MJNewton

I'm confused. You brought the subject of condensation (and it being a problem) up, not us.

Yes, several times now. Zoot won't listen though as he lives in his own little world (by his own admission). I'm wondering why the issue was even raised as it is apparently unfixable because the usual laws of science don't apply.

Damn - no delete. I was trying to make a joke there but reading it back I'm not sure what my joke actually was, and it's certainly not making me laugh. Move along, nothing to see here.... Back to Zoot's pants please.

1 100 ?

Wow, okay, sounds pretty unique. Probably not something I can really help with. Oh, and your humidity meter is faulty.

Now that's not *too* bad (you certainly aren't living in a rainforest despite what your pants might be telling you) with a dew point of 11.5°C, but then I imagine you don't yet have condensation forming - that'll occur overnight as both the internal and external temperatures drop. A dehumidifier would definitely help (reducing the RH to 50% @17.5°C would give a dew point of 7°C so very low) as would ventilation (if we assume the outside temp is now 4°C and 99% RH, bringing that air in and heating it to 17.5°C would give a RH of only 43%).

Book us all on - we'll get a bulk discount. I'll print the thread out and bring it with me. It'll help them help us if they knew what we've been through.

Okay, that's useful. For that temp and RH the dew point is 13.2°C i.e. water will condense out of the air on any surface that's below this temperature. Noting how cold it is getting outside at the moment I could imagine this being quite possible at the bottom of your doors, particularly if there's not much air movement within the room.

Forgive me Zoot but you said something similar about your radiators saying beimg 'hot' to the touch but it turns out they were 40C when actually measured. You were right in a sense, but also wrong given the issue at hand. I'm just interested in figures really. ? Okay, that helps, but honestly - figures would be even better.

You definitely can prove it - temperature and humidity readings inside and outside will show whether you're living in a rainforest or not, and from that you'll/we'll be able to work out what you might be able to do about. Don't be so quick to give up.

Personally I think it has some relevance but is more of a red herring. Like your carpet underlay debacle, I suspect you'd likely find that the frames and units are actually similar/same as those fitted to millions of houses (like mine) across the country, many of which don't suffer condensation issues (again, like mine). Heat loss, and by extension, surface temperature of windows/whatever is important but you should be focussing more on improving heating and ventilation whilst reducing the creation of water vapour to begin with as they are all within your direct control.

I wouldn't be focusing on the frames - I suspect you've got a temperature/humidity/ventilation issue. What's the temperature and humidity in that room like? Last thing at night and first thing in the morning when you discover the condensation would be the ideal measurement times. Middle of the room measurement, not near any wall/ceiling/door.

My preference for a 'real' outside temperature was just an issue of accuracy as my nearest weather station is around 10 miles away and any discrepancies could really throw out my calculations of heat exchanger efficiency/performance.

Basically, given you've got different duct lengths and rooms with different flow rate requirements (eg large rooms vs small rooms, kitchens vs bathrooms vs en suites etc) then you need to 'balance' the flow rate to each vent to give that which is desired. It's not too dissimilar to balancing radiators but instead of throttling the lockshield valves you throttling the ducts by either screwing/unscrewing the outlet plate or, increasingly common, putting in restrictor rings inside the ducts where they join the manifold (the bit where it branches out from a single large duct to the smaller individual room ducts). The latter can be a bit trickier (opening up the ductwork, swapping rings in and out) but does mean reducing a potential source of noise (throttling airflow increases noise) by doing it well away from the rooms. There's loads of information about, but have a start with this thread:

I don't, but I'm wondering if they are overplaying the noise issue somewhat? My unit is nothing fancy (Titon HRV1.25 Q Plus) and I don't have any issues whatsoever with noise. It is mounted on the gable wall in the loft of a 2007 Persimmon-house which aren't known for great noise blocking construction. It sits on some old exhaust hanger rubbers which likely helps. Attenuation of the ducts (for balancing) is done at the manifold (unit) end rather than at the ceiling vents so that may help somewhat at the rooms end. Certainly we don't hear anything in the rooms apart from when boosting but that's not intrusive by any stretch (just airflow; no fan noise or anything) and believe me my wife would make it known if it was! ?

(I forgot to add...) ... as a rate-of-rise humidity sensor so it boosts on a >5% rise in 5 minutes.

I added a Pi-based controller as I was finding the built-in humidity trigger to be a bit hit and miss. The threshold was set on the unit but it was an absolute threshold so just when I got the balance right it'd need tweaking as the seasons changed. Sometimes it wouldn't trigger when I expected it to and sometimes it'd do so when I didn't. As I had an unused Pi Zero and humidity sensor I put it to use even if it was a bit overkill. To lessen this though I add temperature sensors to the four main ducts so I could monitor (and graph) its performance. Useful to begin with when I was still learning about MVHR, and I still look at it occasionally now. Handy for knowing the outside temperature too, and I've always liked graphs. ? I may expand it to have greater control over the summer bypass and summer boost if I get some time to do so.

Great to hear the heat now appears to be coming through, but another slap of frustration given that the suggestion to disable weather compensation was made back in November. If that'd been followed we might well have all been saved from 40-odd pages of toing and froing since, not to mention given Zoot a warmer Christmas. Sigh.

...although not if the TRV is in a room with a thermostat. In that case the TRV should be left open otherwise they'll 'fight' (eg TRV closes down leaving the stat still calling for heat if set higher than what the TRV wants).

On the Domus plenums the interface between the plenum and the 125mm pipe doesn't have a rubber seal - it's just an interference fit between the plastic surfaces. Reasonably airtight but prone to slight movement so I think tape is worthwhile (I've got a feeling the instructions advise the use of sealant).

They were a reasonably good interference fit but, yes, for completeness I did run some aluminium tape around the join (on the inside as access was easier).

I should note that I didn't have any height/clearance issues so didn't need to consider slimline fittings, so don't assume my decision to use GU10s was because the alternatives weren't any good (I don't know either way).

Fair enough. I'll leave you to it.

Come on Zoot, learn to find some information for yourself rather than just asking us about everything. Try Google first and if you get nowhere after reading a few articles post back and I, and others, would be more than happy to help. You really are taking the pi55 now and I am increasingly feeling being taken for granted. Here's the link: https://www.google.co.uk/search?q=setback+temperature

For what it's worth mine's a bank of five and is fine (on a Varilight Pro with the default Mode 1 trailing edge). With Ikea Ledare's I have seen some flicker when multiples are used, but that aside they're not too bad a bulb with a CRI of 90 which is better than most, dim-to-warm and only £2.50 each! The flicker can usually be resolved by just tweaking the brightness level ever so slightly but life's too short for that.