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- 28 December 2019 at 5:42 pm in reply to: GSHP and UFH in thick structural slab. Will I be able to control it? #56454
I struggle to understand why you’re using UFH in such a heat-tight building. It’s a very expensive method of providing radiant heat compared to radiators.
P.S. Sorry for delay in replying. This forum doesn’t seem to get many users nowadays which risks being a catch-22.
London requires new flats to have a CHP system, in practice usually gas-fired.
There’s a separate district heating and cooling discussion group I belong to, not part of the AECB. But if you’re outside London, as I am, this may be of limited applicability to you as there may be little support for the idea.
However, a central system of some kind would seem to be convertible to anything later, i.e. any source of heat. Electric systems, one per flat, certainly aren’t and there’s some concern about the peak in electricity demand in future winters like 2009-10, 2010-11. Gas and hot water can easily be stored, electricity can’t.
Dear Geoff
I very much agree with this. I find it a bit frustrating that issues which used to be discussed in its pages now never feature. Instead one may see a series of modernist buildings in suburban and semi-rural Ireland.
It’s a bit like featuring more thermally-efficient versions of the projects in Self Build and Design. These too are the type of housing that is only affordable to a relatively select group of the UK population.
I was about to suggest to Andy and Sally that people who find the magazine a bit tedious should be allowed to volunteer for a slightly reduced membership charge in exchange for receiving PH+ online-only. That potentially benefits the AECB because the marginal printing and postage costs of a mag. are significant. It reduces paper usage too. I don’t know if anyone else thinks likewise.
BTW, the forum is less easy to use than it was and also appears to have far fewer regular users, incl me. I realise that this may be because of security precautions.
Cheers
David.
On a one-off house, surely just meet the stipulated U-values and air leakage? It may not be worthwhile paying to have it certified to a particular standard but it’s worth modelling it to check predicted heat consumption.
Is that the sort of comment you wanted?
IMO you need radiators for both standards, PH and AECB Silver because a decent one off house will have plenty of glazing to give good daylighting – if not passive solar – and this slightly increases peak heat loss. So not sure what the difficulty is but clearly there is some.
Or with only access to LPG, why would you do it either? The emissions of propane are not far above those of methane/natural gas. Both condensing can be burned in boilers, using top-notch (load compensation) controls.
For about 30 years I've advised clients with fairly low-heat loss houses to use radiators. If one wishes, they can be more stylish and durable than the usual pressed steel panels. None have later regretted the decision.
One client who fitted UFH before I got involved in his project had control problems which were quite difficult to rectify. I don't know if he ever did fully correct them; he may have sold the house before that happened (NB it was sold for other reasons, mainly his growing family wanted more space).
This is reminiscent of the discussion on the forum 9 years ago when the situation was slightly less certain and there hadn’t been a BMJ article. The apparent reality as I now see it is:
The exhaust emissions from burning gaseous, liquid and solid fuels in various appliances differ, sometimes by many orders of magnitude. See the US Brookhaven National Laboratory research. In particular, particle emissions are usually orders of magnitude lower from gaseous fuel combustion than from use of liquid or solid fuels. Solid fuels are by far the most difficult to control, for obvious reasons, and usually need electrostatic precipitators or similar. These are practicable on a 500 MW steam turbine, less so on a small appliance.
Not all exhaust emissions are equal. I’d rather breathe in, e.g. CO2 than SO2. I’d prefer normal rural air at say 5 μg/m3 to air containing 50 μg/m3 PM-2.5s.
As per usual in this area, the US and Canada have set stricter PM-2.5 limits than the EU, https://en.wikipedia.org/wiki/Particulates. That may reflect a smaller number of diesel car interests, although all their lorry and bus diesel engines succeed in meeting stricter emissions limits than EU heavy vehicles.
The science has since moved on another 9 years, or why would the BMJ publish the article that it did revealing that UK wood emissions considerably exceed diesel emissions?
Everyone needs to regularly examine or review their own practices and not assume that medical or scientific papers on the health hazards of particle emissions are wrong or that small-scale combustion is 'harmless'. It's a contradiction to construct a relatively green rural building and fit an un-green fuel source.
The alternative to burning wood is burning something with less toxic emissions. One has or will have quite a long choice, the fossil ones being:
natural gas
LPG
and even
kerosene or light fuel oil.although bio- or renewable synthetic ones should be produced in future.
The combustion of the cleaner fuels on the above list doesn’t pose serious direct health risks. Particles do. So don’t emit particles, other factors being equal. Ditto with visible soot, which is a GHG.
BTW, landfills surrounded by clay and containing any organic waste may eventually produce methane, a clean fuel. I'm sure wood could be dealt with in far better ways but removing trace impurities from biogas and burning the methane in a controlled manner seems less bad than soot, trace CO, some NOx and PM 2.5s now.
