Jeremy Harris

I spent an hour or so in the architectural museum at Bath last week. I got chatting to one of the volunteer staff there, who pointed out that at the time that the grand Regency buildings in Bath were being built, architects were joiners and masons who had gone on to study design, after many years of working "on the tools". The thought that went through my head was that it's a pity this no longer seems to happen, as I doubt that anyone with a solid background in hands-on construction would likely to come up with designs that their clients would be unable to afford.

Sorry, but it's not safe to run the Sunamp heating element from a 13 A FCU. That fuse is going to run damned hot, as it's always likely to be overloaded. Personally I'd never, ever, wire either a Sunamp heater supply or an immersion with a 13 A FCU. Mine is wired to a 20 A DP isolator, with an illuminated switch, and that is wired to a radial in the CU with a 20 A RCBO. The same radial has an FCU fitted with a 3 A fuse for the controller supply. The calculations that matter here are the average and worst case estimate of the supply current. 3 kW at a nominal 230 VAC gives a current of 13.04 A. The heater resistance will be approximately 17.64 ohms. If the voltage were to rise to 240 VAC, the current would rise to ~ 13.6 A, and if the supply voltage was to rise to the maximum allowable, of 253 VAC, then the current would increase to ~ 14.34 A. This may not be enough to blow the fuse, but it will make the fuse run very hot, and it is an inherently unsafe installation.

Yes, a fair bit of the cost was to do with moleing up under the lane etc.

Just the cost of laying 140m of pipe down a single track lane, that's all. I shopped around for the best price, from two or three approved contractors, but all were within a few hundred pounds of each other, or the price from Wessex Water for them to do the whole job. They wanted an additional £14k to run another pipe up the lane for about 85m to take the foul drain. I ended up fitting a treatment plant to deal with the foul drainage (cost ~£3.5K installed, I think, including the drain laid under the lane to the stream) and had a borehole drilled for a water supply (cost around £8k, plus another ~2k for the treatment stuff). One advantage of the borehole and treatment plant is that we don't pay any water or sewerage charges, which more than makes up for the small running cost of both.

The cheapest price I could get to run 140m of water pipe down the lane was nearly £24k. That was using a contractor (approved by highways and Wessex Water) to dig the trench, lay the pipe, and make good, and Wessex Water doing the connections, installing the meter etc. You have to ask Scottish Water for the map. If they are anything like Wessex Water their maps may well not be accurate, though. They sent me a copy of their map by email, but when we came to dig across the lane to put a drain in we found a pipe that they denied was theirs, until I called them out, whereupon they admitted it must be one of their unmapped communication pipes.

You have to go though much the same process as for electricity, which means going to SW. You may find that the pipe across the field isn't a water main, but a communication pipe. This may change things a bit, as although you have a right to be connected to a water main, no such right exists for a connection to a communication pipe. I ran into this, as the nearest water main to us is 140m away, up a single track lane. There's a communication pipe that runs down the single track lane, right in front of our plot (literally 4m away), but we were prohibited from connecting to that, and Wessex Water wanted us to pay for a new pipe to run down the lane in parallel with the existing one.

There's a thread here about Isotex that may be helpful:

I used Autocad, as I have been using it for decades and had a copy. I'd not recommend it for simple drawings, though, as it's expensive and the learning curve is very steep. I believe that Sketch Up is fairly easy to use, and has been used by some. It's probably overkill though, as all that's normally needed is a 2D drawing package. There used to be a free version of TurboCad available, and having used that a bit many years ago it might be an option. Not sure if Draftsight is still available free, but that's another package that I think some here have used in the past.

Welcome. TBH, it would be hard to do an EICR on any house that's more than a few years old and not have one or two C3s on it. All it means is "Improvement is recommended" and can often be down to the judgement of the person doing the EICR. Last one I did I noted a C3 for a cooker switch that was slightly too close to a hob, another C3 for a (metal) consumer unit that didn't have any RCD protection (wasn't required for the date of the installation) and another C3 because the meter tails were only 16mm², again fine for the date of the installation, but they need to be 25mm² to comply with current regs. If you list the C3s here one of us can tell you whether there's anything you need to do about them. The fact that they are C3, and not C2, or even C1, means they aren't very serious issues. One problem is that the old C4 classification has now been removed, as that was very useful for older installations, as it just indicated that the item was compliant with the regulations in force at the date of installation.

Generators are viable, but they do need attention, they cost a fair bit to run and maintain, and they can be noisy. There are some very reliable units around, like the big, heavy, single cylinder Lister ones. They can be silenced fairly well. The friend who runs one has it in a block built shed, with a water jacket around the exhaust and a 50 gallon drum, cast into concrete underground, as the silencer, with a flue pipe leading up from that through the roof of the shed. You can hear it running when outside, but not from inside his house. The big advantage of these heavy Lister engines is that they last decades, and just need a bit of oil, decoking every now and again and their fuel system looked after. There are several Indian companies still making these Listers, so spares are easy to obtain. Not something to be entered into lightly, though, as you need to be prepared to look after the thing, service it, etc, as you will be relying on it for power through much of the winter. There's a chap up the top of Raasay that has been living off grid for many years now, and who has a good blog on his off-grid adventures and life in general, Paul Camelli. His blog is here: https://lifeattheendoftheroad.wordpress.com/ Worth reading and digging out his stuff on generators, wind power, solar, batteries, hydro power etc, as he's learned a lot through experience and recorded most of it over the years. He's off-grid because there's no possibility of getting power up to his remote corner of the island, but has managed to build a new home recently that works well, with all mod cons, despite the lack of mains power.

