Mike

If it's not too close to the hob it could. Another possibility may be to run concealed ducting boxed in over the top of the kitchen cupboards, if you have any, to give more flexibility.

Yes, as per @BotusBuild's photos. It's not required to vent the rooms, however you appear to have 8 ducts pumping air into the ground floor, and you need to pump that same amount of air out from somewhere. If you have only 4 extract pipes, the airflow in them will (on average) therefore have to be twice as fast, and that speed could be more than recommended to avoid noise. You'd need the calculations to know if that's so, but it's possible. You do need extract directly from the kitchen, but away from the hob, and ideally on the far side so that the air flows across the room. As a compromise a wall-mounted vent could work (in the kitchen-dining room wall), unless you want to make to make a feature of a suspended metal pipe & vent.

Don't use chemicals. I use a pressure washer with water only and it works no problem.

You could certainly feed 2 separate manifolds, one for each side of the beam.

If you are building a new house, it's entirely possible to achieve well below 2. As you mentioned in your first post, the Passivhaus standard specifies a maximum of 0.6 ACH and thousands of those have been built. I've seen air test results mentioned below 0.2, though that is exceptional. However achieving that does depend an a high standard of work and attention to detail that you'll only get by using a well trained staff with hawk-eyed supervision (preferably your own). If you're using a single main contractor then you could specify achieving that (0.6 ACH @ 50 Pa) as an essential requirement. If you split it into packages, then you may literally need to take matters into your own hands, and allow enough time for it. Still a flawed assumption. It assumes you have house at ambient outside temp and its the coldest day and you never recover any heat until until at full temp. +1. On top of that, your UFCH will result in fairly constant temperature throughout the day, even if you heat it only during off-peak hours. It's not at all like a radiator system where the heating comes on for a few hours in the morning and evening and needs to respond quickly to achieve the required temperatures, before temperatures drop significantly while it's off. It's not sensible to design the system to be sized to heat the building from cold within X hours; instead it need only be sized to maintain normal temperature on the coldest day of the year. That does mean that if you move in in December you may need to plug in some electric radiators for a while, but after that you should be good.

Always a good idea if you can. However, at least in England & Wales, it is necessary for sewers to be vented to the open air in places so that the sewer gasses - which are toxic and can be explosive - can safely escape. That's normally required at the head of the sewer run, and every few properties (often 5) along the way. That is covered by Part H of the Building Regs, section 1.33: Ventilated discharge stacks may be terminated inside a building when fitted with air admittance valves complying with BS EN 12380:2002. Where these valves are used they should not adversely affect the amount of ventilation necessary for the below ground system which is normally provided by open stacks of the sanitary pipework. If you are required to have an open stack, there are a couple things that you could consider. One possibility, if you're not more than 2 stories high, is reducing the pipe diameter to 75mm diameter(Section 1.32). Another, if you have a nearby detached garage, is to extend the sewer to that, then run the vent pipe out of the garage roof. And, as @Thorfun suggests, it's normally possible to hide top of the pipe with a vent tile.

From the apparent thickness of the wall in the image, I suspect a cavity wall. A measurement of the actual wall thickness would give a good idea. If it is a cavity wall I wouldn't accept the door as installed. @Conor has mentioned several problems, and for a cavity wall I'd add the bypassing of (1) any cavity wall insulation, current or future (2), the vertical DPCs that should have been used where the cavity was closed, and (3) the cavity tray that theoretically should be above the lintel. I'd wonder what they've done about the DPC at floor level too.

Me too. And oil-filled ones can make a real mess when they leak.

@Redbeard is correct - there is a requirement to ventilate a timber frame cavity. No - air contains moisture, and if you lower the temperature enough it will condense, with or without a VCL (although it's sustained high relative humidity that's the problem, rather than the incidence of condensation). The presence / absence / continuity of a vapour control layer will however affect the flow of moisture vapour passing into (and out of) the insulation from / to the room, as will the presence / absence of good controlled ventilation within the room. You also have moisture tracking through the wall from outside, which no VCL will control - from rain, for example - which can be a bigger factor than moisture from internal sources. A ventilated gap behind the insulation can be essential or useful in some specific circumstances - for example if the wall is so irregular that a gap between the wall and the insulation in unavoidable in places (unventilated gaps are always to be avoided), or if the wall is subject to driving rain and it's not feasible to render it / apply a vapour-permiable sealant, or when wanting to achieve very low U-values.

And generate hydrogen sulphide - which is toxic, corrosive & flammable.

I wouldn't touch them myself, but that's a personal reaction to the grotty 20- or 30-year-old panels we used to rip out back in the 90s. The technology is now much better and they are generally well regarded.

I can't help you there - I'm able to do it myself. But no doubt someone else will be able to give you a clue. Think of the heating oil you'll save, rather than the cost :) Most products will have manufacturer's recommendations or BBA certificates to support their use so, if you present everything professionally and on paper it need not be a big issue, at least not for thermal insulation.

Someone will have to do you SAP calculations, so ask them to include the report - much cheaper than paying lawyers to sort out the mess + the cost of rectification afterwards. If they do it properly and include the supporting evidence there should be no grounds for the BCO to dispute it.

It does - see Appendix A, page 75.

