Bitpipe

Another rise coming in October and maybe some respite summer 2023, however dependent on what happens with Ukraine and global energy prices in general.

Not sure this was addressed above but is you hob extract venting directly to outside or is it recirculating? If the former then that will seriously unbalance your MVHR system and may compromise your airtightness such that the MVHR is not effective. You still have a few dead zones which may be troublesome.

You are welcome. I learned it all the hard way

@SteamyTeahas a hit rate of about 1:1000 posts

Great advice above, especially this... My MVHR design & install process had a few distinct phases.. BTW this was all trial and error for me, made loads of mistakes along the way. 1) Airflow strategy: Effectively a refinement of what you've done above but using the suggested principals above.Start with a supply per habitable room and an extract per 'wet' room (kitchen, WC, bathroom etc) Forget about ducting right now but draw arrows on how air will go from supply to extract on your floor plans, navigating doors etc. You should then spot any 'dead' spots and address. Also think about additional extracts near a recirculating hob extractor for example if you find that more than a few metres from the general kitchen extract (as we did). 2)Then think on how you'll join these together and do duct runs to the intake and extract manifolds - irrespective of length we used two runs per extract and one per supply. Retrospectively we should have doubled up ducting on a few very long supply runs but not a big deal really. Duct routing can be diagonal through web joists (shortest path) but will need to navigate around steels and other structural elements. They also have a fixed bend radius which can come into play when you have a lot of them coming together at the manifold. By this stage you should have an idea on total duct length. It usually comes in 50m lengths so round up and maybe add an extra one for unforeseen circumstances. You'll also understand how many ports your intake and extract manifold will need (one for each length of duct) and where these will live. You then need be able to calculate the wide bore steel duct, including bends, angles etc to get from your manifolds to teh MVHR and from your MVHR to external intake / exhaust points. These last two will need insulated as cold air from outside will be coming in one and out the other so they will attract condensation. 3) you're more or less ready to order ducting materials. Steel duct will need adhesive and tape for the joins while the flexible duct just slides into position and is secured with supplied clips or catches in the plenums / manifolds with o-rings making the seals airtight. Silicone lubricant spray is a must to make that an easy job. Builders strap is handy for supporting all kinds of ducting if there is not sufficient local support (like a web joist). 4) At this stage you should have an awareness as to whether steels need penetrations pre-fabricated or where there may be a clash of space with other services (usually foul pipes). Sometime you only realise this when the structure is up which is why having some redundancy in your duct supply is useful. 5) I've not considered any electrical aspects here - your unit will need a 13A supply (plug top or isolated) and you may need to run cable for a secondary wired controller. Boost switches etc can be taken care of by your electrician. You'll also need to run condensate from the unit to a foul drain. 6) install should go to plan but as above, it's easy to miss an obstruction and need to go a longer way round so be prepared for that. This is also where you finalise position of the plenums (wall or ceiling) as structural considerations may dictate that - make sure plenums are installed with the duct ports pointing in the direction that the duct will be coming from to avoid sharp bends. 7) once all plenums are in place (and I faffed about a lot with this) start to run duct from the manifold area to the duct. I found this much easier that the other way round. I used to screw a plank across a doorway and through the centre of a spool BEFORE cutting the ties on the spool so that it could unroll somewhat easily. If you just open the spool, it will knot up very quickly. Equally, pre-cutting lengths is asking for trouble as you risk them being too short or having too much waste. Once the end of the duct is secured in the plenum, cut a generous length next to manifold and move to the next one. You just need to label ducts as intake or extract at the manifold end as a minimum (I used red and blue sharpies). Not a whole lot of use labelling per room. You can then trim each duct and connect to the relevant manifold - this was harder that it sounds as too long or too short and you won't make a good connection. Some trial and error here (obv going from too long and trimming incrementally until perfect fit). '8) Ducting the wide bore stuff is a different game - four connections to make and depends on where your external intake, extract, manifolds & unit are. Leave room to insulate the external ducts. 9) At this point you're done from a first fix point of view. Cut plenums flush to the plasterboard to make life easy for your plasterer and pop in the duct covers. You probably won't mount the MVHR unit itself until second fix. Good luck!

This link has some advice, https://www.gocompare.com/mortgages/buying-at-auctions/

Our build up was 150mm compacted type 1 50mm sand blinding 300mm EPS 200 (could have got away with 200mm) - 200 grade specced by SE, you may get away with 150 (which is same compressive strength as your EPS). DPM Concrete construction. We did not have UFH in the basement slab, but if we had it would have just been tied to the mesh. Using just EPS would simplify your slab sandwich and remove need for second sheet of DPM.

Best revenge is a life well lived. Be prepared for Mr N to tell you what a great house you have in a few years when it's all done (what happened to us).

Did you plan for any walk on glazing? Asking for a friend ( @pocster)

Welcome, I think we need to send out a BuildHub delegation to inspect your works when complete!

Very impressed you got those holes so close together. No idea if that's a good idea or not I remember doing our MVHR through the timber frame, had made no provision for penetrations in steels or frame so was totally winging it. Had to take out a few noggins to get all the duct in, house still standing...

Agree with Nick (obvs) - we only use our electric UFH in the bathrooms to take the chill of the tiles. Do you have space on the roof for a few PV panels to contribute to running the system?

