Jeremy Harris

We built a great one at Penwyllt, as the septic tank kept getting blocked up with "fat bergs " (a consequence of a few dozen cavers having fry ups for breakfast every weekend). In essence it was a deep brick built chamber (only built of bricks as it was right next to the old Penwyllt brickworks, so there were thousands just lying around) that had an inlet pipe around half way up it's depth and an outlet right at the very bottom, that led to the septic tank. Midway across the chamber was a weir, designed to deflect the incoming flow upwards. Above this was a suspended galvanised steel milk crate, resting on ledges just above the top of the weir. The low level outlet pipe went via an inverted U bend, made from 110mm waste pipe fittings, so that it worked as an auto-syphon. The way it worked was pretty simple. The chamber would fill with the kitchen waste water run off (the toilets and showers went directly to the septic tank) and the fat would float up to the top, and clog in the milk crate. The relatively fat free effluent would flow over the weir and when the level on the outlet side exceeded the auto-syphon height it would drain away to the septic tank. Part of the Duty Officer's job each weekend was to lift the lid and check the fat trap. We kept spare milk crates, so if it was looking clogged with a fat berg, it would be lifted out and put on the bonfire to burn off, and a fresh crate dropped in. Before adding this system we used to have to dig the septic tank out at least once a year, as the fat made it impossible for the truck to suck out the sludge. The indication that this was needed was from complaints from those camping in the field in front of the club house (below the septic tank) as it used to over flow across the campsite. Digging the tank out was a thoroughly miserable job. It was a long, rectangular, tank, with the lid made up from a lot of concrete railway sleepers. All these had to be lifted off, the digging party had to don wetsuits, boots and goggles, and climb in to break up the contents, whilst keeping the tank flooded with water so that the tanker could suck up the stuff that was liquid enough. As an aside, shortly after I got my explosives permit, I was Duty Officer one weekend when the tank had to be dug out. I definitely did not want to climb into it, so I made up a handful of small charges (around an ounce of plastic blasting gel in a small screw top aluminium pill can) poked an electric det into each one, wrapped them in electrical tape and pushed them deep into the solid mass at intervals, using a long stick. All the wires were connected up to the exploder, we all stood back, and the handle was wound and the button was pressed. All the charges went off, but they blew the contents of the tank immediately above them vertically, for a considerable height, smattering all the cars in the car park with some of the contents. We were hoping that we'd have fractured the solid mass (the inspiration was the "hot rocks" project in Cornwall), allowing it to be liquefied with water and sucked up. Sadly we had to climb in and dig it out as usual, and then clean up the mess in the car park.........

I still maintain that if you have a house with a low heat loss rate, even under worst case conditions, then a dead simple, but low hysteresis, thermostat should do the job. Say the house takes 10 hours to lose 0.5 deg C in winter (ours is a bit longer than that, more like 24 hours or so). As soon as the temperature in the room drops by 0.1 deg C below the set point, the heating comes on. The heating system then has several hours to pump heat gently in to the house before the temperature drops much below the set point. Likewise, as soon as it has gone 0.1 deg C above the set point the heating will turn off, but the house tends to carry on warming up a bit over the next couple of hours, from the residual heat in the UFH pipes and the time taken for heat to travel from the warmer core of the slab to the surface. It's this latter issue that makes the house comfort level so dependent on keeping the UFH flow temperature as low as possible - the more heat there is sitting in the core of the slab the greater the temperature overshoot when the heating turns off. Overall this system seems to be able to control the house to around -0.2 deg C, +0.7 deg C normally, a fair bit better than the hysteresis on some of the pretty crappy thermostats that have been around for decades. We do occasionally see an overshoot to around 1 deg C over the set point, but that's usually because of a bit of solar gain. We never experience temperatures dropping more than about 0.2 deg C below the set point, no matter what. Personally, I can live with that. That range of temperature variation around the set point seems perfectly acceptable to me, so I really don't see why there needs to be any more complication. Best of all, it uses off the shelf stuff, so can be fixed quickly if anything fails.

