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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
These two books are the perfect starting place to help you get to grips with one of the most vitally important aspects of our society - our homes and living environment.

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    • CommentAuthorGBP-Keith
    • CommentTimeJun 22nd 2008 edited
    Before committing to one of these be aware that unless you have a freely available supply of renewable power you would be financially better off using gas with a condensing bolier.

    take a look at the cost comparisons of major fuels to gas on John Willoughby's fuel price comparison chart.


    You would need a CoP of about 6:1 to come anywhere near gas prices. And CoP's as good as 4:1 are rarer than is admitted.
    • CommentAuthorCWatters
    • CommentTimeJun 22nd 2008 edited
    That appears to conflict with the comparison data here..
    ..but the difference could well be down to assumptions made about different tarrif rates. Notts has them on level pegging at the moment.

    Edit: There is a note here..
    that says "Price relative to gas now distorted by new two tier tariffs and no standing charges. Second tier used for relative prices."
    • CommentAuthorGBP-Keith
    • CommentTimeJun 22nd 2008
    Bear in mind this is a rising scale not a falling one. CoPs are unlikely to go up though.
    • CommentAuthorripnruth
    • CommentTimeJun 22nd 2008
    Total newcomer to all this and have read with fascination and alarm all your entries regarding GSHPs, Biomass boilers, and wind and solar power. I seek the holy grail of a sensible energy solution to a 210 sq m new build on a farm, in a field, in chalk downland - total clean slate but huge confusion! Return on investment is a consideration but even more is the feeling that I've done the best for the next generation - bit syrupy but true - there must be a sensible answer to my query as surely every new build must ask the same question?!
    Rip Kirby
    just to add ,
    for those interested in carbon reduction as a means of enviromental improvement
    I believe the carbon output/Kw would also be lower with mains gas
    unless you achive the higher CoPs
    What if you run your heat pump on cheap rate (E7 or E10 periods only) to heat up a tank of water and draw down on the tank for heating and hot water requirements? That's cheaper than gas. Could it be done and what would the equipment cost?

    Interesting to note that coal seems to be hardly any worse than oil for producing CO2 yet is less than half the price. I'm not a fan of gas (or oil) for heating, or for any other purpose, for energy security reasons.
    • CommentAuthorGBP-Keith
    • CommentTimeJun 22nd 2008 edited
    Don't get me wrong. Heat pumps are a great idea (but only when used in the right context). One day I'll install some extra generating capacity to my renewables system so I can add one here at the farm.

    I'm just worried that people with good intentions are being led along by the nose and being talked into believing that heat-pumps are renewable energy generation equipment whereas in reality they are not.

    Wind turbines do not need a supply of electricity to generate power, neither do PV's.

    Heat pumps should not be on the governments Low carbon Building grant support list.
    • CommentAuthorBowman
    • CommentTimeJun 22nd 2008 edited
    Posted By: (GBP) KeithI'm just worried that people with good intentions are being led along by the nose and being talked into believing that heat-pumps are renewable energy generation equipment whereas in reality they are not.

    Ah now surely that is just the tip of the iceberg, I've had like for like quotes of £20k+ through to ~£5k.
    I don't think there should be a grant support list, but that's another discussion.
    • CommentAuthortony
    • CommentTimeJun 22nd 2008
    Come on guys -- for goodness sake build well enough insulated buildings so you dont need heating systems!! Design the jolly thing out.
    • CommentAuthorfuncrusher
    • CommentTimeJun 22nd 2008
    Keith: sorry, but you seem unable to grasp the basic anaytical framework concerning heat pumps. You are making the facile thermodynamic error of comparing heating 'prime movers' (those running on fuel) with those which do not, but instead require work input. Electricity is not a fuel: it is for practical purposes 'work', and like other forms of work can be used turned into heat (with nearly a 100% efficiency), or used to drive machinery or whatever. Heat pumps are not a prime mover. In principle they are mechanical and though usually electrically powered could use other sources of work energy water wheels

    Whether heat pumps rely on oil, coal, wood, gas,nuclear or water-powered electricity (or some direct mechanical drive) is your choice. What they do is to re-capture the energy lost in thermal power generating plants, and they allow this to be done at remote distances from the generator.

    As Chris indicates, in conjunction with thermal stores thay are the perfect partner to green electricity, which is generally generated at times of nature's choosing, not ours.

    Incidentally, anyone any news of a heatpump which is water driven and extracts heat from the water which powers it? Surely the perfect green solution.
    • CommentAuthorjon
    • CommentTimeJun 23rd 2008
    Sounds good funcrusher, but I didn't understand what the relevance was.
    • CommentTimeJun 23rd 2008
    There is a bit of a reality check needed regarding heat pumps.

