Consensus of Underfloor heating?

Cardew

ichidan wrote: »

I didn't mention the type of Radiator either. I want to know if UFH (whether Wet, Electric, Radioisotype or dragon powered) is economically better than a radiator (regardless of what make). I figured my last paragraph would've covered this difference:

Running a boiler for 24 hours at 27 degrees to run underfloor heating isn't the same as running a boiler for 12 hours at 60-70 degrees to run a radiator. It's not just a simple time equation, temperature and thus fuel/electricity consumption rate has to be factored in. UFH runs at roughly +14 degrees warmer than the cold tap (13 degrees), while a boiler runs at +50 degrees warmer than the cold tap, that's a huge difference.

So these websites are lying then, or at least being very careful with what they are saying:

http://www.homebuilding.co.uk/advice/key-choices/heating/underfloor-heating-or-radiators


http://www.connectingindustry.com/energymanagement/underfloor-heating-vs-radiators-everything-you-need-to-know.aspx


http://www.which.co.uk/energy/creating-an-energy-saving-home/guides/underfloor-heating-systems/underfloor-heating-pros-and-cons/


You see why there is confusion?

The choice of UFH raises an issue that some of the proponents of Heat Pumps choose to ignore.

As you state in an earlier post with the very low water temperatures involved it is necessary to run the heating 24/7 or close enough.

That is fine if you are occupying the property 24/7.

The claims for the system COP of an ASHP are often wildly optimistic, however from the EST trials it would appear that COP=2.5 is realistic.

So the argument put forward by the proponents is that if your ASHP produces, say, 12,500kWh, you only consume 5,000kWh. They then go on to compare the price of 5,000kWh of electricity with 12,500kWh produced by gas/oil/lpg.

However the counter argument is that using a conventional gas/oil/LPG boiler capable of producing water at 80+C will not require 12,500kWh to produce the same level of comfort.

People who are out at work all day might typically set the boiler to come on 20 minutes before getting up and go off, say, 30 minutes later. The heating can then remain off all day and come on again 20 minutes before they return. Similarly most of us have the heating switch off, say an hour before we go to bed. It doesn't matter how cool the house gets during the day, or at night while we are in bed. So on a weekday I suspect an average time for the boiler to run might be 6 hours??

You have applied the above logic to a conventional boiler:

Running a boiler for 24 hours at 27 degrees to run underfloor heating isn't the same as running a boiler for 12 hours at 60-70 degrees to run a radiator.

All of the literature I have read talks about UFH water at 35C. Indeed at what is the lowest water temperature modern boilers can operate? My ancient non - condensing boiler has a range of 54C to 82C.(1-6 on the boiler dial)

Lastly, as I am sure you appreciate, it would be impossible for anyone to give you an answer on the costs of either system. Unless an organisation has run a controlled experiment with two identical houses we will never know.

My gut feeling is that radiators will be cheaper for most people.

macman

Any form of electric heating is 'more efficient'-because it's 100% efficient. But that doesn't make it more economic, because per kWh, it's about 250% more expensive than mains gas, if running on a single rate tariff (and E7 underfloor would make no sense at all). The greater efficiency of electricity does not begin to compensate for the much higher kWh rate.
It's also going to be maybe 200% more expensive than NSH's on E7.

lawnmowerman_2

My GF and I have similar sized flats, mine is conventionally heated, hers has water underfloor heating with a heat exchanger, an airflow system and solar, here's my 2 cents:

• Her heating bills are about 30% higher than mine - which is odd because I work from home and have the heating on all day in the winter. (Off at night)
• When my house is cold (or I am), the temperature warms up within 15 minutes in my flat, there is no discernible difference in hers and you have to put a coat on.
• I save money by switching off or lowering my thermostat when I am not around, there's pretty much no point in her doing the same thing.
• She has a tank to provide hot water, mine is heated on demand. We have occasional cold showers in her flat, but never in mine. (Even if you have just turned it on.)
• Every plumber can fix my system, whereas no one person that we have found has the skill to understand all the complexities of her system - admittedly her solar and airflow didn't help.
• Maintenance is more expensive with her system - honest!

I built a large extension on a house 10 years ago and was a big fan of UFH, luckily I decided against it for cost reasons, but I am very glad I did so. UFH sounds brilliant, but in practice is more expensive to run, less efficient and not as warm as conventional systems. I wouldn't bother.