The heating-on-all-day argument

Insolation= the effect of the sun shining in the windows. Significant if the windows are large and South facing. My own house derives a large part of it's heating from this.

Reply to
harry
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Do you wash? We spend more than that, and that is gas heated with a Combi boiler.

Reply to
philipuk

e uk.d-i-y orthodoxy that you pay for lost heat, and having the place hot 2

4/7 just means more heat loss, so must be more expensive.

His views are misinformed. The effects he ascribes to humidity are mainly due to radiation; he needs to read up on mean radiant temperature.

"What is missing from the whole equation is relative humidity and dew point , and the fact that when a home?s heating is turned down or off, more con densation will occur within the depth of the walls."

A thermostat or air temperature (AT) sensor only detects the air temperat ure and takes no account of radiation. More heat is lost from the body by r adiantion if the walls, floor, ceiling, furnishings' surface temperature is low. You will fell colder at 21 degC AT when the heating has just been swi tched on, than at 21 degC AT when the heating has been on a few hours.

A black globe thermometer/sensor more accurately depicts how humans feel temperature; they are available.

The effect of moisture content on U-values is, IMHO, negligible.

Reply to
Onetap

Because, presumably, in both cases your body is losing heat by radiation but in the former case it's not getting any back by radiation from the walls etc.

Reply to
Tim Streater

Yes, but losing more heat through the radiation component.

The radiation exchange also explains why you 'should' feel comfortable wit h underfloor heating with the thermostat set lower than an equivalent radi ator system would require; never tried it myself.

I can vouch for the fact that when I first fired up a new heating system i n mid-winter, it felt bloody cold for several days, despite the thermostat telling me that I was comfortable.

The standard Q= UAdT equation, although fine for most applications, do esn't work very well for some buildings where there is a large radiant comp onent. There is a more detailed method of calculation in the CIBSE guide wh ich takes account of the radiant and convective components of both the heat loss and heat emitters.

Reply to
Onetap

....'cos the surrounding, heat absorbing surfaces are colder.

Reply to
Onetap

What was the state of the building in which the new system was fired up? New-build? Newly restored/converted/whatever? Had it been heated until a day or two before? Or not in years/ever?

If the radiation component is critical (and I am not saying otherwise), it could actually be more economical (even less overall energy usage) to allow the room temperature to be lower and adding in a low power IR source. Particularly if the room is large and the IR source well directed.

Reply to
polygonum

As cold as could be, not heated at all in that heating season. Windows had gone in a few days/weeks previously.

Reply to
Onetap

So fairly extreme! And maybe in that case, moisture content of the building materials was significant and it took a while to dry out? Even then, I am not so convinced by the journo's insistence that it is conductivity of damp bricks rather than simple latent heat of evaporation. Obviously both are important, but which is the greater?

In the case of yesteryear when we had very simple heating, there always seemed to be a tendency to light a fire/switch on and get the room as toasty warm as possible - i.e. gross overshoot. That would tend to make permanent lower level heating look better but the real comparison should be doing that without the overshoot.

Reply to
polygonum

snipped-for-privacy@davenoise.co.uk...

Then get the thermostat fixed.

MBQ

Reply to
Man at B&Q

We found out the hard way that you don't turn the heating off here when going away for a few days. If the walls get "cold" it takes days for the place to become comfortable again despite the air temp being what it should be. There is a solid internal wall that is 18" thick, 18' high and

25' maybe 30' long. Guesstimate 20 tonnes of stone to hold heat. Does even the temp out in winter and keeps the place cooler in summer. Under floor heating also take ages to warm up or cool down.
Reply to
Dave Liquorice

The balance overall is between the higher overall heat loss from a house maintained at an average higher temperature, and the higher energy losses of a heating system subjected to (possibly inefficient) cycling and possible temperature overshoot of parts of the house with variable thermal time constants.

If the insulation is good enough, an efficient condensing boiler operating at low output to keep a house ticking over is probably no WORSE than cycling it.

And this is more than ever true if the house has got significant thermal mass inside the insulation barrier.

Houses that benefit most from cycling are low thermal mass poor insulation and old boilers..

Houses that benefit the least are large mass well insulated ones, and especially those with e.g. underfloor heating.

Reply to
The Natural Philosopher

well then something is wrong.

I estimate at best we spend £100 a year on hot water for two of us.,

Reply to
The Natural Philosopher

Dave Liquorice :

Similar here. We have solid 18" external walls. Internal walls are a mainly 18" (this detached house was originally three terraced cottages) with a few 12". Things are made worse by the fact that most radiators are mounted on internal walls (because of very low window sills) so heating the external walls is an uphill battle. If it's anywhere near freezing outside, it's not worth turning the heating off, because it takes so long to warm up again.

Reply to
Mike Barnes

You need a good dose of external insulation.

Reply to
harry

I've given the wrong impression there. There was extension that was witho ut windows, newly built and plastered. The rest of the house was mostly unt ouched. It all felt cold for some days after the heating was started. I don 't think drying-out was a major factor, but didn't do any detailed experime ntal-type measurements.

Reply to
Onetap

Agreed. That is my plan for when energy prices treble or worse. Until then, I can live with things as they are.

Reply to
Mike Barnes

Yes. Howell's article doesn't mention construction type or the type of heat emitters. I think his humidity theory is also flawed in that there shouldn't be condensation within the wall structure.

Reply to
Onetap

They already have trebled, or worse.

I use to buy heating oil at 16p a litre. Its now 64p.

Reply to
The Natural Philosopher

In message , Mike Barnes writes

Yeah, it isn't exactly a cheap or non-trivial task. - and we live in a brick Victorian listed building, and it would be pretty ahdr to get taht past the LA :-)

But yes ours behaves similarly with regard to heating,takes ages to get warm if it gets too cold

Reply to
chris French

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