Jeremy Harris

I'll probably be talking to someone at Sunamp in the next week or so, about something else, and if I get the chance I'll raise it as something they might want to look at.

The argument hinges on the fact that with no heating at all the inside of the house won't get cold, it will end up being around the average of the day/night temperatures, probably a bit above that because of solar gain. This means that it's extremely unlikely that the VCL on the inner face of the house will ever get below the dew point of the vapour concentration that penetrates the structure. If I were to take a guess, then I'd say a well-insulated and airtight house, with no occupants and in an average UK location won't ever get below 12 to 15 deg inside, yet it could easily be a lot colder than that part-way through the insulation. Again, it's not something that standard interstitial condensation risk software is that good at, as homes with such high insulation levels and low air leakage rates are not common enough for the "standards" to have caught up yet.

Worth considering an ordinary MVHR and adding an air-to-air heat pump heat and cool units. Depending on the layout this could be a lot cheaper and provide more effective cooling. It's what we'd have done if we'd realised at the design stage that there was a possible problem. I'd have not bought the Genvex Premum 1L but would have gone for a much cheaper standard MVHR and fitted a single air-to-air unit with the outlet high up in the central atrium of our house. These single units are only around £600 to £800 and are far more powerful than the Genvex. Alternatively, if you're fitting an ASHP, then get a reversible one (most monoblocks are, I believe) and then just fit a big duct cooler in the outlet from the MVHR to cool the air down. Again, massively cheaper than fitting something like the Genvex, and just as capable, if not more so.

We had no problem at all with plasterboard in skips. Our skip company (Maidments: http://www.rvmaidment.co.uk/ ) recycle a hell of a lot from every skip load; they empty every skip on the floor of a big warehouse and then sort it and give you back a certificate with all the constituent parts in each load and how much of it was recycled and how much went to landfill. I rang them and said we had a load of plasterboard and did they want to send a second skip for it, to keep it separate. They just asked if I could keep all the plasterboard waste at one end of the skip, separated from the general waste. I got a labourer to make a plasterboard vertical divider in the skip and break up all the plasterboard into small bits and keep it at one end. Worked a treat, we had no extra charge from the skip company and they recycled all the gypsum from that load. I'm not sure what you're supposed to do with all these recycling certificates, no one seems to want to see them, so I've just kept them in a folder.

Glued plugs wouldn't work, as the glue would be in tension on the short grain section, but plates either side would, but not steel as that would mean drilling more holes for bolts. I think bits of 12mm ply glued and screwed either side would be easier to do. Just cut a stack of bits of ply to size, pull the cables out, and go along gluing, screwing and re-drilling the bit of ply in place then replacing the cables. Get the electrician to pay for it...................

This is a good point, that does need sorting. We still had the thermal store fitted when we did our as-built SAP, so avoided the problem. The sensible solution would be for the Sunamp PV to have certification as a thermal store, rather than as an instant water heater that uses stored thermal energy. The problem is that I'm not sure that the standard thermal store test procedure would work for the Sunamp PV. It's perhaps something that Sunamp need to look at, if they feel that there is a serious market for their device in new-build low energy homes. Logically I think it should be treated as an equivalent water volume thermal store with the measured heat loss data from their tests, but I'm not sure how valid that data has to be for SAP. SAP is never checked by anyone, which is why there are so many rubbish new homes with SAP EPCs that are wildly optimistic, and there doesn't seem to be any reason why you couldn't use the equivalent volume (140 litres, I think) thermal store with the certified standing heat loss (around 0.6 kWh/24 hours) in SAP.

