Forum Replies Created
- AuthorPosts
The Thermotech fixing detail is aimed at more standard North American walls which are quite thin. One wouldn't ideally use such a detail in a house with thicker walls designed to minimise thermal bridging. I did my modelling about 10 years ago using FRAME.
David.
Another point, if this is done on a larger scale the carbon monoxide and hydrogen can be combined to form other fuels which may be more useful, such as propane or various alcohols. But the charcoal is still buried on farmland to improve its fertility and produce a yield of even more biomass which ….
D.
This idea was reported in Nature and a good article appeared in Renew (regular journal from EERU, OU). It sounds very promising indeed but the conversion might be safer if carried out on a large scale as the wood produces not only charcoal and producer gas but tars. These are not at all nice, think of all the UK's ex-gasworks and their legacy of contaminated land.
David.
Dirtier air *is* linked to increased mortaliity. Extra CO2 *may* cause increased mortality. The degree of causation is not the same.
Besides, there are ways to heat more cleanly with biomass, helping to combat climate change but without causing the same harm to health:
1. Use wood chips or pellets in large CHP plants, which can fit electrostatic precipitators (widespread in Denmark)
2. Turn forestry wastes, household waste, straw, etc into liquid or gaseous biofuels which can be burned cleanly using known technology (condensing LPG or oil boilers). Probably not enough of this for more than backing up what active and passive solar, insulation & airtightness can't provide.There's a lot more on biomass elsewhere on this forum.
David.
Tahir
Trees absorb CO2 as they grow. Trees on your own site can be regulated and/or controlled (given the will) by either TPOs, planning conditions or by you yourself placing restrictive covenants on the property (to bind future owners). So I can't see any fatal flaws, especially if the calculations of CO2 absorbed are cautious enough and (ideally) are prescribed by law for each species.
I *can* see lots of fatal flaws in the Treasury conditions, some of which I pointed out in the BFF article “Zero Carbon, Zero Reality?” (although that was DCLG). I also see lots of flaws in international carbon offsetting – but trees next to your house aren't subject to the same criticisms as say biogas in Botswana (which isn't regulated/controlled and in any case should be considered part of Botswana's own CO2 reduction potential).
David.
He's now an architect; he's also built his own and other houses.
He used to be a cricketer.I agree, Monbiot's document on biofuels is quite grim. He cites the WTO – but if the WTO is an obstacle to certifying biofuels as sustainable, how can the FSC certify timber which is traded internationally as more sustainable and not be pursued by the WTO?
At least five countries including the USA are now generating bio-methane and putting it into their gas grid. This isn't happening in the UK yet.
Meanwhile the UK Treasury states on its web site that so-called “zero-carbon homes” must not be connected to the gas mains. But they can be all-electric!
I'd ignore them and try to reduce your gas consumption to Gold Standard level or less. If on a large rural site, possibly plant trees to offset residual emissions. If this was allowed for rural low-carbon homes, TPOs could possibly be used to ensure that trees planned now continue to sequestrate CO2 over their life and are not cut down by future owners.
David.
31 March 2007 at 9:00 pm in reply to: Re: Re: Occupant Behaviour and Adaptive Controls: Whole house heating vs. Zoned heat #33849Mark
In a building to the Gold Standard, the variation in temperature from room to room tends to be minimal. It wasn't worthwhile when it was assessed recently on a new house. Zoning isn't worthwhile on Silver either unless the net present value of the fuel savings exceeds the capital cost of setting it up – and overcomes the inconvenience of colder upstairs rooms (bathrooms can't be run as the colder zone so would need to be zoned with living rooms).
The U-value of an intermediate floor may be 2.0 Wm2K, yet the U-value of the opaque envelope including windows may average 0.35-0.45 W/m2K (Silver). So an unheated first floor (even it has a door to the stairs which is kept permanently closed, as old cottages do) will still stabilise at a temperature fairly close to that of a heated ground floor.
