Jeremy Harris

I suspect it's all to do with humidity, and humidity buffering, together with the way our bodies regulate temperature. For particular temperature, say 23 deg C, we'll feel cooler if we are not exposed to radiant heat and if the relative humidity is low. My guess is that the effect of the harr was to condense out moisture during the night, as the air cooled, on to every surface, the ground etc, as the air became too saturated with moisture from the night time temperature drop to hold as much water as vapour. When the weather warmed up the next day you'd have had the double whammy of the local humidity in the house increasing as warm, moist air was drawn in, plus the effect of a bit of radiant gain. Generally we feel hotter when the air is more humid, as perspiration is less effective at cooling our skin, due to the reduced rate of evaporation and hence the reduced evaporative cooling effect.

The bottom of our service trench was around a foot or so below the water table, so that trench filled with water. It would fill up overnight, so we'd just pump it out the next morning. I think we had the pump running in a hole in the bottom of the trench when the DNO jointing team came out to make the new mains supply connections. I know for sure that their pot joint is under water, as the yellow marking tape was floating along the trench the next day. The intermediate earth strap and rod they put in next to the new pot joint was certainly getting a good low impedance, as it was constantly submerged in water.

I deliberately put ours in the services room, so access is easy, just walk into that room through a door from the spare bedroom. There's even a carpet on the floor in front of it so kneeling to check the filters is easier on my knees!

Interesting, as my building inspector asked for a commissioning report that showed that it had been installed, tested and all airflows measured and balanced in accordance with the regs - my guess is that there's an inconsistent approach to applying the regs... You do need to get access to at least be able to regularly check/clean/change the filters. I find that the intake filter on ours is full of crud after 6 months, and I probably need to get into the habit of cleaning it more regularly. One reason the building regs insist that there be easy access to these units is because of the regular servicing requirement, so boarding out a pathway to it would be a good idea.

There's a building regs requirement for it to be easily accessible for servicing, plus the filters need to be cleaned/changed at least every six months (sometimes more frequently), and some models require a regular check and clean of the heat exchanger, too. The intake filter on ours needs cleaning at least every six months, and ideally perhaps a bit more frequently than that, as it doesn't take long to get clogged up. Our unit has a filter alarm that shuts the MVHR down if ignored, and the longest filter change interval that can be set is 6 months.

Welcome. My concern is that it's probably going to be quite hard to separate out the significant impact of different building techniques from any measured data set. My experience has been that the actual building method impact, for any intrinsically low energy house, is probably negligible in terms of any measurements, as there are just too many external variables that completely swamp any slight differences, so I have grave doubts that you'll get meaningful conclusions with regard to performance. There's decades of prior art on low energy construction, and whilst I'd be the first to say that not every conceivable method has been built and tested, the majority have, and the collected data gained over 30 to 40 years or more is very extensive, and certainly of a high enough standard to enable a build method to be selected for any given location, site and ground conditions. There are a few pretty simple rules with regard to design, and these are generally very well documented, such as minimising surface area to volume, build using a high decrement delay factor, shade east, south and west windows (ideally variably), etc, etc.

No, I'm not, and as a scientist with over 40 years experience I'm ducking out - sometimes there is little merit in continuing a debate that is going around in circles and will never reach a meaningful conclusion.

I agree. Years ago I scrounged a 4 wheel sack truck that had been used to transport mail bags and built a bench and storage lockers on top of it. That worked really well. I did it to move tools and instrumentation around Falmouth Docks, but it would have coped quite well with a building site. The wheels were the ones that take 260 x 85 inflatable tyres, which seem to be a common size. Somewhere I've seen a sack truck that had two extra wheels so it could be used horizontally - I'll try and see if I can find out where, as that might be an easy way to make the base. One of these might make a good starting point: https://www.ebay.co.uk/itm/HEAVY-DUTY-GARDEN-TROLLEY-CART-4-WHEEL-BARROW-QUAD-TRAILER-LARGE-WITH-LINING-NEW/322626206008?epid=1358179427&hash=item4b1e053938:g:MI4AAOSwPM9Zfyyb Make up a stout box to fit snugly inside and you could have a combination trolley for shifting stuff around and a movable workbench, just by lifting the bench/box in and out.

