Jeremy Harris

I have to say I agree, poking a cobra up the pipe would have given a pretty quick indication as to where the blockage is, but @ProDave probably doesn't have a cobra to hand, and may well not be able easily get hold of one up where he is, so has to work with what he's got. I could borrow a cobra from someone within half an hour, but that's only because I know a chap in the village that has one, and knowing him is only by luck, as he offered to lend it to me when he was walking past and spotted me struggling to blow a bit of string 30m up a run of buried 50mm cable duct (long story - basically young dickhead ground worker tied a crap knot in the middle of a length of pull rope. I tried to pull a length of SWA through and the knot came undone....).

It's really about having a high heat capacity internal structure, and a low thermal conductivity outer envelope, plus having an outer envelope that has a high enough decrement delay as to largely damp out the impact of diurnal external temperature variation.

I agree wholeheartedly. When giving a talk in our village hall about our house, I was asked what the " -0.9 tonnes of CO2 emissions" bit meant on the EPC. It's not real, of course, for the reasons you've given, in that it just means less CO2 is emitted from other energy generation sources. However, I did work out that it's roughly the same as having around 40 mature trees on our plot, in terms of CO2 sequestration per year. Perhaps a bit far-fetched but it serves to show how much impact even a small area of PV generation can have, relative to using the same area for growing things in order to reduce CO2 emissions (shades of an old, and long-running, debate with a certain biomass fan on another forum!).

But insulation has units that define its performance and it can easily be measured, whereas "thermal mass" has no units and cannot be measured. I can go into a builders merchant and buy insulation that will have well-defined performance. It will be defined in terms of it's thermal conductivity, λ, which is given in units of W/m.K in its specification. Also, we don't have a 300m thick slab in our house, it's 100mm thick.

Ours is underneath the eaves overhang at the back of the house, and high enough up the wall that it never gets wet. The only thing I have to watch it the rate at which cobwebs build up over the heat sink fins. Spiders seem to like living there, perhaps because it's a bit warmer in winter than other nooks and crannies around the house.

Not sure about this. By definition, a house that has a negative CO2 emission rate can't be worse for emissions than one with a positive emission rate, can it?

If you wish to use underfloor heating driven by PV from the roof, then I'm afraid that I think you will be disappointed with the performance. PV generation during the heating season is generally very poor, perhaps only 5% to 10% of the generation capacity outside the heating season. Also, if trying to use solar power to drive underfloor heating, then you are probably better using solar thermal, as that has a much higher efficiency than PV, probably between 2.5 and 3 times better. Having said that, I doubt very much if you would get anywhere near enough solar energy from the roof of any building to be able to heat it during the heating season. We have a passive house that only needs a minimal amount of winter heating, plus a 6.25 kWp PV array in the roof, and we cannot hope to meet a fraction of our heating requirement from PV generation in the winter (and our house has 300mm of insulation under the floor and in the walls, and 400mm in the roof, plus airtight triple glazed doors and windows).

There's only one question that needs to be asked and answered about this, and that is, if "thermal mass" is real, then what are the units used to measure it? What would be a "good" value for "thermal mass", and what would be a poor value? Heat capacity can be measured, and has defined units, see here: https://en.wikipedia.org/wiki/Heat_capacity Thermal conductivity can also be measured, and has defined units, see here: https://en.wikipedia.org/wiki/Thermal_conductivity Decrement delay and the decrement factor are a useful measures of the interaction of heat capacity and thermal conductivity, in the context of the materials from which a house is constructed, and they can also be measured and defined: http://www.greenspec.co.uk/building-design/decrement-delay/ The thermal time constant of the inside of a building can also be measured, and has units: https://en.wikipedia.org/wiki/Time_constant#Thermal_time_constant I've yet to discover any units that can be used to describe "thermal mass", and frankly if it cannot be measured, then it isn't a real physical property, just a loose and ill-defined term to try to describe the complex interaction between heat capacity and thermal conductivity in the context of house building and the way that might relate to its thermal time constant. There is a Wikipedia entry (under review) https://en.wikipedia.org/wiki/Thermal_mass that attempts to describe "thermal mass", but it is flawed is several ways, not least the fact that it tries to tie the heat capacity of a structure to its mass, which is a poor way of trying to describe something, as mass is generally a poor indicator of the heat capacity of any material. For example, plaster has a heat capacity of around 1.09 J.g-1.K-1, yet concrete only has a heat capacity of 0.88 J.g-1.K-1, so a given mass of concrete will store less heat energy at a given temperature than plaster. Going even further, water has a heat capacity of around 4.18 J.g-1.K-1,so will store about 4.75 times as much heat energy as concrete for a given mass. Clearly, trying to use mass as a measure of the ability of a structure to store heat is not really valid, as there are very large variations in the heat capacity of a given mass, depending on the material that that mass consists of.