The house external surface will be above ambient, though, as even with the best insulation there has to be some heat flow through the structure. Also, there will usually be some external surface solar gain, even on a dull day, that will tend to make any external surface that is impacted by even diffuse sunlight a bit warmer than ambient. In the standard U value calculation for any external element there are two assumed surface heat transfer factors included (or there should be, if the calcs are being done properly), one for the internal surfaces and one for the external surfaces. These factors are usually simplified to assume constants for surface emissivity (which determines the radiative heat loss) and still air surface convection loss rate, which depends on surface roughness (which effects both surface area and still air convective flow) and the angle of the surface (vertical surfaces have a lower convective heat loss factor than horizontal or angled surfaces). What changes with wind is that the assumed convective surface heat loss rates in the U value calcs change, quite substantially in the case of a rough surface. Add in a bit of moisture (driving rain or mist) with some wind and you also get a fair bit of evaporative heat loss, as well as increased loss because of the higher heat capacity of water vapour. If the airtightness is good, and there is MVHR, then I doubt that there will be that much change in ventilation heat loss. The resistance to flow of the air leakage paths will be high, whereas the resistance to flow of the MVHR, ducts and terminals will be a lot lower, so most wind-induced increased ventilation will probably flow via the MVHR, pushing the ventilation rate up, but still recovering some heat, albeit at a lower efficiency.

We used to collect rain water at sea to refill the tanks on a friend's yacht. We had a canvas funnel, with a pipe sewn in the end, so the pipe could be stuck in one of the tank fillers. In heavy rain, the procedure was to luff up, tie the main sheet both sides to hold the boom steady, partly lower the main, so there was a sort of gutter along the side of the boom, attach the canvas funnel to it and then lower the topping lift just enough to get rain to flow into the funnel. We'd let the first few minutes worth of water run away, as it was usually salty and mucky, then when it was running clear and tasted OK we'd stick the pipe into one or other of the water tanks. Back then, before reverse osmosis water makers were invented, it was the only way of topping up with fresh water at sea.

Rainwater collected from a roof will always have fairly high concentrations of Escherichia Coli (E.Coli), mainly from bird droppings, but it could well be from any creature that has either been on your roof or eaten by one that's been on your roof (think of all the scavenging birds and their mixed diet). Many birds also carry parasites that can be excreted as cysts, that are difficult to kill, and other diseases that can be harmful directly to humans (pigeons are carriers of psittacosis, cryptococcosis and histoplasmosis, for example, all human diseases). Additionally, unless rainwater storage tanks are underground and kept cool, it's possible that they might become breeding grounds for legionella. As a consequence, rainwater should not really get used anywhere where there is a risk of ingestion or droplet inhalation, at least not without some form of treatment. I'm not at all convinced that toilet flushing is safe, because the cistern will be at room temperature and so it seems likely that any pathogens may well multiply more quickly in such an environment, but mainly because the act of flushing a toilet releases an aerosol of easily inhaled water droplets, especially at lower levels, where small children may be. Few modern washing machines run hot enough to kill pathogens in the supply water, and it seems likely that there will be an increasing trend to cooler wash cycles, as there has been in other countries (I believe even cold washes are getting to be normal in some countries now). As a consequence, clothes washed and rinsed in rainwater from a storage system will probably be contaminated with a wide range of potential pathogens. There are ways around this. The use of a fine filter of 5µ or less, plus UV disinfection, should make the water safe, but such a fine filter will require pre-filters if it is to last any length of time before getting clogged, so you're probably looking at two or three filters in series, plus regular filter changes. The UV lamp in the disinfection unit will need to be on all the time, and will last around 12 months before needing to be changed. All told, I'm of the view that raw rainwater is best kept for watering the garden, and perhaps washing the car, bearing in mind that any pumped system that produces a spray carries a risk of producing fine droplets that may be inhaled.

This was the same for our guy, he works on his own and doesn't get many new build wiring jobs (I think ours was his first). I was still surprised that he could choose a job to be audited. Back when I ran a couple of UKAS accredited labs, all we knew in advance was the date of the inspection, we hadn't a clue what they might choose to look at, not even a list of possible areas of inspection. They literally opened filing cabinets at random, pulled out a file and then asked to see all the evidence supporting everything in it, from calibration stickers and records of all the equipment used to verification that we'd checked that our calibration providers had a traceable audit trail. These audits used to take about a week per lab, with two auditors, then we'd get back their report and whether or not they were revalidating our accreditation about a couple of weeks later. As mentioned before, I've heard rumours that since Grenfell building inspection bodies are looking far more closely at how they work, and it could just be bad timing that @curlewhouse has started inspections during what may be a knee-jerk reaction period. If the same sort of rigour was applied to all new builds then that would make a significant change, but just randomly selecting one self-builder, because they know full well that a single self-builder is no threat to their reputation or, more importantly, their commercial income stream, isn't going to change anything.

Perhaps some sort of audit of inspection standards? I don't know, but I would suspect that the approval bodies for building inspectors are tightening up things. If they are like those for other approved organisation/people schemes, then often those being assessed get some say in presenting evidence that they are working to the required standard. My impression of a Part P audit by one of the bodies was that it was nothing at all like a UKAS audit (been through a few of those over the years..............) and that the approved person could, for example, choose a work example to be audited (in our case our whole house wiring job).

