Jeremy Harris

As above, we went for "full plans". MBC will send you drawings, but more importantly, they sign off the whole structure, foundations, frame, the lot, so there's no requirement for any Part A stuff for Building Control, our LABC just accepted the MBC structural sign off as evidence of compliance. That's mainly what made going for the "full plans" route attractive, as it meant I hardly needed to do any more than would have been needed for a Building Notice application.

I went down the "full plans" route, and looking back I think it was the right way to go for our build. There isn't much more that BC need up-front, and you have the advantage that the building inspector isn't going to ask you to change something part-way through, because it was all approved in principle in advance.

The bits of paper I sent them are here: http://www.mayfly.eu/housebuild/part-fifteen-the-site-is-finally-ready/ I missed a couple of details, about Part P sign off and linked fire/smoke alarms amongst others, so had to send them an addendum pointing out that I'd be using a competent electrician and that I'd be fitting linked alarms, etc; all those docs can be downloaded from that link. When it came to the final Completion Inspection, then I ended up providing a load of stuff that the inspector didn't want to look at! The details of that are here: http://www.mayfly.eu/housebuild/part-forty-three-completion-and-getting-the-vat-back/

A dire combination indeed. It's also my belief that his skin is thicker than that of a rhinoceros - it may be why mine is a bit thin at times, he got the lion's share from our parents.................

Try having a brother, with whom you've never really got on, as a local council HS&E officer......................... This is the same brother, who, when doing a new build wiring job around 30 years ago, went around testing to see whether circuits were live by poking his finger on the line connection. By some fluke he has a very high body resistance, or perhaps just a high skin resistance, which means he can feel 240V but doesn't get a shock from it.

Location is the killer, as you literally have to check every single supplier against your specific location in order to make a fair comparison; you cannot trust the price comparison sites at all, I found. In my case I'd have ended up paying about 20% more if I'd followed their advice. You can get LED work lights, but the ones I looked at were very expensive (admittedly I was in a hurry to buy a couple, as I had two plasterers working in tee shirts and short in a house that was around 30 deg C inside!). I've never seen a conversion kit, but you can buy cheap LED external floodlights quite cheaply, and SOME of them are pretty good. It would be pretty easy to fit one to an old halogen work light frame. They are a real mixed bag, though, with no easy way to tell how bright they are from the supposed rated power. I bought some 240V 20W ones that were very good, and around a tenner each, IIRC, then when I went back and bought two more the same they were rubbish, about half the light output. As usual, Big Clive has some stuff on them on his "let's tear apart Chinese junk and see how rubbish it is" YouTube channel : https://www.youtube.com/user/bigclivedotcom Be aware that you can waste hours there, though, as he does some serious destructive testing of stuff there, and reveals just how bloody dangerous a fair bit of stuff being sold on a well-known auction site can be.

Please do! I was involved in some work years ago that looked at their effectiveness in protecting structures (specifically military antenna masts), and I'm sure I've still got a lot of stuff tucked away on both the probability of a strike and the effectiveness (or often ineffectiveness) of lightning protection systems. I do know for sure that the old adage, "lightning never strikes twice in the same place" is complete cobblers. There's an antenna farm I know well that has at least three or four strikes every year, sometimes more. (also only joking - I'm certain it would stir up controversy! )

It varies with location though, I found. For example, the zero standing charge Green Energy tariff for us is £0.1662/kWh, which is 18% higher than our current tariff, and that 18% difference was just enough to offset the standing charge we pay. They were the second cheapest tariff for us, though, when I checked.

It surprised me, too, but then there were some big loads on for long periods. I reckon we had a 400W halogen on in the garage running every working day for around 2 months, and I ran the borehole pump (around 700W) for about two weeks, 24/7, when I was cleaning it out (or trying to). That means I used around 235 kWh just trying to initially clear the borehole, plus around 384 kWh just for the garage halogen, and there was an outside one that was used on dull days, too. I ended up investing in a fluorescent work light (I already had the halogens) when we had the house airtight and were doing the plastering, as it was impossible to use the halogens indoors, they just made the house far too hot, even in January. Most of the usage in our first six months probably came from just the borehole pump and the garage work light, I'm sure.