Solar panels only work well when you don't need heating, and don't need much lighting. Generation from them pretty much falls off a cliff in October, with very little being generated over the winter months, and doesn't pick up again until the Spring. As most people use more energy in the winter than they do in summer, this leaves a gap of several months of the year where there will be an energy shortfall, which means using something else if off-grid, like a generator, wind power or hydro power.

I don't think there is a simple rule that can be applied for plot pricing, really. It's a free market, and a plot will be worth whatever someone is prepared to pay for it. It's not that unusual for self-builders to pay over the odds for a plot, or buy an existing house, demolish it, and build what they want. I suspect that some end up paying more than the finished house is worth, as they are prepared to pay extra to get the house they really want. Our build came in a little bit under the market value of the completed house, but that's only because the value rose whilst we were building it. If prices here had remained stable, then we'd have paid slightly more overall than the house would have been worth. So much depends on factors like the local prices in the area, the nature of the plot (we bought our plot relatively cheaply as it was fairly difficult to build on, for example) and local house prices. You can buy a very nice plot in some areas for ~£50k, yet the same plot somewhere else could be £300k or more. As for methods of construction, there are loads to choose from. Many of us here have used well-insulated prefabricated timber frame construction, many have used other forms of timber frame construction, many have used ICF systems and many have used conventional block and brick. A lot may come down to what would work well on the plot you have, so I'd leave the decision on which construction method to use until you've found a plot. We looked at several plots, and some would have pretty much dictated the use of some construction methods over others.

Not normally a problem as far as planning is concerned, as it's not normally a planning issue, other than if there is concern over things like the appearance of solar panels. The erection of a wind turbine would need planning consent, and without one it wouldn't be that easy to go off-grid without a generator. A friend who lives near where we used to live went off-grid a few years ago, using a combination of solar panels, a fairly large battery bank and a big single cylinder Lister generator that he converted to run on waste vegetable oil. The Lister also provide heat for some radiators when it's running. He runs his Landrover on the same waste vegetable oil, and has an arrangement with a few local restaurants and chip shops to collect their waste oil and process it. Can always tell when his Landrover drives past, as the exhaust smells like a chip shop. It does normally mean making a fair few lifestyle changes to live off-grid, and the capital cost of the kit needed may well be as high as that of getting a mains electricity supply, so it's really something for either situations where there's no possibility of getting power, or if you have a strong desire to just live off-grid.

The thermal conductivity of concrete is reasonably high, around 1 W/m.K, so heat will fairly quickly even out across the floor. If it didn't, then there would be a risk of the hot spots from resistance wire underfloor heating being dangerously hot, from their own description. I fitted resistance wire underfloor heating in the bathroom at our old house, directly under the floor tiles. The wires were spaced ~100mm apart and you couldn't tell, when walking on the floor in bare feet, where they were, as the tiles were all very evenly heated. This pretty much proves that their hypothesis that small diameter heating wires (ours were ~3mm in diameter, including the silicone insulation) will get very hot is simply wrong. It's also worth looking at the running cost for various UFH options. Using electric UFH at the surface of the floor will not provide much in the way of heat storage, so the heating will almost certainly need to be on during the peak rate period. The electricity cost is likely to be around 12p to 15p/kWh, so if the house needs, say, 1 kW to maintain a comfortable temperature, and needs to be heated for 15 hours per day, then the cost will be around £1.80 to £2.25 per day. The same amount of heat supplied by an electrically driven ASHP will cost around 1/3rd of this, so about £0.60 to £0.75 per day. The same amount of heat provided by an ASHP that is running UFH in an insulated concrete slab, so can be charged mostly overnight at the off-peak rate, will cost even less, perhaps less that £0.45 per day. As a general rule of thumb, an ASHP will run at a COP of better than 3 when running UFH. Our's has been running at a COP of over 3.5 pretty much since installed. This will always make the running cost at least 1/3rd of the cost of direct electric heating, most probably even less most of the time. Being able to heat up a floor slab overnight on cheap rate electricity gives another significant running cost saving.

Definitely. The OS chap came around here around a year or so before I registered the address. It was still "The Plot" when he called, as we hadn't decided on a name, let alone paid the hefty fee to the council.

We had a similar experience, very nice chap turned up in his OS liveried Toyota Yaris Hybrid, went around with his pole and tablet and sure enough, our house appeared on the online maps within a week or two. He told me that the OS get automatic updates on new planning consents from the LAs, and add them to their list.

