Warmup Underfloor Heating vs Central Heating

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isis

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#138064 18-Dec-2013 15:10

Hi,

We've seen lots of new builds with Warmup signs on the front fence and have asked for a quote for our new build. There's not much reviews online on the efficiency etc of these things and was wondering if anyone had experience with this?
The quote is similar in price to a gas central heating.
Is underfloor heating enough to keep the place warm in winter and do we need to top up with heating source?

Cheers

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#954384 18-Dec-2013 15:13

I have a friend with old style under floor heating, they say it worked well all winter. Powering it with an efficient heat pump type arrangement would probably save some money.

Can you choose to heat only the parts of the house you need? I know in our house we keep part of it warm in winter and don't worry so much about the other parts.

mattwnz

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#954389 18-Dec-2013 15:18

Never heard of it, but is it just electric coils under a floor subsrate, or is it proper inconcrete slab underfloor heating, which has water tubes heated by a water heatpump? If it is just coils under the floor, I don't beleive they are any more efficent than a normal electric bar heater, and they can be very expensive to run. A system heated by a water heat pump is an efficent way to heat it, but you also need good insulation. I have a house with underfloor heating coils installed in the 80's and never use it due to cost. When I did run it , it cost an extra $500 per month.

timmmay

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#954392 18-Dec-2013 15:21

In the UK they use radiators on the walls, they work well but you have to plan your house for them. Other things they do include:
- insulating under the floor slab, sometimes double insulating
- double wall construction
- double or triple glazing
- Using modern building materials

If I was building a new house now I'd probably go with a central ducted air conditioning system that can cool as well as heat. I'd want to be able to shut off zones as required, for example spare rooms and such. I probably wouldn't do under floor heating.

scuwp

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#954555 18-Dec-2013 22:59

If it's the electric coil type under the floor, forget about it heating the home, unless you live in northland or something. Keeps ya toes warm on cold tiles, might make a degree or two difference to room temp at best, and costs a fortune to run. I wouldn't hesitate to put the money into a decent central heating/cooling system instead.

Just for some context, we have a 4 year old home with what I consider 'standard' electric underfloor heating in all wet areas and the (large) kitchen floor. After the first winter we got a heat pump installed and never used the underfloor heating again. I miss our last place which had central heating.

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mattwnz

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#954557 18-Dec-2013 23:21

timmmay: In the UK they use radiators on the walls, they work well but you have to plan your house for them. Other things they do include:
- insulating under the floor slab, sometimes double insulating
- double wall construction
- double or triple glazing
- Using modern building materials

If I was building a new house now I'd probably go with a central ducted air conditioning system that can cool as well as heat. I'd want to be able to shut off zones as required, for example spare rooms and such. I probably wouldn't do under floor heating.

Are there cost benefits using and installing a ducted system?You can shut off zones with underfloor, but the benefit of ducted is that it can cool too. But underfoot should be more efficient as it heats a thermal mass so it is warm under feet.

timmmay

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#954586 19-Dec-2013 06:59

mattwnz:
timmmay: In the UK they use radiators on the walls, they work well but you have to plan your house for them. Other things they do include:
- insulating under the floor slab, sometimes double insulating
- double wall construction
- double or triple glazing
- Using modern building materials

If I was building a new house now I'd probably go with a central ducted air conditioning system that can cool as well as heat. I'd want to be able to shut off zones as required, for example spare rooms and such. I probably wouldn't do under floor heating.

Are there cost benefits using and installing a ducted system?You can shut off zones with underfloor, but the benefit of ducted is that it can cool too. But underfoot should be more efficient as it heats a thermal mass so it is warm under feet.

"But underfoot should be more efficient as it heats a thermal mass so it is warm under feet" I'd like some evidence or studies to back that up before I accept it.

Shutting off zones for underfloor may not make sense. It's still physically connected, so the heat will leach into it from other parts of the house. Also it takes days to heat or cool, so it's a long term not short term thing. Still, it should save some power.

No idea about cost/benefit. My concern is comfort and operational cost.

Handle9

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#954602 19-Dec-2013 07:37

Warmup generally do electric underfloor heating. If you are heating your whole house then it is extremely expensive to run as you a using electricity where 1kW in = 1kW out.

What area do you live in and what energy sources are available to you? The reason is that if you have reticulated gas then in slab or ducted central heating is a nice option which is relatively cheap to run. If you don't have reticulated gas then your options are gas bottles or diesel, both of which are really quite expensive to run.

If you do go inslab the prefered way of doing it is by zoning your house. what they do is they have a heat source with a pump feeding into a manifold. This manifold has a number of valves on it to feed each zone, genrally controlled by a thermostat. This is nice for two reasons, you get individual temperature control for each zone, and you get the ability to shut down zones when not in use. The other thing about inslab which is great is that it's silent, other than the boiler and pump.

Ducted heat pumps are OK but I'm not a big fan in a domestic environment. You can't individually control the rooms if you have one heatpump for the whole house. The reason why this is important is that each room has quite different energy needs. If you have a strongly east : west biased house you will see that in the morning the east facing rooms get blasted with the sun while the west facing rooms are quite cool. Then in the afternoon it's the other way.

A single heat pump doesn't allow you to modulate this in any way so you end up with one part of the house hot or cold. It's not ideal for comfort. If you are going down the heat pump route a better solution for comfort is a multi head high wall or console unit. This has a single compressor unit with multiple indoor units. This gives the ability to modulate each room to give good control.