I have looked pretty closely at this. The requirement is to pump air at up to 0.2 bar at a rate of around 60 to 100 litres per minute, for 24 hours a day, non-stop, for years on end. The sort of pumps normally used last two to three years or so between servicing (usually the diaphragm fails, the "motor" parts last practically for ever as there are no bearings). A piston type pump won't deliver the volume, and would wear out too quickly, as you cannot have any oil on the air delivery side (because that would contaminate the tank). You're basically looking at the same requirement as a large fish pond aeration system, and the pumps used in these treatment plants are ones originally designed for aerating big Koi carp ponds (hence the reason many are Japanese). There are a couple of US firms that have come up with smaller scale centrifugal fan blowers, but they suffer from bearing problems, and only one firm makes a DC pump, and that has a bad reputation for early failure. As I mentioned above, a small turbo compressor, driven by a high speed brushless motor, could do the job, but would need some form of lubrication system, that used a food-safe lubricant. That's not just for the bearings, but also for the shaft seal. It's perfectly possible to build the brushless motor into the impeller of the pump, so the coils were fixed and the magnets were set into the rotor, and then devise some form of air bearing support. It would be a lot of close tolerance machining, but I'm pretty sure it could be made to work. It would not be cheap though, and would always be a one-off, so not good for maintenance). There was no drawing or diagram sent to the DNO, I know because I submitted all the documents myself, not the installer (long story, but it centred around there being no registered address for the installation). All the DNO have is what's on the MCS cert. As above, there is no safety issue. The microinverter will be an Enphase or similar, so will have the same certification and safety cut off as any other, and it is perfectly legal to DIY install these on a non-FIT install. 99% of people are just going to assume that we have a PV powered treatment plant. This was offered for a time by BioPure, but they stopped marketing it as the DC pumps failed regularly and the batteries and panels were very prone to being nicked.............

I think you and I are on the same wavelength here! Just to be clear, no laws are being broken here and the system would be safe and it is legal to DIY a connection to an existing circuit, provided it is within the appropriate ratings. The inverter would be an approved one (I'm not sure you can easily buy non-approved ones anyway), the connection is a 2.5mm² length of SWA, terminated in a connection box that has spare ways, and at the other end has a 20 A DP RCBO that was installed and tested in accordance with Part P (and has a chit). The only thing I'm not doing is informing the DNO, for two reasons. Firstly, I don't want FIT for it. Secondly, I can't get it to run through a second export meter without a lot of faffing about, connecting to the existing system is easy. Thirdly, as Alphonsox says, the additional generation is both well inside the tolerance on the existing G59 system (and thanks for pointing out the typo - I'll fix it!) and probably within the degradation that's already occurred in output, so in practice there will be no change. In fact my current system has a 6 kW nominal inverter on a 6.25 kWp registered system, so I'd technically still be inside my G59 approval anyway. These air pumps are low pressure reciprocating diaphragm pumps, so use coils running at 25 Hz (half wave mains, they use diodes to halve the frequency to the coils) that had no bearings, because they run 24/7, 365 days a year. The moving armature is supported on spings, with a magnetic alignment thing, and just moves sideways 25 times a second, pushing/pulling a diaphragm at either end, to give near-continuous air flow. The pressure is low (typically 0.2 bar maximum) and relatively high volume (typically 60 to 100 litres/minute). Bigger commercial systems use centrifugal blowers, and I did seriously look at making one. It would need a very high speed brushless motor (50,000 rpm or more) to get the pressure and flow rate, and my thoughts were to use the compressor side of a small turbocharger connected to a model type brushless motor. The main problem is that I would have had to build in a lubrication system, as neither the turbo shaft bearing or the motor bearings would survive for long without regular lubrication. I did look at a US made brushless blower, but the price was silly.

I'm part way through building a stone box a few metres up from our treatment plant, alongside the drive at the top of a steeply sloping section. The box has two halves, sealed from each other, a top entry compartment that will hold the air pump and alarm unit and an open-fronted compartment (with a roof overhang and the floor sloped slightly outwards) to hold two or three bags of rock salt, as the drive becomes impassible with even a thin layer of snow, I've found. I was semi-thinking of fitting a battery and DC air pump, with a 250V solar panel as the roof. The roof is mono pitched and faces almost due South, and doesn't get that much shade. However, there are no affordable and reliable brushless DC air pumps around, it seems, so I've had another thought. What if I fitted a standard 250W panel as the roof and fitted a microinverter and just connected it up to the existing connection box? The cable running to this unit already has a DP RCBO, so it'd be safe. The export wouldn't register on the export meter, but would offset a little bit of electricity usage, so there would be no effect on our FIT or export readings for payment. The only slight issue is that I have a G59 system, so technically I'd need to get permission. However, an extra 250Wp is barely going to make a difference to the local grid, and much of the time the power generated by the panel would be used locally by the air pump, with not a massive amount of export. Panels are so cheap now that a panel and microinverter is only slightly more expensive than me making a roof and covering it with slate to match the house, and fitted a panel to a timber roof frame would be dead easy and look neat (I'm thinking of a black panel). My inclination is to just do it, and not worry about any consequences, as I doubt whether they would ever come to light, or attract attention if they did. What are the thoughts of others?