Some do, yes. Our IP65 rated one doesn't, as it's designed to be fitted outside, so just has a large finned heat sink with a cover over it, but inverters intended for use indoors can have cooling fans. I think there's probably an advantage in having passive cooling, as fans can and do fail. The disadvantage of passive cooling is that the unit tends to be a bit larger.

I'll also add that I've tried using oxalic acid to get rid of black marks on iroko decking (much like oak as far as staining goes). It was a bit hit and miss, and definitely lightened the wood a fair bit, and not all the black marks came out. I ended up sanding the deck back and painting it with Deks Olje, which wasn't really the look I wanted.

You can get outdoor rated PV inverters, we have one bolted to the back wall of our house. I believe that having the inverter mounted in a shaded location outside is likely to result in longer inverter life, as the most common cause of inverter failure is failure of the internal commutation capacitors. These have a life that is highly dependent on temperature, and running them a few degrees cooler can have a big impact on making them last much longer (I believe that it's something like a 10°C temperature reduction to almost double the working life).

The black marks are actually in the top surface of the wood, they are a chemical reaction between the tannins in the oak and usually something like steel that's been in contact with it, so I don't think you can wash them out.

I just did a rough design initially, to get the terminals more or less where they needed to be, and to estimate the amount of ducting needed, then ran the semi-rigid 75mm/63mm duct along the best routes I could manage, trying to keep the runs as short as practicable and also trying to avoid too many sharp bends. It's hard to predict in advance the exact alignment of the openings in the posi-joists, and the angles you can run ducting across a room when aiming to get a near-diagonal run.

It's so common I'm beginning to wonder why SI haven't yet invented a new unit for it. I've given up pointing out that mass has sod all to do with the thermal time constant of the building, and that it's the combination of heat capacity and thermal conductivity (both of which have units and can be measured and so quantified) of the structure that are the dominant factors. Easy enough to build a net zero energy/carbon home, ours is actually net negative energy/carbon, in that it both generates more energy than it uses and is, in effect, a CO2 sink (the EPC reports the CO2 "emissions" as being -0.9 tonnes per year). Given that the structure of our house is an off-the-shelf build system, then there's no real reason for more houses not to be built to a similar standard.

One way I've seen is to very gently sand blast the oak. Needs doing with care, and tends to be messy, but the results can be very good. I've a feeling the blasting media used isn't actually sand, but something less abrasive. A search on "blast cleaning oak" should find someone close to you that does this, or you can hire the kit and have a go yourself.

How deep is the pipe buried Dave? Just a thought, but you've had some sustained cold weather up there, haven't you, days on end down at around -10 or less? Any chance that the pipe could be relatively shallow at any point on the run, so that it may have frozen up?

The increasing scale of the problem seems to indicate a leak that's steadily getting worse, but as you've mentioned, any leak of that size should be producing a visible effect somewhere. Hard to know what to suggest, especially as you seem to have ruled out the possibility of a leak on both the house side of the stop cock and the section from the meter to the stop cock, which is perhaps the most likely place for any hidden leak.

