Jeremy Harris

Why are some of the steel webs missing on some of the posijoists? From the photo, it looks like some joists only have metal webs on one side, not both.

Because you're on London clay, I think it would be very wise to stick to the same foundation support all the way around, to reduce the risk of differential movement. When it comes to piling systems, then there are several different methods, each with their pros and cons. I would suggest that you don't leave this to the main contractor, but explore the relative cost of different piled solutions yourself first. Often you are trading things like additional material cost, with less labour or mobilisation cost, making a direct comparison challenging. For example, you will incur a one-off mobilisation cost for a CFA piling rig, plus spoil removal cost, plus steel cost, plus concrete cost, plus labour cost. You would incur a probably smaller mobilisation cost for helical screw piles, a higher per-pile cost for materials, a lower labour cost (they are a lot quicker to put in) and virtually no spoil removal cost. The same goes for other systems, there is always a trade off between higher costs in one area and lower in another, that make direct comparison a bit of a pain at times.

Screw piles are just augers that are the piles, so have less ground impact overall. I very much doubt that Thames Water would have the slightest problem with them, as they present a lower risk to their pipe. I suggested helical screw piles specifically because they are low risk. Take a look at a helical screw pile and at an auger pile rig and you'll see what I mean.

London clay is very definitely a soil type that moves a lot with variation in moisture content, so needs care with the foundation design to reduce the risk of movement. You can use a raft or slab foundation on clay, but you won't be able to get it that close to the 1m limit, as it will have to have a fairly deep layer of well-drained stone underneath it to spread the load out and down to reduce the soil bearing stress and ultimately limit any movement the clay could induce in the slab. I think that a piled solution is far and away your best bet, given your space constraints. Piles are pretty much the classic way of getting around London clay heave and would allow you to get the ring beam that supports that outer wall right up to your 1m limit. You can put an insulated slab on top of a piled ring beam, plus there are several other options that could be explored. I don't think that the suggestion you have at the moment from your SE is at all sensible, given the site limitations. The SE has used what seems to be a fairly standard solution for the soil type, but hasn't taken account of your site restrictions, from the sound of it. Much as I'm a great fan of insulated slab foundations, there are places where they cannot be easily used, and in your case, with the need to have a vertical load bearing foundation along a 1m line, with nothing going over that line, you are going to find that you're pretty much forced into using piles, I think. There are lots of piling systems around, ranging from driven steel piles, conventional bored and reinforced concrete poured piles to helical screw piles. The fastest to put in and most probably the ones that would get you closest to your 1m limit, may well be helical screw piles. I looked at using them on a previous plot we were looking to buy and was impressed. It's well-proven technology (some Victorian piers are still standing on ancient cast iron screw piles) and it's a clean and quick solution, with minimal excavation or soil disturbance. It's also a system that is immediately load bearing, so the house can literally be put on the piles as soon as they are driven in.

The obvious solution would seem to be to use a slab foundation, as then the outer walls can sit on the edge of the slab. It's ground-condition dependent as to how close you could get the outer wall to the 1m line, and frankly I don't think any foundation system will get you closer than a few hundred mm to that line, even a slab, due to the need for stone underneath that spreads the load down and out at a 45 deg angle. Helical screw piles are another option, and might get you closer. You can put either a steel or reinforced concrete ring beam on the pile caps to stick the house on. What sort of soil type do you have? Do you have a soil susceptible to movement with water content, like some types of clay? Do you know the maximum allowable soil bearing stress?

