not going to be able to take advice for something like this from a contractor and to be honest you shouldn’t really be taking advice from a contractor anyway. Get someone to come up with a design and layout you're happy with and then then that person or someone else if they're not qualified to work out the phpp (Passive house calculations) for you. This will inform the heating load and hopefully confirm you can use the smaller and cheaper Compact P.

Dardania

Condenser wrote: »

Dardania wrote: »

What you could do is choose the radiators (or underfloor) to suit the temps of a future ATW heat pump, but also to suit a current oil boiler. So temps like flow 50C, return 40C. Will mean bigger rads than you would normally see, but good future proofing. Controls can be very simple (particularly considering it's an older person) - TRVs on all the rads with straightforward programmable thermostat so they can set & forget.
Also, consider trying to functionally separate the domestic hot water from the space heating - so have a DHW cylinder, with solar inputs and electric element also. And only if you can temporarily boost your boiler to output 65C flow should you have a coil from the oil boiler. It'll make it easier to switch the space heating to ATW in future if you're accustomed to using solar with electric backup for domestic hot water.

Are you seriously suggesting a flow temperature of 50c on a heat pump? Do you have any idea how a heat pump works?

Yes - based on this it seems reasonable: https://www.cibsejournal.com/cpd/modules/2010-02/
Not an in-depth knowledge of their workings, but enough to consider their integration with / compare them to other heat source.
What would you recommend?

Dudda

Dardania wrote: »

Yes - based on this it seems reasonable: https://www.cibsejournal.com/cpd/modules/2010-02/
Not an in-depth knowledge of their workings, but enough to consider their integration with / compare them to other heat source.
What would you recommend?

That post is 7 years old which in the world of heat pump technology and efficiency is now fairly old. The point Condenser is trying to make is heat pumps should really be running at a temperature lower than 50 degrees for general heating to get a better COP. You’re not wrong and it’s not that it won’t work. It’s just it could be more efficient.

Dardania

Dudda wrote: »

Dardania wrote: »

Yes - based on this it seems reasonable: https://www.cibsejournal.com/cpd/modules/2010-02/
Not an in-depth knowledge of their workings, but enough to consider their integration with / compare them to other heat source.
What would you recommend?

That post is 7 years old which in the world of heat pump technology and efficiency is now fairly old. The point Condenser is trying to make is heat pumps should really be running at a temperature lower than 50 degrees for general heating to get a better COP. You’re not wrong and it’s not that it won’t work. It’s just it could be more efficient.

Fair point- it's all about trade-offs. I was looking also at the min return temp an oil boiler could take back - e.g. the grant vortex looks for return temps above 40C.

What is a reasonable flow / return temp for a ASHP? I've seen on other sites flow 45C / return 40C - it's a bit tight, but on balance nothing precludes designing to those temps for radiators in an oil boiler context, particularly if the house will be well insulated - the rad sizes or quanity shouldn't be dramatically huge.

For the OP, if they have an identical radiator (heat emitter) design, it enables them make a completely objective decision about their heat input - they can compare the total install and running costs of both the ASHP and the oil boiler option, without too much concern of other elements.
And with respect to COPs dropping - that may not be as much as an issue when compared against the hassle factor of having to remember to check oil tank levels, order oil, flower beds getting hoses dragged through them etc. Obviously if the COP drops massively, the electrical input needed to run the ASHP rises - but again might not be an issue if the heat loss in the house is low.

threeball

Dardania wrote: »

Yes - based on this it seems reasonable: https://www.cibsejournal.com/cpd/modules/2010-02/
Not an in-depth knowledge of their workings, but enough to consider their integration with / compare them to other heat source.
What would you recommend?

No, its not reasonable at all. Its ridiculous. Run a heat pump at 50C and you'll drop the COP at least 30% from rated at best. Running at 50C constantly the discharge temperature will be between 75 and 85C and you'll slowly cook your windings until your compressor fails in 4-5yrs. That's a nice bill on top of running costs that wouldn't save you much over an oil boiler. Condenser is correct to point out how bad an idea that is.

Dardania

threeball wrote: »

Dardania wrote: »

Yes - based on this it seems reasonable: https://www.cibsejournal.com/cpd/modules/2010-02/
Not an in-depth knowledge of their workings, but enough to consider their integration with / compare them to other heat source.
What would you recommend?

