SteamyTea

Or a 8 MW windturbine. Be worth working out how much PV needs to be fitted (with a bit of storage) to run a low energy house all year round, and at what sort of housing density to get around shading problems. Though building one larger solar farm is more efficient as it can be put on class 3b and class 4 farm land, which we have a lot of in Cornwall, and then there are all those old mining sites (I work on one and it is no good for building as too polluted and has holes in it).

And just enough fingers left.

Not as silly as me.

To save me high jacking someone's quite sensible topic, I thought I would have a quick look at straw as a building material. It is often touted as a sustainable, low energy input material, so I thought I would look up how much straw is harvested from a hectare (10,000 m2) of land, a nice size garden, but only 1/13,293,000 of the land area of England. Taking wheat straw, it is an average if 4 tonnes/hectare, the wheat itself was 7.8 tonnes (both 2021 figures and from here). There are some standards for straw bails and the density has to be at least 80 kg/m3 at <20% moisture. Now I think that 'construction' bails have a higher density, but I shall assume 120 kg/m3 for this (weights and measure can be adjusted as better data comes to light). So at 4,000 kg/10,000 m2 and 120 kg /m3, you get 33 m3 out of a hectare. Thermal conductivity has been tested in this paper to be approximately, which goes into different k-values at different densities. They estimated, via testing, that at 120 kg/m3 the k-value was 0. 75 W.m-1,K-1. To get a U-Value of 0.18 W.m-2.K-1 would need 0.41 m thickness (well maybe a little less depending on what it is covered in). That works out at 80 m2 of wall area per hectare. Taking a two storey house 10 m by 7 m by 5 m high, with 25% window and door openings, that works out at 127 m2 external wall area. Or, 1.6 hectares of land (16,000 m2). Just to put that into perspective, on the same area of land you could put a solar farm of approximately 1.5 MW installed capacity. That would yield about 1.5 GWh of electricity each year. That is enough power for about 100 houses. Ok, so you do loose the usefulness of selling some wheat, about £1600/year and the ability to 'grow' enough straw to insulate one house a year. But even 3p/kWh you get £45,000 a year for selling the power. So is building from straw really a good idea? (it is late and I may have made a mistake on my arithmetic, but I am sure others will spot it and put me in my place)

So squeezing the air out, which makes the U-Value worse. SIPs is a bit different in that it is a monocoque construction, the insulation, which is usually an expanding PU foam, bonds the two outer sheets (usually OSB) together. This changes the bending moment of the structure. Maybe @Gus Potter can comment more as I am very rusty on my structural engineering terms these days (took me decades to work out what a 'moment' was). In the past I have worked a lot with structural PU resins, and they are chemical engineering marvels. They do shrink over time which is what has always worried me about SIPs. This can be overcome to a certain extent, but the manufacturing becomes a more complicated processes, though mass production could make them price competitive.

Any reason why it could not be zinc plated?

Looks like a normal timber frame build with straw instead of 'something else' as insulation.

Are you thinking of structural straw bail construction, or just using it for insulation properties? Personally I would avoid both, and most other 'natural' materials, except timber. If straw bail, rammed earth, spit and sawdust were so brilliant, all houses would be built from them.

I did some work on sunpipes for Monodraught about 25 years ago. It is really not that hard to make one as long as there is not much of a bend.

I may well do that, shall see if I can get another 50 quid out of them first. At the rate they have been paying out, I will be paying less for my electric than most people pay for gas.

Just got my latest bill Day Rate 30.71 p/kWh Night Rate 12.27 p/kWH Daily Theft Charge 70.1p/day I have recently had the Ombudsman uphold a complaint against EDF and that totals 200 quid off my last 6 months bills. And now I have another incorrect bill, so that will be another 50 quid back. They are constantly estimating my bill even though they are getting automatic meter readings. And as they put me on monthly billing, they have been sending me bills for a few days usage at a time. How a company can get it so wrong, time after time, is just unbelievable.

Tope one is emission per mass, the second one is emissions per unit energy. Now I don't know of the second one is talking about primary or delivered energy. In the first one, there is also a reference to <3mg/m3. Pumping in extra air to the flu can trick that figure, it is similar to 'throttle hang' on a modern car.

I have no experience but I think a couple of people on here have tried them. I don't see why it would be any different to increasing the radiator size, or the flow temperature. The absolute humidity (the grams H2O/kgair) would stay the same, so the relative Humidity would just follow the normal Temperature/RH curve.

Because I know the thermodynamics.

No. In the data about your heating pump there should be a chart that shows the power delivered for different OAT, it may also show flow temperatures and CoP. Generally a LLH, volumiser or buffer is to reduce short cycling, it does not increase the power or flow temperature. Starting to sound like you have an incorrectly specified system.

What is the performance curve of your heat pump. It may only be delivering half of that at -10. And just a point about science convention, it is kW, not KW, that would be kelvin multiplied by power.

Cement mixes don't dry as such, the H2O reacts and changes the chemistry (trying to get back to limestone), only excess water, which should be minimal, needs to evaporate.

Was the flu designed to account for this? Over cooling flu gasses can cause problems.

Not all of them, I was writing about them 20 years ago, but more on the CO2 neutrality argument.

Might be worth doing as you may just be heating the ground below your house up a bit too much. Do you accept the science behind it though, particularly the particulate problem?

@Ecthelion Have you got UFH and if so, what is the U-Value of it under the pipework?

Does that mean you do not believe the science behind the debate? Isn't that like saying it is OK to steal from a shop because you heard that someone else had done it.

Know idea in reality, so shall call it 'half an average'. If we could nailed down our true environmental footprints to the gram equivalent, then we could easily tax it to change behaviour. But we can't. I suspect that you actually like your wood burner and don't really realise that there is an environmental cost to it.

Degrees in Renewable Energy and Environmental Science, A Master and 2/3rd of a PhD in Energy Usage. Well I have the biggest I suspect.

I am in trouble then as I am sitting in a room that is between 17.25 and 17.562°C. See you all on the other side as I don't have long to go.