TerryE

@oranjeboom it isn't always best to have the window entirely within the thermal layer (as in my case where we've adopted a pretty standard approach for passive houses with stone skin). OK, for a clad frame it makes sense, but you miss the point of my Q. Why pick the middle? As the Väggkonstruktioner link above shows, you need to get the external profile and treatment correct. If you arbitrarily pick a centre location, then you might have to make up special to purpose external framing to keep the windows and frame weather tight. I just think that you need to think through the detailing otherwise you might face an "oh shit" moment in a week or so.

A1: Why are you having your windows centred in the frame? I can't understand the reasoning here. Surely you should start with outside profile, cladding and all and work backwards from there. Don't Norden do a custom external cill for this range in which case this will dictate the cill overhang and how far back into the frame the windows sit. Q1. As previously discussed the VPC is different to the external breather. The key issue externally is weather protection and how this will be implemented over the breather. Q2. If your window is properly sealed the DPC below should be optional. In our case, our frame sits forward of our frame outer surface and closes the 50mm gap between the frame and the stone skin. I have a vertical DPC from the underside of the widow protecting the upstand discussed next. Q3. You normally have a minimum 5mm and typically 10 mm on the sides and top to allow differential expansion, etc. This is foamed and weather protected with a decent exterior silicon. Windows can be bloody heavy so they are typically designed to be supported underneath and therefore sit directly on some hard support. IMO, you are asking for trouble if you don't' do this. I sat my Internorm widows hard on a tanalised 30mm wooden spacer, though most window providers will offer a custom uPVC spacer. (This was to give me enough room to put in battens to carry my internal cills.) Don't bother with Compriband here; wrong application. If you were lining your exterior reveals or overlapping your cladding and needed a weathertight, flexible seal, then Compriband would be one alternative to use for this.

Galvanised or stainless steel or aluminium alloy wire staples pushed into the ESP would do the job, but in our case the "exposed" EPS is below ground level so we've just used a crushed gravel perimeter which will be topped by a line of paving stones -- the type and details still TBD.

To be honest, this type of article irritates me extremely. As you say: light on detail. When I read something like this, my immediate reaction is that this was triggered by a press release accompanying a published paper, so I want to read the paper is open access -- but nothing, no references just a couple of defending comments by Seaniekc who is, I suspect, one of the authors. He references a primary author Yuri Aristov and Google Scholar give a few interesting hits for "Vermiculite CaCl2 Aristov"

It's worth getting to grips with the basic permutations for wiring a single and multiple lights from a switch, from two switches (which you will probably have) and triple ganged switches (which you may have). Recognise the difference between 2+E and 3+E cable profiles, and remember that lighting power is usually daisy chained so just because a cable is live doesn't mean that it is only for one light. I'd also build up a basic layout map, so you can identify and eliminate cables as you go on, so that there are less options for the remaining unidentified ones. This is also best done a a two person job: one to switch and one to test

As Peter says, you need to differentiate between heating zones and heating circuits. You don't want joins in pipes and the standard pipe length is 100m so each circuit wants to be at most 100m and they all need to be as close as possible to the same length. If you balance them and heat them together and in parallel then this is a single zone. We have roughly 75m² slab so we were goign to have 4 circuits but dead areas under units, etc. dropped this so we decided to drop to 3, but in our case we are using the UFH system to pump at most a couple of kW into the roof environment so 3 vs 4 (and moving to 175mm centres) isn't an issue for us. Given that you have a lot glass and the hot spots that this brings, then staying with the standard 150mm might be better in your case.

We have a slightly different financial dynamic: we did the initial work from our savings, but have funded the bulk by taking out a new mortgage on our existing farmhouse, which we will sell as soon as we can after we are nearing completion, so we are cash constrained before this sale but not after. For us the issue might be exhaustion: if the direct electric solution is cheap enough and good enough, then we'd need a compelling argument to rework the system, for example a 10-year payback or some desirable functional improvements. As I was discussion with Jan at least we would be in the situation we we could say with confidence that we need N kWhr/day heating if the ambient is 10°C, M kWhr/day heating if 0°C, etc.. We do / don't need slab cooling, ... so we could properly size and spec our system.