It's a fair bit of hassle to install, but water meters aren't that expensive, so it might be worth fitting one on the house side of the stop cock if there's room: https://www.pipestock.com/meters-gauges/water-meters/single-jet-cold-water Seems a lot of trouble to go to to prove that the water meter is faulty, but it's hard to think of another way to get an accurate cross check. As @Tennentslager has suggested, a test of running off a known volume might work, but I think you'd need to have a pretty big tank to fill, or perhaps rely on filling several baths full, one after the other, to get an idea as to whether the meter was in error.

Sadly there doesn't seem to be any way to prevent cracks developing in the first year or two after a new house has been built, be nice if there was. We've now owned three new houses since 1992, and all suffered from cracks in the plaster in the first year or two. Doesn't seem to matter what the construction method is, either. It was clear that our last house had been (badly) repaired where old cracks in the plaster hadn't been properly filled, and that was block and brick with plastered block internal walls. I spent ages going around raking out badly filled cracks when we first bought that house, and cursing the Polyfilla maniac who had just gone around smearing the stuff over the top then painting it. If only they'd done it properly, and vee'd out the crack, filled it, sanded it smooth and then painted it I'd have not have had to spend a couple of days fixing things properly.

Yes, I've been following all the battery storage companies for a few years now, trying to determine which will stay the course and prove to be able to supply reliable and affordable products and which will fall by the wayside. The big challenge seems to be getting products to market, and that seems to be a slow process for many of the products that have been announced over the past year or so. Be interesting to see how things pan out over the next year or so. BTW, Tesla's offering is out of my price range unless they decide to reduce prices in the very near future.

Best bet is to use the data in building regs, specifically the rainfall region and run-off data in Part H3 Section 1

It won't make any significant difference, as although it might feel warmer on the sunny side of the house, in practice the air temperature won't be much different to that on the shaded side of the house.

They are indeed a PITA. A friend of ours lives in a mid-terrace house with a path running along the back of the houses to an exit on to the road, and they similarly have a right to take coal and rubbish along that path. One of their neighbours tried to stop wheelie bins being taken along the path behind his house, on the basis that he believed that "rubbish" meant hand-carried rubbish, not a noisy wheeled bin. It took months to resolve via solicitors, and ended up being very nasty for all concerned. Best if it can be resolved amicably, without getting too formal, in my view, as once solicitors get involved it can easily sour relationships for years.

I can second @ProDave's observation about battery storage. We have 6.25 kWp of in-roof PV and export nearly double the amount of energy we use (right now we have the dishwasher and washing machine on and are still exporting well over 3 kW). However, even with that relatively high level of PV generation, I cannot make a Tesla PW2 cover the upfront investment, or come close. Even a cheaper battery system only really starts to look as if it might cover the investment if I include the value to us of being able to have a standby power source during power cuts, and to get the sums to add up I had to include the capital cost of a generator to provide that function if we chose not to invest in battery storage. Hopefully the price of battery storage will drop over the next few years, so that it does look to be a viable investment in future. In the meantime, I'm going to take the leap and invest in a battery system as an early adopter, and hope to be able to report on whether or not my estimates of the likely return on investment are reasonable or not.

That's very true, but not something I'd given a lot of thought to. I knew from the outset that we were being guinea pigs for the technology, and installed our Sunamp PV whilst being fully aware that it was, to some extent, a prototype product. Nevertheless I was very impressed indeed with its performance, and that led to me believing that the replacement product, the Sunamp UniQ range, would be at least as good, hopefully a lot better. I'm just disappointed that I have to manually reset the Sunamp UniQ controller every day in order to ensure that we have continued hot water. I'm not using the Sunamp UniQ in a different configuration to the Sunamp PV we had for a couple of years or so, in fact it's using the same wiring. I've spent a fair wedge of additional money in "upgrading" our hot water system and found that in reality I have significantly downgraded it, to the point where it fails to function without daily manual intervention, leaving us with no hot water. In my view that makes the product unfit for purpose. The sooner this is recognised and something done to address it the better.