Probably cost more in postage than it would to buy 10m down at Screwies...

It's the approximation used by UFH installers/system specifiers. That's where I got it from, anyway. Looking at it, it seems to be based on a combination of the radiated heat output (from the Stefan Boltzman equation), with a frig factor added to allow for the conducted/convected contribution. The Stefan Boltzman equation is: P = eσA(T4-TC4) Where: P = power (W) e = emissivity σ = Stefan's Constant = 5.6703 E-8 W/m².K4 A = area (m²) T = temperature of the radiating surface (K) TC = temperature of the surroundings (K)

I don't know, but flexible plastic 20mm electrical conduit has an ID of 16mm and is pretty cheap: https://www.screwfix.com/p/tower-corrugated-conduit-black-20mm-x-10m/50443 £5.29 for 10m is pretty reasonable, even if you end up throwing some away.

Is it an adjustable one? If so, you could try reducing the opening pressure a bit, as that may allow it to bypass and increase the flow rate. I found I needed to play around with the setting on our bypass valve a fair bit. Set it too low and it just bypasses all the time, increasing the return temperature. Setting it too high meant it didn't open when the pressure rose, so the ASHP flagged a flow rate error.

OK, lets take a look at some real numbers here and see whether any of this stacks up. The formula normally used for approximating the heat output from UFH is pretty well proven from experience, and is: Heat output per m²= 8.92 * ΔT^1.1 , where ΔT is the difference in temperature between the room and the floor surface, in °C (it's really K, but °C is the same for this purpose) Let's assume that the room temperature is 21°C, just because that's a fairly typical figure. if the electrical input is 1 kW, there are no losses down through the floor and the floor area is 5m², then that 200 W/m², working from the approximation formula above, and assuming a 21°C room temperature, will give a floor surface temperature for the 5m² of heated floor area of ~34.85°C (which would probably be uncomfortable to walk on). If the heated floor area is increased to 18.4m², then for the same 1 kW of heat input the floor surface temperature drops to ~25.24°C, a far more reasonable temperature. Note that the heat output to the room is exactly the same for both these cases. All Step Warmfloor are doing is trying to pull the wool over customer's eyes by playing around with the heated floor area. They aren't lying, they are just being a bit creative with the way they are presenting thing, in the hope that they can fool people.

Welcome @S7evo. It's not uncommon to get low flow rate errors with an ASHP installation. We had the same initially, due to flow restrictions caused by a valve being slow to open, and I think others have reported much the same with other makes of heat pump (ours is a Glowworm badged Carrier). I think your pipe layout looks OK, and suspect that the issue may be with either a restriction somewhere (like a slow to operate valve, perhaps) or with there not being enough pumping power. I had to play with the speed on the pump in our unit to get it to work reliably without throwing a flow error, for example. I fitted a bypass valve to finally fix our low flow errors, but a better solution might have been to fit a low loss header instead. Next time I drain our system down I'll probably remove the bypass valve and just fit a low loss header, just because that will work with no moving parts or adjustment.

20mm flexible electrical conduit has a bore of about 16mm, and is pretty much ideal for protecting 15mm pipe where it goes through walls. Likewise, 32mm flexible electrical conduit is sort of OK for 22mm pipe (it has a bore of about 25mm, so the pipe's a bit of a sloppy fit).

It seems that this information is disingenuous at best. If a room takes a floor heat output of, say, 100 W/m² (which is very high indeed - such a floor would be verging on being uncomfortably warm to walk on) then it needs a heat output of 100 W/m². If the floor heat output was reduced to 50W/m², the heat to the room would be halved. Of course, halving the heat to the room would be cheaper to run, but then the room would be a lot colder in cool weather. The starting point is to work out the heating requirement for the house. This should be on the design EPC for your build. Work out the actual heated floor area that's practical (i.e. floor area not covered by fitted furniture etc) and then divide the power needed in the coldest weather by the heated floor area and you will end up with the floor heat output needed per m². For example, our house has a floor area of 130m², but a heated floor area of 75m². In the coldest weather we're likely to get here (-10°C outside) the house needs about 1.6 kW of heating. 1600 W / 75m² = 21.33 W/m² This heat output, with a room temperature of 21°C, needs a floor surface temperature of 23.2°C This is the worst case heating requirement, for most of the winter it will be a lot lower than this.

An MVHR in a "cold" loft space normally has to be insulated, as do all the ducts in that space. It also means that the ducts needs to be well sealed to the VCL where they come down into the heated envelope. Given that good access is needed every few months for routine maintenance, filter changes, cleaning out all the dust and flies etc on the intake side, plus occasional cleaning of the heat exchanger, I'm not sure that loft installation is ideal. You also need to ensure that the condensate drain cannot freeze, so that needs to be insulated as well. I mounted our MVHR unit inside the heated envelope, at the rear of our services area. I can access this via a door from the spare bedroom, but space is tight in there and it's far from ideal in terms of cleaning and changing the filters. I'd not particularly want to have to crawl around in a loft doing this every few months.