Facts use to help professional and property owners to determine root of causes and improve outcomes.
Dehumidifiers are a win-win, in that energy results in reduced vapour and heat, entropy means that turning vapour into water releases additional heat – beneficial in winter. However, dehumidifiers are untargeted, the refrigerant types don’t work well in low temperatures and either need constant decanting or a drain, which is at risk of leaking.
Window rot is common in period properties. Phellinus contiguus or window rot is a slow growing white rot. It is very rare that any timbers are structurally significant, other than prehaps holding a window pane in place. The rot can normally be cut out, sanded, filled and painted for protection.
Houses contain about 4 litres of water as vapour. A normal house typically contains 10 grams per cubic meter at 65%RH at 20°C. A 2.5M high room and foot print of a house is 150M2 = 375 x 10 = 3,750 g or 3.7 litres. (1,000 grams in a litre)
Warm air holds more water vapour, a similar amount is absorbed into walls
White surfaces salts
Mould only grows where relative humidity
RSJs are prone to condensation as the metal is normally in contact with the cold external temperatures, either supporting an external wall, adjoing wall or in contact with the sub-floor void or cold ground. Metal loses heat rapidly when there is a relatively large heat difference between the inside and out.
90% of vapour remains in a bathroom after a shower has been switched off and the occupier left the room. That is why it is so important to keep the extractor fan running for 30 minutes. Strangely most extractor fan manufacturers set fans up with a 1 or 5 minute default and builder’s or electricaians, rarely know to change the setting. This shortcoming probably accounts for more isdiagnosed rising damp than any other cause of dampness, probably accounting for £100M of wasted economic activity in the UK every year.
Cupboards by external walls are prone to mould as vapour moves through diffusion, but heat moves mainly through air currents. Humid air become trapped for hours. Mould needs long term high relative humidity to grow, 6 or more hours at 85%RH.
Vapour causes 85% of internal damp issues