Best heating system for new house

irishguy · 13-09-2020 2:37pm #1

Can anyone tell me what the current recommend heating system for a new house build C.250sqm A rated would be?. Air to water heat pump?

sydthebeat · 13-09-2020 3:14pm

irishguy wrote: »

Can anyone tell me what the current recommend heating system for a new house build C.250sqm A rated would be?. Air to water heat pump?

100% of one offs I've been involved with for the last 5 years have been using Air to Water Heat Pumps.

irishguy · 13-09-2020 3:26pm

sydthebeat wrote: »

100% of one offs I've been involved with for the last 5 years have been using Air to Water Heat Pumps.

I assume the house would really need to be A rated for them to work? So would be fine for new builds, but older houses would need alot of work I guess to ensure its comfortable

sydthebeat · 13-09-2020 4:25pm

irishguy wrote: »

I assume the house would really need to be A rated for them to work? So would be fine for new builds, but older houses would need alot of work I guess to ensure its comfortable

All houses since 2011 have had to be A3 (or better) rated.

All houses under NZEB 2019 will be A2 or better

The OP question was specifically about a new build.

If youre taking about retrofitting, research "technical advisor and HLI"

Gumbo · 13-09-2020 4:30pm

irishguy wrote: »

I assume the house would really need to be A rated for them to work? So would be fine for new builds, but older houses would need alot of work I guess to ensure its comfortable

You have no option but to go A2 now with NZEB.
Apartment developments in my area are NZEB now.

irishguy · 13-09-2020 5:42pm

sydthebeat wrote: »

All houses since 2011 have had to be A3 (or better) rated.

All houses under NZEB 2019 will be A2 or better

The OP question was specifically about a new build.

If youre taking about retrofitting, research "technical advisor and HLI"

Thanks for the detailed info. Not sure if we are going to build or retrofit. So just assessing options.

bobbyy gee · 13-09-2020 5:50pm

a passive house would need nearly no heating
https://www.irishtimes.com/life-and-style/homes-and-property/passive-impressive-the-house-that-costs-300-a-year-to-heat-1.4339442?mode=amp

tedimc · 14-09-2020 10:38pm

I've nothing against A2W - I had heard problems with them back in the early 2010s but I think the newer ones are 100%.

I went with Geothermal (vertical borehole) on my A2 380m2 retrofit. Very happy with it, total bills are 1500-1800 per year.

However - looking back, presume the HP costs are roughly the same - the borehole cost about 7k extra. I think geothermal is a little cheaper to run than A2W but I doubt I'll ever justify the 7k in run elec savings.

One argument that swung it for me also was that with the Geothermal system was all indoors. I was told (but take it with a pinch of salt) that I should get 30 years out of the system. Maybe a new compressor, but no outside components to worry about.

RedXIV · 14-09-2020 11:02pm

I've been doing this research myself and interested to see what the difference was in price for geothermal vs A2W. They seem to deliver similarly in capability but the lack of external components was something I was definitely favouring and hence leaning towards geothermal.

Would a 7k difference in price be standard or does it simply depend on the site?

Water John · 14-09-2020 11:16pm

The COP of A2W is a bit over 3:1, the borehole is about 4:1. If the the borewater is pumped through an exchanger and then disposed of down a second borehole, near 6:1 can be achieved.
It's an option I would like to see further explored esp for one off houses that have a borehole and pump already in place. Such a system needs a supply of about 3m cubed/hr.

tedimc · 14-09-2020 11:42pm

RedXIV wrote: »

Would a 7k difference in price be standard or does it simply depend on the site?

It would depend on the site. For reference, we got two bore holes drilled at 110m each from what I recall. I presume smaller/larger houses would need shallower or deeper holes.

However, I assume a certain amount is a fixed cost of getting the machine on-site, setup, etc. Even for a small house, I would expect a minimum of 4-5k. For larger properties or where access is difficult, 10k+ would be realistic.

tedimc · 14-09-2020 11:44pm

Water John wrote: »

The COP of A2W is a bit over 3:1, the borehole is about 4:1. If the the borewater is pumped through an exchanger and then disposed of down a second borehole, near 6:1 can be achieved.
It's an option I would like to see further explored esp for one off houses that have a borehole and pump already in place. Such a system needs a supply of about 3m cubed/hr.

Would the sequencing of this make a difference? We have two bore holes, but the water is sent down one, then the next before going to the heat pump and then back out to the first hole.

tedimc · 14-09-2020 11:46pm

tedimc wrote: »

It would depend on the site. For reference, we got two bore holes drilled at 110m each from what I recall. I presume smaller/larger houses would need shallower or deeper holes.

However, I assume a certain amount is a fixed cost of getting the machine on-site, setup, etc. Even for a small house, I would expect a minimum of 4-5k. For larger properties or where access is difficult, 10k+ would be realistic.

