Humidity Controlled Natural Ventilation in a Crawl Space

by Iñaki Razquin

Institution: Högskolan i Gävle
Year: 2016
Keywords: Ventilation; humidity; mould; Engineering and Technology; Environmental Engineering; Energy Systems; Teknik och teknologier; Naturresursteknik; Energisystem; Energisystem – magisterprogram (sv eller eng); Energy systems – master’s programme (one year) (swe or eng); Energy systems; Energisystem
Posted: 02/05/2017
Record ID: 2133365
Full text PDF: http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-21971


The issue of how to ventilate the crawl space of buildings is often debated, since it affects both heat loss and humidity conditions, where the latter is crucial for the onset of mould growth and other microbiological activities. In this moment, experiments are going on in a historical stone church (Hamrånge church, Sweden), where crawl space air is leaking into the church hall, thus affecting heating requirements, air quality and the thermal comfort for visitors. The experiments include long-term field measurements and computer control of ventilation dampers, installed in order to attain a more favourable natural ventilation in the crawl space. The thesis work consists of analysing the above mentioned issues for this unique case.Nowadays this church has a Humidity Controlled Natural Ventilation. It works comparing Absolute Humidity between indoors and outdoors and depending on it, the dampers placed on some of the crawl space vents open or close themselves to let air go through them.The aim of this thesis is to analyse with all the data provided (taken from Hamrånge church) if a crawl space of the church already described is well ventilated or on the contrary it is not well ventilated. This thesis is not a computer simulation one but it is a data treatment one, analysis from data taken from this church will be done. Also it will be focused on the functioning of the control of the ventilation system to check how representative is where the sensor is placed to open and close the dampers. Besides, energy used in heating of one winter with this way to ventilate the crawl space will be compared with other winters when these devices were not used and vents were opened always.The methodology for the analysis will be performed taking advantage of the computer program Excel to be able to manage all the amount of data. A method taken from other authors will be used in order to study the mould growth risk in the crawl space and also some other studies of the variation of the Temperature, Absolute Humidity and Relative Humidity in the crawl space wile dampers are closed or open. Besides a method to analyse wind direction and speed will be implemented.As a result, after implementing all the analysis, this report will be concluded that this new method is well implemented with good results in terms of heating savings compared with other winters. Besides, although mould is a problem, the place where the sensor to open and close the dampers is the best one among the crawl space which is the one where more mould is expected during summer (from June to September), that is the season of the year when more mould and sooner is expected according with the results.