With unprecedented wildfires in Canada and the increased likelihood of future wildfire activity in North America, Buro Happold’s experts offer advice on how to minimize pollutants in buildings and effective HVAC strategies for AECO professionals.
To protect against smoke infiltration and reduce the impacts of fine particles, called PM2.5, Justin Schultz of Buro Happold’s San Francisco office, as well as John Rozeluk of the Los Angeles office, present solutions to building owners with the aim of reducing health risks in buildings. occupants Both engineers bring extensive experience in building decarbonization and sustainability, as well as wildfire and smoke impact design in the United States.
Wildfire Season Considerations
Current guidance for the wildfire season is to use a high degree of recirculation for ventilation. New buildings and renovations now take this into account to provide energy efficient and cost effective solutions. Obstacles to maintaining a healthy indoor environment include (i) clogged filters in air handling units (AHUs) and (ii) smoke-contaminated fresh air supplies.
Possible interventions and example scenarios offered by Buro Happold experts include:
Inevitable central air recirculation
When air recirculation cannot be avoided or sufficiently reduced, building owners should consider exhaust air purifiers and high-quality filters, known as air filters of high efficiency particles (HEPA) classified MERV 15. The minimum efficiency report value (MERV) indicates the effectiveness of the air filter in reducing particles and pollutants in the air.
Mixed mode ventilation
A mixed mode ventilation system is suitable for natural ventilation most of the time. In the event of poor air quality due to wildfires, a local mechanical ventilation system with heat recovery (MVHR) can be used to provide fresh air.
Local modifications to centralized systems
When only local modifications can be made to a centralized HVAC system, building owners can consider room modifications, such as forming discrete bulkheads to allow horizontal air intake.
Displacement ventilation / UFAD
Underfloor air distribution (UFAD) ventilation introduces air at low levels with a unidirectional air path to extraction outlets located higher in interior spaces. This washes clean air over the occupants and draws pollutants into the ceiling.
“We have to build resilience and flexibility into our designs and engineering, in order to respond appropriately to anything that might happen. During the pandemic, we were trying to increase the volume of outside air and reduce recirculation, which is the opposite of what we need in order to exclude wildfire smoke and filter out particulates.Also, keep in mind that the energy demand to push air through HEPA or MERV 15 filters is very high, when most days a MERV 13 filter is sufficient. Architects and engineers must consider how to design ventilation systems that can be switched from normal use mode to configurations more appropriate for given crisis conditions. This will balance healthy air quality with overall energy use and operating costs,” says Rozeluk, responding to an inquiry from The construction specifier, regarding the role that architects and engineers can play in mitigating the effects of bushfires on IAQ. He added: “We should also explore options for managing the air pressure inside a building, so that in the event of a bushfire, you can resist air entering through typical openings and pathways of the wrapper, reducing the infiltration of smoke-borne particles.”
