Bone Dry Ungood

Cripes is Ireland damp for about 5 months every year. When we came home to Ireland after spending the 1980s+ in foreign, we canvassed opinion about what was essential to know / do / acquire to live our best lives At Home. MaryC was strong in her advocacy: "get a tumble drier; vented to outside". Later we acquired a polytunnel which (regardless of tomatoes, wood-storage and my second-best sofa) served primarily as a laundry aid. Even if we give clothes an additional blast with the tumbler before folding them away in the press. So we are not, like Dau.I and Dau.II, in their teeny Dublin flat, forced to dry laundry on a rack in our living room. 

The drier sort of deals with our laundry-damp [other damps are available] but not the fact that we live, breathe, bathe, and braise in a house built in 1941with 500mm thick rubble-in-courses masonry with no [rising] damp-proof course. The kitchen windows weep visible condensation. The walls are also sopping: it's just harder to see the dribbles . . .and the black mould against the grey granite. A month ago, Dau.II cried enough with the musty cotton goods and bought a MeacoDry Arete® One 12L Dehumidifier for their tiny 2-bed TigerBuilt flat in D7. And last week we followed CanDo Yoof and bought another. Come in, roll up, it's R2D2's kid-sister [R] sucking water from the air and saying Farewell to Fungus. We left the machine [its refrigerant actually] to settle for 2 days and then switched t'bugger on. It registered 95% RH [relative humidity] which was unsurprising: 24hrs after a yellow rain warning that had gone on and on for 18 hours.

How much water vapour can a room support aka is the R6X6 reservoir large enough to bring our kitchen down from 95% RH to 55? Turns out it depends on the temperature [see table under]. But the bottom line / rule-of-thumb is that our 4m x 5m x 3m = 60 m³ kitchen "only" holds about 1 litre of water. We set La Demoiselle Dehum going at 16:00hrs and 95 RH. When I went to bed 7 hours later, she had cranked the kitchen down to 65 but by 06:00 the following morning we had reservoir is full and RH had crept up to 76. Clearly this a work in progress.

°C	g/m3
-20	1
-15	1½
-10	2
-5	3
0	5
5	7
10	9
15	13
20	17
30	30
40	51
50	83
60	130

Being too dry indoors is also a problem: we are designed with wet mucous membranes which allow lungs to get oxygen and these membranes are also the first line of defense against microbes. Too dry and the macrophages cannot patrol and you'll get sick. 

Also wooden furniture. In 1967, my Dad retired from the Navy at 50 and bought a cottage + acre at the edge of the commuter belt for his new workplace East of London. It was before the end of cheap oil and, in winter, the family cranked up the central heating. Until he noticed cracks in some of his inherited dining chairs. Thereafter all the rads acquired a humidifier: a plastic reservoir with a 20x20cm square of porous sponge to wick up the water and disperse it to the circulating air. One of my teen-tasks was to fill these reservoirs with a dinky water-can. It was a neat cheap-as-chips appropriate technology solution.

For most domestic purposes the aim is for 40-60 RH. R6X6 trips off at 55. 

• Storing apples for the winter is best at ~1°C and 95% RH
• Storing flour 50 - 65
• Mixing dough 40 -50
• Proofing dough 70 - 75
• High RH was one of the reasons why N England became the centre for cotton spinning rather than doing this nearer the point of production