If the building's space and water heat consumption is say, 35 kWh/m2yr, there's not much to be saved by running half the building at 19 degC instead of 21 degC. But if the designer is sure that some rooms will never fall below the comfort zone (for their intended use; e.g., circulation or bedrooms) it might be possible to omit radiators to some rooms. This saves on capital cost, instead of costing money.
HTH
David.
Mark
Not so sure about books but try web-searching for the Danish Board of District Heating – hundreds of superb technical papers.
For people to design it …. not all M&E engineers know of anything outside the boundaries of a single building. AFAIK one of the UK's best district heating engineers is William Orchard, director of Orchard Partners (London) Ltd. He isn't an expert on the bigger picture, or on thermal insulation and air barrier detailing, but for heat mains and heat emitters I suspect he's exactly your man. (Since the collapse of communism he's spent a lot of time in eastern Europe improving the energy efficiency of their district heating systems.)
For someone so expert, he has remarkable few documents available on the web.
HTH
David.
I know people who've used NBSLD / SERI-RES extensively. Reliable if user-unfriendly. The minimum temperature without heating is lower in a lowmass than in a high-mass bulding.
It's known from experience and measurements that high- and low-mass buildings behave differently. Insulation and airtightness also make a low-mass building more thermally stable. Don't these engineers acknowledge the results of scientific experiments?!
SAP-2005, which is used to model most dwellings, takes no account of thermal capacity – BREDEM iis a static monthly (or annual) degree-day model. Work in Canada shows that a high-mass dwelling is able to utilise passive solar gains (from large south facing windows) much more effectively than a low-mass dwelling (both were close to Gold Standard insulation and airtightness) On this basis, a low-mass dwelling uses 500-2000 kWh/yr (depending on size) more space heating energy than a high-mass one.
David.
I note that the existing Austrian building already had a leakage rate of only 5 ac/h at 50 Pa! (half or two-fifths that of *new* UK buildings).
AFAIK vertical perimeter insulation is more effective than an umbrella – unless you live in an extremely dry climate and want to store solar heat in the earth inside the umbrella.
David.
Bit concerned that your ground floor is suspended timber
They tend to leak air.
HTH
David
Mark
Tell your contractor / manager firmly that they're not comparing like with like!
Concrete-frame buildings are OK as regards airtightness – as easy (or hard, depending on one's point of view) as load-bearing masonry with concrete floors.
Steel-frame offices / schools are a nightmare as regards airtightness, unless the air barrier can be routed completely outside the frame.
Bill Bordass has lots of horror stories of where they leak like sieves. I've managed to avoid steel-frame except occasionally for steel posts in houses to support the corner where the window wraps around two sides of the building (the steel is well inside the glazing at this point). I was involved in one job which was a steel frame (by order of the QS) but it was never built so we don't know how much it would have leaked despite efforts to make it airtight.
It's like concrete versus timber-frame houses; I was talking to a developer yesterday and we both suspect that the design costs must be higher for the timber-frame house, other factors being equal. In particular, to reach a very high standard of airtightness, the junctions are more complex than they are with solid-walled masonry or concrete-walled buildings. I haven't discussed this point with any architects, what do you think?
David.
Geoff
Those are theoretical figures for Bedzed. I meant the measured ones.
My EE figures are mostly from a govt table of 1995 before BRE was privatised.
David.
700 kg/m2 is totally out of line with Chapman's figure 30 years ago of 100,000 kWh for a 100 m2 semi, say a maximum of 30,000 kg or 300 kg/m2.
Some materials, such as cement have become less energy-intensive in that time, due to process shifts.
I find this discrepancy surprising.
David.
Jim
You say your tariff claimed to buy renewable kWh for your gas? AFAIK no biogas enters the UK gas grid at present – this only happens in “the usual places” (Germany and California are starting to build methane digesters and to connect large dairy farms to the gas network).
Ecotricity doesn't match the full consumption. You apparently have to pay extra than the “green tariff” for that to happen.
David.
- AuthorPosts