    When I show people ours and explain how it works the usual response is one of surprise that it actually consumes electricity rather than generating it. Some people seem to have conflated stories they have half heard of CHP and heat pumps and got the two confused.
    I agree it should not be on the grant list. A friend of my just showed me the plans for his extended house. His 'green' architect specified a heat pump for his underfloor heating, which in the new extension is fine (highly insulated floor with thermal mass), but for the old part of the house he's used oversized radiators. The architect is still proposing 4:1 returns - something he clearly wont get in that configuration. Mind you, I also noticed from the plans that his 'green' architect has specified the minimum required levels of insulation etc... so perhaps 'green architecture' is the latest marketing fad and consumers are being duped slightly into buying these technologies in a bid to appear green?

    Perhaps though the grants could be kept if a minimum of 4:1 ratio can be proven? It would ensure good design and use only when appropriate.
    • CommentAuthorGBP-Keith
    • CommentTimeJun 23rd 2008 edited
    In words and pictures.
    • CommentAuthorSimonH
    • CommentTimeJun 23rd 2008
    Like a few others I don't think there should be any grants. Can you get a nearly £2,500 grant towards external wall insulation for an existing property? Which might save over 10,000kWh/£1000 per year on heat source/house size, or drop emmissions by 5-10 tonnes. Nope. Yet you can get £2,500 for a PV system which will save you £80 a year on your electric bill and reduce emmissions by less than a tonne. I think the grants should be carbon based. In arrears: aka feeder tariffs but on how much carbon you didn't emit that year because of whatever technology you had installed. So things like insualtion will be the natural winners in terms of payback. It might be a bit complicated to adminster though.

    Right now the LCBP should be about demand reduction not alternative sources of energy. So that whatever alternative energy comes along in future we need less of it.

    Keith I agree financially that a gas condensor will be best (on install costs alone), but it misses a point. If you've insualted, updated your tank to a thermal store to allow heating support, what heating source can you use which puts hot water in it and doesn't emit carbon? I don't count wood as carbon neutral as the tree it came from might have lived for another 50 years if it hadn't been cut down (even if you are using the waste wood from pallets/sawmills etc). They fit somewhere between fossils and real renewables - but not as close to solar/HW and PV / wind wave. And the key point - burning wood does emit carbon.

    People don't buy a Audi/BMW/Jag/Mercedes becuase they are cheaper! Given the number of them on the roads I presume there are a lot of people who want the "best" heating system, not the chepaest to run. Whether a heatpump is "best" is subject to debate.

    I see a use for heat pumps as a demand shifter - using off peak, "spare capacity" like Chris has mentioned to fill up an accumulator using off peak green (or even nuclear or worse case coal) electric. Interesting - that no one offers a "nuclear only" tariff yet ;-). It does mean that you need to oversize the ground loop possibly - but again demand reduction should be the first step. You may only need to run the heatpump say 30-40 days per year if you get the insulation right.

    The big problem is that we are using [loads of] gas to generate electricity in powerstations. Which reduces the end to end to about 60%. Instread we should stop doing that and use gas for heating purposes and stick to coal for electric generation [with CCS of course] and use heatpumps to bring the end to end efficiency up to 100-150%.

    • CommentAuthorTuna
    • CommentTimeJun 23rd 2008
    Seems a fair summary Keith. They only seem to make sense if you either have a zero-carbon electricity supply, or have no choice but to use electricty as your heat source.
    • CommentAuthorSimonH
    • CommentTimeJun 23rd 2008
    Keith where did you get the 5:1 figure from? That seems to low? I thought it was more like 2.5:1 for coal and 3:1 for gas. If you look at this diagram the total for electric generation is around 90 million on tonnes oil equiv in, vs 33 out...


    That's saying only 20% of the energy in a lump of coal ends up as electricity.

    The numbers may be skewed if you add in extraction and shipping - becuase you'd have to increase those losses if you gave the fuel to the end users. They'd be getting lorries to drop individual sacks of coal off, and not having trains/container ships full of the stuff delivered in bulk.
    • CommentAuthorAlbert
    • CommentTimeJun 23rd 2008
    They'd be getting lorries to drop individual sacks of coal off, and not having trains/container ships full of the stuff delivered in bulk.

    My old uncle used to do his coal round quite happily with a horse & cart.
    • CommentAuthorgreenman
    • CommentTimeJun 23rd 2008
    Sorry if I'm straying from the point for a second, but I have to question the figures on the original web site - according to John Willoughby, Electricity produces 0.42 kg CO2/KWh, but Coal produces only 0.32 kg CO2/KWh (Anthracite). Is this on the assumption that the electricty is generated in a coal fired power station, and that transporting it to your home produces further emissions? I'm amazed to see the figure for coal being as low as it is, but the electricity figure seems correspondingly high...
    • CommentAuthorSimonH
    • CommentTimeJun 23rd 2008 edited
    Posted By: Albert
    They'd be getting lorries to drop individual sacks of coal off, and not having trains/container ships full of the stuff delivered in bulk.

    My old uncle used to do his coal round quite happily with a horse & cart.

