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This diagram shows a cross-section through a two storey house with arrows showing flows of air through it. Red arrows show movements of warm air and blue arrows movements of cold air. The house has a pitched or sloping roof with a loft space above and an insulated ceiling. At the junction of the pitched roof and the supporting wall at the left cold air is shown entering at a vent at the eaves. This is labelled ‘maintain essential ventilation in roof space from outside’. Near the top of the loft space a blue arrow shows cold air passing through a roof vent. At the junction of the pitched roof and the supporting wall at the right a blue arrow shows cold air passing through a vent at the eaves from the loft space to the outside air. At the bottom of the loft space is an insulated ceiling. Red arrows indicate leakage of warm air from the rooms below at several points: around pipes rising from the bathroom, around light fittings in the ceiling and around the edges of a loft hatch. On the first floor of the house at the left a bathroom is shown. Warm air is shown rising from the bath. One arrow flows towards a ventilation grille on the bathroom wall. This is labelled ‘essential moisture extraction from bathrooms and kitchens’. Another red arrow passes from the bath to a vertical pipe duct in the wall. This is labelled ‘unwanted leakage around pipes and ducts leading to roof space’. On the first floor of the house at the right is a window. A red arrow is shown passing through the top of this. This arrow is labelled ‘essential ventilation through trickle vent’. In the centre of the diagram a staircase is shown rising from left to right. The house has a suspended timber ground floor with an air space beneath. A blue arrow is shown entering the floor space at the bottom of the wall at the left. Another is shown at the right flowing from the floor space to the outside air. The air space under the floor has a label ‘maintain essential ventilation below timber ground floors’. At the left of the diagram a rising blue arrow is shown entering a vertical pipework duct in the wall from the floor air space. Another is shown rising from the floor space into the house through gaps in the stairs. These arrows are labelled ‘air rises up ducts and under stairs causing unwanted draughts in the house’. At the right of the diagram a door is shown. Blue arrows indicate air leakage into the house from the outside around the edges of the door and through the letterbox opening. Beside the door a ventilation grille is shown with a blue arrow descending towards an open fire shown in the centre of the diagram. This arrow is labelled ‘maintain essential ventilation to rooms with fuel-burning appliances’.

 2.3 Cutting ventilation losses