This is way too large for a house with a long heat time constant. I run our thermostat at the optional +/- 0.1 deg C hysteresis setting and if I have the flow temperature to the UFH set too high I will still get several hours of room temperature over-shoot of up to around 1 deg C, even with a thermostat that turns off 0.1 deg C above the set point. There are several ways around control, depending on how low the heating requirement and heat loss is for a particular house, the effective thermal capacity of the interior of the house (really just the first 100mm in depth, at the very most, of all internal surfaces, with the inward facing 50mm having by far the greatest effect) and the local climate. There's a big difference between being in a mild, sheltered, location and being in a severe, exposed location, big enough to radically change how a control system might best be optimised, I think,

I can only sympathise. Dealing with imbeciles is exceedingly frustrating at the best of times, let alone when already under the strain of self-building. On a practical note, then I'd just do as the idiot says and staple at 200mm centres, then spend an hour going around smearing a bit of CT1 or neutral cure silicone over the staples to seal them up. They will go rusty and gaps will open up around the holes they make, but a neutrally curing sealant, like CT1 or a neutral cure silicone will prevent that and seal the pinholes up. The cost would be negligible, and if you use a clear sealant I doubt anyone would ever spot it. Quite why they've picked on your build to flex their muscles may have more to do with their own internal commercial pressures, meaning that they cannot do this with their commercial clients for fear of losing future contracts. Perhaps you're the unwitting scapegoat for their frustrations?

The problem is simplified a fair bit by our perception of "cold". For example, on a cold, clear night, standing inside in front of one of the reasonably decent double glazed windows in our old house felt decidedly chilly. The reason was that the glazing was pretty poor at preventing long wavelength IR from escaping, and with the night sky on a clear night having a very low temperature (typically around zero deg C or perhaps a bit lower on a very clear night with not much water vapour around). Do the same in our new house, with it's triple glazing and two internal pane faces low e coated and you can barely detect that you're standing in front of a window, as the additional radiative heat loss from your skin is very much lower. The room temperature is the same in both cases, all that has changed is the way that your body has sensed it's own rate of heat loss, in this case radiative heat loss. Similarly, our bodies are pretty sensitive at detecting temperature gradients from our peripheral regions. This is one reason why we can stand in front of a roaring fire in a stone built pub, with stone flags on the floor, and still feel as if we're not that warm, despite the high heat level being radiated from the fire. Lift our feet from the stone floor and we feel a lot more comfortable, as their local heat loss rate through the stone floor has decreased (I strongly suspect this is partly why people feel more comfortable with their feet up). UFH feels subjectively more comfortable for the same reason, it reduces the rate of heat loss from our feet and so fools us into thinking we are warmer than we are. Quite a few people have reported that they feel comfortable with a lower overall room air temperature when the heat source is coming from the floor. Conversely, I remember a friends house, built in the 1970's, that had electric radiative heating in the ceiling. That always felt cold, even when the room temperature was at a silly level (and his electricity bills were ludicrous). In our specific case, much of the improved comfort has little to do with the low energy demand and low heat input, but a lot to do with pretty much every surface in the house being very close to being the same temperature, with no cold spots. We perceive this as being comfortable, probably by a similar mechanism that tells us that being evenly wrapped in clothes, or in bed, makes us feel comfortable.

The name is literal. Exactly you say, both valves(if you don't have TRVs) are the same, but to allow one to be set at a fixed position when balancing the system a shield is fitted over the top to lock the spindle in the set position, hence the name "lock shield". The shield is only there to prevent the valve that end from being accidentally moved and upsetting the balance of the system. Last time I bought any standard radiator valves (many years ago now) they came with both a handle and a lock shield in the box, so could be used for either job.