One other point is also ground conditions. Apparently rock is favored as soft ground/bog is very hard to keep the hole open and send the pipe down. Ours was mostly rock.

Water John · 14-09-2020 11:52pm

tedimc wrote: »

Would the sequencing of this make a difference? We have two bore holes, but the water is sent down one, then the next before going to the heat pump and then back out to the first hole.

Is this the brine loop you are talking about?

tedimc · 15-09-2020 12:26am

Water John wrote: »

Is this the brine loop you are talking about?

Sorry - yes the brine loop.

Water John · 15-09-2020 11:23am

Ah, so one borehole wasn't adequate for some reason, maybe house size.

The other system I mentioned was pumping the water out of well A, through a stainless steel exchanger and the cooled water(drops about 2C) down the second well B. The water and pump in well A would also being supplying the house.
So normally the cost is, the second borehole and the exchanger.

Zarco · 15-09-2020 11:30am

Does the geothermal give much trouble now

I know the controls were very complicated when a fault arose, fine if you have a service engineer on call

I worked on the electrical installs which was straightforward enough

irishguy · 15-09-2020 11:31am

But with a 7k difference. Would that not cover the replacement of the external components of an a2w system over that 30 year period? Assuming g2w system would last that long?

Water John · 15-09-2020 11:37am

The diff between A2W and GSHP generally is not massive, say 25%. Now if your heating bill is quite low with and A rated house it would be less than €200/yr.
If working on a budget , the extra 5/6K would be best spent on a mechanical heat recovery ventilation system.

tedimc · 16-09-2020 11:22pm

Zarco wrote: »

Does the geothermal give much trouble now

I know the controls were very complicated when a fault arose, fine if you have a service engineer on call

I worked on the electrical installs which was straightforward enough

Not much really. I did have a compressor fault from day 1 which slowly got worse until it just wouldn't clear. But it got replaced and all good now. There is a bit of setting up the heat curve, etc. but I presume that is the same for all HPs?

tedimc · 16-09-2020 11:26pm

irishguy wrote: »

But with a 7k difference. Would that not cover the replacement of the external components of an a2w system over that 30 year period? Assuming g2w system would last that long?

Probably - at todays prices it would likely replace the whole unit easily I suspect. Also - fast forward 10 years, and the heat pumps would probably be a lot less. Time value of money and all that.

Overall, I'm very happy with the system but no doubt that over the lifetime it may not represent the overall best value.

irishguy · 21-09-2020 8:37pm

I assume heat pumps just heat the house and dont heat water? What would be best for that if they don't.

sydthebeat · 21-09-2020 8:50pm

irishguy wrote: »

I assume heat pumps just heat the house and dont heat water? What would be best for that if they don't.

they do heat water

mr_edge_to_you · 21-09-2020 8:53pm

Haven't posted in this forum in 9 years I reckon.

We put in a vertical source geothermal heatpump in 2010. Without doubt the best decision we made in our build, despite everyone telling us we were mad.

Our house 2500 sq ft with UFH upstairs and downstairs - the control technology has changed massively in the last few years so our controls are pretty basic. We turn the heatpump on at 20 degrees at end of September (set all internal thermostats accordingly) and just leave it alone until April. We have 500l of hot water 24/7. We've no other source of heating other than a non boiler stove. We use the stove for comfort and if we need to get a load of washing dry overnight.

Our ESB bill (family of 4) is approx €1800 per year. We buy a tonne bag of turf for €90 each autumn and a few bags of coal throughout the year. We did put our ESB on a standardised monthly payment plan to avoid the higher bills in the winter.

Someone asked me recently, if the heatpump blew up, would I replace it with the same system - yes.

tedimc · 21-09-2020 9:14pm

irishguy wrote: »

I assume heat pumps just heat the house and dont heat water? What would be best for that if they don't.

Yes ours heats the water as well - most do I think. So much so, I have a Solar Panel system half installed and never finished it I am ashamed to say. My plan was to use Solar for the summer months and turn off the HP.

BoardsMember · 25-09-2020 9:42am

We're looking at a refurb job. Old House, 1920s.

One option is to backfill the cavity below floating floors in the ground floor, primarily to solve for draughts, but also any longer term rot, rodents etc.

This would allow a 2nd option in the refurb of UFH downstairs, which we would consider, especially with more working from home likely. We have rads now.

If we did those 2 options, would we be mad not to do A2W? Up front costs are so expensive.

If we went A2W, is the cost of PV cells/system worth it to run the A2W system....seems like when u need the heat most, you have the least sun.

Last question, is some sort of mechanical ventilation system needed with A2W?