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timmmay

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#954605 19-Dec-2013 07:40

High wall heat pumps are pretty ugly, I have two. A single large outdoor unit with multiple indoor units tends to be more expensive than individual outdoor units, but looks a bit tidier outside.

langers1972

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#954612 19-Dec-2013 08:06

isis: Hi,

We've seen lots of new builds with Warmup signs on the front fence and have asked for a quote for our new build. There's not much reviews online on the efficiency etc of these things and was wondering if anyone had experience with this?
The quote is similar in price to a gas central heating.
Is underfloor heating enough to keep the place warm in winter and do we need to top up with heating source?

Cheers

Gas fired central heating all the way, if you have reticulated gas in the street it's a winner all round.

SumnerBoy

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#954613 19-Dec-2013 08:07

Hey Isis,

I built a house 2 years ago and went down the route of installing underfloor hydronic heating. That is, pipes embedded in my concrete slab with an air-to-water heatpump running outside which warms up water to about 35C and circulates it through the slab - via a manifold.

As another poster mentioned, the manifold allows you to turn zones on/off and restrict flow (which in effect cools down that zone) however in my experience we find it best to just leave everything on 100% and let the whole slab warm up.

Someone else mentioned insulation and I wholeheartedly agree. Spend the money. It makes a world of difference, both in winter and in summer (when the interior of the house remains cool/comfortable on a very hot day).

My running costs for a 2-storey 260sqm house is about $180-190 a month in the middle of winter, with the underfloor running 9pm till 7am every day. The reason for these times is I am on the Day/Night rates from Genesis so electricity is only 11-12c/kWh during that time. And because I have a nice thick slab (200mm) I am able to 'charge' it up during the night when power is cheap, and it radiates warmth all day (I work from home) and into the evening before starting to warm up again after 9pm.

It is a fantastic system and I would be happy to share more details (I also have a temperature probe in the slab which stops heating too much in the spring/autumn months).

I tell anyone who will listen that hydronic underfloor is the way to go. It is a fantastic type of warmth, from the feet up, and being able to walk around on my polished concrete floors in bare feet all year round is a great feeling. Plus it is extremely efficient, but this again comes back to good insulation!

BTW - I am down in ChCh...

SumnerBoy

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#954614 19-Dec-2013 08:09

As others have mentioned, if you have reticulated gas, then radiators are probably worth investigating as well. We don't so it wasn't an option, and a heat pump can't heat the water enough to run radiators. But they would be ideal, much more responsive and controllable.

mclean

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#954686 19-Dec-2013 10:32

In-slab electric heating only makes sense if you have it on a night-rate tariff.

The good things are that it's completely silent (compared to heat pumps) and the large radiant effect of the warm floor makes it feel very comfortable. Because of the radiant effect the "comfortable" room temperature can be a few degrees lower then what you need with heat pumps - a space at say 18 deg with radiant heating can feel the same as 20 or 21 deg with purely convective heaters.

It stores heat in the slab at night during the low-tariff hours. So the down-side is that the heat gets released during the day whether you want or not. If you get a warm day during the heating season it's going to overheat the house and you've wasted energy. The proper way is to turn it down and use it as background heating, target say 15 or 16 deg. Used this way it's a really nice way to heat a house. Of course if you need to add supplementary heating during the day that won't be at the low tariff.

There's also the risk that if a circuit fails in the slab then it's a write-off. Fortunately not very common.

Heat pumps aside, you probably should probably be comparing it with a gas-fired condensing boiler with either in-slab hydronic coils or radiators. If you like to be able to repair/replace things then radiators are good. You still get the radiant effect, plus they can be individually controlled. It used to be that radiators had to go under or near the windows, which can be a bit restrictive on the furniture layout, but if you have double glazing they can go pretty much anywhere.

isis

49 posts

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#954862 19-Dec-2013 14:21

Thanks for the feedback.
Sounds like the Warmup underfloor heating is probably going to cost the earth to run if its using electrical coils.
I am building a double story 250sqm house in Auckland

We've got a quote for a ducted heat pump central heating but has come in at almost 30k! And it was only upstairs that they could run the ducted system. The downstairs consisted of individual heat pumps. It'll probably work out cheaper putting in individual heat pumps at this price!

The other option which we're leaning towards is a gas central heating that can be ducted throughout the whole house at half the price. We have gas on the street.

At this stage, we've made allowance to run the required ducts.
However the downside to gas is its limited to just heating. It'll be nice to be able to have the option to also cool the house down along with other settings.

timmmay

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#954868 19-Dec-2013 14:27

You can have heating ducts for the lower floor, you may just need to change the house design slightly. Alternately force the air down a central duct and have it come up through floor grates, though I doubt this is standard.

With lots of heat pump units you have lots of ugly outdoor units, and potentially long runs between the indoor and outdoor units. That's a bit less efficient I think. It also means lots of ugly high wall devices and lots of remotes. Even four heat pumps is going to be $12K. You could/should also put in a ventilation and heat transfer system which may let you warm some areas indirectly, though I doubt it would be as effective.

Remember with gas you have a per day charge for the life of the building. 50c/day for 50 years is $9K.

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#954878 19-Dec-2013 14:42

We have had a multi room fujitsu heat pump system in our new house and it's amazing, We can turn on or off any room and it cools along with heating. We've see a pretty big decrease in our winter bills ($350-450 down to $180-240) and now it's summer we get a nice cool house aswell.

If i was in an area where it was always cold and you would never need colling in summer then gas might be an option however if you want to cool down in summer then heat pump all the way, ducted so you dont lose space.

Our 10kw unit covering 110m2 cost $7k installed and chills/warms the whole house in under 20 minutes

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