I was asked about water saving measures by BC, and encouraged to install RWH. I argued that it was pointless, as I wasn't on mains water, but there was still some convincing to do (this was with the awkward chap that insisted I needed to fit flow restrictors everywhere). For me the only significant cost of using water for things that could be done using rainwater, like garden watering, car washing and perhaps (if I could be bothered to try and work out how to do it legally) toilet flushing. The latter would be a pain, as it would require some jiggery pokery to maintain the required air gap separation between the house supply back up and the RWH main supply - not that easy with a room-in-roof design, as that rules out having a separate, deep, header tank, with two offset float valves, just to fill the cisterns. At our old house we were using an average of around 380 litres/day for everything, so about 130m³ per year. The cost at the moment is £2.1721/m³, so a total of around £282 a year. I know that most of our water goes on showers, around 240 litres per day. That leaves around 140 litres per day of possible saving. From that possible saving I think I'd need to knock off around 40 litres for stuff that needs drinking water, so we could possibly save around 100 litres per day from an RWH system. Assuming that would be the same for the new house (I don't have any way of metering the water yet) then I do know that the cost per m³ for our own water supply, allowing for a 10 year pump life and energy, filtration and disinfection cost, works out as: Disinfection energy cost ~ £22/year Disinfection UV tube cost ~ £18/year Pump energy cost ~ £0.17/m³ Pump capital cost ~ £65/year Replacement filters ~ £30/year Adding all this up and assuming the same total water consumption as the old house (which will be pretty pessimistic, as all the outlets are set to lower flow rates) gives an annual cost for 130m³ of drinking quality water of around £157.10 per year (I'm surprised that it's cheaper than a mains supply, TBH). Saving 100 litres per day, or 36.5m³/day, would only save the pump energy cost, all the other costs would stay the same, as none are volume-dependent. The saving achieved by fitting a RWH system would only be around £6.21 a year......................

Last night was interesting, as @IanR has noted, as the temperature here dropped to just below zero overnight, our heating didn't need to come on this morning (or yesterday), but the house is now sitting at 21.5 deg C, just from solar gain - it's been clear and sunny most of today so far. That's about 0.7 deg C warmer than it was this time yesterday. So, a predictive system would need to look at a reliable forecast for local temperature, sunshine and wind speed (as @Stones has discovered, accelerated convective heat loss from the outside surface of a house increases a lot with increasing wind speed). From the months I spent trying to get weather compensation to work with my home brew, microcontroller, system, which measured temperature to a bit better than 0.1 deg C, I suspect any predictive system is going to be tough to fine tune. I've just had a look through my software archive for that project, and there were over 60 iterations of the code, and it still didn't work as well as a simple thermostat mounted on the hall wall! The idea of being able to control solar gain is a good one, for those who have houses that are significantly affected by it. The other factor that makes a significant difference to our house is the number of occupants. An hour or so with two extra people in the house warms it up to a noticeable degree. Not enough to be troublesome, just enough to notice. When I had a group of six people visit the temperature increase was enough to trigger the cooling system to kick in, though.

AFAIK, they were only ever a feature of the old brass ones that had a supposedly floating washer on the end of a sliding piston, the ones that looks like this:

All our outside taps (there are three of them) are piped externally to the house in 25mm MDPE. The pipes mainly run in buried ducts, with the exception of one where it is fed via MDPE wrapped with foam insulation and then stuffed inside a length of drainpipe (it's a tight fit!) to protect the insulation. This was an after thought, as I'd not fitted a duct in where we wanted to put this tap. The short MDPE standpipe up to one of the taps isn't insulated, and that does freeze up in cold weather, but it seems that MDPE is resistant to freezing, so no harm results (the tap just stops working when it's frozen). As this is just the tap at the top of the drive, used for washing the car, the fact that it sometimes freezes doesn't matter. I know from all the MDPE feeding water troughs on the farm that the stuff will quite happily withstand freezing cycles with no harm done.

I agree 100%. Every single one of these I've taken apart over the years has had the "floating" piston rod stuck firmly in the bore of the shaft, so that it just moves up and down as the handle is turned. My personal view is that the reason that the water companies became so insistent on having proper double NRVs in recent times is that they know full well that the backflow prevention built-in to a stopcock usually doesn't work................

Worth noting that the max continuous rating for a genuine (there are a LOT of fakes about....) BS1363 plug is about 10A, anything more for long periods of time and the plug will probably overheat. The 13 A rating is an intermittent load one, not a continuous rating. It's one reason that years ago "3 bar" electric fires became harder to find. They were often rated at 1 kW per bar, on our old 240 VAC mains supply (before EU harmonisation). This meant they were drawing around 12.5 A with all three bars on, which was fine when we had the old 15 A round pin sockets, but very marginal when we switched to the BS1363 13 A sockets. The result was that there were a few issues with overheated plugs. When we harmonised our mains LV voltage standard with the EU to 230 VAC (which was just a paper exercise in changing tolerances and ratings) power ratings for appliances were then changed to be at 230 VAC. A 3 kW electric heater would now be designed to deliver 3 kW at the nominal 230 VAC, which gives a current of just over 13 A, above even the intermittent rating of a BS1363 plug. Add in the factor that we didn't actually change our grid LV supply down to 230 VAC when we harmonised, we just adjusted the tolerance to be asymmetric (+6%, -10%), and so most supplies are still, in reality, around 240 VAC, then a 3 kW heater rated at the "new" 230 VAC standard would now deliver 3.13 kW. At the maximum allowable grid voltage of 253 VAC (230 VAC +10%) a heater designed to deliver 3 kW at 230 VAC would now draw about 14.35 A, way over the limit for a 13 A plug.

