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  • David Olivier

    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.

    in reply to: Module 7 webinar questions #48867
    David Olivier

    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.

    in reply to: Magazine Content #46995
    David Olivier

    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.



    in reply to: Calculating Heating Demand #46192
    David Olivier

    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.

    in reply to: Looking for Ground Source Heat pump system quote #39243
    David Olivier

    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).

    in reply to: Biomass – A Burning Issue: 2017 #39247
    David Olivier

    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, 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
    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.

    in reply to: The use of a single room MVHR – are they any good? #39231
    David Olivier

    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.

    in reply to: Does Passivhaus Pay? By David Olivier #39212
    David Olivier

    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.

    David Olivier

    Maybe peoples' attention should be drawn to this:

    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.

    in reply to: Electric Boiler in Passive house calculations. #39165
    David Olivier

    If the electricity is hydro why does it have solar w.h.?

    David Olivier

    If 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.

    in reply to: Passivhaus Design Question #38716
    David Olivier

    North America has differences from northern Europe. Many well-known cities in the NE USA are 10-15 degrees nearer the equator than English cities. Blue skies are more common in winter than they are in N W Europe.

    This winter insolation makes a huge difference to the heat consumption for a given set of U-values, air leakage and for a given level of thermal capacity (assuming south-facing glazing).

    Also the difference in energy performance between heavy and light construction increases (heavy consumes less) as one moves nearer the equator and/or to a climate with more moderate outside temperatures. Louisville, Ky. has a mean annual temperature of 14.6 degC it seems. Southern England averages about 9.5 degC. Big difference.

    I don't think the UK has ever tried to teach the rest of the world to build well. That would be rash, given where Canada or Sweden had got to by 40 years ago.

    I too find the UK treatment of thermal mass simplistic. I'm writing a book which may help rectify this.

    in reply to: Electric or wet underfloor heating #38989
    David Olivier

    I think objections to LPG are inconsistent if the alternative of an ASHP is likely to prove undersized and need resistance heat top up, with greater CO2 emissions. Even without resistance heat, its emissions look level with or higher than LPG and don't forget in the long term it's as possible to make a renewable version of gas as to make renewable electricity.

    Also why should other electricity users who only run lights and appliances and heating controls off it have to pay to reinforce the cables of the rural national grid? At their present size some of these would probably melt if most buildings used heat pumps. Most of it was sized for a peak demand of around 1 kWe per dwelling not 2 or 3 or more kWe.

    See THE GREEN ELECTRICITY ILLUSION written 8 years ago on this site somewhere and points still mostly valid.

    in reply to: Roof Windows #38808
    David Olivier

    Hello Peter

    I suspect that if you check with the mfcr. you will find that the U-value has the product in a vertical position!! This is just one of the bizarre assumptions that European companies get away with.

    Rooflights seem to be so poorly-insulated that for my house I made my own. It's modelled on the two-part construction used in the 1st Canadian Advanced House in Brampton, 1989. In Scandinavia it would be described as 3+1 glazing.

    I think the NFRC in the USA has published some true in situ U-values for sloping glazing in their climate, under design conditions, as has the ASHRAE Handbook. Needless to say they are worse than European quoted figures.

    I suppose it might still work out, inputting the true U-value of this product, and benefiting from the gains of natural light, but there could presumably be a downdraught if the U-value including the installation psi-value is too high.

    So far I haven't detected a downdraught from mine. I'm writing a book on the house and will probably give the details in there.



    in reply to: Room thermometers #38796
    David Olivier


    Weather compensation is explained by these installers If you're near enough to London where they're based it might be worth paying one to visit and do some fine tuning or even suggest modified controls for a condensing boiler which should be run with low water temperatures 24/7 not as hot as possible for two periods/day.

    Or I know a retired mechanical engineer in Essex if any use but he'd similarly want a consulting fee to sort out someone else's heating system (He achieves a measured 96% efficiency using a condensing boiler on the existing radiators).

    It should be more valuable with UFH. Without it there tends to be a regular fluctuation in room temperature. caused by too much heat entering the floor at once.

    Surely a condensing boiler shouldn't need a thermal store for the space heating. Gas can be burned very precisely on demand, as the bills from well-designed and installed systems all bear out although it would ne nice if they were the rule not the exception.


Viewing 15 posts - 1 through 15 (of 392 total)