Barnacles Posted January 24, 2022 Share Posted January 24, 2022 Hi all, i am looking for a small MVHR system for our holiday rental property. We have a lot of condensation and mould problems in the en-suite bathroom and the bedroom suffers slightly from the same. I am looking for a system that will cover the bedroom and en-suite and possibly the living area too (thought there’s no damp/mould etc in there). Unfortunately there’s no way I can incorporate the kitchen in the design, there’s just no way to get a duct to it. The bathroom is small (about 7sq. m) and has mostly solid stone rendered walls. The bedroom is about 22 sq. m and has one stone wall. The living area is 28 sq.m. There is a small cold loft space above the bedroom which is likely where the unit will live, thought f the unit were sufficiently small it could live in the airing cupboard off the bathroom. I had thought that I might use a Vent Axia HR100-R unit and leave the living room out of the system but with an efficiency of up to 70% in a building that struggles to maintain a comfortable temperature already I decided against it. Then I started looking at Boulder and Blauberg’s smaller units but they seem to be inefficient to run. So that brought me to Brookvent’s Aircycle 1.2 (which I have used before in a new build that we did a few years ago and was pretty happy with) but I just can’t shake the feeling that I’m using a sledgehammer to crack a nut. Does anyone have any suggestions or recommendations please. I am trying to keep the spend down (but I don’t want to cut corners) and space is at a premium so the unit needs to be reasonably compact. Thanks, Paul Link to comment Share on other sites More sharing options...
mike2016 Posted January 24, 2022 Share Posted January 24, 2022 What about trying a humidity triggered fan in the bathroom? Something more automatic as people are probably not opening windows etc when taking showers / drying clothes indoors? A dehumidifier on a smart plug / set to a timer to run if you can get one that has a condensate drain? Link to comment Share on other sites More sharing options...
Cpd Posted January 24, 2022 Share Posted January 24, 2022 20 minutes ago, mike2016 said: What about trying a humidity triggered fan in the bathroom? And one in the kitchen as well, it could be a Quick fix, this is what I did in my rental and it sorted out the problem, yes you loose heat but the air is dryer and dry air is easier to heat than wet air…. I don’t mind paying a bit more for electric as long as the lace is clean and mould free. Insulating all cold faces is another very good way at reducing damp. Link to comment Share on other sites More sharing options...
Barnacles Posted January 24, 2022 Author Share Posted January 24, 2022 Hmmm, that's a different way to come at it, interesting. There is a bog-standard humidity controlled extractor fan in the bathroom already but with all the cold surfaces in there it's just doesn't cut it, we still end up with pools of water on the window sills (also stone!!). Insulating the walls would likely be impractical due to the amount of space we'd lose. My only concern with a dehumidifier would be the noise. I haven't used one for about 20 years but the one we had was really noisy, have they got any quieter in recent years? You're spot-on Mike2016, people don't open windows etc. What ever solution I go for has to be fully automated and tamper proof. One thing is for sure, if there's something for guests to tamper with, they will tamper with it ? Link to comment Share on other sites More sharing options...
JohnMo Posted January 24, 2022 Share Posted January 24, 2022 Have you looked at dMEV, easy to install, silent and runs all the time. Just need window vents open or specific wall vent to give good, draft free, cross flow ventilation, you could also include the kitchen in the scheme. No heat recovery though. Or dMVHR, with heat recovery worth reading up about. Link to comment Share on other sites More sharing options...
ProDave Posted January 24, 2022 Share Posted January 24, 2022 MVHR is the way to go. It is constant ventilation you want (with a boost speed when showering) Just get the smallest unit you can find, fresh air into living room and bedroom, exhaust air from bathrooms and kitchen. Link to comment Share on other sites More sharing options...
Radian Posted January 24, 2022 Share Posted January 24, 2022 2 hours ago, ProDave said: MVHR is the way to go. It is constant ventilation you want (with a boost speed when showering) Just get the smallest unit you can find, fresh air into living room and bedroom, exhaust air from bathrooms and kitchen. Smallest = ~£1K right? Link to comment Share on other sites More sharing options...
MikeGrahamT21 Posted January 24, 2022 Share Posted January 24, 2022 PIV might be worth looking into for this... Link to comment Share on other sites More sharing options...
