Jeremy Harris

Is there no way to just mitigate the clay problem by increasing the depth of hardcore under the slab? According to the Kore report, this works OK and is something that I'm pretty sure that Hilliard (Tanner Structural Designs, the people MBC use for the passive slab design) have done before. Our MBC slab is on clay, FWIW, with no problems. Kore specifically state in their info that the design is "suitable for all ground conditions". This is an excerpt from the Kore technical report produced by Hilliard for the passive slab system:

It doesn't matter if that heat doesn't get out, though, does it?

I've just done some testing on these bulbs, to see how they work over such a wide voltage range. The bulb starts to illuminate at 2.8 V, and increases in brightness until it reaches a peak at 4 V, where it's drawing around 116 mA. As the voltage is increased, the brightness dips slightly at 4.05V, then stays exactly the same (as far as I can see) from there up to 12 V, with the supply current reducing very roughly linearly with increasing voltage. At 12 V the current drawn is 36 mA. So it looks like the total power is a maximum of around 464 mW at 4V, reducing to a pretty constant 0.430 mW or so over the rest of the voltage range. Although these are advertised as "0.5W" bulbs, in typical Chinese fashion the actual rating is significantly over-stated. Still, the one I have fitted to an old 6V Duracell torch seems to work OK, and draws around 57 mA, so with 4 off C size industrial Duracell alkaline batteries the torch should work for around 80 hours on a set of batteries, which seems pretty good to me.

It doesn't work well on mine. Sometimes it seems to wake the screen up when you just walk past the thing, other times I need to stand and press one of the buttons to get the screen to wake up, as no amount of waving your hand in front of it will wake it up. I've not spent a lot of time trying to work out just why it is so hit and miss, but may have another read through the manual and see if the sensitivity can be adjusted (I think it can, but it' not something I've looked at or got around to doing yet).

The Ebay link above is very similar to the one I bought. I opted for an all-stainless steel version, just because I wasn't 100% sure of the quality of the chrome on something bought sight unseen, but it seems that Ebay is as good a place as any to get one. They don't seem to be around much in the bigger suppliers yet. Make sure you get one with a thermostatic mixer, that connects to the hot and cold. I fitted the thermostatic mixer under the basin, inside the built in cabinet and then plumbed the feed pipe to the shower fitting inside the adjacent WC cabinet, which made for a neat installation.

No, as in practice you will turn the ventilation rate down to suit the number of occupants, so it makes no difference how big the house volume is. Ignore the building regs minimum for MVHR, as pretty much everyone finds that setting the MVHR to that figure over-ventilates the house (we run at around 2/3rds the building regs minimum and I think we're still over-ventilating a bit - we can probably reduce the ventilation rate by around 15% and still have better ventilation than a house without MVHR.

I'm amazed! That Floureon battery pack for my old 14.4 V Makita that I ordered on impulse yesterday afternoon, arrived lunchtime today, less than 24 hours after ordering it. That has to be some sort of Ebay record. Sadly I won't be able to give it a good test until after Christmas.

Yes, but they are a LOT easier to use. Mine has a thermostatic mixer valve that sets the temperature, so to use it you just point it down the pan, push the trigger and wait a few seconds for it to get to temperature (very quick if you run the hot tap on the basin first). The jet of water is more powerful than a bidet and you can direct it exactly where it's needed. They really are fantastic bits of kit, and once you've got used to one you look back on the horrid practice of smearing one's backside with excrement using toilet paper with horror. Quite why they aren't a standard toilet appliance here I don't know. It was a Muslim friend who first showed me one, a few years ago, and I wanted to fit one to our old house, when I re-did the bathroom, but SWMBO wasn't having it. This time I just fitted one when I built the bathroom and if she doesn't like it, then tough.............

You might want to look at fitting a hand held shower to the loo. I fitted one a while ago and it's brilliant, much, much nicer than toilet paper. They aren't really mainstream here yet, and are mainly marketed to the Muslim population so they can properly perform Wuḍū or Ghusl before prayer, and may be referred to as a shattaf, and look like this: https://www.ebay.co.uk/itm/MX-Thermostatic-Douche-Bidet-Kit-Chrome-Round-Shattaf-Muslim-shower/202032701766?hash=item2f0a166146:g:dtMAAOSwmZFZne~D

We also have triple glazed French windows, but they are slightly poorer thermally than the main glazing, as they have to have a 6mm toughened inner and outer pane, so they are 6 -16 - 4 - 16 - 6, rather than the 4 - 20 - 4 - 20 - 4 that we have for the windows. The U value is slightly poorer, but subjectively they feel as warm when standing next to them on a cold day as the other windows.

