Mike

Worth knowing that, at least in some regions, the water standing charge is based on the size of the meter, so not necessarily good to go with a fat pipe unless you need it / don't mind.

It doesn't necessarily have to be outside - I've seen it I've seen it installed inside in a narrow central London infill house, with boreholes going down through the floor.

The quick answers are: 1 - If comparing blocks of similar density, yes. Otherwise no. 2 - No - standard blocks are more robust 3 - No - for airborne sound block density and thickness are the major factors. For impact sound, you either want a double wall or, on the other side, plasterboard on resilient bars / a fitted wardrobe. A 100mm 3.5N dense or medium weight block is a good compromise, cheap and widely used. Note if you need to chase conduit into the wall, then vertical chases are limited to 1/3 of the wall thickness, and horizontal ones to 1/6 of the wall thickness - so the thinner the wall, the shallower the chases permitted. Which may or may not be a problem, depending on what you're planning.

I've got a Zehnder CA 225, which hits 49dB at 150m³ (about the same as a kitchen extractor hood on low) but I'll eventually be shutting it away behind an acoustically-sealed ceiling trap. I wouldn't put it above a bedroom. The unit + ComfoWell silencers / manifolds + a diabatic HomEvap cooler (on the extract) are squeezed into a space about 750 x 2500 x 400 deep. There are shallower and quieter units available, but it's a matter of juggling size, noise, efficiency and having the pipe connections pointing where you need them (some, like the CA 225, go in one end and out the other, others have all 4 connections on the top). A good place to compare is the Passivhaus list at https://database.passivehouse.com/en/components/list/ventilation_small Not in the Paris area :( I sent enquires to a few I found online, chatted to a couple to make sure they know what I was after, then picked the one I felt happiest with.

Any loft conversion that creates a 'liveable space' (i.e. one used as a room) requires Build Regulations approval. Which, in turn, will mean installing a fire doorset (not just a fire door - a tested combination of door, frame, intumescent seals, etc.). I'm guessing that approval was never obtained, so there may be other important issues that need correcting - they may have sliced through the roof timbers to open the space, or be overloading the joists, for example. Sounds like you need to put in an application and get the situation regularised.

If it's since July 2021 - the last (major) update - it should be fairly good. From then, if they are inaccurate you can seek damages from the landlord / seller / assessor (as appropriate), which is a definite incentive to get them right. Before my current French renovation I commissioned an assessor to model several scenarios. According to them, for me adding MVHR cuts heat lost through ventilation from 43% to 34%. In your case I imagine the result would be more dramatic if the airtightness of the windows is upgraded and taken into account. You'd need space for ducts, which come in various sizes and shapes. You don't need an attic, just a big enough space to put the unit and something firm enough to attach it to. Mine's hung from the ceiling joists. You want MVHR or PIV, not both. But you could potentially have the inlet and exhaust in the courtyard (you want them on the same wall) to take advantage of the cooler air. You could get all 3 modelled by an assessor and then decide.

The response time - electric is directly below the tile adhesive. Hydronic would be slower - it would be embedded in the screed, which would be thicker so take longer to heat. If it's used infrequently that's not likely to be a significant factor.

Sounds like you'd be better off with electric floor heating directly below the floor tiles. Or a wall-mounted fan heater for a really quick warm-up. But do still pack insulation into the void you've dug.

Technically true - I found an article stetting out the situation at https://electriciantraining.co.uk/bs7671-iee-wiring-regulations/ Looks like all EU countries (and some others, including the UK) base their recent national standards on common standards agreed internationally by the European Committee for Standardisation, European Committee for Electrotechnical Standardisation, and European Telecommunications Standards Institute. Indeed those in the EU are required to do so by EU regulation 1025/2012. However there are no doubt some important national differences that could land you in court. For example, here in France I'd prefer to install the Type F power outlets that are found in the majority of EU countries, rather than the French Type E. Both France and Germany share Type CEE 7/7 plugs, so no obvious problem. However old-style French plugs (albeit pretty rare these days) also fit both, but won't connect to earth in a German one, which could be fatal...

Only if the glass is laminated or toughened. Unless you've specified one or the other throughout, then to minimise cost it's likely only been used on glazing positioned where the regulations require it.

One or the other is enough - it just needs to be very airtight. Not that much of a cost - you only need to brush or trowel on a couple of mm thick - the cost is mainly labour. You have a cost whether you choose parge or PIR joint-sealing; probably not much difference.

You can use a superplasticiser, which can significantly cut the water in the mix. If there's less water, it will dry somewhat faster. However they also tend to cut the amount of time that the screed remains workable (from memory, to about 45 minutes), so you have to be set up with a good crew.