Yes, the batteries are a lot larger and heavier, and ideally need an automatic watering system, so are best placed in an outhouse. The lithium packs, like the Pylontech units, can be mounted in a standard 19" electrical rack I think, their dimensions seem to indicate they will. I've seen several suppliers for the Sofar charger/inverter and Pylontech battery combination, like these: http://www.thesolarpeople.co.uk/shop/sofar-solar-4-8kwh-energy-storage/ https://thinkrenewables.co.uk/sofar-solar-48kwh-battery-storage-system The last link seems suspiciously cheap to me, at £2,412 inc VAT and shipping, as that's about £500 cheaper than the same system was a couple of weeks ago. The first link is still the same price as before, £2,795 inc VAT and shipping, At £2,412, with an expected battery life of 12 years (according to their info) then if you could self-consume 75% of the total capacity every day, then you could possibly get back close to £200 a year, which is getting close to breaking even on the capital outlay, assuming 15p/kWh through life. Add in the convenience of having up to 3 kW of emergency back up supply, from a dedicated emergency outlet that's included with this system, and it's looking pretty close to making sense to buy one. Easy to install, too, according to the instructions. I will admit to being tempted by the Sofar offering, if only to give us security of supply during power cuts. Subtracting the cost of a 3 kW emergency generator from the system cost makes the economics look more favourable.

We had a very long and drawn out problem getting an overhead line taken down. In the end the local OpenReach manager suggested that the only way to get the job sufficiently up their priority list was to "accidentally" break it with the digger jib early one morning and then phone him immediately on his mobile to report it. This worked like a dream, within 30 minutes a crew were out to remove the debris and reconnect the ready and waiting underground line. I was told that jobs like this have such a low priority that OpenReach will never get around to doing them; they will always have higher priority tasks to do on any given day. I'd suggest just disconnecting it and coiling it up. Be aware that there will be up to 50VDC on the line, so best to tape up the ends.

OK, as it happens someone else would like it, so all's well!

I have a spare pump you can have for the price of the collection. It needs priming, but once primed it stays primed. It's the WZI750 on this page: http://www.dambat.com/wzi-pumps.html It's barely been used, I ran it for about a week when I was playing with a two-pump system for the house. I also have a 650 litre (I think) rectangular slimline water storage tank and a float switch to turn the pump on and off if you want it. They are all surplus to my requirements, but are big so will need transport. I can help load up this end. I also have some spare 25mm MDPE and fittings, to go with it. Yours if you want it, no charge. Just PM me or say you want it on here. You have first dibs on it; if you don't want it then anyone else is welcome to it all. Edited to add: Found the info on the water tank, it's this 650 litre one: https://www.directwatertanks.co.uk/industrial-tanks/window-cleaning-water-tanks/650-litres-baffled-window-cleaning-water-tank-upright It has a drain cock already fitted at the base (3/4" BSP IIRC) and an overflow pipe fitted to the rear near the top. There are two holes on the top with pipe fittings, one to fill the tank one to feed water out to a pump. Either could be blocked off if not needed. The float switch cable comes out through a cable gland on the top, and is adjustable so you can set when the pump comes on and off. I had it set to turn the pump on when the tank was about 2/3rds empty and te off again when the tank was full, but it's easily adjustable by sliding a weight along the cable.

No need to declare any abstraction of less than 20,000 litres per day and there is no requirement for a licence. The exception is if you divert a watercourse in order to do so, in which case you do need consent. Dropping a suction pipe into a stream isn't diversion. Creating a culvert or gulley that diverts some of the water out of the stream and into a pond or through a garden IS a diversion and does normally require consent and a licence. New rules came into force on 1st January this year but they do not affect those using low volume abstraction. I looked into this as we draw our water from a borehole and are subject the same regulations. To stay legal, I'd be inclined to just drop a submersible pump into the stream and draw what water you need. You are very unlikely to exceed the 20,000 litres per 24 hours limit. I ran our 700 W borehole pump flat out, with a full flow coming out of a length o 25mm MDPE, for around 48 hours non stop and only managed to pull around 26,000 litres per 24 hours from the borehole, which is a heck of a lot of water.

