ABSTRACT
A building that has been renovated to minimize heat loss and infiltration, while avoiding the risk of overheating in summer, will require very little in the way of environmental services. For example, a building located in the south of England and renovated to Passivhaus or EnerPHit standards is likely to be heated by its internal heat sources for most of the winter. In fact, the main problem will be to avoid these same sources causing overheating, even during the winter months. Many existing buildings obtain enough air from outside through leakage to meet the hygiene and comfort requirements of their occupants, even when windows are fully closed. Once this source of fortuitous ventilation air is cut off, through Passivhaus or similar air tightness measures, ventilation will have to enter via alternative routes. Trickle vents would allow an uncontrolled variable rate of ventilation depending primarily on wind pressure and direction. If these vents are closed through the intervention of occupants, then no outside air would enter the building, apart from that entering through opening and closing of doors to outside. When this leads to discomfort, occupants are likely to open windows, allowing significantly more outdoor air to enter the building than if trickle vents had been provided. See also the CarbonLite report comparing natural ventilation with mechanical ventilation with heat recovery (MVHR) in a Passivhaus house. 1
