Ed Davies

Assuming the house is mortgaged, I wonder what the mortgager would think of things which might make the house a lot harder to sell.

For a new build, though, it can affect roof design.

Yep, pretty sure that's right. Apart from anything else, my playing with steep angles for winter generation earlier in this thread wouldn't make any sense if those angles were from the vertical.

That sounds reasonable as the panels will then be making more from indirect light scattered from clouds or just the blue sky above through the rest of the day.

Yes. And being off directly south hammers you more in the winter, too, as when the sun is above the horizon it's to the south. In the summer, if the array is, say, east facing you gain a bit in the morning to compensate for the loss in the evening but in the winter you just lose. This depends on what you're optimising for. If it's total year-round energy harvesting then those sound plausible numbers. However, spare electricity in the summer is less valuable than any you can get in the winter so the results might be different if you're trying to find the optimum energy value.

I think it's a combination of the angle of incidence and the longer path length of the sunlight through the atmosphere. Overall annual production from panels is reduced noticeably for more steeply mounted panels but winter production is severely clobbered by the shallow angles most panels are mounted at; they need to be mounted nearer vertically to optimize that. For a point at the north end of the runways at RAF Syerston (between Nottingham and Newark - an arbitrary East Midlands point I happen to be sufficiently familiar with to pick as a point with a clear southern horizon) putting the panels at various angles PVGIS gives the following outputs: 35° - Annual: 1020 hours, December: 35.8 hours. 75° - Annual: 889 hours, December: 45.8 hours. 90° - Annual: 752 hours, December: 44.4 hours. One of the reasons people say that PV falls off a cliff in winter is that they only look at the output for relatively shallowly mounted panels. For that 75° case the month with the maximum output is April with 96.8 hours production so not much more than twice the December production. Actually, for 75° the worst month for production is January at 43.7 hours. December is the worst month for 35° mounted panels. I guess that's to do with the mix of direct sunlight and indirect sunlight scattered from clouds.

It wouldn't be if there was no way to search the web for sites like: https://www.jablite.co.uk/ and https://www.insulationsuperstore.co.uk/browse/insulation/insulation-board/floor-insulation/jablite-insulation.html

kPa (kilopascals = kN/m²) so 1000 times. But that's the loading for 10% compression which is a bit much. For more realistic 1% compression it's about 1/3rd to just under half that: https://sandbeps.com/wp-content/uploads/2018/02/Floors-datasheet_2018.pdf For context, a 1 kg [¹] object has a weight of about 10 newtons (actually closer to 9.81 N) on the surface of the Earth. EPS200 has a safe working load of 90 kPa for 1% compression so that's nearly 9 tonnes per m². [¹] kg measure mass, not weight.

It'd be interesting to calculate what the incremental cost of adding, say, a metre to the width of @SteamyTea's house would be: an extra 26 m² of external area (gf floor, walls and roof), 7 m² of internal floor area and maybe 5 m² of internal walls and maybe a bit more cable and pipe (though not much pipe with sensible layout). The thing which wouldn't scale would be the joists - presumably they go across the house and 4.5 m long is significantly more than 3.5 m in terms of beefiness required, I think. Maybe a bit more window area. A lot of the other costs would stay the same, e.g., for stairs, plumbing, electrics and so on and particular for the side/partition walls. In exchange the floor area increases by 13 m² which is just short of a 30% increase. I really doubt it'd increase the cost of building the house by anything like that much (and why cost/m² can be so misleading for houses which are unusually large or small). They wouldn't fit across the front of the plot like that but that layout wastes the area of the access to the back. Putting four houses across the N side of the plot and two across the S side might have been better.

Interesting. Rather the opposite of what I had in mind: perhaps supply to 100% and extract to 30% would be better if you're switching on a separate extractor but if it's configurable to do that that'd be OK. Having a completely separate kitchen extract path might be simpler than valves and bypasses. I don't quite see the logic of reducing supply to 30%, though. Doesn't that just depressurise the house so the other 70% is made up from random leakage? A bit theoretical for me as, for most of the cooking I do, I'm pretty sure that a recirculating hood will be sufficient.

Why would cooking smells be spread through the whole house if you have an extract vent in the kitchen, which you would, of course? Would it make sense to turn off the extract side of the MVHR but leave the supply side running? Perhaps even boost the supply side. Do MVHR controller allow that?

AIUI, the air break is there to break a lower-than-atmospheric pressure in the pipe allowing syphoning to happen. But shouldn't it be an AAV - an air admittance valve [¹] which lets air in but prevents liquid getting out? [¹] Not an automatic air vent which lets air out but doesn't let liquid out.

Nope, a thermal store just stores therms; the actual water to be heated is not stored in it (apart from the small quantity in the coil which is completely changed every time a significant draw off is made so not much chance for bugs to breed [¹]). An unvented (or vented) cylinder also stores therms but also the water itself. [¹] Edit to add: maybe not even the volume in the coil if the heat take off is done via a separate heat exchanger.

I have one of these towers (the 7m version): https://www.aluminium-scaffoldtowers.co.uk/diy-access-tower-sale/ 7m refers to the working height, the height you can reach so 2m above the highest platform height (5m) and the highest handrail height (6m). For lower heights it's very useful and I'm OK on it at the maximum height but very nervous of handling even quite small sheets unless it's dead calm and would not be even slightly interested in silly tricks like pushing ladders around and climbing on and off them. If your gutter really is 10m up then something quite a bit more beefy is called for, ideally attached to the wall (tied off through a window or something). As above, DIY might not be the best option.

…and two different time zones: https://www.youtube.com/watch?v=QCwpVtqcqNE

But everybody on that thread is in England (edit: plus one in Wales).

I think they can if it's been more than 5 years. Given that it's obvious I won't be finishing soon they took the option. You don't have to retrospectively change anything which has already been installed or would be impractical to change in the design so it's not that onerous. In theory they could have asked me for a new SAP calculation but I'm so far clear of that that they waived it.

I wonder how they'd react if you just set up for PH levels and say so. I've just been bumped up to 2017 regs on my most recent warrant renewal so this thread was a handy reminder to read the 2017 ventilation rules, which don't seem like much of an improvement in clarity over the 2013 lot. The other changes which affect me are the need for a CO₂ monitor (which I have anyway) and the need for robust walls for fitting handrails in the shower room which other discussions on this forum had prompted me to think about, too. So not a hassle really.

http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11461&page=2#Comment_193433 There's some quibbling further down the thread on how the volume is calculated when the ceiling is higher.

What's the purpose of restricting PD rights for ASHPs to heating only? Is it a general prejudice that cooling is wasteful or is there something more specific? Perhaps that neighbours are more likely to have windows open when cooling is needed and therefore be affected by any noise?

There are all sorts of possibilities depending on what the manufacturer felt like. The mention of modbus_rtu on the error screen points to differential async serial comms of some sort. Whatever, it'll be down to the details of the protocol whether it matters which end is switched on first - for any sensible Modbus implementation it shouldn't matter. At worst switching the controller off and on, with the main unit on, should recover if it's a simple protocol error.

It's not 100% clear but it looks like it's the main unit which has failed and the controller is just moaning that it can't get a sensible response out of it.

Good idea. Probably worth doing that at both ends together.

I think you mean 2.5 kWh/hour which is, of course, 2.5 kW.

Not being sarcastic: have you tried turning it off and on again? Maybe there was a glitch as the power came back on which borked one or other end which would be reset by turning it on with the power in a stable state.