Jeremy Harris

Earth tubes are a way of being able to feed an MVHR with pre-warmed air in winter, or cool air in summer, but they are not easy to get to work well. The pipe has a special silver anti-bacterial, anti-fungal coating and is very expensive. I looked at it briefly, as I'd thought of fitting the pipes behind our big retaining wall, as it holds a fair bit of heat. Once I saw the price, and read about the horrors of not using the special pipe (see here: http://www.greenbuildingadvisor.com/blogs/dept/musings/belgian-passivhaus-rendered-uninhabitable-bad-indoor-air ) I decided not to bother. They may work well in a dry climate, but it seems that they aren't that easy to make safe in the sort of climate we have, as there will often be condensation in the tubes. Stopping stuff growing in them seems to be a significant problem, and I'm not 100% convinced that even the special silver coating will have a long enough working life.

Iceland is a place I've wanted to visit properly for years. I did spend a night there once, a long time ago, but it was by accident, a result of bad weather. I never got to leave the base at Keflavik, though, as none of us had our passports..............

In most of the UK the temperature of the ground, below about a few metres or so is pretty constant for around a couple of hundred metres or more, at around 8 deg C. This heat comes almost entirely from solar gain, with percolating water from the surface carrying heat down to a fair depth. I used to go caving a lot, and wherever you went in the UK the cave temperature would be a pretty constant 8 deg C or so, even 400ft or so down under Wales................ Ground source heat pumps, whether they use surface, water or borehole collectors, are really solar heat collectors, by a round-about route. If you take heat out from under a house, then the ground will cool down more than if you took heat out of a bit of open ground, as there would be no direct replenishment if heat from above. Depending on how permeable the soil is, and how well heat can transfer sideways from adjacent land, you could find that you drop the soil temperature under the slab by a lot, it may well even freeze and heave. Because the heat comes from solar gain and surface water percolation, the collector wouldn't work as well as one on open ground or down a borehole (and our 53m borehole is also a constant 8 deg C, all year around). An under-house collector would also increase the ground floor heat loss, by increasing the temperature differential between the soil under the house and the room temperature, so more insulation would be needed to maintain the same heat loss as before. It's quite common for ground source heat pumps to be wrongly referred to as geothermal heat pumps, domestic ones aren't at all, unless they have collectors going down many hundreds of metres, and only then when in an area where there is either a high level of natural radioactive decay causing localised heating or the Earth's crust is thin. I once went down a Cornish tin mine (Wheal Jane) and at about 1500ft down it was fairly warm (around 30 deg C), due almost entirely to the high natural radioactivity of the granite, rather than true geothermal heating. True geothermal heat (as in from the Earth's core) doesn't really get that noticeable until a lot deeper than this mine, unless you live in an area where the Earth's crust is thin, like Iceland, Yellowstone Park etc.

If the condition can't be justified, because the planners have made an error, then you can ask them to remove it. It sounds to me as if they may have included the condition by default; our PP originally included a condition removing permitted development, and when I questioned why it was there the planning officer just removed it. I later found out that their boiler plate template has around three or four standard conditions that they automatically include, and this was one of them for our area. It only applied to developments inside the conservation area, and our plot is adjacent to, but not within, that area (although it will be inside it at the next review, I've been told).

My experience was that the county archaeologist was very helpful on the phone, and gave me a really good steer as to what might be involved. The problem with that plot was that the owners had gone OTT in the planning application requirement for an archaeological survey, and had had two 5m long trenches, 1m wide and 1m deep dug across the site by the archaeologist they hired. This found a cobbled floor, some wall foundations and a millstone, which then meant that when PP was granted it was public knowledge that there was a lot of archaeology under the site. When I spoke to our county archaeologist, on behalf of another forum member here who was looking at a plot near to where we live, all she wanted was an archaeologist to watch over the top surface being scraped away, as there was a known neolithic settlement in the adjacent field. Worth calling and asking, as if the site has already been disturbed a lot then the chances of there being major archaeological finds may well be pretty low, especially if your not digging down far.

I couldn't agree more! The iPad's not mine, I have a Sony tablet rooted and running Cyanogenmod, as I don't happen to like snooping by anyone.................

Some inverters have two MPPT inputs, so could handle a split array OK without the need for optimisers. Our system is all on a single, un-shaded roof plane, but is still split into two DC strings, each feeding a separate MPPT in the inverter.

That does indeed sound very good, at that price it's not really worth considering the hassle of a DIY set up, I think, plus you'll get the FIT and export payment, even if it is a lot lower than it used to be. I'm tempted to have a think about adding a small East - West split system fitted to our garage roof for that sort of price, as it would help to "flatten" our generation curve a bit. Have to wait until I've finished the other 100 jobs I have to do first, though..............