I've just been looking through the costs for a 3 kWp on/off grid charger inverter system, running from a nominal 48 V battery pack. The Sofar system looks to be about best value, in terms of the charger/inverter unit, and 3 kWp is probably OK for a low energy house. The ME300SE charger inverter is around £900 (probably a bit less if purchased with batteries). Choosing 4.8 kWh as a realistic minimum battery capacity, then using the cheapest reasonable quality lithium packs I can find (the Pylontech modules) 4.8 kWh would cost around £1,900. 4.8 kWh of 100 Ah NiFe cells would cost about the same, around £2,000. Both the inverter charger and lithium batteries have a life of around 10 to 15 years, probably closer to 10 years. So a £2800 investment in the inverter/charger and lithium battery pack, assuming that you managed to usefully use around 75% of the total stored capacity all through it's life, and assuming that the charging electricity was "free", from excess generation that's already available, would just about pay for itself, at a unit price of 15p/kWh, after about 15 years, around the time the system would be at the end of its life. The NiFe system batteries would still be as-new after 15 years, so the system would have paid for itself, only needing the investment in a new charger/inverter to give another 15 years life. Electricity delivered over the second 15 year period would be around 1/3 of the current grid price, using the assumptions above. On the face of it, the NiFe system wins hands down, but you will be waiting many years before you see your investment start to pay off.

Data is rarely, if ever, "consensus". I spent most of my career measuring things, and removing all and every source of measurement error. We only published data when i was just that, irrevocable evidence measured and cross-checked against other sources, with due account taken of any and all sources of measurement error, to the point where there was no significant chance of it being incorrect. I've never, ever, published any data professionally that hasn't been peer reviewed and cross checked multiple times. I've taken part in many peer review processes, where the starting point is always the same - you view the results and conclusions presented with deep scepticism until you have collated enough high quality evidence from independent sources, or your own experiments, to demonstrate whether or not the data in the paper being reviewed is valid. Only then does the paper get published, and often only after a fairly lengthy debate amongst the peer reviewers as to whether the conclusions drawn from the data are valid or not. There's nothing quite as tough as a review by a bunch of scientists, who are, by their very nature, sceptical of claims and cynical of conclusions, until such time as they've seen the hard evidence with their own eyes. As a collective group, good scientists are a pretty difficult bunch, as it's rare for them to naturally agree about anything that hasn't been proved to each and every one of them individually. It's one reason that scientists are rarely definitive, but almost always couch any statement with a certain amount of caution, or with caveats. The latter are often ignored by the media, much to our general annoyance, as ignoring important bounds and caveats then gives the general public a completely false view.

FWIW, I've found that Bimblesolar are importing their Nife cells from Taihang Batteries, part of the Henan Xintaihang Power Source Co. Ltd, Henan, China. If anyone is after some, then I would expect that they can probably buy them for maybe 20% or so less direct from the manufacturer. Using the manufacturer's bulk price as a guide, a pack of 40 off 500 Ah cells (48 V nominal, 24 kWh nominal) would cost around £10k inc shipping, plus VAT and duty. That would give a usable capacity that's close to three times that of a Tesla Powerwall, and a life in excess of 40 years, probably closer to 50 to 60 years. To that you'd need to add in the cost of a charger and inverter, plus, ideally, an automatic watering system, but overall you could end up with a 20 kWh capable house power system for perhaps £15k or so, with an operational life of well over 40 years. Realistically the charger and inverter would probably need replacing three times of so during that time, so the total cost is likely to be close to £20k through life. If half the usable capacity could be used every day, from a renewable charge source (so effectively "free") then at a unit price of 15p per kWh the battery could save up to around £1.50 per day, perhaps £400 a year (allowing for cloudy days where the pack can't be fully charged. At £20k, it still looks like the investment wouldn't be recovered until around 50 years, though, so probably not yet a viable solution. It does have the advantage that the cells are probably still going to be fine after 50 years, though, based on my long experience of using and abusing them. A smaller capacity system would probably reach pay back a bit more quickly, but it's still marginal.

