Heated Flooring - Cost to run?

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mattwnz

20141 posts

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#1576692 19-Jun-2016 19:01

kiwirock:

I used to have underfloor coil type. The coils were only in most foot traffic area so it doesn't waste energy heating up tiles say over by the dinning table, just the living area and bathroom etc...

A big factor will be how the heating is controlled from the power company and what your unit price is. Our's was on a night only meter that was half the price of the 24 hour meter and less than a controlled/boost meter.

Edit:

Anything other than a night only meter is a bit of a power waster. You end up switching a heatpump or a heater on during the day to be really warm... then the thermostat clicks off for the underfloor and you end up cold tiles.

So we'd set the thermostat in the living room to the highest (32degrees) so we used it as a night storage heater to get the tiles as warm as possible on the cheaper rate and to start warming even if the living room was still warm from people using it a few hours earlier.

Many houses in the 70's and 80's had underfloor heating installed, the old coil type in the slab, and probably without any insulation under it. But many people rarely used it due to the high heating cost involved, and that was back when power was cheap. I do wonder what the point is of putting underfloor heating is these days, apart from to take the coldness off the tiles in a bathroom, where wearing slipper would fix that. Wouldn't i be better just not to install tiles, and go for floorboards or lino in wet areas.

Quinny

885 posts

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#1576693 19-Jun-2016 19:01

Names and usage vary so be very careful. This might help. But many will use one meaning another. Hope it helps.

Hydronic underfloor - economical but expensive to install. The BEST.

Underfloor - In slab coils - older style but newer versions around, often on night rate

Undertile - electric element on top of concrete and under the tiles. I am not a fan as this can be very expensive to run.

Undercarpet - heating mats under the carpet. See undertile.

mclean

581 posts

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#1576907 20-Jun-2016 09:52

The idea that you can save power by running the heating continuously, instead of switching it on only when you need it, is a myth. It takes less energy to heat up the floor again than it does to keep it warm continuously.

kiwirock

685 posts

Ultimate Geek

#1577275 20-Jun-2016 16:59

That depends on a number of factors, the most notably time.

It comes down to how often you require the warmth, vs how long it takes to start delivering a noticeable increase in warmth vs speed of heat loss.

There are other financial considerations to include in the equation of continuously warm homes. Health costs. Kids... runny noses, ear ache, flus that hang around for ages in a colder house over night etc... higher humidity in the house from absorption in soft furnishings when the house is cold and moisture laden at night.

These days I'm using a heatpump. I find switching the heat-pump off at night takes ages to warm back up in the morning (at least an hour in this place on timer)... it works harder, ices up and performs numerous defrosts in the morning all wasting power, and on a -3 degree night the living space has dropped to below 9 degrees or less.

The unit hardly works at all left on over night, hardly does any defrosts, the house is warmer and health wise there doesn't seem to be anywhere near the same length of lingering colds and flus over the winter period.

For underfloor though, I never worked out how cheaper it was to leave on. It took a good night or two to start noticing the floor getting warm so switching this off and on wasn't an option if you wanted a warm floor.

Another factor is electricity rates. It was certainly cheaper to heat it at night than it would have been to heat during the day at twice the unit price. Hence setting the thermostat for its warmest to store heat in the slab so other heat sources during peak rates weren't required. Switching this on only when you needed it the most was not only impossible given the wiring configuration, if changed, would have cost twice as much to heat up.

True you only get out what you put in. A standard convection heater running on low at a pace that keeps up with heat loss is no different than a heater on high for a shorter amount of time if both are set to the same temperature. However, humidity also plays a roll. Continuous warmth helps remove moisture from soft furnishings making it easier to get rid of, and makes the air even easier to heat and keeps the air more healthy over cold damp winters. So there are other knock on effects to take in to consideration.

timmmay

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#1577280 20-Jun-2016 17:05

kiwirock:

These days I'm using a heatpump. I find switching the heat-pump off at night takes ages to warm back up in the morning (at least an hour in this place on timer)... it works harder, ices up and performs numerous defrosts in the morning all wasting power, and on a -3 degree night the living space has dropped to below 9 degrees or less.

Based on this I have to wonder about your insulation. When it gets to zero degrees outside in the middle of winter, if it's 22 when we go to bed it's 16 - 18 in the morning. The heat pump makes the house much warmer again in a few minutes, but takes 20 - 30 minutes to thoroughly warm it. This is my 100 year old house, with reasonable insulation.

Only on the coldest maybe three nights of the year do we leave the heat pumps running.

mattwnz

20141 posts

Uber Geek

#1577283 20-Jun-2016 17:09

Quinny:

Names and usage vary so be very careful. This might help. But many will use one meaning another. Hope it helps.

Hydronic underfloor - economical but expensive to install. The BEST.

Underfloor - In slab coils - older style but newer versions around, often on night rate

Undertile - electric element on top of concrete and under the tiles. I am not a fan as this can be very expensive to run.

Undercarpet - heating mats under the carpet. See undertile.

I think the under tile is probably ok, if you put it on a timer, so you have a warm floor in the morning and evening. But to run all the time and use it as the primary way to heat a room is pricey. Far cheaper to use a heat pump. But IMO, just buying slippers is a heck of a lot cheaper, or put down cork tiles or some other type of flooring that isn't icey cold to walk on when it is cold..

mclean

581 posts

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#1577334 20-Jun-2016 18:02

kiwirock: That depends on a number of factors, the most notably time. It comes down to how often you require the warmth, vs how long it takes to start delivering a noticeable increase in warmth vs speed of heat loss.....

Yes, I am only talking about energy use. You can save MONEY, but not energy, by using night rate electricity. My point was that you save even more if you can turn it off when you don't need it - there's no energy penalty in letting the floor cool down and heating it up again.

For heat pumps you may be right about the defrost cycles - it would be interesting to see if that's true over a normal range of conditions. I doubt it.

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