Non-Dispersive Infra Red (NDIR) CO2 sensors (the very reliable and accurate ones) are around £80 - £100. I have a few that I bought for around £20 each, that were surplus, sold off when a building monitor manufacturer went bust, that I use to monitor the house CO2 level 24/7, with the data logged to a USB stick. It would be easy to add a system to switch the MVHR on and off, but I can't really see any benefit for us. For most of the year (like now) we generate far more electricity than we use, and we get paid the same whether we use it or not, so the few tens of watts the MVHR uses makes no difference at all during the day, and at night the chances are we'd want the MVHR on anyway.

This time of the year there is a pretty wide diurnal temperature variation; last week I had to scrape frost of the car windows in the morning, yet we had a lot of sunshine during the day. I suspect that there is still a worthwhile benefit from having the MVHR on at night, even if you turn it off during the day, when you have doors or windows open.

Yes, the first plot we tried to buy had one as a planning condition. I rang the county archaeologist to find out what it entailed and it was a bit open ended. The best case was that we'd have to pay for an archaeologist to be on site for any days when there was any excavation work, and he advised that often they would allow a student to do this, at that time for around £120 a day (versus over £200 a day for a "proper" archaeologist). The snag is that the archaeologist has the authority to close you down if they find anything, and you have to pay the full cost of any ensuing investigation, as well as bear the cost of having to stop work. In the case of the plot were wanted to buy, because there had already been two long test trenches dug across the plot as a part of getting PP, they knew there was archaeology there, and we had a rough estimate that the costs during the build were likely to be around £20k, plus a few weeks delay.

Let me try it first, Nick, to see if the resistor trick works. I have a 2.1A cigarette lighter USB adapter around somewhere, that I know doesn't charge the iPad either, so if I try with that and it works I'll risk taking the built-in USB charging socket in the car out and trying to modify it. The car has two USB sockets, one for low power charging and connecting a USB stick for playing music or updating the sat nav, the other for high current charging. The latter is supposed to charge an iPad, but from reading that article it looks like Apple changed the charger design after the car was designed.

Where I screwed backing boards to the airtight lining board, to space out back boxes correctly (our battens were 50mmx 50mm, so 45mm boxes had to be brought forward to ensure there was no gap) I just put a dab of PU foaming adhesive (the fast cure Evo brand stuff, that comes in gun cartridges) around the screws. This seemed to work OK, so we did the same for all the back box screws into the spacer boards, just in case they penetrated right through.

You could always try the trick of adding four resistors to the data pins on the charger USB socket. Having read the info in that link I'm going to see if I can do this to the high power USB socket in the car, as it'd be handy to be able to charge the iPad from it. The same socket charges my Sony tablet fine, so I'm pretty sure it's just because the iPad isn't seeing the right voltage on the data pins to tell it that it's an Apple charger.

It may be worth it, it depends on whether the additional FIT and export payment would cover the extra cost in a reasonable period. Bear in mind that the inverter probably has a life of around 10 years, so 2 or 3 inverter replacements need to be factored in to the cost. Things have changed a great deal in the past few years, so it's no longer as clear-cut as to whether an MCS installed PV system is worth the extra cost. Back when our 6.25 kWp array was connected, we managed to get a reasonably good deal, although nothing like as good as those who installed system a year or so earlier. We're now getting 14.23p/kWh of generation, plus 5.03p per kWh of deemed export, which for us is a bit over £1000 a year. We're already about a third of the way towards paying for the system, even though our system cost was around £2k more expensive than the same system today.

Should be OK, Nick, as the car USB socket is rated at 2.1A, and is supposed to work fine with Apple stuff. The problem seems to be that, as per that link, the USB socket doesn't have the signalling connections that Apple use on later generation devices to determine whether the charger is a genuine Apple one or not. From that article, it seems that adding four resistors to provide the signalling voltages to the data lines in the USB connector (which aren't normally used in most chargers) should fool the iPad into thinking it's connected to an Apple charger.

You can turn it off whenever you like, it's primarily there to provide clean ventilation air and recover heat that would otherwise be wasted, but there's no point in having it on when you don't need either heat recovery or ventilation. For us it's not worth getting up to push the off button, as any time we might want it off it will be running from the excess PV generation, so there's zero running cost in just leaving it on all the time.

Some friends of ours have a bamboo slatted duck board in their shower, and we're thinking of doing the same. It's non-slip and looks fairly easy to take out and clean.