Depends. Using WiFi can be done, but it takes up a lot of processor overhead, so isn't ideal. If you want to use things on a WiFi LAN then you'd be better using something like a cheap ESP8266 and coding it using something like Node Red. If you're happy to use a non-WiFi wireless solution using a licence exempt system, then it's dead easy to use these with a PIC. If you opt to use a PICaxe, which is a PIC pre-loaded with a pretty good BASIC-like interpreter, then coding for hardware stuff becomes pretty easy. The sticking point with it is that the PICaxe is designed for education, so is pretty cheap and easy to use for STEM type projects, but it lacks native floating point math support and that may or may not be an issue. Driving things like serial data over wireless links is dead easy though. Our PV diverter works like this, as do other monitors around the place. It's just a matter of sending serial data to a cheap wireless transceiver, and getting it back again via a serial input. Having no floating point math, and only a restricted numerical capability (positive integers only up to 216) seems limiting, but in reality it's not really. There are pretty easy techniques to get around these, like using twos-complement to express negative numbers and adjusting the way data is handled internally to remain within the integer size limit. The lack of floating point is really just a display issue, as you don't need to think in decimal at all when doing all the math in the processing. There are various PIC compilers around for other languages, some free, some paid for, and some include floating point math and a larger integer range, I believe. I grew up using 8 bit microcontrollers to build instrumentation with, so my view is heavily influenced by that, mind. After 30 odd years or more of working within 8 bit limitations you tend to develop a library of techniques to overcome some of the limitations. The ESP8266 scene is probably worth a look, though, as it's all open source and no where near as messy as the world of Arduino has become. The Arduino concept was great, but there is now so much SOUP** around that frankly I wouldn't trust anything made with one. I've had far too much experience of the way SOUP causes unsuspected problems, because the person who used it in their code didn't fully understand either the competence (or lack of) or what was going on in the head of the person that originally wrote the SOUP (and which made have been modified by person or persons unknown since, anyway). ** Software Of Unknown Provenance, in this case Arduino C libraries written by unknown people and often used blindly by people who haven't a clue as to what their source code looked like, or wouldn't understand it if they saw it.

It'll be a code problem, not a hardware problem, for sure. Even a 50p PIC can read the data from a BME280 and stick it up on a display, having corrected the data using the calibration factors that are built in. I suspect the code you have is not initialising the BME280 to enable all three sensors, or may not be reading the full register range from OxF7 to 0xFE in burst mode. It may well be just using the cut-down burst read mode from 0xF7 to 0xFC, which will only output data and correction factors for the temperature and pressure sensors. It may not even be reading the registers in burst mode at all, and according to the data sheet this is not recommended, because it may cause bytes to get mixed up if the registers are read one by one.

Not sure why you're not seeing the data from all three registers in the BME280. By default it uses all three when taking a reading, so it comes down to your code. I've never used high level stuff to do this, I've always used the raw I2C commands to just read the registers, then done some bit manipulation to get meaningful values. There are several modes in which the BME280 can be operated in at the basic level, which each being best suited to a particular application. The native resolution is high, but it includes the ability to oversample to reduce noise, and also includes an IIR filter to smooth the data if a fast response time isn't required. I think you probably need to look at the I2C write commands that are being sent to the BME280, both to set the initial operating mode and to ensure the data is in the registers, ready to be read using the I2C read commands. All three sensors in the BME280 can be configured to be enabled or skipped during initialisation, and it seems like that the I2C write commands you're sending at initialisation may be disabling the humidity sensor. That may well cause the humidity register to be empty when you try and read it. Within the BME 280 there are several uniquely addressable registers, that are best burst read, starting at address 0xF7 and ending at address 0xFE (to read temperature, pressure and humidity). The data are read out in unsigned 20 bit format for temperature and pressure and 16 bit format for humidity, hence the need for bit manipulation after a data read to reconstitute the data into meaningful bytes an words. You also have to take account of the calibration constants that the device also puts out and use these to correct the raw data (each device has it's own calibration constants hard stored internally and read out with every full register read). Cycling though I2C sensors is dead easy, no need to mess about with turning them on and off. Each sensor has a unique address on the I2C bus, so will only accept write or read commands when they are preceded by that sensors address. As such you can select a sensor on the bus to read, send it a write command (if it needs it) to tell it to make a measurement, then read the data, when it's ready, using a read command. The same applies to one-wire devices, with the address being the hard-coded serial number of a particular device in that case. Some conventional serial data connected sensors can be uniquely addressed and accessed like this, some can't. The particle detector I've opted to use can't be uniquely addressed, so is going to use two data lines that are dedicated solely to sending and receiving it's data.

