Green Building Bible, Fourth Edition |
These two books are the perfect starting place to help you get to grips with one of the most vitally important aspects of our society - our homes and living environment. PLEASE NOTE: A download link for Volume 1 will be sent to you by email and Volume 2 will be sent to you by post as a book. |
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Posted By: jamesheathHi,
My understanding is that mechanically ventilated houses have
a) a higher rate of ventilation then normal houses
b) dryer air generally
c) more evenly warm rooms
Posted By: GreenfishSo no mirror heaters, but do think about power in the bathroom.
b) MVHR means that the Relative Humidity inside the house will track the RH that is outside. If you live in the warm and damp western side of the UK (> 80% outside, and only 10deg cooler) then inside it will never feel dry or even rarely be below 60% inside unless you run an air conditioner or dehumidifier.
Posted By: djhYou are absolutely right, that is a better way to express it.b) MVHR means that the Relative Humidity inside the house will track the RH that is outside. If you live in the warm and damp western side of the UK (> 80% outside, and only 10deg cooler) then inside it will never feel dry or even rarely be below 60% inside unless you run an air conditioner or dehumidifier.
I think it's less confusing to say that the specific humidity inside tracks that outside, since the relationship between the relative humidity inside and outside isn't simple tracking but also depends on the temperature difference.
My house doesn't follow that rule though and it markedly differs from the PHPP predictions (it's more even and mostly stays between 45-50% all the time) so humidity buffering can clearly be important in some circumstances.
Posted By: GreenfishWhere are you located a dry part of the country?
And curious any build specifics that could provide the buffering?
Just want to emphasise that location/local climate makes a big difference to internal RH. I was quite worried when I first got a hygrometer and measured the RH to find we were above the golden 60% value. Yes the new plaster was still drying, but even after that RH below 60% is rare unless I heat the house up more than we need. Then I did the sums. If it is a persistent 20C and 80% outside like we had this summer then the MVHR will pull in that moisture, and at 20C indoors the RH will also be 80%.
Our house is always warmer than outdoors so we never have RH as high as outdoors, but our outside RH is never as high as 80% except when it's raining, plus or minus a bit. Are you close to some permanent water?
Posted By: jamesheathWith that in mind, do I need mirror demisters?Yes. I love the fact that (a portion of) the mirror never steams up. I just bought the really small Demista, Ă‚ÂŁ20, 5W does the job perfectly.
Posted By: djhWesthall is another place near the coastApart from the altitude difference they seems closely matched.
Posted By: delpradoWhat is the view on towel radiators? I guess electric so it can be on at any time of year when heating is off?
Posted By: GreenfishMVHR does a good job at drying towels, but it helps if they are opened out not tightly folded. More open hanging space for them would be good.
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