With the unprecedented wildfires in Canada and the increased likelihood of future wildfires across North America, experts at Buro Happold offer advice on minimizing indoor pollutants and effective HVAC system strategies for AECO professionals.
To protect against smoke ingress and reduce the impact of particulate matter (PM2.5), Justin Schultz from Buro Happold’s San Francisco office and John Rozeluk from the Los Angeles office present building owners with solutions aimed at reducing health risks for building occupants. Both engineers have extensive experience in building decarbonization and sustainability, as well as planning for the impact of wildfires and smoke throughout the United States
Forest fire season considerations
The current recommendation for wildfire season is to use high levels of agitation for ventilation. This is now taken into account in new buildings and renovations in order to offer energy-efficient and cost-effective solutions. Obstacles to maintaining a healthy indoor environment include (i) clogged filters in air handling units (AHUs) and (ii) fresh air intakes polluted by smoke.
Possible interventions and sample scenarios by Buro Happold’s experts include:
Unavoidable central air recirculation
When air recirculation cannot be avoided or sufficiently reduced, building owners should consider exhaust air scrubbers and high-quality filters called high-efficiency particulate air (HEPA) filters with a MERV 15 rating. The Minimum Efficiency Report Value (MERV) indicates the effectiveness of an air filter in reducing particles and pollutants in the air.
Mixed mode ventilation
A mixed-mode ventilation system is suitable for natural ventilation in most cases. In the event of poor air quality due to forest fires, a local mechanical ventilation system with heat recovery (MVHR) can be used to supply fresh air.
Local changes to central systems
If only local changes are possible on a centralized HVAC system, building owners can consider changes in the space, e.g. B. the formation of discrete partitions to allow horizontal air supply.
Displacement ventilation / UFAD
Displacement ventilation or underfloor air distribution (UFAD) introduces air at low levels with a unidirectional airpath to exhaust vents higher in the interior. This flushes clean air over the occupants and extracts pollutants from the ceiling.
“We need to build resilience and responsiveness into our designs and constructions to be able to respond appropriately to anything that might happen.” During the pandemic, we’ve tried to increase the volume of outside air and reduce circulation, which is the opposite of what we need to shut out wildfire smoke and filter out particulates. Also, keep in mind that the energy required to push the air through HEPA or MERV 15 filters is very high, although most days a MERV 13 filter will suffice. Architects and engineers need to think about how to design ventilation systems that can be switched from a normal usage mode to settings better suited to specific crisis conditions. This balances healthy air quality with overall energy use and operating costs,” says Rozeluk, responding to a query from The Construction Specifier about the role architects and engineers can play in mitigating the impact of wildfires on indoor air quality. He added: “We should also look at ways to control the air pressure inside a building so that in the event of a wildfire you can prevent air from entering through the typical openings and passageways in the envelope, thereby reducing the ingress of smoke-borne particles.”
