Underfloor heating options for new build in Hikuai, Coromandel

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EmmaOffshore

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#209021 9-Mar-2017 13:49

Hi there

We are in the process of designing a new build house for the Hikuai region in Coromandel.

Something we are having trouble deciding on is whether we should have the pipework for underfloor heating installed when our concrete slab is poured.

We are fairly confident that it won't be part of our initial budget to have a heat source to actually run the underfloor heating so would be installing the pipe work only to kind of future proof ourselves if we needed and because its one of those things you just can't do later once the slab is set.

The house site is elevated, and the Hikuai region is known for its rainfall (such as the last few days), so we'll be in the clouds and colder / damper more often than those in coastal areas like Tairua nearby.

There are a few things to note about our house design that make the decision a wee bit trickier:

At this stage we won't be installing a hot water tank. We are planning on using LPG + Infinity unit for hot water instead - any comments on this are also welcome :-)
We will be having a fireplace in the main living/kitchen/dining space where the underfloor heating would be mostly placed
Due to our lack of hot water tank we don't plan to install a wetback as we won't have anywhere to put the hot water - again any comments on this also welcome
Our build budget is pretty tight so the extra cost for the pipework is definitely money we could use elsewhere to good effect

So I guess the main things I would be keen to hear about from people are:

Any regrets or happy stories from people who did or didn't get underfloor heating in a new build slab
Thoughts overall on an exposed slab with no underfloor heating
Are we going overboard even considering underfloor heating in Hikuai? We currently live in Wellington so might have a colder outlook on things

Thanks heaps for any comments

Emma

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#1733690 9-Mar-2017 13:56

I took a freestanding fireplace out of my house. They need space around the chimney so it doesn't make the ceiling catch fire. Wind whipped through that hole and made the whole area cold, plus they're messy things. Taking it out made the whole house warmer the 99% of the time it wasn't lit. When it was lit it heated that room quickly, but made no difference to the rest of the house. You'd need a heat distribution system to heat the rest of the house.

How much would it cost to install the pipework for underfloor heating? I'd tend to do it.

We have heat pumps at home, my wife hates them, they're loud and drafty. She much prefers radiators like she had back in the UK. Much quieter, and a different feel to the heat. They take up wall space though. Ducted heat pump is another option.

EmmaOffshore

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#1733705 9-Mar-2017 14:17

timmmay:

I took a freestanding fireplace out of my house. They need space around the chimney so it doesn't make the ceiling catch fire. Wind whipped through that hole and made the whole area cold, plus they're messy things. Taking it out made the whole house warmer the 99% of the time it wasn't lit. When it was lit it heated that room quickly, but made no difference to the rest of the house. You'd need a heat distribution system to heat the rest of the house.

How much would it cost to install the pipework for underfloor heating? I'd tend to do it.

We have heat pumps at home, my wife hates them, they're loud and drafty. She much prefers radiators like she had back in the UK. Much quieter, and a different feel to the heat. They take up wall space though. Ducted heat pump is another option.

Thanks for your response Timmay.

We're building a small house, so the concrete slab covers approx 65% of it, and we're looking at a heat transfer to a bedroom wing to heat 3 bedrooms if using fire for primary heat.

Will cost us approx 7.5k plus GST for the pipework and associated install costs for the underfloor heating, without the heat source. We don't want heatpumps as never liked them and don't like the look of them. Hoping that a modern doubleglazed and well designed N facing house might not need that much heating for 70% of the year...

timmmay

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#1733722 9-Mar-2017 14:27

In Wellington we use heating nine months of the year, in an older house that's been well insulated, including double glazing. It is warmer up north, but is it that much warmer?

Why is the whole house not on the slab?

Using a fire as your primary heat source sounds like a real pain in the butt. You can do radiators that use an efficient heat pump outside to heat the water. Or just do under floor, that sounds much nicer.

A ducted heat pump looks like ducts in the ceiling, and you can integrate ventilation.

mattwnz

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#1733736 9-Mar-2017 14:36

We looked at it as an option but decided against it. It is slow to react, and quite expensive to run. Plus you need good slab insulation including edge insulation which can be difficult to detail welll. Also it only hearst it doesn't cool, unlike a heat pump.

EmmaOffshore

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#1733737 9-Mar-2017 14:36

House is not all on a slab as we have a wing that sticks out above ground level due to the shape of the building site- and budget we have available means easier for that section to be on piles.

It might be that much warmer up in the Coromandel, we don't really know. We have family on the coast about 40 minutes north of Hikuai and they probably use a heat pump for maximum 3 months of the year in 10 year old house with single glazing. Even with single glazing and not particularly designed for passive heat, their place holds the heat really well.

Why fire? We quite like fires.

timmmay

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#1733738 9-Mar-2017 14:42

I quite liked fires too, until I had to feed and clean it!

gcorgnet

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#1733743 9-Mar-2017 14:50

timmmay:

I quite liked fires too, until I had to feed and clean it!

I have the same thing to say about kids ;-)

Aredwood

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#1734629 11-Mar-2017 01:26

Are you wanting lowest install costs or lowest running costs. Infinity on Lpg is definitely cheapest for install costs. Running costs - often cheaper than electricity as lots of people keep going on the wrong power price plans.

Which lines company services that area and what pricing plans do they offer? If they offer a decent night rate plan, Then a large electric cylinder with wetback will be the lowest running costs. As you will probably only need the electricity when you are not using the fire.

