Underfloor Heating - the biggest con ever

theoldmiser

TELLIT01 said:

We have UFH in our conservatory and it works very well for us.  In the winter months it's set low and keeps the chill off the room.  When we have visitors we turn it up and it's the room everybody heads for.  I think it is, in part, the warmth under foot which makes people feel warm all over.  With the whole floor being heated, the spread of heat is far more even than radiators or electric fan or convector heaters too.

Really? I fail to see how you would keep warm air in only one part of a room, just because it's coming from a radiator or electric convector heater. I have never, ever had this problem. I don't think it's possible, I think you're imagining it. You could easily use a £20 convector heater to keep the chill off the room, and to turn up and make it the room everybody heads for. Is the rest of the house cold or something? Do people walk around with bare feet in your house? Having warm feet doesn't make me feel warm all over - i.e. if you wore three layers of socks and walked around naked in the middle of Winter, would you feel warm all over?

theoldmiser

Chickereeeee said:

I don't really know why UFH is called 'radiant' anyway, as most heat dleivery would be via conduction or convection. 

Exactly. It isn't 'radiant' heat when you get a few inches above the floor (i.e. 99% of the volume of the room), it's convection. The same as a £20 electric convection heater, but they don't 'look good' so people would rather spend thousands of pounds, LOL.

theoldmiser

mcplumb said:

Retro fit UFH, I probably wouldn't bother with. In a new build with MVHR I can't think of a better solution (other than if the customer tiles the whole ground floor - flow temps are so low you need a cold day/increased flow temp to take that edge off). From experience customers love UFH because they have warm floors, in an energy efficient house those floors will barely get warm - to get a warm floor you need to open a window and reduce air temp

I can think of a better solution - electric convector heaters. Strangely enough, like most people, I wear socks and slippers at home, and I have carpets, so I don't know what temperature the floor is.

theoldmiser

daveyjp said:

Works from a standard combi, every room individually controlled (lounge at 20, elsewhere at 18) and because the solid floor and screed is a heat sink it is very efficient once warmed through, which begins in late Autumn when they set the heating water temp to 45 degrees.  Previously the property had a suspended timber floor throughout with no insulation.

I've been there in mid winter and they have had lounge windows open to cool the lounge down, even though the heating isn't operating.

Those two paragraphs prove that it ISN'T an efficient system at all! The second paragraph shows that (in this case) it's difficult to control the heat once you have spent all that energy heating up the floor. With radiators or electric convector heaters, you can heat up a room in a few minutes, and as soon as you turn off the heat, the room will cool down. How much energy does it take to heat the house, compared to radiators or electic convector heaters? Has anybody ever done any tests on this? It must be easy - find a house with underfloor heating, and take readings of the outside temperature throughout the year, look at how much energy the underfloor heating is using, then stop using the underfloor heating and use electric convector heaters or gas central heating in the same house, and measure the outside temperatures, and see how much energy that uses, taking into account the outside temps.

theoldmiser

Chickereeeee said:

'Anthracite' coloured radiators are fairly common. Also, white radiators give out 30% more heat than chrome for the same size, and black ones even more.

Really? Do you have any evidence for that?

theoldmiser

ComicGeek said:

It's not significantly heating up the ceiling and walls, as air flow then removes some of that radiated heat via convective from the surface (and then hopefully your thermostat turns off the heating when the required air temp is reached). You want the surfaces to be warm though, as that is a key part of comfort - if the surfaces are too cold then your own body will be radiating heat to them, and you feel cold.  

So your body stops radiating heat if the surfaces of the WALLS in your room are warmer than your body? Seriously? Only if you're standing pressed up against the wall, I imagine!

theoldmiser

avoidtheupsidedownbottles said:

Always thought UFH in the bathroom would be a good match with Economy7 for an hour or two before getting up time.  Also for upstairs bathrooms, you don't have the problem of needing an insulated floor like one does at ground level

I just use a wall fan heater that I turn on as soon as go in the bathroom, so it's on for about ten minutes while I have a shower and dry myself. So 0.5Kw/hr of electricity, (3Kw x one sixth of an hour = 0.5Kw/hr) - worth it to me.

Apodemus

theoldmiser said:

ComicGeek said:

It's not significantly heating up the ceiling and walls, as air flow then removes some of that radiated heat via convective from the surface (and then hopefully your thermostat turns off the heating when the required air temp is reached). You want the surfaces to be warm though, as that is a key part of comfort - if the surfaces are too cold then your own body will be radiating heat to them, and you feel cold.  

So your body stops radiating heat if the surfaces of the WALLS in your room are warmer than your body? Seriously? Only if you're standing pressed up against the wall, I imagine!

Lol! At least nobody has suggested that the walls are radiating the cold! 

Actually the question of heat radiating from the body is quite interesting.  I was pleasantly surprised, when insulating my bathroom with foil-coated foam insulation, just how much warmer the room felt....then disappointed when that warmth disappeared once I covered the insulation with plaster-board!  All the conditions were the same, except that I had covered the reflective surface.  I can only assume that what I was feeling was radiated heat from the reflective foil surface and since the only source of heat in the room was me, I was getting some of my own body heat being reflected back...?

grumbler

theoldmiser said:

Chickereeeee said:

'Anthracite' coloured radiators are fairly common. Also, white radiators give out 30% more heat than chrome for the same size, and black ones even more.

Really? Do you have any evidence for that?

White radiator emits more.

https://www.engineering.com/Ask@/qactid/1/qaqid/3075.aspx

"Most paints emit in the .90 range which is very high. Chrome has an emissiviy or "E" value of .05."

(not sure if it's 0.05 or 0.5).

theoldmiser said:

ComicGeek said:

It's not significantly heating up the ceiling and walls, as air flow then removes some of that radiated heat via convective from the surface (and then hopefully your thermostat turns off the heating when the required air temp is reached). You want the surfaces to be warm though, as that is a key part of comfort - if the surfaces are too cold then your own body will be radiating heat to them, and you feel cold.  

So your body stops radiating heat if the surfaces of the WALLS in your room are warmer than your body? Seriously? Only if you're standing pressed up against the wall, I imagine!

Pressing against the wall doesn't stop radiation.

If the walls are warmer than your body, then the body absorbs more heat than radiates, i.e. on balance stops losing heat by radiating it.

Eldi_Dos

Apodemus said:

theoldmiser said:

ComicGeek said:

It's not significantly heating up the ceiling and walls, as air flow then removes some of that radiated heat via convective from the surface (and then hopefully your thermostat turns off the heating when the required air temp is reached). You want the surfaces to be warm though, as that is a key part of comfort - if the surfaces are too cold then your own body will be radiating heat to them, and you feel cold.  

So your body stops radiating heat if the surfaces of the WALLS in your room are warmer than your body? Seriously? Only if you're standing pressed up against the wall, I imagine

, when insulating my bathroom with foil-coated foam insulation, 

Did you notice any change in wi-fi in the house when you used this?