by Pooja Shukla, Senior Director, Innovation & Research, GBCI India I U.S. Green Building Council
Indoor air quality (IAQ) and energy efficiency are both essential considerations when designing building systems and they are closely interconnected. However, they are often treated as distinct issues and their intricate link does not get enough attention.
India remains home to 13 of the world’s 20 most polluted cities. In 2024, the average annual particulate matter (PM2.5) levels in the country was 50.6 µg/m³. This is ten times higher than the World Health Organization’s (WHO) recommended limit of 5 µg/m³. Cities in the National Capital Region (NCR) of India, such as Delhi, Gurugram and Noida, reported PM2.5 levels well above safe thresholds. Delhi reported an annual average level of 104.7 µg/m³, earning it the title of the world’s most polluted capital city. These numbers are not just abstract metrics. They represent a severe health hazard for people residing in these cities. Our entire Indian population lives in areas where the yearly average PM2.5 levels are higher than what the WHO considers to be safe, posing a serious threat to human health and shortening the average Indian lifespan by 5.3 years.
Indoor Air Quality: The Invisible Challenge
We know that outdoor air pollution has become a pressing health concern in urban areas across India. However, what most don’t realize is that this pollution does not just remain outside. If the outdoor air is not filtered properly, the pollution permeates into our homes, offices, and schools, creating an invisible yet significant challenge of unhealthy IAQ.
We spend a major portion of our lives indoors. If that indoor air is filled with the same harmful pollutants as outdoors– microscopic particles like PM2.5 and PM10, we are constantly breathing unsafe air, even in the safe confines of our buildings. This is a serious health risk and can lead to respiratory problems, allergies, and several other short and long-term health issues.
For buildings located in regions with high ambient air pollution, the design, operation, and maintenance of building Heating, Ventilation, and Air Conditioning (HVAC) systems, plays an incredibly important role in ensuring safe indoor air delivery and requires careful consideration by building professionals.
The Conundrum: Filtration Efficiency vs. Energy Consumption
A key strategy to improve IAQ is to install high-efficiency air filters in the HVAC system. These filters are designed to capture harmful particulate matter, preventing them from circulating indoors. However, high-efficiency filters are generally denser and have finer pores to trap smaller particles. While this increases their filtration efficiency, it results in an increased airflow resistance due to higher pressure drop across filters.
To deliver the same air flow, the system’s fans have to work more therefore consuming more energy. Considering that HVAC systems account for a substantial portion (around 40%) of an office building’s energy consumption, and fans accounting for around 34% of the total HVAC energy consumption, this can have a notable impact on the overall building energy consumption.
Typically, for the building teams, the filter selection process is a trade-off between the filtration efficiency and impact on energy consumption. However, technological advancements in the air filter media industry have tried to address this issue and now offer alternatives that have high filtration efficiency with low-pressure drop.
GBCI India’s Research: A Path Forward
At GBCI India, we recently conducted a collaborative research project with Hollingsworth & Vose to investigate the real-world performance of two advanced filter media technologies in Indian conditions. We examined their filtration efficiency and the impact on energy consumption.
Our study involved field-based research in an office building in Noida – a city grappling with persistent air pollution. It was a retrofit project that compared the performance of the building’s existing air filters with two types of advanced media filters, all with the same MERV 14 rating (a measure of filtration efficiency). However, all three filters were manufactured using media with different specifications. We monitored their performance over five months, collecting data on air quality and energy consumption.
What We Discovered: No More Trade-Offs?
The findings were promising. Our research showed that high-efficiency filters with advanced media can deliver healthy IAQ, even in highly polluted environments, while reducing building energy consumption.
Amongst the filters investigated, the advanced electret media filters had the best performance. These filters had electret media that had a single charged layer and utilized triboelectric effects between dissimilar fibers to create exceptionally strong and durable electrostatic forces, offering high filtration efficiency and high air permeability. These filters brought down the indoor PM to healthy levels even when the outdoor levels were extremely high. We found that, switching to these filters could result in a notable reduction (up to 29%) in HVAC fan energy consumption compared to the existing filters.
This means that building owners and facility managers can maintain healthy IAQ without increasing the building’s energy burden.
The Importance of Filter Maintenance and Selection Criteria
Our research also highlighted two other important aspects:
- Filter Maintenance: Regular cleaning and maintenance of filters, as recommended by the manufacturer, is essential to ensure optimal performance throughout their life. Dust buildup on filters makes them more resistant to airflow and increases energy consumption. It is an often -overlooked aspect of building operations.
- Filter Selection Criteria: While the filtration efficiency rating (MERV rating) is important, it is not the only factor to consider. Other technical specifications, such as the rated pressure drop and dust holding capacity, also play a significant role in the overall performance of the filters.
Looking Ahead: Healthy and Sustainable Buildings
This research offers useful insights, especially in an Indian context. As we strive towards making our built environment more sustainable and climate-friendly, we should make healthy buildings a priority. And safe indoor air is fundamental to healthy buildings.
This study provides compelling evidence that innovations in air filtration technology can help us achieve this goal without compromising our energy efficiency targets. By embracing these technological advancements, we can create indoor environments that protect our health while optimizing the energy footprint.
The challenge of balancing IAQ and energy efficiency is complex, but it’s not insurmountable. It requires a collaborative effort from researchers, manufacturers, building professionals, and policymakers. By working together, we can make our buildings healthier and more sustainable.
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