Energy myth-busting: Is it cheaper to have heating on all day?

DonSwan

John_Pierpoint wrote: »

The answer to both those questions, for any individual wall, is that we don't know.
It would cost a lot to find out; however in the majority of homes it is not a problem, even when the cavity that is there to protect against penetrating damp, is filled with fibre. (one of the reasons why my cavity is filled with polystyrene).

With respect, I suggest that we do know. The BRE has carried out extensive research and has shown that interstitial condensation is a significant factor in UK homes built with masonry walls. And that explains why many people have reported that keeping the heating on saves fuel and money.

dtse

not finding any mention of these things on MSE site or forum , anyone got experience of them ? do they work ? do they save money ?
been trawling internet for a while & I cannot find any impartial source of info on them , makes me a bit suspicious....
magicthermodynamicbox dot co dot uk
thanks !

John_Pierpoint

Search the thread above, it has been discussed.
Basically the Spanish think it does work economically but the British government agencies have yet to be persuaded it works economically in the British climate.

John_Pierpoint

DonSwan wrote: »

With respect, I suggest that we do know. The BRE has carried out extensive research and has shown that interstitial condensation is a significant factor in UK homes built with masonry walls. And that explains why many people have reported that keeping the heating on saves fuel and money.

Please link to their useful physical research results so we can judge for ourselves.

The reason I question your second hand judgement is that I've been to a presentation given by SPAB, covering practical work done at a university. This demonstrates that the effect in solid walls is nothing like as great as the theoretical effect publicised by the BRE, in typical British winters. Even then it only became a theoretical problem if the walls were insulated internally, without a vapour barrier OR when the wall was in poor condition and exposed to driven rain.

[I know from practical experience that sticking 50mm of porous expanded polystyrene with no vapour barrier on the inside of a cold wall is asking for mould problems, a vapour barrier could be simply sticking wallpaper over the polystyrene and painting it with gloss paint. ]

There is a nation that has done extensive practical work on its own building materials, which are different from ours, and yes in their climate some cold walls can have problems that take years to build up. The country is Germany surprise surprise.
If you live in Germany and you know the internal structure of your walls, you can indeed buy software and feed in your parameters of weather, humidity and internal temperature etc, etc, and make a rational choice to use heating to dry out your walls 24 hours per day.

In the UK you are just guessing and in a typical well maintained home with cavity walls, interstitial condensation won't be an issue.

What ever has become of all those Barratt homes built with timber framing in the late 1970s, where the guys on site did not understand the purpose of the plastic sheets that came with the kit? So they cheerfully walked on it. Punched holes in it. Tore it to get the wiring through etc,.
There used to be a joke that went "What is the difference between bad breath, AIDS, and a Barratts home?..........."

Someone like my sister, who is foolish enough to live in a brick house, part built in the 1600s, would probably be well advised to keep the inside of her home cool, open her windows every morning for 20 minutes to ventilate the house and keep what heating there is on constantly, all be it on a set back temperature.

That way of living is not money saving or carbon saving, but is morally acceptable if you grow your own logs?:D

dtse

Thanks John Pierpoint , it's a long thread , still not finding it , apologies for the newbie question but am I using the wrong search terms , what SHOULD I be searching for please

John_Pierpoint

Try this:
http://www.silverspray.co.uk/2012/03/27/ecobuild-thermodynamic-panels-heat-exchanger/

More entries on Google if you search....................... thermodynamic-panels

Heat pumps are most efficient when they raise the temperature the minimum amount.
That is ground source from (say) 10 degrees to underfloor heating at 35 degrees,
This needs a paddock roughly 2.5 times the floor area of the home, from which the heat can be extracted.
If the input heat source is is a black radiator/collector on the outside of the wall, covered in frost on a cold night, it is going to need to be a dirty big radiator to extract significant heat at zero degrees to be pumped up to 35 for under floor or 55 for ordinary radiators.
I suppose if the radiator is sufficiently high off the ground a defrost cycle could build a pile of ice outside on the ground from the vapour in the air converted to ice. There is some useful latent heat in there.

dtse

Thanks , much appreciated , does not sound as though it will be much use when needed most in Scotland !

John_Pierpoint

Yes if all you wanted was the lowest carbon hot water produced from one machine 365 days per year in a house with no heating and no gas - then this it it

If the remote(?) property has trees, I would burn logs and have solar thermal for the summer time. Even at the now much lower FiT payable, solar PV might make sense, it depends or your view of the UK's share of future world resources of energy (and your conscience about what you leave your grandchildren)

dtse

Thanks John , it's an old build townhouse , on the outskirts of Edinburgh, we have solar panels & lots of insulation, new condenser boiler , but heating is still an issue due to high ceilings . The "magic box" was presented to us as a way of reducing gas bills in winter but I was sceptical due to what seemed to be improbably large savings quoted & high initial cost.

dtse

oh , and apparently we are only allowed to burn "smokeless" fuels so wood is out.