{"id":2081,"date":"2018-05-24T10:04:00","date_gmt":"2018-05-24T08:04:00","guid":{"rendered":"https:\/\/www.ntnu.no\/blogger\/teknat\/?p=2081"},"modified":"2021-07-06T11:41:22","modified_gmt":"2021-07-06T09:41:22","slug":"opening-windows-the-best-way-to-ventilate-a-building","status":"publish","type":"post","link":"https:\/\/www.ntnu.no\/blogger\/teknat\/2018\/05\/24\/opening-windows-the-best-way-to-ventilate-a-building\/","title":{"rendered":"Is opening windows the best way to ventilate a building?"},"content":{"rendered":"\n

That\u2019s a question architects and engineers don\u2019t manage to agree on!<\/strong><\/p>\n\n\n\n

<\/p>\n\n\n\n

Using windows and openings to ventilate is called natural ventilation in opposition to mechanical ventilation where fans are used to move the air.<\/p>\n\n\n\n

\"Wide
Window ventilation. Photo: Maria Justo Alonso<\/figcaption><\/figure><\/div>\n\n\n\n

Most engineers (\u201cmyself included\u201d) feel anxiety when they hear that windows are going to be actively and solely used to provide fresh air, and here are the four most important reasons for their concern:<\/p>\n\n\n\n

  1. When we ventilate a building with an open window, we are exposed to unfiltered air. This air carries particulate matter (aka PM) such as carcinogenic particles from car engines and allergy triggers (pollen, dust, etc). 83 % of the population of the cities, for which PM data exist, are exposed to levels exceeding the air quality guidelines. Mortality from cardiovascular and respiratory diseases and lung cancer are known to be connected to fine particles (PM smaller than 10 \u03bcm).<\/li>
  2. When we ventilate with an open window, the warm air that is removed from a room leaves the building without allowing for heat recovery. In cold climates, temperature differences be-tween indoor and outdoor air often exceed 30 \u00b0C during winter, which means that a lot of en-ergy is needed to warm up the supplied air. Reduced supply of fresh air leads to increased concentrations of many kinds of pollutants indoors. In addition, window-opening procedures are highly dependent on the outdoor weather conditions and cultures. Users will normally open windows during warm periods and leave them closed during cold or windy periods. Over ventilating may yield an increase of energy use and too little ventilation may mean higher concentrations of pollutants, possible mould growth, and high concentrations of CO2, all related to lower performance in offices and health issues.<\/li>
  3. When we ventilate with an open window, we hear noise from traffic; or for instance, the school next to your office where kids are playing.<\/li>
  4. When we open a window in cold climates, we are exposed to draft. In countries like Norway, an open window during wintertime means an open door to cold draft and complaints.<\/li><\/ol>\n\n\n\n

    However, despite all these \u201cfacts\u201d, architects keep on talking about natural ventilation as the ultimate solution to provide fresh air to a building. Why do they do that?<\/p>\n\n\n\n

    \"Large
    «Ugly ventilation»? Photo: Maria Justo Alonso<\/figcaption><\/figure><\/div>\n\n\n\n