Welcome, have you looked at a plot with a house already on it? Quite often buying a dilapidated property that'e being marketed as renovation can be cost effective to demolish and rebuild as you still get the zero rated VAT and if the house / bungalow is very tired you'd be stripping it back to the bare bones anyway. Plus services and access are already taken care of.

For our bathrooms we put a 6mm insulated board on top of the OSB, laid the wire mat on that and covered with 4mm ish self levelling latex compound. Provided a nice flat surface for tiling but would have suited laminate also.

Well, not so sure about that... This is a real risk - friends built a basement near us and found an underground Thames feeder stream running through their plot during survey. Had to de-water during build (expensive) and SE designed a very meaty slab to prevent the hydrostatic pressure pushing the basement out of the ground. As it was their rainwater harvesting tank popped out twice during the build. I can see the logic here, we had a small area where our external basement stairs come to ground level and while it made sense for the excavation & retaining wall to follow the line of the stairs, was much simpler to just chop out and cast a square box, what you loose on the additional muck away and concrete you gain on speed and simplicity of construction. From their data sheet, https://www.recticelinsulation.com/sites/default/files/downloads/Eurothane GP Technical Datasheet.pdf the compressive strength of 150mm board is 140KPa for 10% deflection, so almost equivalent to EPS 150 grade. By comparison EPS 200 which our SE specced has a strength of 200KPa for 10% deflection. EPS 250 and 300 is often specced for sub slab applications also. The calculation will depend on the weight of the whole structure above the insulation and point loads will factor also - one for your SE. WRT insulation thickness, you need a thicker EPS sheet than PIR to get the same R Value - we used 300mm for under the slab and 200mm (of EPS 70 grade) for the outside basement walls - so the trade off is more excavation & muck away vs cost of PIR / cost of EPS. You can obviously stack up individual thinner sheets of insulation to get the thickness you need or buy as a single block.

We have no shoes policy in whole house. Have resin on GF which is non conductive underfoot so always feels warm irrespective of whether UFH is active (only comes on during winter). Engineered wood upstairs and karndean in basement, both behave similarly. Bathrooms have ceramic tile and we have low power (150w) electric UFH there to warm it in mornings, just to take the cold feet feeling away.

Yup. Our house is basically square so the four first floor bedrooms are identical in size. Ours has a dressing area and ensuite so feels bigger but I've never understood the need for a mega bedroom suite. Kids are the same and there's a guest room also. The two rooms in roof are probably the biggest bedrooms in the house but neither used much really.

The MBC crew (all Irish) would always go the extra mile for a bacon sandwich.

Early in the build I arranged for a full skip to be collected. The window installers had nudged it out of the way with their tele handler so it was in an awkward spot. Skip driver came and said he couldn't get it out, I would need whoever put it there to put it back. I said that was not possible, so he replied that he'd do the extra work 'for a drink'. I said 'Great, tea or coffee' and an awkward silence ensued. Penny dropped. Gave him a fiver and he got on with it.

Two adults, two teenagers in a, just under, 400m2 passive house. 4KW PV on roof which brings in around £750 per year in FiT etc Pre price hikes we were looking at under £4/ day on electric and under £2/day for gas averaged out over the year - so £6*365=£2190. Subtracting the FIT gives £1440. Gas usage has not really changed since we moved in, about 12,000KWh per year but electricity usage is ticking up past 7,000 KWh as the kids get older.

Look, you have PP which you can start to move on - go ahead with some ground works i.e. limited demo works, site clearance and (drainage etc) and get your BC (would always recommend private vs LA) to acknowledge this as a formal start. We did similar bits and bobs - demo of garage, some extension of fouls to connect caravan (but they were part of final services plan) to formally commence some 8 months ahead of the proper works themselves.

Will be a whole new app but should be straightforward.

Correct, however given it won't change the elevations or massing I doubt you'll have much issue. We got planning on the second go with a 1/2 basement - original issues were ridge height and some other aesthetic details that we simplified. Once secured, we went back to planning with a full footprint basement, ground level light wells etc. Zero comments and a quick approval. Having a dedicated plant room makes life easier also - frees up useful living space and makes your first fix easier. Also building into a slope will be less complex than digging a big hole like my & @Thorfun's basements and BC won't be as concerned about means of fire escape (we needed to choose between sprinkler or independent exit, going for the latter). Also water management is easier as a good land drain to the rear plus either waterproof concrete or external tanking (or both) should suffice.

Not sure what value a passageway would add, you're effectively doubling up on the wall requirement (ok, in this scenario the rear wall is timber and the retaining wall more substantial).

Great, that will be useful for your SE also. Get a few quotes, you may be surprised. There are often economies of scale in groundworks. You may also save by simplifying other aspects of the design. Also, if you create extra space, you don't need to fit it out initially. Standard ceiling height is 2400mm (conveniently the size of a plasterboard sheet) our ground floor is just a smidge under this at 2350mm and it feels fine. First floor is 2300, also feels fine so 2575mm should feel spacious. Yes, works well for them as they don't do any concrete work other than the slab. However you can should get a quote for your own passive style slab & 3/4 basement wall from a groundworker - it's really just a concrete wall/slab with appropriate EPS underneath and to the sides. We did our basement like this and it was straightforward for MBC to drop their frame on the top. They waited until it was in place and came to do final measurements before putting frame into production so no surprises. You could have suspended timber floor for the dining / kitchen level also (would need some steel to support) and if you go for a low energy design then the UFH only needs to be in the ground slab - also that heating is in the slab itself, not on top, so you save on screed and on slab insulation.