DAMPNESS AND MOULD IN HOUSES IS UNHEALTHY

Bay of Plenty Beacon, Volume 13, Issue 60, 4 March 1949, Page 6

DAMPNESS AND MOULD IN HOUSES IS UNHEALTHY

The presence of mould on the walls or ceilings of rooms is not only unsightly; it is costly and unhealthy since it calls for frequent re-decora-tion, and damp living conditions cause illness. The Department of Scientific and Industrial Research, from the investigations extending over a considerable period undertaken by the Dominion Physical Laboratory, have shown that the cause of mould, (excluding extraneous conditions) is the prevalence of a high humidity indoors, and this humidity arises mainly from insufficient insulation in the walls and ceilings of the houses and from inadequate natural ventilation of the rooms. Observations were carried out duing all seasons in both modern and old houses in many localities, and it was concluded that the insulation in many houses was below a moderate standard, and that the rooms of all houses of modern light construction should be provided with natural ventilation capable normally of giving at least three changes of air per hour when windows and doors are closed. Emphasis is placed on the necessity of keeping fanlights or windows open in calm weather—and especially at night. Mould Spores

Mould spores are ever present in the air that circulates about the home. They will germinate and grow wherever size and paste used in paper-hanging, and the casein of distemper, are available as food, provided the relative humidity approaches 100 per cent for at least three days. Whilst it is rare in New Zealand for climatic conditions alone to be such as to maintain this high humidity, the research has shown that the occupants of a house cause the high humidity that is favourable to the growth of mould spores, and this growth is encouraged by calm wet weather. Other things being equal, a cold house is damp compared with a warm house because it requires more moisture to raise warm air to a given humidity than it does for cold air, and if warm air is cooled its humidity increases. This would suggest that there is a contradiction in the recommendation for more ventilation, but extensive investigations show that adequate prevention of high humidity can only be maintained when there is a maximum permissible heat loss through walls, ceilings, floors and windows, together with a minimum appropriate ventilation rate that must not be lowered.

In many houses of recent construction, insulation is required in the wall cavity, since this space is commonly flooded with cold air. The object of the builder has apparently been the prevention of dry rot, but it has been found in some cases that the air changes in this space have been up to 60 times more than is necessary for this purpose. Insulation ,of the wall cavity should not be attempted without consulting an architect. It may be that insulation of the ceiling will prove sufficient. ' Rock wool is recommended, because it is vermin proof, and it should be laid on top of the ceiling boards between the rafters to a depth of two to three inches, with possibly a strong paper covering tacked to the rafters to prevent the material blowing away.

Tests Of Ventilation V/ith regard to the tepts of ventilation, it was found in houses of modern type that are air changed four to six times an hour in a closed room with a brightly burning fire; without a fire but with an open chimney it might change twice an hour in calm weather and three to four times in breezy conditions; and in a clcfeed room without an open chimney it might take nearly two hours to make a complete change of air in calm weather. The investigations indicate the difficulty of securmg ad equate ventilation in all room:--.. In breezy v/c-aihc-v an open ch'm my c.• an chic kwh system c natural vwvkwtkm 1n a room is generally sufficient, but in calm weather it is clearly necessary to supplement the air by throwing open the windows as well.