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It's possible that high levels of reinforcing steel plus the clay bricks account for some of the reportedly high EE in Bedzed. Clay bricks can be 5x as energy-intensive as concrete (per m3). On my figures, the plastic pipes in a typical new house account for almost as much EE as the concrete. All I can say is that the EE of my own house doesn't appear to be as high as this although I've only calculated the wood, concrete, screed, stone tiles, steel and insulation so far, not the services.
Incidentally, do any of you know how much energy Bedzed actually uses in kWh/m2yr (or kWh/yr.dwelling) of gas and electricity? The biomass part of the CHP never worked, and for some reason it wasn't converted to gas CHP, so some householders reportedly connected up to gas central heating.
David.
I would go to a Passive House Conference and try and corner a German architect to find out what they use when they don't want a polymer render. Some definitely use lime-sand-cement.
David.
A recent report stated that it's worse than I thought. No green electricity tariff even contracts for enough renewable kWh to match their customers' consumption in kWh.
We also know that the suppliers as a whole didn't reach the “binding” legal obligation of 5% renewable electricity in 2005.
I think it's verging on misrepresentation.
David.
If you do a survey of the relative particulate and PAH emissions of all these brands, do let us know. Okofen appears to have strikingly low emissions (for particles) but I have no data on other brands.
David.
My view is that it should do that; the saving buys quite a lot of insulation and airtightness. In particular, if a heat pump of present-day efficiencies is compared to gas, the heat pump offers little if no CO2 saving. (There is a saving versus oil, albeit of dubious cost-efectiveness versus other measures which you can invest in.)
Heat pump COPs may improve in the years before the boiler needs replacing and a well-designed heating system can use almost any source of low-grade heat. So you're not really closing long-term options by doing this.
It might still be worth installing green electricity on your roof though such as PV to make a contribution to the national grid.
David.
10 kW is reasonable, most gas boilers are too large as well.
Thermal stores tend to need excessive temps. vs unvented cylinders.
If in north Essex have you met Mike Garnham? (Pebmarsh) He built two very low-energy houses, lives in one (thatched cottage aesthetics). Very low oil bill.
David
Can a house using OSB as the air barrier be made airtight? BRE's 1993 housing project in the Orkney Islands using plasterboard for this purpose failed dismally; the air leakage rose from 1 to over 4 within a few years.
David.
On one recent project (a 2.5 storey Gold Standard house in N. Wales) the structural engineer was asked if we could use 150 mm dense blocks but he checked and said no, use 200 mm. (170-180 mm would be the minimum – but it's not made in the UK). He also required the solid south wall to be reinforced between the fairly large windows by using 200 mm hollows and some vertical bars).
In the past this same engineer had been good in my view at designing out unnecessary structure so it seems unlikely that as I had hoped solid walls could be thinned down to 150 mm concrete block (widely used in Switzerland). or even 100 mm concrete (used in the Netherlands on row houses).
The manual handling regs. are another obstacle – they are interpreted as setting a weight limit, but they don't actually. Clearly in Germany builders are still allowed to lift 175 mm calcium silicate blocks (they use cranes more than we do) but this is arguably a better way:
David.
8 March 2007 at 11:07 am in reply to: Cold bridges at the founds/ground slab interface and Sleeper walls #33549It's not normally recommended for the heat emitters to have a similar or higher thermal capacity relative to the building which they heat. The nearest I can think of to this in the UK which succeeded is the Elizabeth Fry Bldg at UEA whch does have radiant floor heating using an all-air system, and hence a high thermal mass in emitters, but it has very high thermal capacity in the rest of the building, higher than in the cores of the concrete floors. Also it had M&E engineers on hand to design a control system, rectify gross installation errors and fine-tune it long after initial occupation.
Putting heat into a concrete floor is only usually viable iif it's used as a heat sink/store for ambient energy; e.g. solar heat, i.e., on winter days when solar collectors can't produce hot enough water to store in the insulated tank (was done in Switzerland in a pioneering project 17 years ago). Again, it needs a high thermal capacity building, in order to minimise the temperature fluctuations arising from the occasional uncontrolled heat inputs into the concrete slab. You'd still be advised in that type of house not to put your backup heat into the heat store but to put it straight into the house interior (i.e. radiators or fan coils).
I think you need to find a good M&E consultant to design a control system. Inevitably it will need to be continuously-heated with weather compensation, which is fine in priciple – indeed used in rest of Europe – but very different from normal UK practice.
David.
Probably designed for the kind of house which also has an Aga and several Range Rovers!
D.
As matter of interest, has anyone checked the total greenhouse gas emissions of wool insulation? Sheep (ruminants) produce a lot of CH4 which is a more powerful greenhouse gas than CO2.
D.
Thanks.
Backup to solar in highly-efficient houses, not main heating fuel.
I've now found an article on the topic in Sustainable Building Feb 2007 by Andrew Robertson (author mentioned above by Chris). It has a major weakness though in that it does ignore energy efficiency, which could lead to just such a nightmare of large country houses with palm oil-fired Agas and Range Rovers. I don't want to see that either, but neither do I want to breathe their wood smoke.
Converting brand new boilers doesn't seem sensible so I hope some German or Austrian products will come onto the market which are already biodiesel-compatible. It appears that UK manfacturers except poss bioflam.com aren't interested (no change there, then).
David.
1 March 2007 at 7:25 pm in reply to: Space heating back-up systems: For when it goes wrong (or you are refurbishing) #33753Mark
But the airflow then exceeds what a normnal ventilation air supply can provide, needing more fanpower (and recirculation).
And convective heating may not be all that comfortable if the thermal envelope has defects in it. Radiant floor heating does compensate a little for downdraughts and for the pool of cold air which collects on the floor of normal UK buildings.
David.
I can see no good reason why automatic WMs and dishwashers can't be hot fill. But the number available gets less year by year, especially with dishwashers. Yet sensors which are used to do clever things with the clothes wash could certainly also measure the temperature of the incoming hot water (in case it's too hot for delicate fabrics) and mix it with cold as needed.
I don't really understand how the energy label can ignore this feature. If 80% of the energy input to one of these appliances is heat rather than motive power (it's probably even more), then obtaining the hot water from a CHP system could reduce the primary energy consumption of the appliance by almost 75%, compared to a cold-fill version (electrically-heated).
David.
There might not be a problem in an average home but the risk to avoid is backdrafting in a more airtight home. See Mark's recent posting on R-2000 homes in Canada where they did all the necessary work to write the safety regs. The R-2000 standard requires a leakage rate less than 1.5 ac/h @ 50 Pa; the UK average is 12-14 and <1.5 is extremely rare.
Gas cookers are permitted to be unvented and the peak gas input is >7 kW but an extract fan meeting the current Part F would be a very good idea with those.
I know a house where the woodstove air supply is a pipe from under the ground floor and is shut off when not in use, but the law can be perverse so best to check current Regs. (Part F.)
David.
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