Septic tank leach fields/soakaways always fail within about ten years, but it's rare for that failure to be noticeable unless the water table is high. To work properly, a septic tank absolutely must have an aerobic tertiary treatment system that does 99% of the effluent treatment. Traditionally with was done by using aerobic soil bacteria around the leach field. The snag is that over a period of 5 to 10 years these aerobic bacteria tend to build up bacterial ,films that prevent atmospheric oxygen from permeating the surrounding soil. What then happens is that the effectiveness of the tertiary treatment drops and the leach field becomes septic, with predominately anaerobic bacteria feeding from the effluent. This isn't good news, as it means that the effluent that drains away has a very high biological oxygen demand (BOD), which makes it exceptionally harmful if it enters a watercourse, plus it allows the proliferation of anaerobic pathogens, which are generally significantly more harmful to both humans and wildlife. There are lots of ways around the problem, but the best fix is to convert the anaerobic septic tank (the clue is in it's name as to the type of bacteria in contains) to an aerobic treatment plant. The effluent from an aerobic treatment plant has a very low BOD, so can be far more safely discharged and tends not to have the same biofilm problem, simply because the BOD of the effluent is too low to support the growth of the bacteria that tend to form biofilms that clog things up.

Yes, they are importing them from China, but you can buy them direct for a fair bit less. I did get some prices for dry-shipped cells from a similar Chinese supplier a few years ago and they weren't bad, and certainly cheaper than the US/Canadian made ones that are, I believe, still in production. Note that the company linked isn't selling Edison manufactured cells, they are selling Chinese copies and being careful not to use the Edison name in the actual cell description! BTW, buying dry-shipped cells makes a lot of sense, as the electrolyte is easy to obtain and mix up and not being filled reduces the shipping weight a great deal.

Why is it that non-scientists choose to use false principles and grossly inaccurate generalisations to deride, even deliberately insult, those of us that spent many years studying to become scientists? What's worse, some seem to assume that scientists must be trained to have closed minds and be unable to examine and analyse data that doesn't reinforce the hypothesis they are testing, when nothing could be further than the truth. Apart from being very offensive, such thinking flies in the face of the way I, and everyone of my former colleagues, ever worked. Hundreds of times we found data that didn't match our initial hypothesis, and every time that happened our eyes would light up at the thought of the new questions we needed to ask and then test. Finally. I have no idea why the term "social science" is misused, to pretend that social studies are really a science. In my view it is not a science and never has been, at best it's a bunch of untested ideas that someone with more ego than common sense has gathered together and tried to falsely claim as demonstrable fact.

NiFe cells get around the limited cell life problem pretty much completely; they last practically forever in my experience of using them for a decade or more (although don't ever mention that fact on a certain other forum - you'll get kicked off for heresy...). I've personally used 50 + year old NiFe cells that were still at full rated capacity after all those years, and pulled very high current from them to run high speed 35mm cine cameras with no problems (a 10,000 fps 35mm cine camera needs a couple of hundred amps or more to spin up). They are far from perfect though. The have a Peukert number that's lower than that for lead acid, plus a higher self-discharge current and a relatively wide voltage range between discharged and fully charged. They do self balance, like lead acid, though, and only require a simple constant current charger with a voltage/temperature triggered cut off, so battery management is a great deal easier than any lithium ion chemistry. They are massive for their capacity, too, and require watering regularly, but again that's easy to arrange with an automatic cell watering system. All told, as a long life house supply NiFe cells are a very good option, if you can generate enough excess energy to make up for the fairly high round-trip loss because of their Peukert number. If we could still get hold of the really big NiFe cells that were very readily available on the surplus market a few decades ago then I'd use them for sure. However, right now the choice is to make your own (not that hard to do if you can find some old telephone exchange glass cases) or import them from somewhere like China (the Chinese are manufacturing them in large sizes, for standby power, submarines etc).

