AIVC - Air Infiltration and Ventilation Centre

Search form

EBC

You are here

Home  |  maintenance

Feedback on installation, maintenance, and aging of mechanical humidity-controlled ventilation exhaust units

Stéphane Berthin, François Parsy, 2018
demand-controlled ventilation | humidity | installation | maintenance | feedback
Bibliographic info: 39th AIVC Conference "Smart Ventilation for Buildings", Antibes Juan-Les-Pins, France, 18-19 September 2018
Languages: English Pages (count): 12

With 35 years of existence and more than 10 million equipped dwellings, mechanical humidity-based demand-controlled ventilation (RH-DCV) can provide a comprehensive feedback on installation, aging, and maintenance of its components. Their working principle is based on the extensions and retractions of a hygroscopic fabric, which pulls on a shutter to modify the device’s cross-section – hence the airflow – upon humidity changes in their environment. 

In 2006, before generalizing the usage of RH-DCV in French residential buildings, the Ministry for Housing ordered an evaluation of these systems after prolonged on-site operation. For this purpose, the COSTIC laboratory selected 21 social housings in the Parisian suburb, and collected 57 exhaust units after 6 years of in-situ functioning. 

During the collecting phase, the first on-site observations were the following: 



  • 12 % of the exhaust units were installed in incorrect rooms (kitchen/bathroom swap, for instance). 

  • 14 % of the units had suffered damage, either due to voluntary modifications by the occupants (e.g. blocking of the shutter), or to bad re-assembly after maintenance. In 1 out of 3 dwellings, at least one device presented such defects. 

  • 75 % of the units showed an absence of sufficient maintenance (dusting), when 58 % visually exhibited clogging of the canal. 



The devices were first characterized on a laboratory test bench as-collected (i.e. still soiled). Characterization of RH-DCV units consists in plotting the volume-flow crossing the unit as a function of relative humidity. 



  • 100 % of the non-damaged exhaust units exhibited a conform hygroscopic behavior or showed a slight shift of their characteristic when still soiled. 

  • 46 % of the kitchen units complied with factory specifications despite the absence of maintenance. 

  • 100 % of the bathroom exhaust units showed an airflow reduced by 5 m3/h. 



Devices were then cleaned and properly re-assembled. The shutter and shutter-case (passive elements) were replaced when irreversible damaged was observed. 



  • 75 % of the units complied with factory specifications after cleaning. 

  • Among the other 25 %, the kitchen elements showed an increase of volume flow lower than 3 m3/h, while bathroom units exhibited a decrease lower than 2 m3/h. 



For the same study, self-adjusting exhaust units were also collected and tested. These devices were installed in utility-rooms. Their working principle is based on the deformation of a membrane solely due to pressure forces to maintain a constant airflow despite pressure variations in the ventilation ductwork. 



  • 100 % of the soiled units were out of their specification, with volume flows 4 to 10 m3/h (25 to 65 %) lower than their initial setting.  

  • Once cleaned, 100 % of the units complied with factory specifications. 



The results of this samples collection highlight the necessity of ventilation units’ maintenance; it also shows the robustness of RH-DCV settings after prolonged in-situ operation. 


Related publications

This report summarizes the work of the initial working phase of IEA ECB Annex 62 Ventil
Maria Kolokotroni, Per Heiselberg, Lorenzo Pagliano, Jie Han, Regina Bokel, Peter Holzer, Annamaria Belleri, Denmark
This summary report presents insights on recommendations into how ventilative cooling i
Christoffer Plesner, Flourentzos Flourentzou, Guoqiang Zhang, Hilde Breesch, Per Heiselberg, Michal Pomianowski, Peter Holzer, Maria Kolokotroni, Annamaria Belleri, Denmark
Overheating in buildings is an emerging challenge at the design stage and during operat
Peter Holzer, Theofanis Psomas, Denmark