No, its not reasonable at all. Its ridiculous. Run a heat pump at 50C and you'll drop the COP at least 30% from rated at best. Running at 50C constantly the discharge temperature will be between 75 and 85C and you'll slowly cook your windings until your compressor fails in 4-5yrs. That's a nice bill on top of running costs that wouldn't save you much over an oil boiler. Condenser is correct to point out how bad an idea that is.

Very informative - thank you for your criticism. The information out on the web is not easily found, compared to say finding info on how traditional boilers work - so to have real world experience fed back it's invaluable.
Goes to show the challenge of retrofitting heat pumps to replace existing radiator type systems.

Out of curiousity, what is the optimal flow / return temp for a heat pump?
And do they do any sort of seasonal weather compensation like gas boilers do?

Condenser

Dardania wrote: »

Very informative - thank you for your criticism. The information out on the web is not easily found, compared to say finding info on how traditional boilers work - so to have real world experience fed back it's invaluable.
Goes to show the challenge of retrofitting heat pumps to replace existing radiator type systems.

Out of curiousity, what is the optimal flow / return temp for a heat pump?
And do they do any sort of seasonal weather compensation like gas boilers do?

The lower the better with heat pumps. You'll gain 2-3% for every degree less you need to produce and lose 2-3% for every degree increase. They are normally rated at a flow temp of 35c. Most decent machines have weather compensation to take advantage of this.

1874

The Nilan Compact P sounds very interesting,
Id wondered what the options might be for heating water in a house where insulation and airtightness were in place to a high standard. I concluded it would be necessary to have supplementary heating, a gas boiler fed from a bottled supply. I didn't know if this would be possible to have a very low power gas boiler fed from a bottled supply that could supply a heat exchanger to supplement air temperature in ducting after a MHV unit, as I saw a heat exchanger which was for that purpose, but didnt know if such low power gas boilers existed. I also expected that the hot water required would be by this method also, possibly supplementing solar or PV (im not sure if the latter is viable for heating water).

I was looking to post in an existing forum to enquire about retrofitting energy saving options to try estimate what might be possible to create a very energy efficient house, but that might not necessarily be Passiv house standard, (mainly due to the unknown factor if there is insulation under the ground floor concrete) and the potential cost and disruption of digging that all up to be replaced.

Id ruled out the idea of Air sourced heat pumps from what Ive read about them, although I always wondered why ASHP weren't sheltered to limit the effects of frost or if there was some means other than using electricity or operating the unit in reverse to overcome freezing conditions, such as blowing exhaust ventilation air over the heat exchanger?
I had always thought that ventilation for heat recovery, and water or space heating as completely seperate things, but the Nilan seems to be able to deal with everything, heating-ventilation/extraction, DHW, and air sourced heat pump that can be used to space heat? am I missing something here, I did think Air or ground sourced heat pumps were not sufficient for heating radiators or underfloor heating?
all the same, why am I not hearing this as being the next best thin to sliced bread? its PH approved!? so Im taking that it does what it says on the tin?

Anyway, my original question was, can I go about insulating a house, airtightness and windows that are good airtightness (or is the cost difference for passive house standard not much more cost?), have MVHR, such as the Nilan P or similar, but not dig up a concrete ground floor.

Could I have a good or very good performing house energy wise? that may not be PH standard, but better than supposed good A rated builds currently that have gaping holes in the wall for ventilation? questionable airtightness and unknown/non existant insulation under the concrete ground floor slab?

mrawkward

I renovated my 1970s huge window 140sqm bungalow last year, It already had double glazed PVC windows which were in good order. I had external wall insulation fitted and doubled the attic insulation. 8.5Kw Mitsubishi Air source heat pump and matching cylinder. Aereco managed/powered ventilation system for kitchen and both bathrooms, all other room vents were replaced with smart vents (unpowered). Removed 2 year old gas boiler, replaced solid fuel burner with a video fire.

Outcome: Much nicer aesthetic external finish, house at 21C 24/7/365 with unlimited hot water. Reduced total energy bills from €4K to €1.4K pa and now about to add 3.2Kw PV solar panel setup to take this down even further. BER went from D2 to B2.

As i suffer from old rugby knee arthritis, the comfort bonus is beyond a simple cash value in addition to the saving above. I got grants for HRI tax relief, SEAI grants and €1200 of free energy from Electric Ireland for my carbon credits. Could not be more pleased.