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Have a close look at the picture above. It's what I suggested for the roof. ( Although you could do the whole house) It's from the "monopoly framing" system by Matt Risinger on YouTube. It's a really great concept for air sealing and dealing with thermal bridging in complex house shapes, it's not mine. I rarely have original thoughts! The timber frame is built with no bits sticking out. Then air sealed externally. In this case taping the sheathing. Then any overhangs are added and finally a layer of PIR or maybe Rockwool/woodfiber. Finally the external cladding. Air sealing from outside is dead easy on a timber frame building like this. 10 times easier than doing it inside. Likewise an unbroken layer of external insulation is simple to do and really performs excellently. I would be happy to tape 11mm OSB as an airtight layer so long as you could avoid rain until it was covered.

We had a separate DPC on the external leaf 150mm above external ground level. There's no need for a tray here. Just let the EPS beads fill to the bottom of the cavity.

The orange 150, above, is supposed to represent the height difference across the orange tray. I've just realised the top bar is drawn a little low, & my 2 minutes, or whatever is allowed, of editing time has expired.

We're moving our electricity supply and National Grid said they only put in three phase in this situation. I initially was quite pleased about this - it felt future proof. I'm now looking at solar and battery combinations, and installers seem less experienced with three phase systems and the cost seems higher. There's the benefit of being guaranteed ~12kW export balanced across the three phases. We're also planning to put in an ASHP and I assume that we would now need to put in a three phase ASHP to spread the load over the phases, and again there looks like there's less choice and potentially more cost involved. It feels like going three phase has added cost and complexity at this point. Is it possible to run it all off one phase or push National Grid to put single phase in? It feels like an own goal with three phase to not have the heat pump and battery on the same phase, but then the system will be out of balance. Am I missing something or does it all have to be three phase to play nicely together.

Looking for some assistance with a detail: Need to infill above this window on gable end (lintels are steel beams on inner and outer leaves). The builder doesn't want to use masonry because it won't tie into the steel and he thinks it's just going to end up unsafe. He suggested timber frame, but I guess it would need to be strapped down, which is again problematic over the window. If we go with a timber frame, do you think straps either side of the steel would be sufficient? Timber frame just on the outer leaf? or on both? Any alternative ideas?

I thought I'd put up a clearer picture of the poor detail @Gus Potter pointed out so that anybody who's interested can see it clearly. I'm wondering if the cavity tray went in under a full block (see orange line), this would make the arrangement sufficiently robust. We could also attach some steel brackets under the window (green line), with bolts into resin & appropriate attention to air tightness detail, behind the brackets. I've only just come up with this idea. No doubt there will be a proper way to do it, which will work better & cost less - please advise. The cill projection, at about 100mm, looks vulnerable & is much wider than I want. I've asked for this to be reduced to 45mm.

Yup. Zero discernible diagnosis going on here afaic. I’m stating facts. They’ve not stayed to diagnose, they didn’t rectify the zero pressure on the heating situation, they’re just swapping out knee-jerk items hoping that the most common fault is the fault here. The flip side is that someone better could come and actually do some investigation, and THEN start handing out invoices or requests for deposits; (requesting a deposit for stock EV’s is crazy). This screams of them not wanting to be left out of pocket or holding the baby if their assumed fix doesn’t fix it. I expect they’ll get paid and be gone, but the issue won’t be gone, just forgotten for a while. Cold water coming out of a heated UVC is not an issue for T&PRV, so it looks like the issue is the 6bar PRV has opened on the multi-block which means it is that which has failed; likely needs to be stripped down and cleaned / serviced, and then tested for normal operation, before anything else gets changed at (likely significant) cost. I’d be asking what makes them think the EV’s “have failed?”. I'd be asking if the fault returns will they then come and fix what it actually was that’s wrong, on their dollar. I'd be asking why after a service you were left with a system with zero pressure in it. Just crap. Seriously?

Mine is Proctor Roofshield Standard blurb The Roofshield breathable membrane is unique due to its patented melt blown core and its three layer nonwoven spun bonded polypropylene construction. It has been designed for use as a pitched roof underlay that is fixed beneath the slates and tiles. The Proctor Roofshield breathable membrane will provide you with a secondary barrier to wind, rain, and snow. It is successfully able to eliminate the incidence of inner condensation in pitched roofs due its air permeability and low vapour resistance. If you’re looking for the most cost effective solution to controlling condensation in a pitched roof, then look no further than the Roofshield breathable membrane. This is currently the only product on the market that can offer you all of the following: Air permeability Doesn’t need an additional vapour control layer Hydrophobically treated Low vapour resistance Supplied in rolls of 1 m x 50 m UV resistance Water resistance

DPM then 75mm PIR and joists with 18mm floor boards with UFH system on top (22mm). Not really, it would look really awkward with the rest of the external wall on that side. We have submitted to the BCO now with the timber wall solution from Celotex with the following layers + a VCL between the service void and 90mm studs instead of relying on taped PIR joints. What I'm thinking is that perhaps the service void could be turned 90deg (i.e. lying down) to reduce cold bridges and even make it easier for cables as they will run horizontally rather than vertically. I bet there are good reasons not to do it, but it seems reasonable when thinking about the thermal bridges.

