Do you mean that the outside rh was 82%? Does your MVHR system measure outdoor as well as indoor rh, I wonder?
That is correct. My MVHR monitors 4 relative humidities, air taken into the system (Outdoor Air), air supplied to the house (Supply Air), air extracted from the house (Extract Air) and air expelled outside (Exhaust Air).
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Thanks, Tim. That’s impressive.
Zehnder ComfoAir 350Q
The figures on the screenshot don’t add up if you try converting humidities. That is because my condensate drain is flowing like a mountain beck.
Good stuff, thanks. Our indoor measurements are, temp= 18degC to 20.5degC (depending on which room etc) and r.h.= 45% to 65% ; would we expect sensations of dry skin and/or dry eyes in these conditions? Not that I’m thinking of denying what my partner has told me… just trying to understand it all, esp re. possible ASHP installation.
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45% to 65% is mostly in normal range, with 65% being above it. No, I would not expect any dryness conditions associated with the range in question.
However, everyone is different, so I suppose it’s possible. If you do deliberately increase humidity be aware of any cold corners or spaces out of normal circulation, such as fitted cupboards, and check for the first signs of mould. Not that it is likely at anything below 80% but cold areas will have higher humidity.
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My instinct is definitely against increasing indoors humidity because a) humidity is often fairly high already, and b) there have been some patches of black mould as humid air has hit cold areas, eg reveals of older, not-yet-replaced windows - this has been greatly reduced by the dMEV constantly extracting from the bathroom to outside, and c) in colder weather, higher indoors humidity can often contribute to (subjective) sensations of coolness. I think.
Humidity can magnify sensations of cold or heat, which is why British winters can feel colder than Swiss ones and jungles can feel hotter than scrubland at the same temperature.
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As winter has got cooler and the humidity in external air has dropped we have found that one room, the master bedroom, has developed a lower humidity during the day. This is less the case in other rooms but activity in those rooms may be adding the missing moisture.
The master bedroom does not feel dry to us with a humidity of 30% or less. In fact during overnight occupancy you can see the humidity rising from 27% to 31% and then falling again during the day. The room has an MVHR inlet valve.
The MVHR humidity readings at the time of the above are
So external air is being supplied at a humidity of 24% and the average house humidity at extraction is 37%. No cooking, showers or baths are in progress. There are clothes drying but they are now adding very little humidity, having been washed overnight and been drying all day.
If the humidity, or lack of it, in your home is causing dry skin then an active humidifier may be needed. Mrs G and the children all use moisturisers but then African skin tends to be dry. If the dryness is irritating the airways it should be addressed urgently.
After considering various external shading options for the first floor I’ve decided that we have to go the internal route.
I visited the blinds-2-go website and found that I could enter a referral code. I presume that you have one if you can find it. Would you mind sharing on this forum?
I hope you get something for each person that orders using it.
Will check & get back to you
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Hi Tim,
We have no code as the purchase was made in 2021.
Apologies
Not to worry. It was just an off chance. It would have been nice for you too if you got rewarded for referrals.
Thanks for looking.