The island already has that. Currently the micro-grid that supplies all the properties has 112 kWp of hydro capacity, just under 10 kWp of PV capacity 24 kWp of wind generation capacity plus a diesel generator and a battery back-up system and inverter. Given that baseload electricity can be provided by a pretty high percentage renewable scheme, I would concentrate any secondary microgeneration on site at peak shaving, rather than base load provision. Hot water is an obvious first priority, as it's very easy to store heat, with none of the cycle life problems that electric batteries have. After that it starts to get tricky to reduce loads. Heat storage for heating is unlikely to make sense, as the very time when you need heat will be the time when there's little in the way of renewable generation. Combined heat and power might be a winter option worth looking at. The same friend who makes his own biodiesel for his Landrover has been running his house off-grid for many years, with pretty much all his winter demand coming from a home made combined heat and power system. He uses a big single cylinder Lister generator, with a heat exchanger on the buried in the ground oil drum exhaust silencer and runs his radiators from the waste heat from the engine and exhaust cooling system. He runs the Lister on waste vegetable oil he gets for free, by just filtering it and pre-heating it to make it thin enough to flow through the engine injector OK. There are better CHP solutions around, now, though, including small Stirling engine versions. I'm not 100% convinced that I'd look at battery storage just yet, primarily as the choice is limited and it would be an expensive investment. Opt for an off-the-shelf system like a Tesla Power wall or a Power vault, and it's not going to integrate easily, because both really need a grid tie, and have to be frigged with to work as stand alone systems. Opt for a more conventional off grid system, with something like Rolls lead acid batteries and an inverter/charger system and you're well and truly into DIY, with a fair bit of maintenance work, too. I think my starting point would be to make the house so efficient that the heating demand is tiny (a bit like ours), and then you should be able to manage everything except hot water from the 5 kW microgrid supply. The big demand is hot water, it will dominate energy usage usually, and there I think it gets to be a tough call as to whether to go for solar thermal or PV. Normally it's a no-brainer to go for PV, because it's a heck of a lot cheaper to buy and install, plus you can export any excess generation. In this case I don't think that may apply, as being able to store a LOT of hot water may well be a really big advantage. One option not mentioned yet would be to forget about the Sunamp PV altogether, as I don't think it's the right product for this application, and look at fitting a large evacuated tube solar thermal array plus either a very big water filled thermal store, or better, if the budget allows, a Sunamp Stack, which would be a lot smaller and have a lot lower heat losses, allowing more hot water storage. As a backup, then a low capacity inline electrical heater, that could be run off the microgrid during low demand periods, might do the job. I think I'd aim to try and store maybe three days worth of hot water, if possible (that's a guess - I've not looked at the insolation data for Eigg yet!).

The Sunamp PV control system power is separate, as the unit has 4 core cable, with two line connections, one connected to the grid to run the control system and one the switched line from the PV system. I agree, hot water from a Sunamp would make a lot of sense, the issue is how to provide a winter back up. There will be around 30% of the year when the Sunamp won't be able to meet the hot water needs, and with only very limited "grid" power it's unlikely that a system to charge it from the grid when there hasn't been sun for a few days is going to work. A Sunamp PV would charge from wind as easily as from PV, as all it does is detect whether there is power on the switched line and then start the charge process. It would need regulating, as I don't know the limits for the Sunamp switched line input, but suspect it expects to see close to the same voltage and frequency as the main grid supply. Perhaps an LPG multipoint might be an option as a boost heater after the Sunamp PV to make up for the shortfall in winter? Depends whether cylinders of LPG are available on the island and the cost, but I doubt much gas would be used over the course of a year.

