Our 43-year-old house has ventilation bricks in the external walls and vents in the plasterboard lining of the rooms. Are the vents there to air both the wall space and the living space? It has been suggested that we block the internal vents to reduce the electricity we use for heating. Is this safe, and have views on home ventilation changed since our house was built?
There was considerable disagreement about this answer, but architects and surveyors converged on the answer below. And Peter Meehan from Catford, London, proposed an evergreen and sensible tactic: ask an expert before acting – Ed
• Homes built in southern Australia were of cavity brick or timber construction until the 1950s, when builders switched to the more modern construction of a timber frame, lined internally with plasterboard or dry wall, with a single skin of external brickwork.
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Floors were traditionally timber-lined and framed, suspended above the ground. It is necessary to ventilate the subfloor space to prevent the growth of destructive rot and mould and it was considered important to ventilate the insides of rooms with vents near the ceilings to provide a healthy series of constant air changes.
As it turns out, these latter vents often proved redundant because more air changes can be achieved through the normal opening of windows and doors. It was good practice to ventilate the wall cavity because, contrary to popular belief, bricks are porous and the insides of wall cavities become damp. Vents in older homes therefore fulfilled several roles, providing ventilation to the subfloor, wall cavities and interior of the home.
Modern central-heating systems have replaced the need for air changes through the wall vents and most new homes are now built on concrete slabs. The cavity side of timber wall frames are lined with an impervious barrier, so vents are not needed here either.
It is likely the questioner’s home will be of brick-skin construction, most likely with a suspended timber floor, a lined cavity and insulated walls. If so, you can safely block up your internal wall vents and this will save you considerable expense on heating because the vents actually exhaust the warm air that rises to the ceiling. It is important, though, to retain the low-level external vents to ensure there is good air flow underneath your timber floors.
Robert Caulfield, Camberwell, Victoria, Australia