[Greenbuilding] Relative humidity in heated houses

[jfstraube]

Rob Tom said
> I've just assumed that it was understood that too low humidity has the effect of drying out the protective mucous layer on our nasal membranes making them and us more susceptible to cold and flu viruses, not to mention the "crusty nose" syndrome, dry itchy skin, dandruff etc.
> 
> Me ? I like the feel of 45-60% interior RH in winter, which I don't find at all surprising given that our bodies are roughly that percentage water.

These are true physioloigcally proven responses, AT LOW RH, which means usually well below 25%RH (not 40%!), and I think (experientially) below more like 15% (and I am pretty sure there is a problem in airplanes, which have RH levels sometime below 10%).  People dont usually have a good sense of the RH in their space. I carry a Kestrel 3000 with me whenever I travel to measure RH, and compare it to my reference at UW from time to time.

I dont know what kind of a house you have Rob, but in Ottawa, museums stuggle to maintain 50%RH, let alone higer, in the winter, and they use special construction, triple glazing, heated windwo frames, etc.  Double glazed residential windows have rivers of water flowing off of them at 50%RH during Ottawa winter nights.  How do you manage to get to 60%?

PS. Much of our evolution occurred in the savannah's of Africa, which have modest RH levels at best, and it is this reason that we dont evaporate too much water even though we are mostly water.