Natural Ventilation

Closely tied with building form and envelope design, this strategy can provide part or all of a building’s ventilation needs and can be used to remove excess heat. Heating and cooling requirements are driven by climate, building type, internal loads and building envelope design, but for most commercial buildings the greatest need is for cooling. Because it relies on the climate, the cooling capacity of natural ventilation is limited and varies with weather conditions. If peak cooling loads can be limited to the capacity of natural ventilation to remove excess heat, a significant amount of energy can be saved by offsetting the need for both mechanical ventilation and cooling. If needed, efficient systems such as hydronic heating and/or cooling and displacement ventilation can be used to supplement natural ventilation.

The fundamental principle behind effective natural ventilation is to create building configurations and envelope openings that take advantage of natural air movements from wind, pressure differentials, and the buoyancy of warm air to circulate fresh air to occupied building areas and to remove excess heat. Components can include: operable windows, a double skin facade assembly, louvers, dampers, and atria. To minimize use of electric fans, high and low openings and various thermal flue configurations can take advantage of the stack effect. As with daylighting, natural ventilation requires manual or automated controls to help manage temperature, humidity, air quality, air speed, and acoustics. Operable windows are an effective means of allowing user control of temperature and ventilation.

Although standard for residential buildings in North America, and for buildings of nearly all types in Europe, only a small percentage of American commercial buildings are naturally ventilated. The design effect can be subtle through louvers or the use of windows with concealed frames, or can engage more significant elements as in the case of ventilation stacks.

The book, Natural Ventilation in Northwest Buildings,  by G.Z. Brown, is an excellent resource on this topic, covering a range of strategies specifically for the Northwest climate.

KEY LESSON
Of the many possible natural ventilation components, operable windows are an effective means of allowing user control of temperature and ventilation.

Additional case study examples:
- Nearly all of the case studies incorporate natural ventilation. See case study page