The built in oven we were originally planning to order came with a 13 A lead and plug, but the design changed just before we placed the order and the replacement model that we ended up buying, needed a 16A wired supply. It was nuisance, as I'd already made provision for a 13 A outlet to connect the built in oven to. There was no problem with the cable rating on the radial, as it was 6mm² T&E. What it did mean was that I had to fit an additional MCB in a small box inside on of the adjacent cupboards in order to provide protection and local switching for the oven and it's supply cable, something that would have been done by the 13 A outlet and plug if we'd had the original oven supplied.

When you have a house where the heat loss time constant is long, over ten hours or more for a 1 deg drop in temperature in winter with no heating, all these clever controls really become superfluous. You just ensure that there's "just" enough heat put in to the house to maintain a comfortable temperature, as it becomes impractical to set back temperatures during the day, or over night, or whatever, because the cooling time is way too long. The tricky bit is maintaining comfortable differential temperatures, so that bedrooms, for example, remain slightly cooler than the living area. An upside down house might do this better than a conventional design, but I've found that just closing the bedroom doors tends to work OK, as that stops pretty much all the heat from downstairs getting to the bedrooms. This only really works for us because the bedrooms both have ensuite bathrooms, so there is, in effect, a closed cycle bit of the MVHR where the fresh air fed to the bedrooms gets pulled out through each attached bathroom, with little air being pulled in under the bedroom doors from the main house.

The ones I fitted are Computherm Q3 RF models, but they do a cheaper wired version, the Q3, plus a smarter one, the Q7. Here's the first link I could find to a seller with the Q3, you may find it cheaper by shopping around: https://www.amazon.co.uk/Computherm-Q3-Wired-Room-Thermostat/dp/B00SNHCWQC The hysteresis is set by a link on the back, either +/- 0.2 deg or +/- 0.1 deg.

As a tip from someone with three of the same taps, replace the cross head centre screw with a brass one. The brass coloured one in there is brass plated crap steel and will rust like an anchor inside 6 months. IIRC, a standard brass countersunk M4 screw fits a treat.

Our glass has a g value of 0.65, so we get a pretty high level of solar gain (too much in some areas) but a Uw of around 0.7 to 0.8 (varies a bit from one window to another). This would work well for your sun room, although you may still need shading, even where you are, to reduce the solar gain sometimes. The key is in understanding that the anti-long wavelength IR reflective coatings (the low e coating) are one way, in effect. They are sputtered on to the inner faces of the inner panes, (so the inner face of the outer pane and the inner face of the centre pane) and they control the emissivity at those surfaces, reflecting long wavelength IR inwards through the interstitial gap between the panes, but allowing long wavelength IR from outside to come in with only a slight reduction. They are a bit like one way mirrors, that allow light (in this case long wavelength IR) to flow in, with little attenuation, but reflect back in long wavelength IR that is trying to get out.

I've got around ten separate bits of this LED strip stuck underneath surfaces and not one bit has come loose yet. The longest any bit has been up is around 3 years, and I'd say if it was going to fall off it would have done so by now.

It all depends on so many variables, though, that it's hard to compare one system with another. If I used weather compensation, for example, and increased the flow temp with cold weather (I did try it) then the house room temperature shoots way, way over the set temperature, and takes hours to cool back down again. The reason is that the house only needs a small amount of heating and the time response of the in-slab UFH is pretty sluggish, maybe an hour or two before the room temperature starts to change noticeably when the UFH kicks in. Half a degree difference in floor surface temperature doubles the heat output at the typical temperature our house sits at, equivalent to around an extra 500 W or so, which is a massive increase when the house only needs around 300 to 400 W to stay warm in winter. I absolutely have to keep the UFH flow temperature below 26 deg C as a maximum, any more than that and the house temperature starts to swing up and down by over a degree or two, and just doesn't regulate well.

We were lucky in that the landscaper we used was still VAT registered at the time, so we got him to get all topsoil, turf etc and just zero rate the whole job. As it turned out, he could get both topsoil and turf at a better price than I could. He also had his own plant, so there were no complications with plant hire. HMRC didn't question any of the landscaping work receipts at all, although they were pretty thorough and threw out our first claim (returning the crate full of receipts.........) because of a misunderstanding between there being a cycle storage building shown on the plans that we hadn't built (it was only there to meet the CfSH requirement that originally applied).