Mike

Not answering your question, but why would the alucald ones need replacing after only 9 years?

That's an interesting proposition and an attractive price. I wouldn't recommend it to someone unfamiliar to the industry though, not unless they're confident taking on the contracting + payment + variation processes by themselves, or unless their architect is going to get involved in them.

That's an unusual octagonal access hatch...

And Ubbink have a 180mm pipe / duct adapter to suit? So you'd screw the tile upside down (sideways?) - I guess physically that could work, provided you can get the duct connections within the space. However if upside down then the upturned cowl would be liable to collect snow / leaves / other debris which might cause a maintenance problem, and you'd also need the exhaust duct sloping back towards the MVHR unit (it couldn't fall towards the vent as otherwise there's a risk that the upturned cowl would collect condensate too), but that may not be a problem to achieve. Sideways would probably be preferable. However, what's the problem you're trying to solve & why are you trying to avoid regular wall terminals?

It's not an exciting topic, but here's a YouTube video that illustrates, in detail, how a Bill of Quantities is prepared in accordance with the common NRM2 standard: https://m.youtube.com/watch?persist_app=1&app=m&v=nshlJXDRZds The BoQ reflects the architects / engineer's drawings, so it will only be as right as they are. If they change / have items missing / don't reflect actual conditions on (or in) the ground, then they will no longer be right. Based on the BoQ, a QS can use their experience to provide you with an indication of the expected cost of the work. If they have recent experience of similar projects in the same geographical area, then the chances of them being in the right ball-park are fairly good (except when market conditions and prices are rapidly changing), but they won't be 'right' (spot on). It's also worth knowing that small contractors may not be used to pricing BoQs item-by-item due to the time and money it takes, so may not do so; they may normally price from drawings alone. If they give you a lump sum instead (or anything less than a fully priced BoQ) then the BoQ will be less useful (perhaps not useful at all) in assessing the value of work undertaken (for payments) & the cost of variations once construction starts. On the other hand, if you do get fully priced BoQs from more than one contractor (3 are typically asked), then you or your QS can usefully compare them and also sport potential errors in pricing. And, as @saveasteading says, if you get different contractors to price different parts of the BoQ, rather than going to a single contractor for the whole, then there will be items that fall through the gaps. Not to mention that any delays by one contractor that impact another will likely result in additional costs - and the same if it's you that's causing the delay. So using a QS isn't a panacea, but can be useful - particularly if you plan to choose a single contractor.

Not sure what you man by 'under', but first check that they can support the required airflow rate No problem, provided they respect the distances from windows required by the Building Regs.

Yes, I'm sure they must (in Europe, at least) to avoid damaging the heat exchanger. Here in France we get extended sub-zero temperatures from time to time and, since I have an apartment, it doesn't take long for the air quality to deteriorate without the MVHR air supply or an open window. As that's the worst time of year to open a window, it was definitely worth the the extra €300 for the preheater. But, in a larger home and/or somewhere with milder winters, that would be a lesser concern.

Just pulled up the standard text on the topic from the PassivHaus certificate, which provides some guidance: Indoor air humidity can be increased by using a system with moisture recovery in a cool, temperate climate, especially during the winter. These higher humidity levels will reduce evaporation from building elements and furniture during the heating period and thus have a positive effect on the building’s heating demand. In order to account for this effect, the heat recovery efficiency is increased by a certain percentage, depending on the achieved level of moisture recovery. In case the unit’s moisture recovery rate is larger than 60 % its airflow rate must be controlled based on the indoor air humidity, in order to prevent temporarily elevated humidity levels. Application of humidity recovery: ■ In cool temperate climates, heat exchangers with moisture recovery should generally only be used if the moisture load inside the building is comparatively low (e.g. in a residential building with an occupancy rate significantly below the average). ■ If moisture recovery > 60 % is to be used in a building with an average occupancy rate and typical use, the energy balance of the building is to be calculated with an increased airflow rate. While the heat recovery efficiency may be increased, enthalpy units have no advantage in that respect compared to standard units, when looking at their database as a whole (though Efficiency Ratio, not heat recovery rate, is the key figure).

My knowledge of the French industry is limited, but I've not come across any reference to that profile being fixed with adhesive over here. I've only seen them used standing off the wall (so that insulation can be fitted) on adjustable nylon brackets - though the brackets can be fixed with with adhesive in new build, as per the 3rd of these images.

+1. I seem to recall that they're more commonly used in Nordic countries.

A few options: Have a structural engineer design a heavy traditional cut roof the roof capable of resisting wind loads without straps (Building Regs Approved Doc A says 'vertical strapping may be omitted if the roof: a. has a pitch of 15° or more, and b. is tiled or slated, and c. is of a type known by local experience to be resistant to wind gusts, and d. has main timber members spanning onto the supported wall at not more than 1.2m centres') Cast a suitably heavy reinforced concrete ring beam around the top of the wall and fix the roof to that - again, a Structural Engineer would be required for the design and to prove it is adequate Fix the straps to the cavity face of the inner leaf, subject to the knock-on impact of this on insulation / cavity closure & satisfying your BCO.

Not the first time we've had that stupidity. Since it's presumably too late to reposition the post here's one potential solution - search for others. The cold will still travel through the steel, bypassing the insulation so not going to solve the problem.

Very entertaining! Never has I seen such cheer in the face of such financial pain. Great architecture though and yes, the site manager was a star. Looking forward to the follow-up in 5 / 10 / 15 years time...