It is a fantastic view, but you only use two of these to appreciate it: Seriously, I can understand why you have chosen all the window area -- as long as you are happy with the heating and cooling consequences of that choice, and have addressed them in your design. In our case we currently live in the centre of a village in a farmhouse built as part of a ribbon development from 1680-1850s. As with other farms, the farmland that was part of the farm attached to the house was split off and developed as a housing estate in the early 70s. The LPA have insisted that we build our new house which sits in a plot divided off from our garden in a style that is sympathetic to the adjacent traditional stone cottages -- but to our rear we overlook some rather tired and poorly maintained 1970s houses, so no nice view

I've got so much on my plate at the moment that I considering deferring ASHP selection and installation until a second phase starting 12-15 months after we have moved in and settled down. We (actually MBC) have put three UFH circuits in our slab as well as the ducting and electricity feeds. So it will just be a case of retrofitting the ASHP. This also gives a clean break with any Planning / BReg sign-offs. We will need supplemental heating in the winter from day 1, so I am looking at installing an inline heater to drive the UFH as a single zone as @Stones suggests. We will have a far better handle on the heating / cooling requirements after instrumenting the house through a full year of occupation, and we can then correctly size any ASHP or alternative system. PS. I really can't understand all this fascination with glass. @jamiehamy, you must have what 15m² of glass there. It's U-value is at least 10× worse than wall and this must generate up to ~8kW solar gain in direct sunlight which must all play havoc with your internal temperature control.

Oh f***, we are facing the same scenario, but I've haven't plucked up courage to apply. You've just cheered me up -- not.

Jason, with a decent insulation layer and a stone skin, the decrement delay factor is so large that using minimum temperatures is a mistake, IMO. At worst you should use daily averaged minimums, and even consider a 90 %ile or the likes. In our case we rarely get daily averages under -5°C and if push comes to shove we can always get a 2kW electric oil heater out as an emergency boost. But we'll never get anywhere close to that with a 5kVA ASHP. OK, up where you live, it's a bit more wild and chilly during the winter, but I still think that its a mistake to compound contingencies because you still need to optimise your system for the likely load and if you have oversized 3 or 4× then this will be hard to do. In our case, I ran the figure on the extra costs to use the ASHP for DHW and not and doing so didn't give sensible paybacks. We can always rejig our design in a year or two if this assumption was incorrect.

Whatever you get, just make sure that you can get compatible blades, cos an eBay item will prob have well worn ones. You will also need a workshop vac system; my little 150mm one generates enough waste. God knows what a big jobbie will do!!

@jack, I just don't know how anyone can do a build whilst holding down a job at the same time. We picked up most things because we are working one site most days for 10+ hours when the builders are here. Still missed a couple to my great annoyance, but my internal cills are OK. The only prob with the external ones is that we wanted DPC one stone course below and both my builder and stone mason didn't think it necessary so "forgot": "the important one is the DPC above the lintel"

Alex, I think that you've mentioned this before. At the end of the day, your contract was with Ecohause Internorm and non-performance or damage of work carried out by the subcontractors was their responsibility, not yours. I think that their T&Cs absolutely suck, but because that are non-negotiable, your rights under the Consumer Rights Act et al still apply: EI must supply product which is fit-for-purpose and to specification; this includes installation (and the consequences of failures in this). You have right to insist on this. You should put an honest value on the consequences of any installation failures and try to resolve this with EI. The next step is a solicitors letter and the smalls claims court, so if you get no joy with EI then its time to have a chat with your solicitor. In our case the Ecohause Internorm SW installation team did a pretty good job, and the installation leader mentioned that the installation was particularly trouble-free -- they'd costed for 3 days for 3 guys but in the end it took them just of over 1½! @jack, as a result of my IT PM experience I always get paranoid where subcontractors have an interface and in this case of fitting the windows we had 3: MBC for the frame; EI for the windows and my builder for the external stone skin, so I spent a lot of time tying down the exact details of the framing and how the windows were to be supported. I left nothing to an assumption that any one subcontractor would "do the right thing". It is a bit late in your case but I am bloody glad that I did and I've seem quite a few other self builders fall into this bear-trap.

@Mikey_1980, what MBC or any passive supplier does varies from client to client because soils conditions and water tables vary. Mains drainage is only mains drainage when it is connected to the mains, which is very unlikely to happen these days. Our slab design called for us to install a perimeter land drain at 0.5m outside the perimeter of our slab. I cursed Hilliard (the MBC SE) for this at the time because installing it was a PITA for me, but I thanked him many times in retrospect over the next 6 months for him making us do this. He knows his stuff

Jason, If it did then there'd be something wrong with the thermal design of the house. Our net loss in a typical January is estimated at around 11 kWhr / day or less than 0.5 kW sustain. OK our slab isn't going to perform as well as modelled but this isn't going to lift this by more than about 25-30%. If the minimum output of a 5 kW ASHP is say 1.5 kW then it's mark/space ratio should still be around 30% in the depths of winter. And as Nick says, the thermal capacity of the slab will totally dominate any mark/ space ripples. As Jeremy kept repeating: do the calculations and have faith in them. The main complication from a design PoV is whether you are going to attempt to use the ASHP to prime for DHW and to do this you need a TS or a zones PWC as in Jack's case. Here you have to balance the gearing of the ASHP against the extra heat losses from a TS or PWC. Your call.

