Ed Davies

Good point about cleaning the heat sink - I hadn't thought of that.

It should do. The standard way to do it is to measure the airflow at a range of positive and negative pressures and fit a formula then use that to work out the leakage at 50 Pa.

I hope I did, too. Some thoughts on the subject: https://edavies.me.uk/2012/12/sketchup-component-layers/ https://edavies.me.uk/2014/01/sketchup-components-and-groups/ My preference is to use components rather than groups, as explained in the second of those posts.

Slightly surprised it doesn't cycle through 888888 to make it obvious if any of the LCD segments have failed. I thought most did.

Then let's have an honest debate, you have to reduce peak usage to even out demand, so peak rate metering and charging is the tool to achieve that and encourage you to change your usage patterns. Who said anything about evening out demand? That's not necessarily what you want with renewables, rather you want to match demand to available generation which might not itself be all that even. E.g., charge cars and various heat stores while the sun shines or the wind blows.

They'd probably argue that they makes large-scale grid renewables plausible. There's probably an element of truth in that.

It's possible @JSHarris and @SlivenClod are talking past each other here: AC = air conditioning, perhaps. AC = active cooling, perhaps. I don't think @JSHarris has air conditioning as such (might be wrong - maybe he has a cooler in the MVHR, can't remember). What he does have, though, is an air source heat pump (ASHP) driving the underfloor heating (UFH) which can operate in cooling mode (so UFC???) to drop the ground floor slab temperature a few degrees and thereby cool the house.

Probably the least wasteful plan (particularly as you could keep the in-line heater as a backup) but might not work with SAP, could finish up with too high emissions depending on the house construction.

Obviously. However the foam could be a perfectly good air barrier but still off gas horrid stuff so your assertion that off gassing being a problem implies a crap air barrier is a bit tenuous.

Yes. Friend did that for the lighting on a barn conversion - just a cupboard full of terminal blocks with separate cables to each light fitting and light switch. Probably only cost one more roll of cable and a few boxes of terminal blocks. I'll be doing something similar on my house though probably with two “central” locations, one in each loft. Sockets don't need individual radials, of course, but there's a lot to be said for having a few on their own ones which can be controlled separately (or go on separate RCDs).

I'll be going for the exact opposite: have a bunch of relatively simple and generic sensors and actuators around the house and one central brain that can be easily replaced. Maybe a bit of very limited intelligence in separate safety subsystems to protect against things like overheating thermal stores or solar thermal and battery over- and undercharge if the central brain fails but most of the convenience and optimization intelligence to be kept in one place. Apart from anything else, keeping the sensors and actuators simple makes for easier to maintain and understand documentation. If somebody comes along in the future and finds the central bit too mind boggling they can at least keep the peripheral bits and replace the central bit without having to dig holes in the wall to replace hindbrains everywhere.

But aren't these foams intended to be the air barrier?

I believe you have dropped a zero here - 1kWp of PV has the potential of delivering about 1MWh per year in optimum conditions, England. I, too, hope you've dropped a zero here. Typically you'd expect something like 800 to a 1000 hours worth of generation per year in the UK for a decent installation depending on location and orientation. For a somewhat sub-optimal one to get 550 hours (so giving 5500 kWh) might be reasonable; 55 hours would be stunningly awful.

Because it'll also be leaking flue gasses?

For a two-storey box (house) with an 8x8 metre ground floor and 5 metre height the surface area (walls, ground floor, upstairs ceiling) would be 336 m². Assuming leakage of 5 m³/m²/h at 50 pascals and practical leakage being about 1/20th of the air test measurement that'd be 336 × 5 / 20 = 68 m³/h. Air has a density of around 1.28 kg/m³ and a specific heat capacity of 1006 J/kg·K so for a temperature difference of 30 K between inside and out that'd result in a heat loss of: 30 K × 68m³/h × 1.28 kg/m³ × 1006 J/kg·K / 3600 s/h ~= 730 W. I can see slightly different assumptions resulting in @JSHarris's “1,672 W at -10°C to just under 3,000 W” but not @ProDave's “worst case heat loss (-10 outside +20 inside) went from 2.2Kw up to 15.6Kw”. I suspect @ProDave is taking the 50 pascal leakage rate too literally but maybe there's something else going on. Apart from anything else, windy conditions don't tend to be extremely cold.

Some piccies might help anybody else who feels a sudden urge to dismantle one of these.

3 to 5 ACH is indeed likely some of the time but surely a house with minimal leakage for building regulations not to require mechanical ventilation (5 m³/m²/h, I think) would have a much lower air change rate most of the time in practice. 50 pascals corresponds to a wind speed of around 8.8 m/s (just under 20 mph) which is relatively uncommon even in exposed locations. Also, a blower door test blows (or sucks) on all four walls and the floor and ceiling whereas wind tends to, in effect, blow on just one wall and suck on the opposite one. IIRC, a rule of thumb is that the actual ACH, on average, is likely to be about 1/20th of the test result. Of course, what's of interest is the typical ACH during the worst bit of the heating season. Still…

Do these things get nicked? If not, why not?

My understanding: if it was all one quote/invoice for both supply and fit then it should be zero rated. If separate then the supply should be normal rate which you can reclaim, labour should be zero rated. If they charge normal rate on the labour then you need to get them to update the invoice, you can't reclaim it.

Probably from Canadian Solar, main manufacturing in both Canada and China: https://en.wikipedia.org/wiki/Canadian_Solar

@joe90 has MVHR.

It seems to me that people worry too much about objections. Having looked through the planning paperwork for a few sites for sale, OPP has been granted despite objections from neighbours on grounds which really weren't relevant to planning. So, unless you think they're likely to point out a planning aspect that the planners might otherwise miss or not prioritise I'd make the decision on whether or how to approach them based mostly on future relationships.

18.71 p/kWh, 28.82 p/day. Changed on the April 1st from 16.89 p/kWh, 29.53 p/day so a net increase for me, using 4.6 kWh/day for this bill, of 7.662 p/day or £27.96/year. Could be worth shopping around but really hope not to be here more than a year anyway.

Yep, those EAHPs remind me of the cartoon of the becalmed sailor using bellows to blow on the sails.