The main difference is life and efficiency. Peurkert factor for lead acid struggles to get better than about 0.85, that for lithium ion is close to unity, to round trip losses from lithium ion are around virtually non existent, versus 20 to 30% for lead acid. Lead acid cycle life may be as high as 2000 cycles if babied, lithium ion will easily make 20,000 cycles. The conservative life of a Lithium ion system would be around tens years, that for a similar cycled lead acid pack might around 5 years for equivalent capacity reduction. Looking at the pay back from self-consumption, ignoring the standing charge and assuming 0.15p/kWh, then if you could realistically average 80% of the rated storage capacity all the time for self-consumption, you might be able to save around 3.5 to 4 kWH per day for self use, so about 50 to 60p per day energy saving. At £2,800 the basic (and fairly optimistic) payback period might be as short as 5,600 days, or over 15 years, for the very best case. BTW, a 110 Ah 12V leisure batter might do 400 to 500 cycles at the very most, and only store a total of 1.32 kWh, and a usable kWH of only about 70% of that. Used in a household system they would barely last a year, and would only deliver around 1 kWh per day at the very most.

Ideally insulate over them, but frankly the hassle of doing that, as it'll raise the floor etc, probably isn't worth it for the small improvement by reducing thermal bridging. Tight fitting insulation to the sides of the joists, foamed in place, with significantly reduce the thermal bridging through the joists anyway, by reducing 3D heat flow to almost wholly 2D. Leave the underfloor vents open so that the cold space under the insulation remains well-ventilated, to prevent damp build up. Plywood is a good choice for a sub-floor, but you could equally well consider using T&G OSB3, which might be cheaper and would do as good a job if glued and screwed down well (our first floor is 18mm T&G OSB3 on 400mm centre joists and is fine). The drawing looks fine, I just think you can do away with the L brackets and just fix the PIR in place with low expansion foam. Others may care to comment on this, but it's what I'd do.

Microinverters often have a monitoring system built in that reports back to a data collection unit, so you can check performance and health. For the sort of shaded conditions you describe then microinverters are a good choice, but equally good, and perhaps more reliable (the jury's out on that) might be to fit panel optimisers, like the Solar Edge system. Optimisers don't have the high voltage switched mode inverters built in, so are a lot simpler internally. All they do is optimise the output from each individual panel using a maximum power point tracker (MPPT). This deals with partial shade every bit as well as a microinverter system, but means that you still run DC down to a conventional inverter. The advantage is really that the primary cause for concern in the microinverters (and big inverters), the high voltage commutation capacitors, aren't up on the roof, but remain in the main inverter. Commutation capacitor life is the primary life-limiting factor in an inverter, and is proportional to temperature - the cooler you can keep the capacitors the longer they will last.

This is getting to be pretty unbelievable, especially given the fact that they know that getting stuff, or engineers, out to where you are is a pain. Looks to me like that's been sat for a long time with uninhibited water in it, many months for sure. With luck the PHE may be OK, as it should be above the pump, so may well have stayed dry. Being made of stainless will have helped, too.

I wonder if the Bosch packs have something similar to the Makita packs? If a Makita LiIon pack gets out of balance, after being stored for a time whilst discharged, then when plugged into the charger it will give a battery error warning (flashing red charge light). If you try and charge it three times like this, the battery will be permanently disabled by the charger and turned into junk. This happened to me, and I managed to save the pack by taking it apart, charging the individual cells one by one and then fitting a replacement battery management system circuit board (there's no way to repair a board that's been "bricked" by the Makita charger). Bosch may possibly have a similar system, but there's no way to know without taking the pack apart. I found out about the Makita "feature" because there were a lot of online complaints about battery packs being bricked when they were still under warranty. A friend who works in a tool store let me have a big box of Makita "scrap" batteries, which were all repairable by replacing the battery management system board.