Ventilation and moisture control

Ventilation is the primary method used in housing to purge ‘stale’ inside air, cool indoor temperatures, and provide a feeling of air movement. Introducing ‘fresh’ outside air indoors often improves oxygen levels, reduces airborne toxins, and reduces humidity levels (Baggs et al. 1996). Through all these functions venting assists with physiological and psychological comfort (Ballinger et al. 1992). Reducing and controlling moisture inside houses is important in cold weather because a high level of moisture indoors leads to the growth of mould. Mould can affect occupants’ health. High levels of moisture can also undermine building materials and structures (Waters 2001).

Ventilation can be achieved by opening windows and doors, constructing mechanical or passive vent holes, or through permanent gaps in building structures. All houses in the study could be vented, but a few only had limited opportunities (Appendix O, Table O-1). Paul and Vanessa’s and Olive’s houses had windows that were painted shut by previous owners; reopening windows required patience, skill and time. Olive chose to leave her windows painted shut as indoors stayed cool in summer anyway; she had a number of well-placed doors for venting and felt the painted windows

repelled intruders. Paul and Vanessa chose to renovate their windows because they were keen to improve the intake of fresh air from outside.

Venting and moisture extraction were also achieved in eleven houses using

mechanical extractor fans in ceilings in bathrooms and kitchens. While extractor fans were somewhat helpful, they only really moved air into roof spaces or recycled air back into the same space after filtering it. Moving moist air to unvented roof spaces can create moisture problems in roof cavities, undermining structures, claddings and insulation. Some participants had vents in their eaves to release moist air from roof spaces. Recycling air back to the same place after filtering meant that moisture and deoxygenated air stayed in the same space. Air conditioning systems used as heaters (heat pumps) in winter could also help to dry the air as they warmed it, which was helpful, but could not replace the indoor air and required the use of a significant amount of electricity.

Ventilation practices can clash with methods that reduce heat-flow or retain warmth indoors in winter. Advocates of passive design and energy efficiency often

recommend venting indoors spaces as a method to cool houses during warmer weather; and advise closing and draught-proofing houses to restrict venting during cooler weather (Building Design Professionals 1995; Edwards 2001; Roaf et al. 2005). Their reasoning is that warmth and energy efficiency are more important than venting for replacement air. In Tasmania, energy efficiency advice follows this reasoning, suggesting that householders increase the heat-flow resistance of roofs, ceiling, floors and walls, and seal their houses to limit draughts (Sustainable Living Tasmania 2007c). Following this advice means that houses will be poorly vented during cold weather. When houses are closed and venting is limited moisture levels build inside. When it is cold as well, moisture will settle on surfaces and will support mould growth. Effective moisture reduction and control requires air replacement (venting) with drier air, as well as temperature control.

In winter, participant householders either closed their houses to resist heat flow all the time (12 houses in autumn and 13 in winter); or they would vent at certain times and close their houses when they were cold and wanted to use their heaters. In winter venting was mainly used to refresh air and to keep indoor spaces dry. For example,

unless it was a really cold day (below 13°C) Troy and Nat would vent during the day to keep their house ‘fresh’ and to ensure their dog could move in and out of the house. They only used heat in the evening when they had the house fully closed with the living and dining rooms zoned off from the rest of the house. They would again open windows in their bedroom for fresh air while they slept. Their practice of venting in cold weather did not follow standard energy efficiency advice but suited their needs and limited moisture levels building indoors.

In all dwellings in the study, moisture levels needed management. Most householders reported that they had to wipe windows daily during cold weather, and thought that moist windows were a normal effect of winter living. Coupled with the generally poor thermal resistance of the building shells, moisture from kitchens, showers and respiration provided large amounts of moisture in participant homes that condensed on windows and walls. Condensation reports signified that the dwellings were poorly ventilated and sub-optimally retained warmth.

Susan reported high levels of moisture on her windows in cold weather but managed to reduce condensed moisture levels on windows by regular venting year round and by installing whirly gigs in her roof.108 Helen was challenged with moisture and mould109 in her laundry, which she minimised by venting the house during the day all year round. Del and Kirk had moisture on windows in winter, but (in contrast to Susan, Helen and Troy and Nat) did not vent because they were trying to stay warm. They tried (often unsuccessfully) to avoid the worst effects of their moisture-laden air by maintaining warmer indoor temperatures.

108 _{The whirly gigs are venting devices that are installed in the roof cladding and allow air to flow in}

and back out of the roof space. The whirly gigs most likely assisted with window moisture levels by reducing the overall moisture levels by extracting roof space moisture build-up from the kitchen and bathroom extractor fans.

109 _{Mould was a subject participants chose not to discuss at length, perhaps because mould and}

moisture are associated with lack of cleanliness, which remains stigmatized, or because they viewed moisture management as a normal and obvious part of life.