Thanks Peter, the float level switch input will be there on all units, so if a switch is connected (a normally open one that closes when the level is too high) then that part of the alarm works as well, if the switch isn't fitted the unit just ignores it. It's about 10p to add a connector for a float switch to the unit, the rest is just code, which is free.

You're the very first person I've heard of whose BCO has raised this as an issue, so my thoughts are that it's really a problem to your specific BCO, who seems to want something that isn't a mandatory requirement. There are quite a few here with passive slabs now, and I can't recall anyone having a problem with building control at all, which sort of indicates where the problem lies, I think. As for mainstream builders, well, 80% of what they build never gets inspected anyway, and that which does seems to get passed with glaring failures to comply with the building regs. It's only really self-builders and small builders who are subjected to real scrutiny by building control now, the big boys certainly aren't,as a walk around any big development will show pretty quickly.

Tony's right. The holes are WAY TOO CLOSE to the end of the timber and well inside the shear zone. They are also far too close together. My fix would be to pull the cables out and glue and screw some 12mm ply either side of every area like this that has holes far too near the end of a timber. If these are done one side at a time, then drilled, then the other side done and drilled, it shouldn't be a big job. Take the ply back twice the distance of the area with the holes and glue it with a PU adhesive and screw it with relatively short screws, the idea is to replace the lost shear capability in the end. If those holes well away from the end of the timber and spaced further apart them I doubt they'd be a problem. As it is, a significant part of the adjacent nail plate fastenings are really doing much, as they are into a short-grain section.

I agree, Peter S, a "gentle" beeper would be fine, just enough to get your attention without being ear-splittingly loud. Peter W, it is PIC based, as are all the sensor systems in our new build. I have data being logged to an SD card every 6 minutes from a load of temperature sensors around he place. I also have a portable stand-alone logger that monitors temperature, relative humidity and CO2 levels, and logs that to a µSD card every 6 minutes (some here have borrowed it). The excess PV diverter that's been running for a fair time now, initially switching power to an immersion, now doing the same to the Sunamp PV is similarly home made and runs using an 868MHz data link from the meter box outside to the internal switch unit. The same unit "broadcasts" import/export power levels every 10 seconds to any receiver in the house, so that it's easy to see the current state. Yet another of these devices runs my electric car charge points (an EVSE in EV parlance) and generates the required signals, and interprets them, for J1772 protocol control. I currently have four home-made EVSE units, ranging from micro-miniature ones built inside J1772 connectors, to the proper boxes at the new house, one with a built in energy meter for my car normal charging and another "guest" 32A charger on the garage, that accepts the standard IEC62196-2 cables that most EVs are supplied with for use with public charge points. At any one time that are at least half a dozen or more microcontrollers working away in the new house! The basic logger is in this blog post: which also has a photo of a remote energy monitor that picks up the 433MHz "broadcast" from the main outdoor energy metering system.

No, there is no requirement for BBA approval at all. The Kore system does have it via the back door though, as is has NSAI approval which is accepted in the UK as BBA approval (I know this for sure, as our whole frame, windows, slab etc all have NSAI approval, and our BCO confirmed that this was generally accepted as being equivalent to BBA).