I managed to get a tariff from SSE where the standing charge is £0.148/day and the unit charge is £0.1404/kWh, which for us hits the "sweet spot". Ebico were around 20% more expensive, mainly because of the high standing charge. I was also surprised at how much electricity we used in the first 6 months, when it was just a site, with the house frame going up and first fix going on. I think a fair bit of that was from power tools, portable lights etc. It was winter, and we quite often had one or two 400W halogen lights on outside, one on almost all the time in the garage, that was being used as a site workshop, and one outside the house when things like the cladding were going on.

Quite a lot! We're the opposite to you, in an extremely sheltered location, and our heating requirement is less than predicted, which I believe is mainly down to not being in an exposed area. If you're somewhere exposed, then I'd say air leakage and ventilation heat loss probably dominates over all other heat losses, even with just building regs minimum allowable insulation levels. It also depends on the size of the house too. As houses get bigger, ventilation heat loss becomes a greater proportion of the total heat loss. Add the two, a big house in an exposed area, and I think achieving a good airtightness result would really pay a big dividend in terms of savings in heating.

I recently went through this exercise to see whether we could save anything, given our low electricity usage, as the standing charge was the major part of each bill. I have to say that it's very, very frustrating, as the price comparison sites don't have all the tariffs on, and even when they do I found the tariff information was often wrong. All told I spent a very frustrating few hours putting together a spreadsheet, listing all the suppliers that seemed reasonable and then getting tariff data directly from their own website (not easy, as some suppliers do their best to hide the standing charge!). Anyway, I learned three things: 1. - price comparison websites are generally pretty useless if your electricity usage is low, and they don't list all the available tariffs anyway, only those the suppliers pay them to. 2. - The market is extremely volatile, with tariff schemes changing very quickly, I suspect this is to deliberately cause confusion with consumers. 3. - If a supplier advertises a tariff it doesn't mean that will actually offer it. I selected a supplier with a low standing charge and an acceptable unit charge, called them and they denied the tariff existed. I had to point them to their own web page and get the chap on the phone to go on the internet, rather than their internal system, to prove this. In the end we agreed a tariff with a supplier this way. It's not listed on their website, has no fixed term, but they agreed on a breakdown of standing charge and unit charge that was the best for us, and that's what we've gone with. I know I'll probably have to do this again within a year or so, because they are bound to change the tariff, but I have at least got a bit of experience of dealing with them now. BTW, for our original site supply there was only one no-standing charge supplier, Ebico, and the unit charge was so high that we wouldn't have saved anything in the first year, even though our usage wasn't great. Worth checking, as charges vary a fair bit from region to region.

That's a very good price! When I was hunting around, part of the problem was getting suppliers to quote a price, as there were very few giving online retail prices, and those that were were silly prices. IIRC, we were quoted around £4k, supply only, for the 4 kW Kingspan unit, and that was the smallest I could find where I could also get a price. There almost seemed to be a closed shop surrounding the prices of these things, with some suppliers putting a ridiculous markup on them, way more than the markup on something like a boiler.

Thanks, Joe, TBH, I dug around for a definitive paper (and by that I mean trustworthy, as in written by someone with the right credentials, relevant competence and ideally manufacturer support as well) when I decided to switch from copper to plastic in our build. Be careful to look at the exceptions to the general rule that bonding isn't required with plastic pipe, as there are areas where you do still need to bond metal parts of the system, depending on whether there is electrical equipment connected to sections of metal pipe, and the class of those items of equipment. It's all covered in that paper fairly clearly, I found, with the general rule that short lengths of copper pipe, such as those used to neatly terminate pipework in a cabinet, don't generally need bonding unless they are over 0.5m in length, or unless they are connected to electrical equipment. Because we have, like a few mainly plastic pipe systems, some areas where there is copper pipe connected to plastic pipe in several locations, there was still a mandatory requirement to bond some things, like the copper pipes connected to the Sunamp PV, those connected to the Stiebel Eltron water heater and those connected to the boiling water tap. There's no requirement to earth bond a plastic main connected to plastic piping, and so all our cold water stuff from the incoming supply and all the filtration etc, didn't need bonding anywhere, as the only electrical connection was an SELV timer, powered by a double insulated power supply, and even that was in a plastic housing, with composite (non-conductive) filtration tanks.

