New Build - Heating and warm water

Forums › Home Workshop DIY › New Build - Heating and warm water

olivernz

362 posts

Ultimate Geek

ID Verified

Trusted

Lifetime subscriber

#273129 5-Aug-2020 17:49

Looks like I am crazy after all and I am intending to build.

This is in Kapiti will be about 200sqm, concrete floor with bedrooms carpet. Ideally I'd go full on zero energy home but that might be just a bit too costly. So it will be as well insulated as I can + underfloor heating. Now the question is, what to drive the underfloor heating with. I was thinking heat pump for heating and hot water supported by solar panels (water). There is no gas on site hence I thought heating with gas bottles might not be viable.

Any other ideas or anyone? Any experience building something this complex and running it?

Cheers Oliver

Scott3

3340 posts

Uber Geek

Lifetime subscriber

#2535416 5-Aug-2020 18:10

LPG (bottled gas) costs heaps more to run than heat pumps (in some cases it is even more expensive than resistance electric heating). Basically non viable to do new LPG central heating.

I would do an air sourced heat pump hydronic underfloor heating system. If you start running into budget constraints a ducted heat pump system would be cheaper and have the advantage of being able to cool as well.

I would have hot water independent. A toss up between heat pump hot water & solar thermal with electric resistance boost. I would probiably lean towards the latter.

GoodSync

GoodSync. Easily back up and sync your files with GoodSync. Simple and secure file backup and synchronisation software will ensure that your files are never lost (affiliate link).

timmmay

19639 posts

Uber Geek

Trusted

Lifetime subscriber

#2535420 5-Aug-2020 18:13

I'd also prefer ducted central heating for the summer cooling. If you can do under floor and ducted, great, but that seems excessive, just ducted with good insulation between the slab and the carpet would probably be sufficient. I think in the UK you put down polystyrene, then concrete, and there's poly on the edges to keep the slab insulated. Maybe it would slowly warm from inside.

Summers feel like they're getting hotter.

olivernz

362 posts

Ultimate Geek

ID Verified

Trusted

Lifetime subscriber

#2535425 5-Aug-2020 18:25

@Scott3 Thanks for that. Wasn't aware gas was so deer.

@timmay Since we will have polished concrete through most of the house I guess underfloor is best and coming from Europe we like our central heating.

Although in saying all that has anyone here got experience with passive/zero energy houses? It's a relatively new thing here so expect it to be bloody expensive.

timmmay

19639 posts

Uber Geek

Trusted

Lifetime subscriber

#2535428 5-Aug-2020 18:39

Definitely think you should follow up the heating option with someone with experience of your situation. Underfloor heating seems fine, but I really do value cooling. We have heat pumps in the lounge / kitchen and when they fail I'll possibly go for ducted mostly to get air conditioning for the bedrooms in summer.

Scott3

3340 posts

Uber Geek

Lifetime subscriber

#2535430 5-Aug-2020 18:43

olivernz:

@Scott3 Thanks for that. Wasn't aware gas was so deer.

@timmay Since we will have polished concrete through most of the house I guess underfloor is best and coming from Europe we like our central heating.

Although in saying all that has anyone here got experience with passive/zero energy houses? It's a relatively new thing here so expect it to be bloody expensive.

Natural gas (piped street gas) is about 7c/kWh (plus a roughly $30 a month connection fee).

LPG gas in 45kg cylinders costs $110 - $140 each, plus an annual rental fee of $130. The low end of that range works out to

614kWh in a 45kg cylidner, so the low end of that price range works out to be 18c/kWh.

I pay less than the above for my power (on a standard user plan). Gas continuous water heaters are roughly 90% effichent, good gas boilers are about 95%. Electric resistance heaters are 100%, and heat pumps are roughly 300% (heat output per power input).

edge

410 posts

Ultimate Geek

Trusted

Lifetime subscriber

#2535479 5-Aug-2020 20:44

We're in the process of building in Kapiti as well :-) (about 290 sq.m. including garage). Our slab is down, with us living in the workshop and the builder due back in October (all planned in advance, I hasten to add!) and we have gone with heatpump powered hydronic heating in the slab - with the same unit also providing hot water for the house. 50mm poly under the whole house (including garage, although it is not heated) and Insulfound edge insulation for the slab. I decided that this was the best way to go considering all the options (we have no reticulated gas or water either!).

Other than the usual double glazing and heaps of insulation we haven't gone for a "passive house" design. We will only have carpet in the two bedrooms - the rest will be 20mm engineered timber flooring, which works OK with hydronic heating (although bare concrete requires less energy input, we are not fans of concrete floors in our old age!!). There is a massive amount of glass in the house so I am not sure just how summer temperatures will be managed, apart from good airflow through the house. My plan is to plumb/wire in for an internal heat pump in case we need cooling in summer in future - but I won't put it in to start with.