Welcome, The problem with small grids like this is that they have no "spinning reserve" so there is no big "virtual flywheel" to maintain grid frequency, and no energy storage. The limited frequency stability of the system on Eigg comes solely from the hydro plus some small battery storage capacity and a back up diesel gen set, as both the wind and PV will be going up and down like a yo-yo. There's no way a grid tie inverter will lock into such a system without changes to the way the hydro plant and battery storage adjusts for variations in PV and wind generation, unless the island invests in either a lot more battery storage (to create a bigger "virtual flywheel spinning reserve") or perhaps something like hydro pumped storage. My guess is that more battery storage may well be in the long term plan for the island, or perhaps conversion of some of the hydro to pumped storage, to achieve the same effect. In some ways the problem is a bit like that in South Australia, on a much smaller scale, where inadequate spinning reserve, due to a high reliance on renewables and inadequate maintenance of the reserve generation, led to grid collapse when there was a sequence of unintended generator failures combined with reduced renewable output. As I understand the micro-grid on Eigg, the base load is handled by the hydro, backed up by the batteries and the diesel back-up generator, which can be throttled up and down as the PV and wind vary, so the hydro is acting as the frequency stabilising factor on the grid. A normal big grid relies on several phase locked fast response power stations to do this, hence the term spinning reserve. When there is enough wind and/or PV to meet the base load then the hydro and/or the battery storage can throttle back, and perhaps some of the wind turbines can be braked, but the system will be very sensitive to load variations. Adding more microgeneration with only such a relatively small "virtual spinning reserve" is going to create a lot of problems at peak renewable generation times. There's the added problem that the micro-grid may well not be adequately frequency stable as it need to be for a normal grid tie inverter to lock in. I doubt this relative lack of frequency stability matters at all for a micro-grid like this, so they just live with it. What they need is to get Elon Musk to get interested in giving them a big storage system - that should fix the problem and allow a far more stable micro-grid frequency and allow the incorporation of local microgeneration. In the meantime, having two systems in a new build is easy to do and makes sense, given the relatively low 5 kW maximum load per house.

Thanks, but no need to, as I have it on DVD as an original production copy, along with a load of "behind the scenes" photos, like this cheeky one:

OK, I've spent a few hours today sorting out the basics, and looking for sensors. So far I've ordered one of these: http://www.aqmd.gov/docs/default-source/aq-spec/resources-page/plantower-pms5003-manual_v2-3.pdf?sfvrsn=2 particulate sensors, as it seem to be the best compromise between cost and performance. It automatically bins particulates into up to 2.5µ and 2.5µ to 10µ bins and outputs the data in an easily read binary form, that pretty much any microcontroller or single board computer could use. These are also readily available on Ebay for around £16 to £17, so I've ordered one to try. There's a slight problem with laser particulate sensors like this being spoofed by water clinging to tiny particles, which means they tend to under read PM2.5s when the humidity is high, or more specifically when the particles may be at around dew point for the air humidity. So this means measuring humidity and temperature. I've opted to go for the BME280 combined temperature, humidity and barometric air pressure sensor, as it's cheap, accurate and linear: https://ae-bst.resource.bosch.com/media/_tech/media/datasheets/BST-BME280_DS001-12.pdf I've found plenty of suppliers for this as a module, already fitted to a breakout board, for just over £1 each, so have 5 on their way. The easy way to get both accurate time and position data is a cheap GPS module. I have one of these running as the master clock in the new house, and it's like having your own atomic time reference at home, it's that accurate, plus it never needs setting. The price of these modules has come down, so I've managed to get a small (roughly 20mm square) one for less than £6. The one I've opted for uses the Ublox chipset, and I know from past experience that these are dead easy to use. The remaining problem is to measure NOx, but I've found a sensor that seems to do the job OK, the MICS-2714: https://sgx.cdistore.com/datasheets/sgx/1107-Datasheet-MiCS-2714.pdf It's not ideal in terms of the package, but there are a few suppliers that sell it on a break out board, that should make it easier to use. I'm just digging out the best one at the moment. I think I've sorted the NOx sensor problem. I found an updated version of the one I'd found earlier, that includes CO sensing, plus I can buy it from Bangood.com for around £22 mounted on a breakout board. The sensor is the MICS-4514 : https://sgx.cdistore.com/datasheets/sgx/1107-Datasheet-MiCS-2714.pdf I'm looking at two display options, either a display directly on the measurement box, or a remote display with a wireless link. The latter might be more useful for a sensor unit that's to be permanently located, the former maybe more useful for a portable unit, perhaps one run from a car power supply. So, the basic box at the moment should be able to measure and record time, position, PM2.5 concentration, PM10 concentration, air temperature, relative humidity, air pressure and NOx concentration, which is probably good enough. I still need to make a few decisions on things like power supply, frequency of taking measurements etc, as some of the sensors are quite power-hungry, so won't run for long on a battery supply. When I've worked out the full power budget, and worked through how long it takes each sensor to warm up and be ready to take a reading, I should be in a better position to see what options there are for powering the unit. My preference for a fixed unit, would be to have it sheltered under a solar panel that charges a battery to operate it and radios data back to an indoor display that can both show the data and log it to a USB stick. I could make it so that it connects to the LAN etc, but frankly I'm averse to connecting anything home brew to a WLAN, just on privacy and security grounds. It would be easy enough to get these sensors to work on something like an ESP8266 I think, if anyone wants to go down the route of integrating sensing into their WLAN. My solution may not suit everyone, as I'll undoubtedly use a couple of PICs to do the hardware stuff, drive displays etc, on the ground that they are dirt cheap, very lower power and I can write code for them in my sleep. Any microcontroller system or SBC could be used, albeit with greater cost and code complexity, it's really just personal choice. I'll try and stick to the basic building blocks of code, how to read the sensors, how to do the arithmetic to get the results into a meaningful form, ways to display and log the data, etc, rather than go for a full blown set of instructions on how to build a specific unit. If I get it going, then I may find time to publish details of exactly what I've done and the code I've used, but that may not suit everyone.