What I did was to dig a sump hole and let the land drain vent into that. OK, our plot was at the bottom of the garden or our current house, so it was convenient for us to do this manually. Even so, our slab was lower than the gardens on 3 sides, so any heavy rain invariably created a moat around the house at its worst maybe 10-15cm below FFL. Even so we used a pond-pump in the sump hole to dump the water onto the pavement and this could drop the water level maybe 20cm across the entire site in 3-4 hours. The land drain and the MOT3 subbase did their job fantastically -- the moat around the entire house would drop and end up in the sump to be pumped away. This was enough to keep the slab perimeter OK until our builder put in the land drains around 6 months later.

@Barney12, we had a ~450mm gradient over our slab footprint but have gone for a single FFL throughout. The main driver here was keeping the ridgeline down. The rear garden will be terraced, no lawn just paved areas and deep bed planters. The lawn is on the level area out front. I personally feel that having a split level GFL is a PITA and extremely wheelchair unfriendly.

Earthwool is a PITA. It is so uncivilised handling it. We used Rockwool Flexislab 50mm x 1200 x 400mm batts in both our stud partitions and in our intermediate floors. Still not good to handle but a lot better than earthwool and its a lot easier to cut and is self supporting. This is less than current BRegs for the ceiling insulation, but to be honest our BInsp didn't seem to be worried about it anyway. The pre boarding out photos don't show any obvious difference between 50mm and 100mm.

The FFL is a good point. I just used my dumpy and a reference point at the pavement at our site entrance. The dumpy is optional so long as the reference is in line of sight / range of their site levelling laser.

Even so my original comment applies: the MBC team will create a pad that is 1-1½m wider than the house footprint so any corner markers will get wiped out. All www or his surveyer need to do is to bang in 4 rebar spikes well ouside this area to give two taught lines: one for the front and one for a side wall. This will fix the slab precisely so the MBC crew will do the rest.

@NickfromwalesThe mental image of you standing bollock naked under one of those would put a sane man off his lunch.

Dave, IIRC you have a pretty thermally efficient house so the number of heating days (and even modest heating days) should be small -- even where you live. You need to do the maths on the sustained heating demands but reckon on roughly 7W/Km² where the temperature is the delta between the slab and the room temperature (RT). We estimate that we'll only rarely want the slab more than a couple of degrees warmer than RT. This is why JSH went for the approach of using a buffer tank at ~35°C and a mix-down to circulate through the slab at 25°C. This is the approach the we are going to adopt as well. This means that having an AHSP minimum O/P of 30% isn't that much of the issue. You need some control logic, but your ASHP will maintain the buffer tank in the 25-35°C range, and this will trickle feed the slab circuit. The "mark" length will be dictated by the heat required to raise buffer tank capacity by ~10°C in temp, and the "space" dependent on insulation-dependent heat losses around the tank and the draw-down into the slab. I need to play with the heating algos, but my current thinking is to prime the buffer tank at or near the end of cheap rate so the slab is up to RT+ 2 and the buffer tank at temperature by 08:00, then only do buffer tank reheats during the day if needed. As far as DHW goes, we are planning on using SunAmps heated by E7. The SunAmps are raised to full ~85°C using its internal heater overnight, and these are then used to via a heat exchanger and mixer to raise the CW feed from a year-round average mains feed of say 15°C to 45°C or whatever for DHW. In order to use the ASHP in this scenario I would have to preheat the CW via heat exchanger from the buffer tank, but this assumes that we are using the ASHP to maintain the buffer tank at 35°C 24×7 year-round. However we won't be using the buffer tank for slab heating ~10 months a year, so I suspect that the overall heat losses from maintaining the buffer tank at 35° will exceed any gains here. So the bottom line is that we've decided to use E7 only to heat the SunAmps. This keeps the design KISS and has minimal heat losses. Hence the price of the DHW will be the cost of heating actual DHW used by ~30°C (year round average) at E7 rates, except on the very odd occasion where we have guests and a high demand and therefore need a daytime boost. PS, the bloody planners stopped us installing PV

OK, if your underlying base is sand then MOT 1 makes sense. Unless MBC have changed their approach from every other slab that I know of, the same crew will do the ground works, EPS formwork, rebar and pour in one continuous operation over about 6-7 days. There isn't a nice break to invite your surveyor back. Have a chat with your MBC project manager.

I suspect that Nick is talking about the house in general rather than the bath tap. Congrats. We're only about 6 months behind you