Ventilation -Natural

Overview

Ventilation is a major issue in the design of new homes. Modern houses are designed to be air-tight in order to reduce the heat loss caused by draughts. Following the maxim ‘build tight, ventilate right’, air for ventilation is provided in the winter by small trickle vents in the windows. Mechanical ventilation is sometimes used if a house is built to a very high standard of air-tightness. The traditional homes of Cheltenham are not air-tight; quite the opposite. They are often draughty and lose a lot of heat because warm air can so easily escape through all the gaps and cracks in the building fabric. This is why draught-proofing is such an effective way of in reducing heat loss in traditional homes. Nonetheless, even after draught-proofing, a Regency or Victorian home may have a higher rate of cold air infiltration than a home built to modern building standards.

Modern lifestyles create a lot of moisture indoors thanks to all our cooking, cleaning, clothes drying, showering and bathing. Despite the draughtiness of traditional homes, many people still actively ventilate rooms by opening windows or using extractor fans in order to reduce the risk of indoor condensation and mould.

Natural ventilation

Natural ventilation relies on the natural movement of air rather than electric fans. It is useful in the summer for cooling: windows left open will encourage air flow through a home and open chimneys will draw warm air out of the building. Natural ventilation is usually inappropriate in the winter because so much heated air is lost. You may need a low background air flow to supply a heating appliance but even this is not necessary if the appliance has a balanced flue (i.e. the flue draws in air as well as letting fumes out). All modern combi boilers have balanced flues.

Natural ventilation remains important in unheated parts of your home where there is a risk of condensation such as loft spaces or underneath suspended timber floors. If you insulate your loft or your floor, make sure that you do not block up the gaps at the eaves in the loft or the air bricks beneath the floor as these keep the loft and subfloor dry.