Well, in the late 1970s the US DOE tested some and LBL tested some and they found significant short circuiting
Not surprised.
I am increasingly sceptical that MVHR can be beneficial in small buildings in relation to MEV, given the economies of scale and the limited value in UK conditions of the heat to be recovered in relation to the full rate electricity which operates the fan/s.
30 March 2016 at 3:32 pm in reply to: Re: Re: EWI using direct or ventilated rendered finish? #39222Did someone mention usng PIR foam?
My understanding is that the EWI systems proven over time; e.g., possibly up to 60 years in Germany (though not with the thicknesses used today), have relied upon EPS or XPS foam under the render.
Also I understand cork has a long track record of use.
If PIR foam was used, was the manufacturer consulted and were they content with the proposal?
We cannot do everything. Resources are always finite on a finite planet. I wasn't saying we should only do things with short payback times. But a 75-100 year payback time seemed a bit steep.
Using scarce capital on replacing G fridge-freezers by A+++, and other measures like it, would yield CO2 returns sometimes 10-100 times greater. Ditto replacing controls on even gas condensing boilers, etc, etc.
Long term, we shouldn't be heating buildings via gas boilers, as I tried to imply in the article, in part via a reference to Denmark. I hope we're not doing so in 2100 although I won't be around to know either way.
It obviously tends to happen after a cold night. Cold nights are clear nights. As the winter sun comes up, it dispels the condensation. It initially covers almost 100% of the windows except the glazing edge but it steadily fades away in the morning sun.
I don't find it to be a great problem in practice. You could recess the windows into the wall, and plant trees near that wall of the house to shield the glass from the sky, but unless you're careful you will then lose your passive solar gains.
As noted, ice on the inside of windows is a worse problem, although the patterns formed are extremely beautiful. That was common in in the 1960s in almost unheated houses. In severe winters like 1963 you had a series of repeat performances.
I can think of other methods to combat the issue but they won't cure it without either increasing the building heat loss or reducing the passive gains.
Maybe peoples' attention should be drawn to this:
http://woodburnersmoke.net/Dorothy-Woodsmoke_Cancer_May2011.pdf
Local wood combustion may not be the best method to heat a house which is designed to have a relatively low environmental impact.
It's true that the impacts of PM 2.5 particles are still being researched, and it's true that wood smoke isn't the same as coal amoke, which isn't the same as diesel engine emissions. However, I don't think it's realistic to expect wood smoke particles to have an opposite impact on health vs. the impact on health of diesel smoke particles. Diesel cars have already been declared by some sectors of the media to be a health hazard.
If the electricity is hydro why does it have solar w.h.?
But it appears that early cavities had metal many times larger in cross section than the coat hanger-type steel ties which have since failed. If they are checked and are still there after 125 years,that seems quite good.
65-75 mm of PU foam could give a better U-value than new houses built in 2000.
3 December 2013 at 2:59 pm in reply to: Much needed research into building retrofit still needing be done…? #38840If the budget is 0, don't do it!? Wait until commonsense prevails. If UK dwellings are paying £1400/y for gas and electricity, that's £28,000 over a 20 y period and any half-sensible country will at some point decide that part of this £28,000 should go into improved insulation/draughtproofing, not into heating the atmosphere.
TF external walls and masonry party walls are probably not that unusual. A lot of “CW” houses also have TF panels above and below the windows.
“Another point about air leakage is that Fraunhofer research is showing that moisture transported by bulk air leakage into and thro walls etc, has a massive effect on the moisture situation within those walls – puts diffusion in the shade.”
No, to my knowledge this was first pointed out in Canada or the USA almost 40 years ago!
I repeated it in an AECB mag. article in about 2001 and did a few simple calcs. to illustrate that air movement transported more water than diffusion.
I don't know where 0.6 ac/h @ 50 Pa came from but it's anomalous using volumetric leakage because it allows a leaky building envelope in office blocks, with a relatively high permeability. This could be uncomfortable if it contains a few large leaks. In detached houses, 0.6 ac/h forces an extremely tight envelope.
Questions have been raised too about where the R-2000 max. of 1.5 ac/h @ 50 Pa (set in c.1980) came from. Possibly because the Saskatchewan Conservation House achieved 0.8 in 1976. The resulting permeability of about 0.8-1.5 m/h in a detached house apparently gives few if any comfort problems even in central Canada.
The pressure difference due to the stack effect will be much higher than 2 Pa in winter in say a 3-storey house.
The nearest PHPP house file I could find saves 9 kWh/m2yr on going from 2 to 0.5 ac/h at 50 Pa. It's above PH heat loss though.
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