I couldn't agree more about the SAP score, as long as it passes and you get the home you want, who cares? Any summer overheating can be resolved by something like a cheap air-to-air heat pump, like a split AC unit, fitted somewhere central. These things are remarkably cheap for what is, in essence, something that's as complex inside as any ASHP, with the sole exception of the water circuit, with it's different heat exchanger.

A smaller ASHP would also probably get around the issue. Ours is only a 7 kW max model because Glowworm, along with a few other boiler companies that were importing badge-engineered ASHPs, pulled out of the market for a time, because, I think, there were a fair few performance issues due to poor installation design. That meant I was able to by an "old stock" unit from a former Glowworm installer for probably less than cost price, £1700, including delivery and the programming unit. In reality, a 4 kW unit would be more than adequate, but the cheapest inverter drive 4 kW unit was around double the price I paid, so I accepted having something that's a bit over-size. In the event it's probably a good thing, as it allows the buffer tank to re-heat quickly when it's being used to pre-heat the incoming water for the DHW supply, and provide a 6 to 7 kWh heat input most of the time that DHW is being drawn off, which significantly helps the pre-heat system. When we're in fall-back DHW mode, with just the preheat and instant water heater, it means that we have a total of around 20 kW available to "instantly" heat the DHW; 7 kW from the ASHP, 3 Kw from the Sunamp PV (it turns it's heater on when there's a DHW demand) and 9.6 kW from the Stiebel Eltron DHC-E. I'm happy to keep the buffer tank, as it does a very good job of pre-heating the DHW, and provides a thermo-syphon to the PHE upstairs, so the PHE is always warm, even before the flow switch kicks in on demand to turn the PHE primary circulator pump on. I'll be interested to see how your direct inline heater works, as ages ago I concluded that, if you weren't bothered about the SAP score and were happy to use E7, then that was probably the best way to go.

In general no requirement for earth bonding with an all plastic pipe installation, but there are some areas where if you have metal pipe sections and electrical equipment (like a water heater) you still require main bonding. There's a useful paper that Hepworth sent out, and that is now buried on their website about this. It wasn't written by them, but by an IEE chap, but it's pretty much chapter and verse on what should and should not be done. It also gives the reasoning behind the decisions, which is helpful. Plastic pipe earth bonding requirements

I've been called worse, without any reason, I can assure you!

As far as I can tell, the ASHP never goes into short-cycle protection mode with the 70 litre buffer, so I think that's probably a good indication that it's big enough. It still leaves the question open as to whether it's too big, but as a 70 litre buffer is pretty small and cheap, it probably isn't worth the effort of finding out. I don't think the buffer has any significant impact on the evenness of the slab temperature, mainly because it always runs at a higher temperature than the slab flow temperature, so is really just a parallel heat source as far as the slab is concerned. Either the buffer or the ASHP can provide massively more heat at any instant than the slab needs.

Good idea, Terry, I'll try and get a concise and readily understood list together later. Right now I'm busy writing a blog article on domestic electrical installation earthing schemes.

All I can say is that I had cause to check three Y strainer filters in our installation, when I re-jigged all the plumbing around to accommodate the Sunamp PV, and I removed two pressure reducing valves at the same time, as I lowered the overall system pressure to between 3 and 4 bar (one advantage of having a borehole system). All three gauze filters had crud in them, almost all of it installation-related. I was a bit surprised, as I was careful to keep everything clean, but tiny bits of PTFE tape and a few small bits of copper were caught in the gauze filters. I now only have two Y strainers, and I did check the incoming "mains" one a few months ago, perhaps a year after I'd last had it apart. It was as clean as a whistle, so I think the major problem is installation-related crud, rather than anything coming in later. Having said that, we are on a borehole supply, so no one but me ever messes with it. A mains supply may well have the same sort of issue with stuff that gets washed in from water company maintenance elsewhere.