As for underfloor heating - good for rooms with 0 or very little solar gain. Otherwise the slow response times kill it.

nickb800

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#1734664 11-Mar-2017 09:12

Just to be clear - is this a holiday house or permanently occupied house? Just wondering as it is an area with a lot of holiday houses. That will affect the inital investment versus running cost equation

SATTV

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#1734670 11-Mar-2017 09:42

My old boss put pipes in the floor of his aircraft hanger when he built it at Ardmore.

He then connected it up to solar tubes. There was no hot water tank or may have been a small kitchen type one.

The slab apparently is always warm and when he put his plan in there and it is wet, it drys a lot faster and better i.e. gets into the spaces.

If it was me I would absolutely do it, I would make room for a small hot water cylinder and heat it by solar and wetback. ( or a larger outdoor tank on the roof or under the portion that is not a slab )

Doing this sort of thing when building is the best time to do it.

In saying that, it is easy to spend someone elses money.

A well designed house north / north west facing with large double glazed windows and uncovered concrete walls and floors that see the sun will help a lot with passive heating.

Best of luck.

Regards

John

I know enough to be dangerous

Sidestep

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#1734672 11-Mar-2017 09:52

I'd vote for installing the pipe, heat rises..!

I'm a big fan of underfloor heating.
Lived in Western Canada for many years, very cold winters, houses commonly well insulated & heated with forced air furnaces, & messed around with hydronic heating systems a bit there.

We pulled out an existing furnace & retro fitted an old two story house with underfloor heating & a much smaller ducted furnace backup during a renovation.
Then installed underfloor heating in the garage, basement & lower level of a wood furnace heated new build.

With that bit of experience my wife & I designed (& installed) one in a large old (wooden) barn in a rural area that we converted into an office/workshop for our business.
We'd pulled out the basic heating (forced air/gas furnace/radiator + gas infrared radiant) during the renovation & planned installation of a more modern, similar system.

But we ended up basically building new inside the old shell - pouring a new concrete floor in most of it (an 80'x40' 6" slab) and building a (20'x40') living area & (25'x35') loft/office.
We designed a basic system of zones (workshop, office, bathroom shower, kitchen etc) & before the pour tied off loops of orange (oxy barrier) PEX at 18" on the rebar, and along the upstairs joists, all returning to one manifold area.
When turned on the (180K Btu) gas boiler maintained heat in a boiler loop, 3 manifolds fed zones controlled by thermostats, each individual loop had a ball valve.

It worked well. We ran glycol in case of a failure and freeze up. Could heat the most important zones in 24 hours, the whole place up to temperature in 3-4 days, easily coped with -20°C.
We probably made it overly complex. After a few years we ended up reducing the number of thermostats & just adjusting zones with the ball valves.
One useful thing we'd done was run a couple of loops around the outside edge of the slabs. After an initial heating period we could shut down most of loops & just run heat around the outside to maintain the temperature.
A big roller door opening & closing for vehicle access to the workshop did let heat out but the warm floor brought it back up pretty quickly.
It was a really nice heat. Once found a mechanic stretched out asleep on the floor under a vehicle he was supposed to be servicing. The farm dog & cats would sneak in to lie on the floor.

In NZ (rural very Far North, mild climate) we have a wood frame house, Solar water with electric backup & wood fire/wetback. Family of 4 (2 adults, 2 pre teens). We have unlimited wood.
Never use the electric HW element - in fact it has failed & I haven't bothered replacing it. We have an excess of hot water from the fire all winter - often boils in the pipes.
We'll be replacing the solar with a new, more efficient system this year and likely underfloor heating at the same time. Mainly to redistribute the heat from the fire to the bedrooms at night.
We've got a basic ducted (fan forced) air system, but we end up with hot air at ceiling level, cold floors. We've considered radiators (passive & fan forced) but I just like warm floors!

(ha - I've written a novel, too much coffee today!)

EmmaOffshore

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#1734698 11-Mar-2017 10:55

nickb800:

Just to be clear - is this a holiday house or permanently occupied house? Just wondering as it is an area with a lot of holiday houses. That will affect the inital investment versus running cost equation

It'll be a permanently occupied home. If a holiday home I think we'd be happy without underfloor!

EmmaOffshore

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#1734699 11-Mar-2017 10:58

Aredwood:

Are you wanting lowest install costs or lowest running costs. Infinity on Lpg is definitely cheapest for install costs. Running costs - often cheaper than electricity as lots of people keep going on the wrong power price plans.

Which lines company services that area and what pricing plans do they offer? If they offer a decent night rate plan, Then a large electric cylinder with wetback will be the lowest running costs. As you will probably only need the electricity when you are not using the fire.

As for underfloor heating - good for rooms with 0 or very little solar gain. Otherwise the slow response times kill it.

We're happy to look at a whole of life cost - so interested in lower costs balancing install and running. Infinity on LPG doesn't look too bad in that regard. We're wondering about installing solar HW in future if money allows.

We'll look into the lines companies though - we're not on a plan with night rates at the moment so hadn't even thought of that.

Couple of the rooms in the slab will have little solar gain. An installer has suggested we *might* get some movement of heat in the underfloor pipes to the less warm areas if we install them and fill with water and don't hook up a heating source in the short term, so could be worth a gamble.