Definitions: Gross internal volume, Habitable room, Infiltration

Gross internal volume – the total internal volume of the heated space, including the volume of all furniture, internal walls, internal floors, etc. Habitable room – is a room used for dwelling purposes but which is not solely a kitchen, utility room, bathroom, cellar or sanitary accommodation. Infiltration – the uncontrolled exchange of air between inside a building and outside through cracks, porosity and other unintentional openings in a building, caused by pressure difference effects of the wind and/or stack effect.