Beats me, too. Both the ones I've fitted have been on to shower wallboard, and in both cases I just drilled a hole, fitted the shower hose fitting up tight with a back nut to the wallboard before I fixed it to the wall permanently, then fitted the elbow. On one, which was fixed to a solid block wall, I chiselled out a channel in the wall and fitted a flexible hose with an elbow on the end to the 1/2" BSM threaded stub, on the other, I just used the flex in the plastic pipe coming up inside the stud wall to give me enough room to fix things. Both times the hose connector was fitted tight and then blanked off for a pressure test before I finally bonded the wallboard back.

So it's now up on YouTube. Great. My other half will be SO impressed (not)................... Every time it was shown as a repeat on C4 she would cringe, knowing full well that some of her mates at work would have seen it, and whenever I've done anything on TV she just thinks I'm a walking embarrassment. The whole topic of talking about doing another TV show has been forbidden in this household for years now......................

What to they do for a seal? The ones I have (just looked at a spare, slightly different design) have had seals on the rear of the thing to seal against the tiles/wall. The spare I've just looked at has an O ring in a groove on the back, and judging from the annular rebate in the one pictured I'd have thought a seal may fit in there? Ours also had a back nut with a big flange to hold the thing in place and pull it back tight to the shower wall board we used. The elbow sat back from this and would never had been able to pull the fitting tight up against the wall, it was a good 50mm back inside the wall.

You mean this Lisa Rogers, chatting to us just before I drive the boat in the race - ('tis me with the grey beard, lifejacket and helmet....):

Yes and no. If you use PVA with the "proper" biscuits, then yes, they do indeed swell up and make the joint tight. If you use a PU adhesive, then they don't seem to swell up at all, and retain a slightly sloppy fit, but then the foaming action of the PU adhesive takes care of that.

Yes, the usual benefit of having the warranty supplier and building control supplier from the same company/organisation is that there is a saving in inspection fees, as warranty inspections can be combined with building control inspections, instead of having two inspection call outs each time.

So not quite double, but not far off!

That sounds like a good price! I wonder what the mark up is when you buy one here in rip-off Britain? I bet it's like the ludicrous MVHR pricing situation, where it's practically half price to buy from outside the UK.

