Tim S wrote:
The Natural Philosopher coughed up some electrons that declared:

I have a roomstat set to 18C and SWMBO says its 'fine with a jumper on'

By running 24x7, that 18C is utterly even: with timing, I used to feel
cold until the stat showed 19-20C.

That's interesting. Do you have a feel for whether it was much more
expensive to run at 18C all the time.

To be honest, what used to happen is that there would be a two hour burn
in the morning, which would make the passageway with the pipes a magnet
for the cats, and then the temp would still be only up at about 15-16 in
this sort of weather, and the timing comes on around 3pm, and it would
not be fully warm by 8pm..so 5 hours of full boiler output more or less,
mostly warming the slab, not the room.

Now I've gone 24x7, the most significant thing is that he return temps
out of the floor are MUCH higher, showing the slab isn't icy, and the
boiler is cycling as a result. i.e. its doing about a 50/50 cycle in the
night, with about a couple of hours between demand for heat, but the
boiler is only doing about a 50/50 cycles in that time..

My gut feeling is that its no worse, and may in fact be a bit BETTER.

Mainly due to the fact that there are no cold spots. The sta is mounted
on a massive concrete brick faced double chimney stack..so that used to
suck heat requiring a higher temp elsewhere. like the outside walls
etc..now its all evened out, I suspect the air temps are better.

The other issue is that during fast heat up periods, the floor gets
super warm - especially under the sofas. I suspect that in itself
increases heat losses from the floor downwards as well.

I am tempted to leave it like that all year long, and simply let the
stat take care of everything. In summer the nighttime temps in that room
are seldom below 18 anyway.


BTW - found an approximation formula for U-values of uninsulated floors:

http://www.warmafloor.co.uk/knowledg...insulation.asp

(some good reading material there)

U = 0.05 + 1.65(P/A) - 0.6(P/A)^2

where P=length of exposed perimeter wall, A=floor area.

I've got IIRC a P/A of 0.5, so base U-value of 0.73.

Thats not too bad. Whats teh values for suspended block and beam :-(

I'll try some numbers with that after I call the gas/leccy boards...

Cheers

Tim