Pressure distribution around the thermal envelope - a parametric study of the impact from wind and temperature on contaminant transport within a building

Paper i proceeding, 2020

Several school buildings in Sweden have indoor air quality problems. The contaminant source is often  assumed  to  come  from  within  the  construction,  for  example  from  the  crawl  space  or  attic  space.  Contaminants,  in  these  cases,  are  transported  by  air  leaking  between  compartments  in  the  building.  Here,  the  driving  force  for  the  air  leakage  is  difference  in  pressure  and,  therefore,  determining  pressure  also  determines  the  direction  of  contaminant  transport. 
In  many  cases,  measures  to  improve  the  air  quality  are  taken without a thorough understanding of how it might affect the pressure distribution in the building. In this  paper  a  numerical  model  is  used  to  examine  how  different  climate  scenarios  and  different  building  configurations affect the leakage and contaminant transport in a building with a crawl space.
Results show that  for  leaky  buildings  the  ventilation  rate  increases  with  increased  wind  and  therefore  the  contaminant  concentration  decreases.  The  worst  scenario  in  terms  of  high  contaminant  concentration  is  mild  days  with  little  wind.  Also,  when  installing  an  exhaust  fan  in  the  crawl  space  with  the  purpose  to  prevent  air  from  leaking  from  the  crawl  space  to  the  classroom  it  is  advisable  to  also  consider  the  airtightness  and  the  climate, not only the pressure difference across the floor.