Thanks very much for pointing out this error - I hadn't spotted that one. Although, I don't understand which bits are, "the shaped insulation". I'd expected the air brick periscopes would be drawn, hard up against the outer leaf, & I'd have more EPS beads under the cavity tray & between the periscope & inner leaf, right down to the trench blocks. As it is, there's a gap on one side of the periscope & some unspecified board on the other side. The brick sized cross section at the bottom of the inner leaf, on top of the block & beam, is a Marmox Thermoblock. Yes, it does. Thank you. Yes, it's hard for me to learn, especially with the house build being just one of several significant responsibilities I must devote time to. I am keen to learn all about this, but when I began this project, I didn't imagine I'd be forced to learn in so much detail, to mitigate the losses from people who want to rip me off & others who are just incompetent. I have already been thinking, with his limited talent, this arch tec’ is only going to be able to get us so far & unless I start again with somebody else (4th re-start) with the drawings, I’m going to need to pay somebody who knows what they’re doing to go through everything the current arch tec’ draws & re-work the details he’s not able to design properly. I know I can’t trust my arch tec’s work, because, even with my very limited understanding of what needs to be done, I can spot many errors & I can see he doesn’t fully understand how to do his job properly. Even if I start again with somebody else, there’s no guarantee the next person would be any better. I came across Richard Bendy, who may be the right person to check over the drawings. I haven’t made contact yet: https://www.thehealthyhome.uk Ideally, my arch tec’ would pay Richard to show him where he’s gone wrong, & teach him how to do what I’ve contracted him to do, but I know this won't happen. Richard Bendy's services include training architects. Re. paying professionals: I had a good meeting with a proper architect, who has designed & overseen the completion of some certified passive houses. His quote (& this is for a house that has already been designed to PP level & for which PP has been granted) was £28,272 inc VAT. This included 12 hours for electrical layouts, which my current AT’s contract doesn’t specify, & some of the things that my AT has so far failed to include in his drawings, such as door threshold detail & intermediate floor to external wall detail, were specified in the £28k+ quote. There was also a substantial fee for, “building contract admin, PD & on-site support”, which I negotiated down from the quoted fee to £2,160/month (inc VAT) for the duration of the project. I was told that it would be very unusual to proceed without this monthly fee, but if I chose to do so, I’d be completely on my own once the drawings had been handed over & I wouldn’t be able to call for help with the build (a condition arising from the architect’s insurance policies). So that’s £50k, assuming we pay the monthly fee for 10 months & don’t need any extra drawings. & this fee was based on me providing the .dwg format drawings (which I had only as .pdf) from the AT that I was about to sack, for being quite a lot worse than the current one. A prominent member on here explained, many architects overcharge for work that’s often sub-standard. He highly recommended the AT I‘m trying to work with now. This BH member gives out good advice here on BH all the time & I trusted his judgement. Here’s an excerpt from the current AT’s quote: My fee to prepare a detailed set of construction drawings for a dwelling of this scale and design, including detailed floor plans, 2 x sections, annotated elevations, site plan showing drainage and services, specific details of key elements which require further thought/ironing out such as the cantilevered box and corner glazing and a set of construction notes/specification, would be £6000 plus VAT, 50% of which would be payable upon instruction with the balance payable upon issue of final drawings. This is an all inclusive fee for the complete set of drawings and details. There are no further charges for any amendments required or liaison with structural engineers or building control, or indeed yourself. Therefore there are no nasty surprises further down the line. Thanks again, Gus. I’m away from Friday, for 9 days, so I must just explain: any comment anybody posts will be gratefully received, although I won’t respond until the week after next, because I’ll be having a fantastic time snowboarding & screen time will be limited to essential work comms only.

Lewis deck?

You want to go and look at it, it’s like you gave a load of school kids some crayons and said draw me a load of houses. 😂😂

Honda EU10i working well with my 5yr-old Multiplus offgrid system. I use it fairly seldomly, in winter mostly. Run it at 80% capacity to keep the exhaust hot and prevent carbon buildup. Before the EU10i i had a cheaper Honda frame generator that I couldn't get to work with the Multi.

Sorry - my fault. I should have quoted or namechecked you when I posted, so you'd have receive a notification.

I’m assuming the membrane will be air and vapour permeable to allow vapour out and air in to flow between the gaps in the sarking board? Thats a different membrane to the standard “breathable” type and more than likely expensive. Sorry if gone off topic a bit but just thinking out loud 😁

Just saw now. Will have a look shortly.

You can either suck air from the loft and blow out of room vents, or suck in through room vents and blow out of wet rooms. I prefer the later but either will work. PIV may be easier to install. But either way I would want it humidity controlled to limit ventilation when possible. So fan humidity controlled and room vents the same. This way you only really ventilate where it's needed. So if PIV, find one with humidity control of fan speed Or dMEV fans in wetrooms only, something like Greenwood CV2 or CV3.

Hi I have a 85sq m Bungalow which is pretty well sealed up, so consequently got mould problems. Thinking about getting some window vents fitted and a PIV system, what does anybody think of these, whats a good make to get, should I get one with a heater in or not, are they expensive to run with a heater in. anything I have missed ?Thanks in advance

Tbf who is going to self build anything other than detached?

No it's an MVHR combined inlet and outlet

Do you think those labour rates are accurate for your region? Materials are quite easy to cost up, but humans cost lots these days!

Our perc test failed for soakaways, so our planning has insisted on all surface water being piped into a drain with a rumble strip and then on out to the ditch. Aren't we fortunate?!

Hi GoneWest, Was that a Passivhaus?

Thanks @SimonD - I didn't know about the Type 1 vs 3 thing. Is that in the BRegs? My site is quite a decent size and there will be about a third of an acre left after build for water to run off to, if that makes sense, but I've no idea about this stuff and it does concern me I'll run into issues with BC inspections and sign-offs!

Hi JohnMo, It's a warm construction - PIR outside of stud and OSB3. So unbroken layer of PIR on top of OSB3 (carried by the stud wall) PIR held in place by counter battens. Stud voids to be used as utility voids and probably not insulated unless client wants additional. My question is whether it needs a dedicated VCL over the OSB3 or not. My guess is no - dew point being somewhere toward outer surface of a completely unbroken layer of PIR - where no moisture laden air can reach.