Part H, Section 1 of the Building Regulations specifies how gutter sizes should be calculated so that they don't overflow in normal circumstances. Someone should have done those calculations.

In England and Wales, BCOs are required (under Section 8 of the The Building (Approved Inspectors etc. ) Regulations 2010) to 'take such steps (which may include the making of tests of building work and the taking of samples of material) as are reasonable to enable the approved inspector to be satisfied within the limits of professional skill and care that [most sections of the regulations are complied with]'. Consequently they are free to inspect the work as they wish, not just at the set intervals, provided they are being reasonable. If that is during normal working hours, then I imagine that would be viewed as reasonable.

Sounds good! You'll probably need to apply a parge coat over the brickwork to ensure all the joints are airtight. You really don't want moisture (in the form or rain or the like) penetrating the external brickwork to any great extent. It's moisture vapour, coming (mostly) from within the house, that natural fibres are good at buffering (adsorption). You don't want them soaking up liquid (absorption). The U-values of 0.5 & 0.35 that I mentioned are only 'safe' if the wall is protected from rain penetration or ground moisture, which yours seems to be. The Glaser method that Ubakus uses just isn't up to predicting problems with internal wall insulation. None at all - the results aren't valid for the purpose. There are many factors it fails to take into account.

Not if it's indicating that the glass is laminated or toughened - it could be either way. However if you specified a coating on the glass, then that needs to be on the correct face; shine the LED light on your phone through it and the reflection of the glass with the coating will be a different colour - then you need to work out which face it's reflecting from.

Ubakus uses the Glaser modelling technique which, unfortunately, is too simplistic. The gold standard is dynamic modelling (WUFI being the main software used), which takes into account multiple factors - like those you mention (location, orientation, aspect) as well as climate data - and models the element over the course of several years. However if you're not going too low with the U-value then that's normally not necessary. Wall U-values down to 0.5 W/m²K are normally 'safe', while research in Scotland suggest that values down to 0.35 are likely safe too. FWIW I have a very peculiar non-ventilated ceiling that I'd like to insulate to the max (with hemp insulation batts), so I have just commissioned someone to model that in WUFI to determine how low I can go.

It's correct that condensation can cause problems with gypsum & plasterboard, but there's no need to worry at the exposed wall surface. What you don't want though is gypsum left on the original wall that you're insulating, as that's where condensation is most likely.

On my French renovation, I'm using hemp batts. There's at least one UK company producing an equivalent - Hemspan Bio Wall. A key advantage of natural fibres is that (unlike other products) they are usually good at the adsorption / desorption of water vapour - that is taking water vapour from the air into the fibre's cell walls (often a considerable quantity) and releasing it again. There are several technical benefits to that, provided you have a construction that's vapour-open ('breathable') to take advantage of those properties: it reduces the risk of condensation improves thermal comfort by keeping the air within a comfortable relative humidity range for longer improves air quality by keeping the air within a healthy relative humidity range for longer (at <40% RH respiratory infections are more likely; at >60% bacteria and mould thrive) tends to reduce heating and cooling requirements (adsorption of moisture releases heat, desorption takes heat, though research into quantifying this in buildings is limited) There are also non-technical benefits - they use renewable materials, have low carbon emissions, support (potentially local) agriculture, and tend to be pleasant products to work with. On the other hand they take up more space than PU foam or the like for the equivalent u-value. My IWI is 100mm / 145mm thick depending on elevation & space available.

A lifetime of '20,000 hours' is most likely referring to the 'catastrophic failure rate', often 10%, under which no more than 10% of the bulbs should fail within that time. But someone has to buy the ones that make up that 10% - looks like it could have been you For a step-up from GU 10s, without going to sealed units, take a look at @Carrerahill's tip of using Tridonic LED modules. I'll be installing a batch over the next few weeks. The only sealed lights that I'm installing are are in-floor uplighters by Collingwood Lighting - expensive but they've a good reputation.

Not sure what was on that thread, but there's the independently assessed Passivhaus list here: https://database.passivehouse.com/en/components/list/ventilation_small. But you won't find Nuaire among them.

Then the tiles and adhesive. adds up to a bloody lot. Still depends what the structure can support. My 1840s structural timber floor is overlaid with 50-100mm lightweight concrete + 180mm insulation + 75mm screed + floor tiles...

I used the Postsaver wrap on my last fence, but only 5 years back so much too soon to know how well it performs.

I'd follow the manufactures recommendations in full. Well actually, I'd use mortar...

Zehnder mention in their literature that 'Return diffusers or grilles in a bathroom should not be located directly in a shower. However, locating them near the shower is ideal' ...exactly as you are planning :)