Seems like I'd be mad to backfill the cavity and not do UFH, but then one thing leads to another, and I end up with spending 20k or so more on the refurb than I actually need to. Late 40s and will be here for life, 2 young teenage kids will be here for a while too....

sydthebeat · 25-09-2020 9:57am

BoardsMember wrote: »

We're looking at a refurb job. Old House, 1920s.

One option is to backfill the cavity below floating floors in the ground floor, primarily to solve for draughts, but also any longer term rot, rodents etc.

This would allow a 2nd option in the refurb of UFH downstairs, which we would consider, especially with more working from home likely. We have rads now.

If we did those 2 options, would we be mad not to do A2W? Up front costs are so expensive.

If we went A2W, is the cost of PV cells/system worth it to run the A2W system....seems like when u need the heat most, you have the least sun.

Last question, is some sort of mechanical ventilation system needed with A2W?

Seems like I'd be mad to backfill the cavity and not do UFH, but then one thing leads to another, and I end up with spending 20k or so more on the refurb than I actually need to. Late 40s and will be here for life, 2 young teenage kids will be here for a while too....

Heres a little pic i use to show how you should prioritise energy saving measures:

the more you focus on the top of the pyramid the less you have to worry about the bottom.

so if you really concentrate on getting your insulation levels, air tightness and thermal bridge details as best as you can.. .then you are reducing your energy demand way down.... and there is no need for a large expensive heating system

mr_edge_to_you · 25-09-2020 10:01am

sydthebeat wrote: »

Heres a little pic i use to show how you should prioritise energy saving measures:

the more you focus on the top of the pyramid the less you have to worry about the bottom.

so if you really concentrate on getting your insulation levels, air tightness and thermal bridge details as best as you can.. .then you are reducing your energy demand way down.... and there is no need for a large expensive heating system

Excellent graphic - Sydthebeat is still the voice of sense and logic on this forum I see!!!!

BoardsMember · 25-09-2020 10:07am

sydthebeat wrote: »

Heres a little pic i use to show how you should prioritise energy saving measures:

the more you focus on the top of the pyramid the less you have to worry about the bottom.

so if you really concentrate on getting your insulation levels, air tightness and thermal bridge details as best as you can.. .then you are reducing your energy demand way down.... and there is no need for a large expensive heating system

Thanks a mill Syd, that is so simple and so relatable, avoids the confusion that my overly long post suggested.

Can you give me a little more info on Thermal Bridges? What should I be looking out for, noting our house is redbrick so EWI not an option. Is it about avoiding cold bridges etc, ie no mould.

Calahonda52 · 25-09-2020 11:10am

BoardsMember wrote: »

Thanks a mill Syd, that is so simple and so relatable, avoids the confusion that my overly long post suggested.

Can you give me a little more info on Thermal Bridges? What should I be looking out for, noting our house is redbrick so EWI not an option. Is it about avoiding cold bridges etc, ie no mould.

Yep, Syd is THE MAN when it comes to this stuff.

https://en.wikipedia.org/wiki/Thermal_bridge
explains them pretty well

When we look at these issues, to get the A/T layer correct we use a illustrative test where , on a section through the house, you place the pen on where the a/t layer will be and move the pen around the internal perimeter back to the starting point.
If you need to lift the pen, say at the first floor ceiling connection, then the a/t layer is not continuous.

Same principle with insulation, where the line represents a constant thermal conductivity.

Both are well illustrated in the dry lining sketch in the link above, 3rd one down

thermal bridge at junction. Heat moves from the floor structure through the wall because there is no thermal break.

Properly done, EWI is the best answer as its like a wooly hat, when it joins up with the roof/ceiling insulation.
The best design is like a round tower

Re the triangle, you will also hear that A/T should go above Insulation: however the underlying principle is the same, reduce the heating demand and then design the heating system.

BoardsMember · 25-09-2020 11:46am

Calahonda52 wrote: »

Yep, Syd is THE MAN when it comes to this stuff.

https://en.wikipedia.org/wiki/Thermal_bridge
explains them pretty well

When we look at these issues, to get the A/T layer correct we use a illustrative test where , on a section through the house, you place the pen on where the a/t layer will be and move the pen around the internal perimeter back to the starting point.
If you need to lift the pen, say at the first floor ceiling connection, then the a/t layer is not continuous.

Same principle with insulation, where the line represents a constant thermal conductivity.

Both are well illustrated in the dry lining sketch in the link above, 3rd one down

thermal bridge at junction. Heat moves from the floor structure through the wall because there is no thermal break.

Properly done, EWI is the best answer as its like a wooly hat, when it joins up with the roof/ceiling insulation.
The best design is like a round tower

Re the triangle, you will also hear that A/T should go above Insulation: however the underlying principle is the same, reduce the heating demand and then design the heating system.

You're not bad yourself Calahonda!

I thought A/T would be top alright, but agree it and insulation would be the top 2.

Thanks for the info.

Best heating system for new house

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