Cognis0

...I should have said that this is retrofit into a 16th century cottage, not a new build before the ceilings go up!!

I've just started installing a Zehnder MVHR system and I'd be grateful for advice/observations about fixing the plenums/valves. These plenums have a flat top section which need (it seems) to be fixed to the underside of the floor above! I'm not sure what the designer had in mind, but can't see how it is feasible to fix the plenums in place in this manner. Once the plenums have been fixing between the joists I then have to fix galvanised "Circular Long Threaded Mounting Frame Vent Galvanised VRGLs" into the plenums (adhesive?) for the valves to screw into.. The whole design is nonsense ~ surely it is not beyond the wit of man to design room extract/intake valves that can be installed entirely from below ceiling level once the 75mm flexible ducting has been fed through from above?

Why would it fall down?! As I said, this would need adequate support at the top, which is normal with these radiators. "side wall nowhere near as strong.." Not sure what you mean by that, my walls are 24" of solid stone! Cast radiators are not inefficient, they are far more effective than modern steel radiators and our flow temperature will be about 40 degrees (from heat pump). Apologies of I did not make myself clear, but the advice I was seeking was about the water circulating through the radiator and if this could be plumbed BBOE...

My civils/structural engineering background makes me inclined to think these radiators are actually more stable on their ends..!

A silly question I'm sure..! Anyway, there is limited wall space so I'd like to consider mounting a 4'x2' plain type Edwardian cast iron radiator vertically (on it's side). Of course its heavy, so I will need to craft some feet to fit and provide adequate support at the top. In plumbing terms is this likely to cause any issues with water circulating through the rad? Can I plumb this BBOE (both valves at the bottom)? Thanks...

Yes, that sounds about right. I'm sure there are better ways to do most things...!

Yes, a simple flow path from supply to extract is what I have suggested (extracting air from the bathrooms as well as the bedrooms), and the flow path from ground to first floors seems more logical than the complex air movements produced with wet room only extract. The standard methodology doesn't make much sense to me ~ a bathroom produces water vapour for half an hour so in the mornings and I read somewhere the average shower puts about 250ml water into the air, so a lot of air/vapour needs to be extracted relatively quickly. Whilst sleeping a person puts about the same amount of water into the air overnight, but this needs to be done at a slower rate extending over the whole night. I am sure I will end up with a standard installation, but I do have doubts about the current methods used...

Although I spent years planning for a Passivhaus new build, having failed to find a suitable site we have ended up in a 16th century origins thatched house!! With an old house I had abandoned the idea of MVHR, but with the amount of condensation and mold we are seeing this is now back on the table. Before I get started on working out what is needed, there is a fundamental issue it would be good to get feedback on. Most of the condensation and mold we see is on and around bedroom windows over-night/morning. Bedrooms also have lots of dust and who knows what else in the air which needs to be extracted. So to my small brain we need to see extract vents in the bedrooms rather than supply vents. In fact my limited brain power tells that the best whole house ventilation solution would be to have air extracted from all of the first floor rooms with heat-recovery fresh air then being supplied back to the ground floor reception rooms (open plan arrangements). Fresh/warm air would then rise up the central staircase and back to the bedrooms... Please let me know what is wrong with my logic here. Many thanks

That's helpful, thanks Iceverge...

I've removed the ceiling in our lean-to extension to form a nice airy/open kitchen/family space. I plan to insulate between the rafters with 140mm flexible wood-fibre and then over the top with 60mm wood-fibre t&g. On top of this, for VCL/airtightness, I was thinking of using Passive Purple liquid membrane in white which would also provide a decorative finish. This should avoid the need to scim plaster and paint. Does anyone have any comments/see flaws in this plan?

Thanks, that's helpful. Can you please clarify what the issue would be with an anode? I am a bit mystified by EASHP which also reheats the ventilation (or some with wet heating). Most of the heat coming through the MVHR is recycled by the heat exchanger back to supply; by the time the DHW is heated it's difficult to understand what energy can be left to provide any meaningful contribution to space heating! Cheers....

Hi @Gone West.. Can you recommend EASHP unit? Vaillant do the aroSTOR which looks interesting. Would you recommend a single supplier/installer for all MVHR and EASHP together? Thanks

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Would you mind sharing which company designed/supplied your MVHR kit? Many thanks.

Although members here have tried to set me on the right path and divert my "unhealthy" interest in PVT, it remains alluring and is still on my radar. A Dutch company, Triple Solar, have been supplying PVT panels for heat pumps for some time (over 1000 installations I think), and have recently launched their own dedicated heat pump: https://triplesolar.eu/pvt-warmtepomp/ . They claim an SPF of 5.6 for space heating and 3.8 for DHW. As an alternative to digging up the garden for ground source, this seems to be very attractive. They don't yet have a distributor in the UK, but I will do more research and post anything I find which might be interesting. If anyone has observations at this early stage I would, of course be delighted to read them...