No, it's not wide open to interpretation. Part L 4.13 defines it: If achieving the U-value in Table 4.3, column (b) either: a. is not technically or functionally feasible or b. would not achieve a simple payback of 15 years or less then the element should be upgraded to the lowest U-value that both: a. is technically and functionally feasible and b. can achieve a simple payback not exceeding 15 years. Generally a thermal element once upgraded should not have a U-value greater than 0.7W/(m3'K). A lesser standard for the thermal element may be acceptable where work complies with Part C of the Building Regulations on protection from the harmful effects of interstitial and surface condensation.

From the outside to the MVHR unit, and from the MVHR unit to the distribution manifolds all the connections should be compatible with regular 200mm metal spiral ducts (DIN EN 12237, I think), so yes, you should be able to mix and match brands here. For the 90mm semi-flexible duct from the manifolds to the individual room outlets, there's a good chance that everything will be compatible, but it would be safer to ask the supplier as I think they're outside the scope of the standard (though they may all come from the same factory in China). Or use your consumer rights to send back anything bought online within 14 days if it's not compatible. FWIW I bought unbranded 75mm semi-flexible duct and it was compatible. It's recommended to minimise the number of bends on the main ducts. If you can't physically do that then the resistance of the bends becomes more important and a brand with smoother bends may be preferable.

WUFI, however i's not cheap and not straightforward, so normally only used by a consultant and when risks are thought to be high high. Which is why people generally use rules of thumb or manufacturer's recommendations instead.

A few observations: That's very disappointing, and something a good contractor should have spotted as a problem, irrespective of the 'architect'. At a guess, they aren't RGE qualified? I'd choose one that was for any further work - or a different one, if they are. Sounds like a good plan to boost the insulation. I'd consider wood fibre and Rockwool, though would prefer cork to either if the budget would stretch that far (it's a 'good' thermal & acoustic insulator, breathable, fire-resistant, non-toxic, & pretty solid - but expensive). And certainly improve airtightness as much as possible. Thermal phase shift (decrement delay) is a useful concept in connection with summer heating where the insulation makes up most of the material between inside and outside - for example in loft rooms - though having the PIV pumping in warm outside summer air would probably nullify any benefit. Where stone / brick / block makes up most of the thickness, that material will dominate the calculation. Where it's useful, in France 10hrs+ is considered a useful target. I did calculate it for my 145mm hemp-insulated mansard and, from memory, it was around 9 hours ignoring the timber sarking; with the sarking it was very much longer. Ubakus isn't useful for calculating moisture risk; it uses the old Glaser method which only considers a single point in time. Condensation in the insulation is only a problem if it remains as water for an extended period, and Glaser tells you nothing about that. Nor does it take into account the adsorption / desorption of water vapour that is particularly pronounced (and beneficial) in many natural insulations, including Biofib Trio, and absent from most (all?) non-natural insulations.

Domestic MVHR units have space for 1 intake filter and many people would just rely on that. Adding a filter box before the MVHR unit allows 2-stage filtering. The additional filter is normally significantly bigger, so can last for longer without changing it (useful if the outside air is particularly dirty). You can then use a finer filter on the MVHR unit. Alternatively filter boxes can be used hold a carbon filter - they can remove smells, VOCs and the like that regular filters can't - perhaps including cigarette smoke, if the main MVHR filter isn't cutting it (though feedback here is that they normally can). You'd want a regular filter before a carbon filter, so you'd install it either between a first filter in a filter box and the MVHR unit (in the same filter box, if it's an option), or else between the MVHR unit and the supply manifold.

I've mostly constructed single-sided metal stud partitions to create a void that's filled with either 100mm or 145mm of hemp-based insulation (100mm wedged behind the studwork everywhere, plus 45mm within the depth of the metal stud itself where external rain penetration is unlikely or impossible). In case you're wondering, the use of timber for studs in virtually unknown here in France. In a few places where space is tight - reveals, for example - I'll be applying 20mm of cork insulation direct to the existing wall, probably bedded in a thin coat of plasterboard adhesive (scheduled for late November). In preparation, the plaster on brick/stone walls was hacked off and replastered in sand - hydraulic lime to even it up and improve airtightness.

Yes, it's a cheap win. Heat is typically lost through insulation over the course of days, but is lost through air leakage within minutes or hours.

True, and improving airtightness should be a priority where feasible. But efficiency doesn't have to be the objective, particularly if rooms are stuffy with mould growing, though there are indeed other options apart from MVHR.

At a guess, they still have a shortfall in alternatives after loosing & taking nuclear plants off-line with the Fukushima disaster?

Welcome to the forum - an interesting challenge. What's wrong with the loft? A loft / garage / kitchen (or anywhere else) would be preferable, even if the bedroom is little used. Not that MVHR is very noisy, but at night noises seem louder, and I'd not consider it myself. It may be better to wait and incorporate it into one of those future extensions you mention. Unless you can easily swap the hot water tank into the wardrobe & put the MVHR where that is - probably unlikely though. For efficiency, the best place to look is https://database.passivehouse.com/en/components/list/ventilation_small? - the Efficiency Ratio is the most important number, but not the cheapest units. It's good if it's a solid wall. (Over)sizing the unit so it runs at low speed is a good way of minimising noise in general. Not in principle. Very short lengths - just enough to undo the connection - are OK. Not sure that many people do it though. Swapping the gas hob for electric would significantly improve the air quality.

You've got it - that's what you're looking for: Hot water temperature at supply connection min. 2 °C higher than mixed water temperature :)