Everyone knows the cornerstone to any sustainable project design is integrating passive strategies. The first passive strategy for most is some form of natural daylighting – add some windows and daylight dimming and there you go. Onto the next passive strategy: natural ventilation. Make the windows operable and you’re good to go, right? If only it was that simple.
For natural ventilation, the system relies on more than just putting in some operable windows and vents and calling it a day. To work effectively the natural ventilation system requires pressure differences to move the fresh air throughout the building. Understanding the balance between supply and exhaust is critical to identify location and sizes of openings. The design of this system cannot be done by the engineer alone like other mechanical systems. It requires an integrated design approach between the engineers and architects from the start of the project to develop a natural ventilation system that works effectively and is fully integrated into the building façade and interiors.
The benefits for natural ventilation include lower capital costs, lower operating costs, occupant preferences and productivity, the list goes on. The one that hits home the most is the reduced environmental impact. As you increase mechanical cooling loads, you directly affect the regional heating effect that then demands more energy to address the extra cooling needed. It becomes a vicious cycle that compounds the issue of climate change.
Natural ventilation seems like a no brainer and yet very few projects have natural ventilation as part of their design and there is even fewer that operate well. Looking at projects overseas in Europe, the US is far behind in comparison. There are several items to keep in mind when understanding the differences. First, the weather in many of the areas overseas is much milder which allows for longer periods to utilize natural ventilation while maintaining an acceptable thermal comfort. And speaking of thermal comfort, the range accepted by Americans is different than Europeans.
We love our air conditioning and don’t like to feel warm in the summer. Ironically we end up wearing more sweaters in the summer than winter sometimes. There is a mindset about acceptable thermal comfort that needs to be overcome. Finally, code in some countries mandates natural ventilation. In the US the code limits the application of natural ventilation due to smoke and fire transfer issues. In the latest iteration of ASHRAE 62.1, it is now mandated that mechanical ventilation systems be provided in certain climate zones, removing the lower capital cost argument for natural ventilation when this used to be an alternative option for code compliance.
But fear not. There is still a lot that can be done, working to integrate natural ventilation into project designs. This year I’ve had the opportunity to meet and work with organizations and companies that are leading the industry in this arena. Overseas, Breathing Buildings is a company that came about from the research partnership between University of Cambridge, MIT and the BP Institute. The company develops and sells low energy ventilation systems. Here in the US, they are partnered with Price to develop these natural ventilation systems and work with project teams to integrate the systems into their project design effectively.
Last month, I was out at the Centre for the Built Environment (CBE) at the University of California Berkeley, participating in their semi-annual Industry Advisory Board Conference. The CBE is “a place where prominent industry leaders and internationally recognized researchers cooperate to produce substantial, holistic, and far-sighted research on buildings.” Reviewing their latest research activities, I was heartened to see the advances in the industry, especially in the area of natural ventilation.
Natural ventilation is a challenging system to design effectively. It was something that our predecessors had down to a fine art a century ago. In today’s world, things have changed and it is through the work and research of organizations, companies and design professionals that the new generation of natural ventilation systems continues to exist and grow.
Suzanne Robinson, , PE LEED AP BD+C is the Director of Sustainability at Vanderweil Engineers, a MEP consulting firm. Vanderweil Engineers has been exploring new and innovative approaches to the built world with clients all over the globe.