    Actually - if you think about it, maybe going back to coal might not be such a bad idea. My house was built in 1964 and originally had a coal boiler just outside the back door and a coal fire in the lounge. Imagine having to keep toping that up twice a day and lugging buckets of coal around. It's so easy to turn up the heat on a thermostat and not see just how much gas is getting burnt in your boiler. In may case it was 1200 m3 in 5 months, or a box one meter high and wide, but 1.2 kilometers long :-( That helped me visualise what sustainable isn't! Anyone know if gas usage is based on the volume at atmospheric pressure, or the pressure it comes down the pipe at?

    I'm only joking of course about coal of course it's horribly dirty when burnt and causes all sort of breathing difficulties. Likewise - cold rooms aren't good for people with lung problems, and can be the cuase of the lung problems in the first place - damp/mold spores etc.

    Interestingly - I'd be happier to see everyone with borehole heat pumps and coal CCS, that I am with everyone having 90% efficient condensing boilers. The trouble is a typical bore hole costs about £5000 and a heat pump another £5000. A gas boiler is around £1000. So it's back to the issue of demand reduction really. Unless someone can magic away that £9000 difference.

    Given that my fridge is a heat pump and uses about 250W according to my Electrisave, why, does a 1kW input heatpump cost £3000 when my fridge only cost £200?? In terms of heat shifting capabilty the fridge is much better value per £ than a domestic scale pump. Maybe it would be possible to buy a bank of used fridges (or freezers) and plumb the cooling fins into a thermal store?

    Albert - I went to an agricultural show at the weekend and saw some magnificent Suffolk Punch horses. Coming from Yorkshire I didn't like the inference that they were better than Shires because they didn't need a midday feed to work but I was aghast to learn that there are more Giant Pandas in the world than this breed of horse. Bring back the coal wagon - or what about using them for Tesco grocery deliveries?
    Posted By: SimonHGiven that my fridge is a heat pump and uses about 250W according to my Electrisave, why, does a 1kW input heatpump cost £3000 when my fridge only cost £200??

    Because there are millions of fridges and only a few thousand heat pumps (in the UK at least). Economy of scale. Imagine you're the sales rep for a fridge company or a heatpump company. How much markup would you need to get a decent salary with the volume of sales you could get? The price of goods is not related to the cost of the components - e.g. Nike shoes cost around $1.50 to make but were selling at upwards of $100. Of course, that latter example contradicts my price versus volume argument - but fridges and heatpumps are not really fashion items (at least, at the low end).

    As for all the guff about CO2 emissions, it's only true for the UK at the current generation mix. I agree burning the gas directly for heat is better than wasting it in powerstations, but that trend will soon be over when the gas runs out. In the long term, heatpumps are an ideal choice since electricity is so flexible whereas primary fuels like oil, gas, coal etc. are extremely inflexible. Funcrusher has it right of course.

    I'm lucky that where I live we have pretty much 100% hydroelectricity so there's no guilt with using a heatpump at all.

    Paul in Montreal.
    • CommentAuthorjon
    • CommentTimeJun 23rd 2008
    So it's worth doing sometime but, right now, there are better things to be spending resources on?
    • CommentAuthorGBP-Keith
    • CommentTimeJun 23rd 2008 edited
    Posted By: Paul in Montreal I agree burning the gas directly for heat is better than wasting it in powerstations.

    Wonders will never cease. Paul has agreed with me for once.:cheer:
    The first thing to do should be to reduce demand. This will always have the best return. However, some climates, like my own, are virtually impossible to reduce demand down to zero. In these cases, a heatpump is good solution IMHO, especially when used in collaboration with "low grade" sources of heat as it can make them usable.

    Paul in Montreal.
    Posted By: (GBP) KeithPaul has agreed with me for once.

    Keith, there's many things I agree with you on - the problem is that this forum is becoming more international and much of what you say is only correct in the narrow context of the UK. I might disagree about making CO2 a prime focus, but the overall message of reducing demand as much as possible is, I believe, the most important one.

    Paul in Montreal
    • CommentAuthorLizM
    • CommentTimeJun 24th 2008
    I worry when you get black and white statements from government saying that heat pumps reduce your CO2 emissions. From reading the forums and other things, it seems like GSHP's efficiency is overstated, at least for domestic use. You might get people replacing gas boilers with GSHP and so making their emissions worse than if they'd bought a condensing boiler. They probably reduce your emissions if you replace an oil boiler though.
    The key to this thorny debate the carbon intensity of heat vs. the carbon intensity of electricity. I think that this little graph should help to answer most of the questions in a fairly clear fashion. As long as the carbon intensity of gas is lower than that of a heat pump gas is the most sensible option (assuming gas is locally available.)

    We should consider the problem of grid capacity as well. I don't think it is a good idea to add to peak load electricity demand, particularly if you already have a gas supply to your property. However, if you can run the heat pump at off-peak times to heat up a store of water then it's worth considering and could be cheaper to run.
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