Design and installation of passive stack ventilation in retrofitted apartment buildings.

Almost 60% of French residential buildings were built before the seventies, and an important part of those is to be retrofitted for complying with new needs with regard to acoustic insulation and energy saving. Retrofitting modifies the airtightness of the building envelope and can lead to an insufficient air change rate in passive stack ventilated buildings ; the existing ventilation system has therefore to be redesigned in order to insure adequate indoor air quality. Dimensioning of the stack effect ventilation system for multi-storey dwellings is a critical issue, as the air flow rate depends on many parameters as outdoor temperature, wind, distribution of air inlets and envelope air leakages, ducts area and length, characteristics of outlets and cowls. Research work has been initiated by the CSTB, GDF and SOCOTEC (commissioning authority) to produce a design and installation guide of ventilation system and flue system for gas appliances by passive stack effect in apartment buildings. The guide is aims at helping engineers, building consultants and professional building owners to properly choose and dimension the ventilation system based on general and continuous air renewal. Results of this research work and main features of the guide are presented in the paper, in a first part the suitable system design is given according to the typology of the existing building and the different measures to be taken are listed. The choice and dimensioning of ventilation components are operated in order to comply with indoor air quality requirements. Dimensioning was derived from simulation results obtained by a numerical model developed at CSTB; predicting the ventilation rates, which has been described in the 15th AIVC Conference paper. The dimensioning of the ventilation system depends on the stack height and section area of ducts. The guide also deals with requirements and specifications concerning gas appliances, schedule of operation conditions of renovation work taking into account personal protection during this work, installation, commissioning and maintenance, use instructions for the occupants and building managers.