BBA is only one of many approval schemes though, and there's no legal requirement for any product used to have been approved by a scheme anyway. Certainly our LABC weren't phased at all by the Kore system, even though they'd never seen it before. Are your building control body being awkward for some reason? It's be interesting to know why, as I've not heard of any of the various control bodies having any problems accepting an SE's report before. The Kore slab is PassivHaus certified, and there is a load of detail on it on their website: https://www.kore-system.com/kore-products/floor-insulation/kore-passive-slab/what-is-kore-passive-slab Just noted that it is certified as BBA equivalent anyway, it has NSAI, which is accepted here: https://www.kore-system.com/hubfs/docs/KORE_Passive_Slab_Mini_Brochure_20152809.pdf Nice to see that Kore have made their design guide downloadable, too, should keep a lot of BCOs happy: https://www.kore-system.com/hubfs/docs/KORE_Passive_Slab_Design_Guide.pdf

They stop a bit further South, in my experience. Coming back from the North the work 'phone would start ringing coming down the hill towards Fort William, usually around the Southern end of Loch Garry on the A87. There were times when it was very nice to spend a couple of weeks in an area where there was no contact from work at all. For some reason Government took the invention of the mobile 'phone as an indication that employees were paid a salary and expected to answer the 'phone 24/7, 365 days a year.....................

I would advise caution, because all of the commonly available interstitial condensation risk analysis tools are, as far as I'm aware, non-dynamic. As you improve the overall insulation level dynamic effects assume greater significance, and these are not predicted well by the normal condensation risk software. Most of the risk comes from water vapour penetrating from outside, so the idea is to have the VCL at a point where it will ALWAYS be at a temperature that is above the local dew point for any condition, particularly the case where you have a cold night and a cold house (on holiday perhaps) where the structure cools, followed by a warm damp morning that creates a high external humidity level and drives water vapour inwards through the structure. You have to be absolutely certain that under such conditions there isn't going to be a condition where moisture could form. Once formed, moisture will take much longer to vaporise and travel back out, because of the relatively high energy needed to drive the phase change from water to vapour. I've looked at some of the interstitial condensation risk software and all that I've looked at has been sub-optimal (in one case dysfunctional) when used for a higher than normal level of insulation in a structure. My personal view is that the easy and safe way to approach this is to always put the VCL inside ALL the insulation, as this then removes the risk, to all intents and purposes, irrespective of what a bit of software says.

I'm pretty sure the Kore system has a BBA chit now, and Isoquick seems to have a raft of approvals: http://www.isoquick.co.uk/index.htm and I thought that Supergrund (now Kingspan Aeroground) also had a load of approvals, too. FWIW, our BCO passed the Kore system with barely a glance at the spec, and asked no questions at all about it.

Currently I have enough parts to build 4 units, so on the basis of first come, first served, I'll start with a batch of four for Calvinmiddle, Peter Starck, Alphonsox, and the prototype for us. Cost is probably going to end up around £25 to £30 at a guess; I haven't added up the cost of the parts yet, but will do over the weekend. I think it's unlikely to be much over £30, worst case. It could probably pay for itself fairly quickly if it prevents an early pump failure from monitoring the pressure, or allows optimisation of emptying periods (i.e. don't empty the unit until the pressure starts to creep up, perhaps). I'll stick the design on here as an open project, so that anyone with the interest and a bit of experience could build one. The main reason that such a thing is affordable now is the advent of mass-produced home blood pressure monitors, as pressure sensors have always been far too expensive in the past. I'm using a small and very cheap pressure sensor that's intended to be used in a blood pressure monitor and only costs less than £2. The test sensor I was using for development is one scrounged from a bin at work back in the late 80's that, IIRC, cost around £400 or so. The display will be a large character 8 digit LCD, with gentle backlight, that will normally just display the air pressure, in bar, at the pump (so this alarm units sense pipe will need to be tee'd into the air pump outlet, as those will existing alarms will know). I can fit a beeper to the internal unit or just rely on a bright red LED flashing away, with the fault condition showing on the display. I'm in two minds about adding the beeper at the moment. It's cheap (around £1) and easy to do, but it could be a nuisance if it starts beeping in the middle of the night. The treatment plant end will have an input for a level switch, simply because I already have a level switch on our system, but this can be ignored for those who don't have pumped systems.