The regs don't relate to the ground floor, they relate to the entrance floor, so if the ground floor is not where the front door is located then the regs in Part M don't apply.

Interestingly, these bulbs appear to have a buck/boost converter. The current drawn increases as the voltage reduces from 18 V, as you'd expect for a buck converter, then the current stabilises between about 5 V down to about 4 V, then it jumps up when the supply voltage drops below 4V and starts increasing again. Given that the Vf of the LED will be around 3 to 3.3V, and these bulbs work right down to about 2.5 V, below the Vf of the LED, I think there may well be a boost element in there as well. If I had a spare one I'd be tempted to try and take it apart to see what's in there, just out of curiosity.

Indeed it is, I'm amazed that they managed to fit one in the base of one of these small bulbs, but they have, as when tested the current reduces as the voltage increases, exactly as expected for such a device.

The snag is that the efficiency of such a set up would be dreadful at 12 V and the resistor will get very hot. The bulbs I listed have a high efficiency wide voltage range, constant current, DC-DC converter in the base, so barely run warm. A typical white LED run hard will have a forward voltage of around 3 to 3.3 V, and for 0.5 W the forward current will be around 0.15 A to 0.17 A (from I = P/V). The series resistor will need to drop between 8.7V and 9 V, so the power dissipated in the resistor would be around 1.3 to 1.5 W (from P = V*I), three times more power than the LED is using, dropping the efficiency to around 25% before taking into account the LED efficiency. Also, a resistor running at around this power will be far too large to fit in the bulb base and if it could be squeezed in it would get very hot. Better to get the bulbs with the relatively high efficiency DC DC converter in the base, I think. The bulbs I linked to barely get warm when running, certainly they are a lot cooler than the 0.5 W incandescent bulb they replaced.

It's a great shame that the major benefit of triple isn't emphasised in that article, and is just ignored. Triple glazing isn't primarily about the U value, in fact I think the U value is probably one of the least important factors in most of the UK. Double glazing can achieve good U values, but cannot get close to the comfort improvement that triple glazing gives, because it only allows a single pane of low emissivity coated glass to be used (because the coating is fragile and has to be on the inner face of the outer pane). Triple glazing allows two low emissivity coated panes to be used, the inner face of the outer pane and the inner face of the centre pane. That just about doubles the long wavelength IR reflected back into the room, and as far as comfort goes, our bodies are very good at detecting high radiated heat loss, so standing in front of glazing that reflects most of our radiated body heat back feels, subjectively, a great deal warmer. We still have our old house, with decent double glazing and a single low emissivity coated pane. Although the U value of that glazing isn't bad, it feels, subjectively, pretty cold when you stand or sit in front of a window, and it encourages you to pull the curtains early, even when the room temperature is OK. In the new house you cannot notice any difference between standing in front of a window on a very cold day and standing in front of a wall, as the windows reflect back the majority of your body heat, more than the walls do I think. I think more needs to be made of this point, as it often seems to be missed in our obsession with U values.

It's an interesting point that the MVHR efficiency figures assume constant RH, I believe, whereas in reality there is a great deal of heat recovery from the condensate on cold days, I'm sure, especially given the high heat capacity of water. I might have a dig around and see what sort of contribution this makes - my guess is that it's pretty significant whenever the MVHR is handling warm, moist air from a shower or bath .

We have a Victorian-style hoist up, 5 bar airer/drier in the utility room, over the top of the work surface. That room isn't well heated, it's around 21 deg C usually, just from the UFH, and it's on the North side of the house, pretty much below ground level, with the only light coming from the glazing in the top of the East-facing back door. There is an MVHR extract terminal immediately above the hoisted airer location. Anything put on that airer and hoisted up dries very quickly, even sopping wet towels. I think the key is that the MVHR extract is constantly drawing the moist air away, so the RH local to the stuff on the airer is a fair bit lower than it would be otherwise, and this then increases the evaporation rate.

I've just fitted a cheap 6V LED bulb to a very old torch, with surprisingly good results. The beam has a bright spot in the middle, but there is a decent spread of lower intensity light that makes the torch better than it was with the incandescent bulb. The bulbs I used were these: https://www.ebay.co.uk/itm/P13-5S-LED-Focus-DC-Flashlight-Replacement-Bulb-Torch-Work-Light-DC3-12V-4-5V-6V/322336571927?hash=item4b0cc1c217:m:mVeG4zafc5mofuWLfrboPMw They are OK on 12 V, too, although the torch I fitted one to was a 6 V one.