SteamyTea Posted January 24, 2022 Share Posted January 24, 2022 I would have thought that the best (in price and thermal recovery efficiency) you can find would do. The real cost is in the fitting, especially in a house already built. If you can relatively easily plumb it into the bathroom and kitchen, you are more that halfway there. You can plumb in the rest at your leisure i.e when doing other work or major decorating. Like ASHPs, being oversize is not a problem, they just run slower and quiet, with better efficiency. Link to comment Share on other sites More sharing options...
Barnacles Posted January 24, 2022 Author Share Posted January 24, 2022 I've spent the day looking at various options and concluded that MVHR is the way to go. The layout doesn't really lend itself to PIV, I did almost plump for a dMVHR (as much to make my life easier on the install as anything!) but then in the end I figured I that MVHR is the "belt and braces" approach which will hopefully tick all the right boxes. I have quite a few bits and piece left over from previous MVHR and A/C installs so I can save money on the overall spend and I found a Nuaire unit for £699. Along with the other bits I need to buy I should be able to bring it in under £850 or so and I'm happy to fit it myself as it's relatively easy to work in the loft space. It's still more than I wanted to spend initially but if it cuts down on the maintenance and keeps the place fresh it's got to be a winner. Many thanks for all the suggestions and advice they're very much appreciated. Link to comment Share on other sites More sharing options...
Dan F Posted January 24, 2022 Share Posted January 24, 2022 (edited) Have you seen Lunos? They have various options incuding MVHR, none of which use any ducting, with really good efficiencies. https://www.partel.co.uk/lunos-decentralised-ventilation-systems Edited January 24, 2022 by Dan F Link to comment Share on other sites More sharing options...
Barnacles Posted January 28, 2022 Author Share Posted January 28, 2022 Just a quick update. I bought a Nuaire MRXBOX unit which arrived earlier this week and I've spent most of the week cramped up in a cold loft doing the installation. I'm almost there, I just have the condensate drain to connect up next week. The Nuaire unit is very compact and neat and looks to be well made. I can't wait to get it fired up and see what a difference it makes. Just as a side note, having read a few opinions on the subject I decided (controversially) to try drawing the supply air from within the loft through a filter box. It's the first time I've been in the loft since buying the place and there's a lot of mould on the underside of the membrane so I believe there's not enough ventilation in the roof space. My thinking is that by drawing the air from the loft it will pull fresh air in to the loft and better ventilate it. I realise that in summer the air in the loft will be very warm and my solution is just to turn the MVHR unit off in summer as most guests have doors and windows open most of the time anyway. I'll be keeping an eye on it and if I notice any adverse side effects I can easily drill another hole in the outside wall and run another duct. As ever, I'm grateful for all the knowledge, wisdom and help offered here ?? Link to comment Share on other sites More sharing options...
ProDave Posted January 28, 2022 Share Posted January 28, 2022 6 minutes ago, Barnacles said: Just as a side note, having read a few opinions on the subject I decided (controversially) to try drawing the supply air from within the loft through a filter box. It's the first time I've been in the loft since buying the place and there's a lot of mould on the underside of the membrane so I believe there's not enough ventilation in the roof space. My thinking is that by drawing the air from the loft it will pull fresh air in to the loft and better ventilate it. I realise that in summer the air in the loft will be very warm and my solution is just to turn the MVHR unit off in summer as most guests have doors and windows open most of the time anyway. Let us know how that goes. Okay if there are air vents from outside into the loft. If not you might find it draws air from the rooms into the loft to provide the supply air? Link to comment Share on other sites More sharing options...
Barnacles Posted January 29, 2022 Author Share Posted January 29, 2022 18 hours ago, ProDave said: Let us know how that goes. Okay if there are air vents from outside into the loft. If not you might find it draws air from the rooms into the loft to provide the supply air? Yeah, I was worried about that. There are some air air vents but they are small. The bathroom currently has an extractor fan in the ceiling which is ducted through the loft to an outlet. Once the system is running and the bathroom extractor fan is rendered obsolete I think I'll leave that outlet open to allow more air into the roof space. The outlet is at the opposite end of the building to the MVHR unit so it should pull air right through the loft. If it's not sufficient I'll stick in a few strategically placed soffit vents and see how that goes. The building envelope does appear to be reasonably well sealed but I'll be running around with the silicone or expanding foam where there are pipes and cables that puncture the envelope. I'll keep you updated. Link to comment Share on other sites More sharing options...
SteamyTea Posted January 29, 2022 Share Posted January 29, 2022 If the loft space is thermally isolated from the rooms below, I think it is a good idea. If you add up all the flow rates you can work out how much cold air will get drawn into the loft. Link to comment Share on other sites More sharing options...
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