I can easily fit an external antenna, but 8m is pretty short range so the antenna inside the plastic box I'm looking at using should be OK. I've tested the basic data link and it looks good for well over 50m. With a bit of luck this weekend I'll get the first pair of units built so I can start testing. I can emulate your case by just fitting the alarm transmitted down in the equipment box of our present set up, as that's inset down into the top of the tank so partially below ground. If it works OK from there to the back corner of our house, in the utility room where I'm going to fit the alarm and display, about 25m away, then it should be fine for your case I think. The parts are pretty cheap, its things like the weather tight plastic housings that are the most expensive parts. The internal display and alarm will, I hope, just fit into a standard socket wall box, I'll try and fit it in a single, but it may need to be a double. What I've done in the past is to machine a hole for a display into a blanking plate for a standard box. This seems to give a neat appearance and matches well enough with other fittings. It will have to have a lead to a 13A plug with the appropriate fuse, though, just to be "portable" and avoid the need for wiring regs stuff.

Sounds very much like the arrangement I'm putting in place. Currently the pump and alarm are inside the unit. under the lid in the internal equipment box. This works OK, but is pretty difficult to get at, so I'm in the process of building a concrete base that will have a small stone box built on it, with two compartments, one for the air pump and alarm unit and the other as a silo for some rock salt, as our drive is so steep that the slightest bit of snow makes it impassable. I don't like the idea of relying wholly on the external alarm (and mine seems much the same as yours, a plastic box with a rechargeable battery and a beeper plus a flashing light), as there is a good chance that we may not see it for some time. Also, as Peter noted above, the back pressure on the pump seems to build as the sediment layer gets deeper, so something that indicates the air pressure seems useful, as you can watch for an increase and use that as an indicator as to when to order a pump out. I've bought a bag of inexpensive pressure sensors, so it's pretty straightforward to just transmit the pressure to the internal box and then let the internal box handle the alarm sensing. In our case, we have the pumped outlet version so there is a second alarm feature that senses when a level switch has detected an over-level event, signalling an alarm that the emptying pump has stopped working. It'd be easy to monitor a level switch as well and transmit the state of that as a part of the data transmission.

I've started designing a remote alarm/air pump pressure system, prompted by this series of posts quoted from the closed Ebuild forum: Following on from the above, I decided it would be nice to have our alarm relocated with an indoor display, that would not only provide the "low pressure" and "high level" alarms at a convenient location, but with the addition of an indoor pressure display, to give early warning of sediment build up, so avoiding (hopefully) the problem that Peter reported. I have the pressure sensors, have tested them and the interface to a wireless data link that will comfortably work for 50 to 60m through walls. I have three choices. I can make the outdoor unit larger and fit a battery a solar panel, and have the indoor unit as a hand-held battery powered unit that could interrogate the external unit on request. The power demands make this arrangement impractical for giving a real-time alarm, it would rely on being interrogated to find out whether things were still OK, its major shortcoming. The next option is to have a solar powered external unit transmitting to a mains powered internal unit. This would provide continuous monitoring and alarm, at the cost of a solar powered external unit that would be relatively large (because of the battery and solar panel size) an would cost more, plus the battery would need replacement every few years. The final option is to have a mains powered unit inside and outside the house. This would probably be the best solution if there is mains power available at the treatment plant, as it would be the most reliable. In terms of power, it would use less than 1W at each end. This post is really to see if anyone is interested, as I'm making one for our build, and it's very little trouble to make one or two extra. I'm probably going to opt for mains powered at both ends, as that suits us better, but there really isn't much to choose in terms of hassle to make other types. Anyone interested?

If you look at your meter, then (assuming it's a new one) then it will indicate clearly when you're not using any power from the grid, but are exporting. Usually the red LED stays on solidly, indicating reverse current flow, rather than flashing for each Wh used. The digital display may well alternate between the energy reading and a message that indicates that current is flowing back to the grid. Whenever the meter has a solid red light or other reverse flow indication then the PV system is powering everything in the house with enough left over to export some to the grid.

Although the manual for ours says 200mm minimum rear clearance, you would really struggle to fit it with that small a gap, as the flexi pipes won't really bend around that sort of radius (and, as I found, you need to have a loop to stop vibration transfer). 300mm seems a sensible minimum, and is probably around the distance between the rear of ours and the wall.

Ours is specified as minimums of 200mm rear clearance, 300mm side clearance, 1000mm front clearance, so maybe they are all a bit different, depending on how air flows through them? The intake on ours is at the left hand side and across around 3/4 of the rear, so maybe units that only have an intake at the rear need more clearance.