If I've understood Joe right, I think he's looking at something like a hot water tank that's mainly kept at an efficient ASHP flow temp (so typically no more that 40 deg C to prevent defrosting lowering the COP a lot) and then using a modulating instant water heater to provide the boost up to a good hot water temperature at the taps. Such a tank would need an anti-legionella boost every couple of weeks, to around 60 deg C or so. I can vouch for this working well, as it's our standby DHW system in the event the Sunamp PV doesn't get enough charge, or runs out of charge due to heavy hot water demand. The ASHP heats our buffer to around 35 to 40 deg C, and this then preheats the incoming cold main to 30 to 35 deg C. The modulating instant water heater then boosts this up to the 42 deg minimum acceptable temperature for us (I tested this, anything under 42 deg C and the shower's too cool, anything over 42 deg C just wastes energy by heating the water to a higher than needed temperature). One thing to watch is that all these modulating instant water heaters work in the same way; they control the power to the element by pulsing the heating element on and off, with a variable duty cycle at the mains frequency zero crossing point so they don't cause a lot of EMI. They do this to avoid the electrical noise that would be caused by phase control, and they use a low frequency to get a wide range of control and stay within the regs on flicker frequency and amplitude. However, if you have dimmable LED lighting, then you almost certainly will see some flicker when the heater is modulating. We only had one dimmable LED power supply in our house, in the WC, and it's how I know that the heater makes the LEDs flicker! I replaced the LED power supply with a wide voltage range, non-dimmable one and the problem went away. It's hardly surprising that there are small voltage fluctuations with these modulating heaters, ours is switching around 10 kW at a rate of a few Hz, and that's bound to cause a small pulsed voltage drop on the whole installation. The drop is within the limits allowed, but enough that something as sensitive as an LED, with its very fast response time, to be affected by, if it's not eliminated by the power supply.

Although plastic pipe is very good in all respects, the de-skilling of the trade of plumbing does concern me (as does the de-skilling in a number of other trades). We run the risk of proper plumbers becoming like the master thatchers that work a fair bit in our area, an old and rare set of skills that only exists to service older buildings. The knock on effect we're already seeing. We bought a brand new house once (never again!) and that had been built by a developer who'd used workers (I can't possibly call them tradesmen) who were pretty dire. It had plastic plumbing that was a complete mess, with no pipe clips anywhere that I could see - they had just cable tied pipes together. The lack of skill was evidence everywhere in the build, from the concrete floors not being anywhere near level to the step flashing around the chimney having been fitted with the overlaps the wrong way around (and, we found when getting the leaks fixed, no soakers fitted either). A wander around any big development will show loads of poor workmanship, almost certainly because the big developers aren't prepared to pay the going rate for decent tradespeople, and I have a feeling we're probably building a generation of houses in big developments that will be lucky if they last 30 years, largely because of the way they are thrown together.

Overall, that's a good approximation to the way our (very similar) slab behaves (and thanks for the copy of the model - I foresee a weekend ahead of being distracted into playing with it!). One thing I mentioned before, that in our house seems to have a noticeable impact on the behaviour, is caused by the inevitable bunching of the UFH pipes where they approach the manifold. In our case there is only one door way, around 1.5m from the manifold, and almost opposite it, so as a consequence the pipe density there is high, and we have an area in the utility room and a part of the dining area of the kitchen where the slab heats up more quickly, particularly when the Δt is relatively high (for us, flow temperatures above about 25°C , up to the worst case I've found so far at 28°C ). Because of the layout of our house, and the fact that the kitchen/dining room is the room with probably the greatest incidental heat gain (including solar gain) we end up with that room getting noticeably warmer and the heat then spread around the house by air convection much as through the UFH. I've been around with the IR thermometer and the thermal imaging camera, and the hotspot in the floor is very clear when the flow temperature is up around 28°C, but barely visible when the flow temperature is around 24°C . Having said that, I did disconnect the buffer tank (easy for me - I just pulled out the valve relay) and it's clear that it's not really doing anything in terms of keeping the house temperature stable, the slab is doing that, together with the relatively high heat capacity of the plasterboard lining and the underlying cellulose insulation.. The only effect of having no buffer was to make the ASHP keep shutting down early, to the point where instead of just modulating down to its lowest level (which is around 1.2 kW output) and continuing to run, it went into anti-short cycle mode and shut itself down for 20 minutes, then restarted. The result was a much longer period of ASHP operation (around 2 1/2 hours) rather than the hour or so it normally runs for every two or three days. The cause was almost certainly the low Δt between flow and return without the buffer.

I've been digging around, but can't find it on this PC, but I do know that we looked at fitting a mist system, and the only reason we didn't was the price. I'm sure that somewhere on Ebuild there is a discussion on mist fire suppression systems, and I'm also sure there was more than one option. I'll try and see if I can find the thread in the archive, as it may help.