haddock

The house is located in sunny Manchester. We do have some dry spells here and there isn't any correlation between rain and the problem, so that's one reason why I'm thinking it's condensation. (There is a strong correlation between outside temperature and the problem however.) I've also had hosepipes running on the roof for long periods through dry spells without any effect. It's been ongoing for three years now so the damage you're seeing has been very gradual. I can't remember the figure but the airtightness test on the house was apparently very impressive, so surely I'd see symptoms like this if the MVHR wasn't working as it should? There is definitely an insulation problem however — part of the skylight support has a long metal flange that runs continuously from the interior to the exterior. Up on the roof on a freezing night it is warm to the touch when all the other glass and metalwork is icy cold. Just because I think I have a condensation problem and I presume running it too high isn't going to cause any trouble(?) Once the issue is resolved, I'll see how low I can take it without causing a problem.

Good morning, I've been doing some experiments today trying to understand how my MVHR is supposed to work and wondered if the experts here might be able to help. I say supposed to work as I'm having a lot of water dripping from the ceiling around skylights, where moist air is coming into contact with colder surfaces: In the garage there's a Brink Renovent Medium which I have running at 290m3/h and a Brink Allure gas heating system which blasts hot air through floor vents around the house: As well as the floor vents in every room, there are three ceiling grilles, one in each of the three bathrooms. You can see a floor vent and a bathroom ceiling grille in this pic: There's a much larger grille at ceiling height in the main living space: My highly scientific experiments with cigarette smoke and a hygrometer have determined the following: 1. Each floor vent blows out a lot of air, and there are a lot of them, maybe 15 to 20. The total flow rate must be quite impressive. The heating fan can be set to blow air all the time or only when it's actually heating. When the heating is active, the air coming out of these vents is very low humidity. I can't discern any air coming from them when only the MVHR unit is running, but the output from the MVHR would be so thinly distributed anyway. The metal grilles do feel surprisingly cold when only the MVHR is running, so perhaps fresh air is trickling out. 2. The three ceiling grilles in the bathrooms suck in air all the time the MVHR is running, but the one in the main bathroom is barely working. The air flow at these vents is the same regardless of whether the heating is running. 3. The large grille in the living space has really surprised me this morning. It blows out air when only the MVHR is running, but sucks it in when the heating fan is also on. In both cases, the flow rate is high. I did wonder where the heating got its air input from. This large grille is right where all the condensation damage is occurring (see previous pic), so it seems key to find out whether the living space is supposed to be ventilated by air flowing in or out of that grille. I can then configure the heating fan to stay on all the time, or only when actually heating (which is not very often as the house has a massive solar gain). If you're still with me, here's a floor plan: Possibility A: Air is supposed to flow into the large living space grille (heating fan on all the time) In this case, the air would primarily be moving from the floor vents in the living space, right to left as shown in the plan, and into the large grille. Possibility B: Air is supposed to flow out of the large living space grille (heating fan only on when heating) In this case, air emerges from the large grille in the living space and eventually makes its way to the three bathrooms where it's extracted. If this is how it's supposed to work, I'm not surprised there are problems because (a) the only thing sucking air across the long skylight in the living space is the grille in the main bathroom at the top of the plan, and it isn't working properly, and (b) what if the doors are closed?? I have water dripping from the ceiling today and the girlfriend just got dripped on, so I really need to get this sorted out! Haven't had the heating fan on for weeks so if (A) is how it's supposed to work then that'll be why. If you made it this far, thank you! Max

Many thanks for the background on this. Main takeaway for me is that the flow rate is too low to cool the house really effectively, but it's still something I'd like to get sorted out. I've had a quote of £1,000 to retrofit the official Renovent automatic bypass but wonder whether the money might be better spent getting a new unit from another manufacturer that has a built-in bypass and also humidity/CO2 sensing. I'm currently running the Brink at full blast (300m3/hr) all the time because there's a problem with huge amounts of condensation forming in the ceiling voids. That may be a posting for another day.

Really struggling with these hot nights and unfortunately not having a summer bypass fitted on my Brink Renovent HR Medium. Can't leave windows open because it's a bungalow and, well there aren't really any, only patio doors. Unfortunately not a good idea to leave those open at night around here. Tonight I've tried improvising a summer bypass by simply removing the heat exchanger (and the filters) from the unit. To be honest it's rather late and I can't quite get my head around the effect of this. Will it just be pumping air in and directly out without going around the house? It doesn't seem to be. The temperature at the floor output vents has dropped by 2 degrees already so I'm wondering if this harebrained scheme might actually be working!