Influence of building air tightness on ventilation losses.

The Building Air Tightness is an important parameter on ventilation systems performanceand energy losses.Yet, the total amount of leakage is as important on performances as their effective positionin the room.Some calculations have been run according to prEN 13465 from TC156 WG2 for differentbuildings (single house, dwellings and commercial buildings) varying air tightness, valueand repartition for different ventilation systems (natural, mechanical exhaust, mechanicalexhaust and supply).All these calculations have been compared focusing on ventilation losses during heatingseason in Paris.Some double zone calculations on the commercial building (offices and stock area) havealso been run to be compared to uniform single zone repartition.Calculations confirm the importance of air tightness on ventilation losses and showvariations due to repartition hypothesis which must therefore be chosen carefully. Veryoften, air-tigthness value and its repartition are unknown and the hypothesis made oncalculations are most important on results.