Based on my experience of buying from Poland, a great deal less that you would be charged by a UK re-seller! You can buy it from the Ukraine for €315: https://kaminova.com.ua/en/bio-fireplace-kratki-juliet-1800x650.html

Inside the unit, apart from the heat batteries, there are a couple of standard non-return valves, a standard variable speed circulating pump (Grundfos IIRC), a standard looking, off-the-shelf ultrasonic flow sensor, what looks line a standard small diameter immersion heater, a standard resettable over-temperature switch on the heating chamber, a standard off-the-shelf pressure relief valve and a custom control circuit board, that has some standard relays on it. It's hard to estimate lifetimes, but if I was to have a guess, then I'd say the pump is probably good for at least 20 years, based on experience with very similar central heating pumps, probably the same, or longer, for the NRVs and PRV. The heating element may well have around the same lifetime, but that depends to some extent on the water quality. The lifetime of the electronics is hard to judge. I have a plug in digital time switch that is now getting on for 25 years old and has been in daily use all that time. It did have a capacitor fail a few years ago, but that was a ten minute job to replace and it now works fine again. My guess is that the ultrasonic flow sensor will have a long life, as it's essentially an industrial product, and looking at it it's probably an easy replacement if it were to fail. My guess is that the most likely components to fail might be relays (after probably a decade or two) and maybe some electrolytic capacitors. I can't see it being a major job to fix anything in there, really. I've already had to replace the resettable over-temperature switch on mine, as early units (and mine was one of the first batch) were fitted with thermal switches that could have dodgy riveted connections, so self-heated and cut out, but that's been fixed by a component change. Overall I'd say the unit almost certainly has a significantly higher reliability and life to something like a boiler, perhaps around 1.5 to 2 times the life at a guess, maybe longer. PS: I should add that my stripping and replacing a part on my Sunamp PV was sanctioned by Sunamp ! I was an early guinea pig and so one or two minor niggles were to be expected, and Sunamp were quite content to talk me through diagnostic and repair procedures and let me get on with it. Like most modern products, there is a degree of built in fault detection and component sub-assembly level diagnostics built-in, making fault finding pretty easy.

I've had a router biscuit jointer bit for a few years now, and the smallest bag of biscuits I could buy is still nearly full. I reckon it would take me three or four lifetimes to use them all up on DIY and self-build types jobs!

Essentially moonshine/ Poitín or any other home made spirit is made the same way. You ferment a mash of anything with sugar in it, like grain, beet, rice, sugar cane or whatever, much as you would make a strong home brew beer. When the fermentation stops, you filter off the liquid and distill it, to extract the ethanol. With a fermented base there will be lots of other volatiles, oils and at least a couple of alcohols in the mix, so the tradition is to throw away the first part the heads) that comes off, as that has the nasty stuff in in (like methanol) keep the good stuff from the middle part of the run and chuck the stuff that comes off at the end (the tails) back in for the next fermentation, as it doesn't have much ethanol left in it. The traditionally distillers who make stuff like whisky use this method, as they couldn't control the vapour temperature at the run off point to the condenser, where the ethanol was condensed back to liquid. With a controlled heat source to the source brew it's easy to just get the ethanol out, as it comes off at around 78 deg C, so you can get a better yield. In the case of vodka, that's just pretty pure ethanol diluted with water to make it drinkable, so the above process is just to separate out the ethanol from the water. Water vapour will be at a higher temperature (around 100 deg C, whereas ethanol vapour will be at around 78 deg C, so by controlling the temperature (and usign a reflux column that sends some condensate back down to be re-heated) you can pull off just the ethanol. As for home made diesel, yes, that's easy to make, but a bit more involved. You start off with old vegetable oil, usually waste from deep fat fryers, then heat it and mix it with sodium methoxide, which you have to make using methanol and sodium hydroxide (dead easy to do). After a while of heating (people who do this often use old hot water cylinders as the heated reaction vessel) the mixture separates into glycerin and diesel oil. You draw off the diesel and you can wash out the remaining glycerin and then dry the diesel if you want to get it really clean. You can also recover some of the methanol from the waste glycerin, for the next batch, which reduces the cost still further.