At a large scale, rotary vane heat exchangers are very good indeed, we had them fitted in the main air handling system of the large office/lab complex that was built as a part of the last programme I managed before retiring. In that case the vane drum was around 2m in diameter and maybe a metre thick, with the vanes rotating slowly between the two sides, so they were warmed by the exhaust air then rotated so that the warm fins heated the incoming fresh air. I can't remember the heat recovery efficiency, but it was up around 90% or so. At the domestic scale I'm not convinced that having another rotating part makes sense, and I suspect the efficiency drops. The other problem is that the vane rotational speed needs to be varied depending on the temperature differential and air mass flow rate on either side, so the control unit has to be able to measure the four temperatures, both the inlet and exhaust side flow rate and probably the humidity, and set the vane rotational rate to allow the most effective heat recovery. If the vane drum rotates too slowly then efficiency is lost because the warm side vanes will reach max temperature long before they rotate to the fresh air side and if the vane drum rotates too quickly there won't be enough time for the warm side vanes to warm up to close to the extract air temperature before they rotate to the fresh air side. Not an easy thing to set up, so I assume that the control unit has a fair degree of in-built intelligence to monitor all the sensors and set the drum to rotate at the optimum speed. It goes without saying that these units are pretty fussy about being balanced correctly, too, and are upset by high winds.......................

Interested to see how these go, as I still have some 14.4 V Makita stuff and the one Chinese battery I bought has worked well, better than the original Makita ones. I see that Floureon are selling the 14.4V Makita pack for under £11 - just bought the last one, so I hope it is OK..............

Rotary vane heat exchangers can give very high efficiency figures, they are the standard type of heat recovery system used on commercial buildings, the downside being that when scaled down there is another geared motor and slowly rotating moving part (the vane heat exchanger) that means that their efficiency doesn't scale well and smaller units are barely better than standard fixed heat exchangers, which is one reason that they aren't that common in domestic properties. My guess is that the electric duct heater is coming on a lot, and that it may well be down to the way the unit is set up. If there is a way to disable the duct heater, then that would probably be a good starting point. In all probability the duct heater isn't needed in the climate up there, anyway.

I believe there are already a few rural wireless mesh networks that are up and running. It was the option our village was exploring before the fibre cabinet was installed (with funding from the Local Authority). The idea was to put up a main link exactly where the fibre cabinet is (it's next to an exchange cabinet and the village youth club) and fit the master transceiver to the roof of the youth club (which is owned by the village). This would then allow what amounted to a boosted wifi network to connect all of the village that was within range, with repeater nodes set up on people's houses to allow the network to have wider coverage (I'd offered to be one of those nodes). The capital cost is fairly high, but the running costs are low, as the transceivers are all operating at low power - the key to them working well is having good antenna systems. Our estimate was that we would have been able to cover around 180 properties, with broadband speeds of around 25 Mbs. The FTTC system we have gives around 50 Mbs to about 10 properties, with the rest being down below 10 Mbs, and is barely better than ADSL, because of the long loop of copper than both have to use. The easiest fix for bit over half the village would be to re-route the main copper trunk line, so it doesn't double back on itself. That would reduce the copper distance by between one third and a half of the present distance and substantially increase both ADSL and VDSL speeds. I'm about to try an experiment with a roof mounted mast and high gain Yagi antenna pointed at the nearest 3G/4G mast, with that coupled directly to a modem that has an external antenna connection, to see if I can get better speeds. I can just about get a signal at roof top level using one of the cheap Chinese repeaters, it's really a question as to whether a proper modem will have better performance, which I suspect it may well do.

+ 1 to the above. I had to remove a very similar arrangement in our old house because it meant that the dishwasher protruded a couple of inches out beyond the edge of the worktop.

Sounds like our cabling, which runs around in a big loop, with us on the end. It sort of evolved as the village expanded, so they decided to run the main run from the local exchange up one road, that forks not far from the exchange. Unfortunately, most of the housing development went up the other fork, so instead of running another cable from the exchange they doubled the existing one back on itself then up the other fork...................

We were blocked from having a grant towards setting up a rural broadband network here. We had lots of interest, and passed the threshold for the number of committed users, but when the local council supported fitting a fibre cabinet (that realistically only gives over 10 Mbs to around ten houses, because of it's location) we were told that we already had "super fast broadband" so were no longer eligible for any grants etc. What's happened here is that Openreach installed the fibre cabinet right at the very end of the wire network, so the vast majority of those who want to use it still have a copper loop that is a km or two long, which kills the speed. The length of copper from the cabinet to our house is around 1.5 km, yet the cabinet is physically only about 300m away.