The cable is the white one that came with the iPad, with the unique Apple connector on one end and what looks like a standard USB plug on the other. The iPad charges fine using the white charger it came with, but won't charge from the other 2.1A USB charger we have or the 2.1A USB socket in the car (which is odd, as the car handbook specifically says that this socket is intended for charging iPhones/iPads). I've not bothered looking into it further, but just assumed that Apple do something to signal to the iPad when a non-Apple charger is used. Edited to add: Found the reason for the problem, after a bit of web searching. It seems that Apple have made the USB connection non-standard, so a charger needs to put a particular voltage on the USB data lines (not normally used on chargers) in order for them to work. There's a description here: https://learn.adafruit.com/minty-boost/icharging

It's a pain, and I'm not sure there is a way to reduce the number of these things, at least not without a bit of DIY. I've rationalised all my cordless tools to 18V Makita ones now, so at least only have one type of battery pack, but that still leaves laptops, ebookreaders, tablet, iPad, two phones and several other bits of kit with different chargers. I have got rid of the power supplies for the VDSL modem, wireless router, switch and network storage, by making a battery-backed power supply that runs the lot (using PoE for a couple of things). Some things use USB chargers (camera, iPad, tablet, ebook reader and phones) so I tried to rationalise these, but was slightly thwarted because the iPad doesn't seem to work on a standard USB charger, only the special Apple one. No idea why, as it's not the current rating that's the problem.

No problem at all, other than wasting a small amount of energy, which if you've got a PV array is of no consequence.

Not sure who's mentioned the Earlex, but I can confirm that they aren't great for spraying paint at all. I had a very similar one many years ago, it was fine for spraying wood preservative on the fences we had at the time, but wouldn't handle paint unless it was thinned so much as to be like water. I can't imagine trying to paint a house interior with one. In contrast, the Spraytech is supposed to be able to spray unthinned emulsion paint, as long as it's well-stirred and ideally filtered to remove any lumps. I've not got around to trying it yet, as I've been side tracked into making the garage loft storage area accessible, with a loft hatch, ladder and a small electric winch to lift stuff up there easily. Having not looked at the garage loft floor until last week (it was roofed over before I got a chance to see it) I'm surprised how much space there is up there. The hatch and ladder are now fitted, the electric winch should be fitted tomorrow, then I can shift all the stuff that's cluttering the garage up and get room to prep and paint it properly. The Spraytech should be able to spray floor primer and paint, too, which should make that job a lot easier. I still haven't got around to taking a photo, but it's very similar looking to the Titan 400:

I think the flip side is that we can all benefit from the art of design that a good architect contributes. I know that, when I decided to not use an architect (only because I couldn't find a local one that understood low energy house design) I really struggled with getting the house to look right. My solution was to spend the best part of a year doing several iterations of the design, making models and changing things until I thought the design was about as good as I could make it. No architect would have the luxury of taking such an approach, and I'm sure my design could have been significantly improved by input from someone with a far better eye for design than me. I approached the design from a performance standpoint primarily, fitting in the spaces we wanted within the bounds of what would work for good energy efficiency. Every single element of the design was driven by the desire to reduce heat loss and excessive solar gain, whilst giving us the features we wanted. Doing that and making the house look good is a difficult challenge, as the performance requirements place significant constraints on the design. I've said this before, but I'm convinced that there is a need to join together the engineering skills needed to build a house with a good level of performance with the artistic design skills of architects. This seems to happen in commercial design; my last programme when I was working had a lab and office build project of around £96M as a part of it, and the design team were very integrated, with architects and engineers working side by side, on an equal footing, driven by our requirement that the building should meet or exceed the BREEAM Excellent rating (it was the first public sector building in the UK to achieve this, in fact). I've met one former commercial architect who wants to adopt the same approach to house design, but sadly I encountered around ten times that number who seemed to have the view that design came first and performance was something for an engineer to sort out afterwards. One of the architects even openly said this to me; the one that suggested fitting four large roof lights in the South elevation. I questioned whether the house might overheat with such an arrangement and the reply was that "the engineers will sort that out". Interestingly, the one architect I've met who is very interested in low energy house design has a very good understanding of the engineering and physics needed to model house performance.

I trimmed all the terminal connections before skimming, so they didn't get in the way. Having them sat back a few mm didn't matter, as the push fit terminal stubs were plenty long enough to engage in the connections.

I had exactly the same problem with motion detection, everything from rain to spiders building webs across the camera would set record going. In the end I binned it, and built a doppler radar motion alarm, that triggers the system to record when it detects motion (doppler radar because it's far less susceptible to false alarms than passive infra red). The snag is that my system is a one-off, that uses a radio link to trigger the alarm recording.