+1 to a door between entrance & kitchen - in fact I'd probably make a full hallway:

Prior to looking at active cooling solutions, consider passive measures to minimizing the build-up of summer heat within the building. In particular solar shading of windows and the use of wood fibre or hemp insulation to maximize decrement delay, plus the use of appliances with high energy efficiency ratings to minimize their heat output. For active cooling, take a look at using underfloor central heating in cooling mode.

You can - floatovoltaics :)

The main box is an attenuated manifold - item 990323502. Plus you need one end plate with a 150mm connection to suit your 150mm duct (item 990323568, by the look of it), and one end plate with 10 pipe connections (75 or 90mm - 990323614 / 990323615 depending on what you have). So yes, 3 items in total. Check those codes though! Yes, something counter-intuitive happening there - something to do with the extended dimension -v- the wavelength, I suppose. However I note that the figures on the last line - with the 10 x 75/90mm end plate - are different to those in the French brochure. Either the English or the French figures have to be wrong (though whichever is correct still gives good attenuation). I just went looking for the German version, but the one I found doesn't quote any figures at all... Looking again at the French figures, they give them for two connected boxes (160mm end plate + manifold core + manifold core + 10 x 75/90mm end plate) as well as for the single arrangement; the result is more intuitive: 32Hz is really low - I guess it's not normally a concern. I don't think you actually mentioned which MVHR unit you have, BTW?

Here's an alternative for the North East corner that doubles the wardrobe space in Bed 4, and removes the WC from the Bed 3 wall, albeit at the expense of bedroom width in bedrooms 3 & 4. You could probably rework the en-suite & corridor end to avoid cutting space from Bed 3. But everything's a compromise. There's space at the end of the corridor for a shallow storage cupboard.

Having slept in a bedroom with a bath and over-bath shower against the wall (by coincidence in that split-level house), it was a problem for me.

It's true that it can impede mobility on the ground floor but, having lived in a split-level house, it was an interesting & worthwhile feature.

Overall it looks fairly well thought out. A few of minor points: Ditch the sliding doors off the Master Bedroom for something quieter. The wardrobe space in Bedroom 4 is not very generous. Ensure that the partition between Bedroom 4 and the adjacent bathroom sound-proofed Ensure that the partition between Bedroom 3 and the adjacent en-suite is sound-proofed Where will the SVP serving that en-suite run downstairs? For safety, move the hob away from the corner of the kitchen island Do you really need 3 sink bowls in the kitchen (and 2 more in the utility)?

+1. If the Frankische unit is in good working order, then there is nothing to be gained by replacing it. Just build a well insulated enclosure around it - something that should have been done when it was installed and something that your 'specialist' should know. And something that a replacement unit should have too. Several Frankische units have PassivHaus certificates confirming their suitability in cool temperate climates. The larger version of the Komfovent has a similar certificate (and similar-ish performance - compare the Efficiency Ratios), so there's no particular reason to choose one over the other on those grounds. The common reason for choosing an MVHR unit with a rotary heat exchanger (such as the Komfovent) is that they can - if the right materials are used - recover moisture from the outgoing air and transfer it to the incoming air, preventing the air within the building from becoming too dry (which can be an issue in cold climates where the air already has low relative humidity). Komfovent suggest that their units can do that (they "regenerate[s] humidity in winter"), however the PassivHaus certificate for their larger unit makes no mention of this - which suggest that they didn't get that aspect tested & raises a doubt about how effectively it can do it. It also introduces another mechanical moving part which can go wrong. Perhaps, due to their large commercial range of rotary MVHR units, it was just easy for them to scale down their existing rotary technology for their domestic products? BTW, if the Frankische needs replacing for other reasons, then that PassivHaus database is a good place to look for quality alternatives.

Zehnder aren't cheap, but that looks like list price. It should be possible to knock at least 30% off that. The supplier I used (in Germany but delivery to France, not sure if they'll deliver to the UK post-Brexit) are currently offering the main body at a 43% discount (€205 including VAT). You also only need one unit to silence 10 terminals.

Very useful results. So it is the lower end of the frequency range causing the problem. If I were choosing only between the 2 Zehnder options, I'd choose the silenced manifold. BTW, results would normally measured at 1m distance from the source of the noise (ceiling terminal in your case), so the chances are that the 14dB reduction provided by the silenced manifold at 250Hz would be enough, even if your chart suggests that you have 42.5dB of 250Hz noise a few mm away from the Bedroom 2 terminal. You could measure again at 1m to give help decide. No - that is for the manifold only. It helps to know that the manifold is modular - that is you can fit different 'end plates' to it depending on what you want to connect. The results in the table above are measured for the following: a connector plate for 1 x DN160 or 180 or 200 duct on one end (the first part in yellow) a connector plate with 10 x 75 or 90mm semi-rigid duct connectors on the other (the second part in yellow) the CW-S520 is the main body of the manifold (not in yellow). Note that there is a regular manifold body too, without the sound attenuation - the 'S' indicates that it's a silencer version. You would want a connector plate for a 150mm duct (Zehnder 990323568, by the look of it), which isn't one of the ones they used in the test, but the size is so similar to the ones that they did use that performance would undoubtedly be similar / identical.

BTW, to illustrate why it's useful, compare the frequency attenuation of the Zehnder CSI (above) with this one for the Zehnder silenced manifold that I mentioned on the previous page: The silenced manifold beats the dedicated silencer at frequencies of 63, 125, 4000 & 8000 Hz.