Building rating schemes deliver energy savings, but they only deliver a “perceived” improvement in air quality.

As more tall buildings are constructed and the quest for super energy efficiency is pursued, building occupants are increasingly dislocated from the natural environment. The necessity to incorporate interior landscapes for building occupants to feel a connection with nature is a reflection of our evolution, and is being recognized as fundamental to our health and well-being.

Green walls are increasingly seen as an effective means of achieving some of these aims, with flexibility of location and a space-saving small footprint.

But what if these green walls were efficient air filters as well, actively cleaning the air of pollutants, particulate matter, volatile organic compounds (VOCs), bacteria and viruses, and delivering clean, pollutant free, high quality indoor air directly to the breathing zone?

Cambridge Civic Centre, Ontario Canada, First Canadian Gold LEED building featuring a 4 storey Active Green Wall Biofilter (100m2) installed in 2007 and Integrated into the HVAC system.

First Canadian Gold LEED building featuring a four-storey Active Green Wall Biofilter installed in 2007 and integrated into the HVAC system.
Cambridge Civic Centre, Ontario Canada


To breathe clean air we need better air filtration

The one unchanging aspect common in all buildings and sustainable cities is the air we breathe. For building occupants, achieving high quality indoor air is non-negotiable. They offer improved quality of life for employees, tenants and building occupants. The key aspects common to all are health and well-being, environmental amenities and economic paybacks.

Green wall air filtration can help to achieve high quality indoor air, while giving visual contact with natural elements.

Indoor Air Quality Management

Indoor air quality is usually managed through a combination of source control, dilution ventilation and air cleaning.

Source Control

There are no regulations on chemical emissions from commonly used building materials. De facto environmental certification schemes have been developed by industry associations that include material emission limits, but the legal standing of these certifications raise considerable doubts.

According to the US EPA, “no-VOC” latex paint does not necessarily mean no emissions. Colouring tints contain high VOC levels, and linseed oil used as a drying agent in “low VOC paints” reacts with ozone, nitrogen oxides or hydroxides (usually from outside supply air) to form oxidation products that are potentially irritating or harmful to health.

Many studies are now demonstrating adverse health effects at levels of air pollutants well below published air quality guidelines.

Neither indoor nor outdoor environmental sampling is a good predictor of personal exposure, and energy rating systems are not an indicator of clean, uncontaminated indoor air.

Dilution Ventilation

The conventional approach to improve indoor air quality is to dilute pollutants, but this substantially increases building operating costs, consuming as much as 30 per cent of the total energy use with little appreciable improvement in “breathable” air quality.

Building codes mandate that new (and green retrofit) buildings be designed for ventilation rates appropriate for maximum occupancy, a condition that almost never exists. Providing ventilation over and above code requirements may provide little or no health benefit, with the gap between operational loads and design loads leading to a 20 per cent increase in air conditioning system energy use.

High quality active green wall air filtration not only delivers substantial energy and cost savings, but also has a measurable effect on building occupant health and well-being, as well as performance improvement, with clean, pollutant free, high quality indoor air returned directly to the breathing zone.

High Efficiency Particulate Air (HEPA)

HEPA filtration is another way of delivering clean air. Although HEPA filters provide high filtration efficiency, they remove only particulates and require an additional activated carbon filter system to remove gaseous pollutants (VOCs). These carbon filters are generally not recyclable and become a source of toxic waste. Existing air conditioning (HVAC) systems cannot usually be upgraded to HEPA filters without a complete retrofit of the air handling system due to the high pressure drop and potential leakage associated with them.

Active green wall air filtration

The more functions that can be served by one design element, the more resource conserving and cost efficient the design. Bio filtration of the air circulating within the building envelope enables clean, cool air to be delivered, reducing the need for 20 to 30 per cent of outside air to be conditioned, saving commensurate energy costs, and contributing to thermal comfort by on average, a 0.5 degree Celsius temperature decrease and a potential 10 per cent RH increase.

Operating 24/7 and strategically located, active green wall air filters can present an environmentally positive corporate image, while making a real difference in “breathable” air quality.

Active green wall air filtration, a self-regenerating air filter solution, gives the option of minimum code-compliant fresh air rates while delivering high quality clean, fresh air to building occupants at low cost, with a less than two-year payback, either incorporated into the building’s air handling system or as a free standing unit, ranging from room size to multi-storey.

While most companies quantify asset value on a balance sheet, the value at risk includes intangibles such as higher tenant retention, healthier work environment, reduced liability/risk, Improved reputation/profile, and property brand differentiation. These factors have all been proven to add asset value over time by reducing turnover and operational costs and improving a building’s reputation in the  market.

Schematic make up of an active indoor air biofilter Image courtesy of Nedlaw Living Walls Inc

Schematic make up of an active indoor air biofilter
Image courtesy of Nedlaw Living Walls Inc