Good luck with the build planning :-)

"It is useless to attempt to reason a man out of what he was never reasoned into."
— most commonly attributed to Jonathan Swift, author/theologian

timmmay

19639 posts

Uber Geek

Trusted

Lifetime subscriber

#2535481 5-Aug-2020 20:57

edge:

There is a massive amount of glass in the house so I am not sure just how summer temperatures will be managed, apart from good airflow through the house. My plan is to plumb/wire in for an internal heat pump in case we need cooling in summer in future - but I won't put it in to start with.

I suggest you consider light colored sunshade blinds to reflect heat away, and consider that you might want to install either a single room or ducted heat pump in the future.

jonb

1739 posts

Uber Geek

Trusted

#2535484 5-Aug-2020 20:58

As you are interested in low emission/passive, have a look if geothermal/ground loop heat pump type system is feasible.

https://www.centralheating.co.nz/assets/resources/Introduction-geothermal-heating.pdf

bfginger

1237 posts

Uber Geek

#2535507 5-Aug-2020 23:44

Are you going for slab edge and under slab insulation? Atop slab underfloor heating sounds preferable to in-slab.

Heating the slab is most appropriate for 24/7 heating cold climates where responsiveness is less important and outdoors doesn't heat up during the day in winter. Mid day winter sun can be strong in New Zealand. I know someone with in-slab heating and it takes a while to heat up the thermal mass. It's like a firehose that doesn't turn off or on very quickly.

The Daikin Altherma can handle heating, cooling and hot water

https://www.daikin.co.nz/our-product-range/altherma-hydronic-heating

You have to be careful of placement as a large heat pump unit can be noisy.

The default for immigrants is always to think in terms of central heating after what they had back home. I'd prefer to put that huge expense into better joinery with thermal break and good low-e and more insulation. The sun in New Zealand is strong so it's good to harness it in winter and shade it in summer. A good ventilation system can even out temperatures across the house. Winter sun is very weak in most of Europe.

MikeAqua

7627 posts

Uber Geek

#2535557 6-Aug-2020 08:47

Also the Mitsubishi EcoDan range, can do central heating (radiator or underfloor) and HWC heating - a either specialist HWC or via a coil in a conventional cylinder.

I've looked into ground source and it's crushingly expensive in NZ. The payback just isn't there, because of the very high price.

Mike

edge

410 posts

Ultimate Geek

Trusted

Lifetime subscriber

#2535766 6-Aug-2020 13:25

MikeAqua:
I've looked into ground source and it's crushingly expensive in NZ. The payback just isn't there, because of the very high price.

Exactly this! I certainly looked into it as well and came to the same conclusion - no comparison really, unfortunately.

"It is useless to attempt to reason a man out of what he was never reasoned into."
— most commonly attributed to Jonathan Swift, author/theologian

olivernz

362 posts

Ultimate Geek

ID Verified

Trusted

Lifetime subscriber

#2536071 7-Aug-2020 08:52

Thanks for all the great posts! Will work through them.

I am still very much at the beginning of this and earthworks will be a challenge anyway but I am aiming to make the house as insulated as possible all round. For flooring so far looking at X-Pod (or similar) with all the insulation I can get. Styro may cause more cracking on what i am building on (never mind environmental impact). And aiming to have most of the house polished concrete. Not sure if we will have a fireplace (would be more decorative than for heating). But I will explore all heat-pump options. enough to read up on above.

Of course i am seeking professional advice too but i always like to hear from people that actually have the stuff installed.

I should also start a convo on "What did you wish you had done when you were building" ;-)

olivernz

362 posts

Ultimate Geek

ID Verified

Trusted

Lifetime subscriber

#2536082 7-Aug-2020 09:18

Ok, looking at geothermal heat pump I think that's a solid no. In climates where it get's below 0 degrees every winter sure, it makes sense but not in Kapiti.

timmmay

19639 posts

Uber Geek

Trusted

Lifetime subscriber

#2536084 7-Aug-2020 09:20

Fireplaces tend to need a decent sized hole in the ceiling which lets in / out drafts and makes the whole house colder. When I took my fireplace out, sealed the ceiling and insulated over it room and the whole house got warmer. Adding heat pumps was another great step. I wouldn't do fireplaces for that reason, and also because they really hurt the local air quality.

pipe60

119 posts

Master Geek

#2536429 7-Aug-2020 19:31

We put heating in our slab run off a wood burner that does domestic and under floor water.

https://www.marshallheaters.co.nz/

We did 140mm framing with R4 insulation in the walls and ceilling which has made for a warm house in winter and keeps the heat out in summer.