Indoor Air Quality vs. Energy: A False Choice –Take the Long View with Integrated Solutions

Contributing authors:
Alan Scott, FAIA, LEED Fellow, WELL AP, CEM – Intertek Building Science Solutions
David Okada, P.E. – Engineering Economics, Inc.
Brendon Mattis, P.E. LEED AP – Engineering Economics, Inc.

(Part 2 of 2)

In Part 1 of this paper, we reviewed the context for the perceived conflict between indoor air quality (IAQ) and energy efficiency, and the importance of moving past that to seek integrated solutions that address both of these critical building performance factors. We now have a greater understanding of the importance of IAQ to support both the health and cognitive performance of building occupants, and we know that aggressive decarbonization of buildings is required to address climate change. Here in Part 2, we review how the integrated commissioning approach guides solutions to achieve multiple goals, and dive deeper into specific solutions to improve both energy efficiency and IAQ.

Integrated Cx Approach Achieves Multiple Goals

In both new building design and existing building operations, solutions to optimize indoor air quality and comfort while also reducing energy use and carbon emissions are readily available, ranging from minor specification changes to complete system substitutions.

Buttressing all of these is the implementation of a commissioning process to confirm proper functional performance in all operating modes.

1. Clarify IAQ, Ventilation, and Energy Goals
For both new and existing buildings, now is the time to set the clear path forward for IAQ and energy performance, starting with goal setting. Start by thinking long term:

  • What are the conditions likely to create the greatest value for occupants and ownership?
  • What conditions hit the sweet spot of supporting the productivity, health, and satisfaction of occupants?
  • What level of energy consumption and associated greenhouse emissions will meet company objectives and future regulations?
  • What additional information do building operators need to track and manage building operation? For existing buildings, it may be appropriate to identify short-term solutions for building operation, as well as setting long-term improvement goals.

Recording the key priorities, assumptions, and references along with these goals will help future operators and decision makers adopt the goals and adapt the building over time.

2. Assess Existing Assets and Make a Plan
Consistent with CDC, local government, and industry guidelines, many building owners and operators started looking at HVAC system performance much more closely during the pandemic, however this often took place within a compressed timeframe and a narrow focus on temporary settings. To consistently deliver good IAQ and efficiency over time, most facilities will need to take a second look at their systems to build on the COVID-related investigations and “fill in the gaps” relative to current goals.

Energy audits, building performance assessments, and retro-commissioning (RCx) address both energy performance and IAQ, seeking strategic investments and low-cost/no-cost improvements for energy and ventilation.

Plan the approach to include a budget for an implementation phase and a performance verification phase. More complex buildings will need multiple phases of work to complete upgrades while maintaining operation. Phases can be timed to coincide with tenant improvements and replacement timeframes for major equipment. It is important to have a prioritized capital improvement plan in place, as building health and performance assessments do little to move the needle without implementing the measures in a systematic and timely manner.

3. Leverage Available Financial Resources
A crucial element of planning is securing financing. In addition to traditional loans and utility/government incentives, newer financing options are now available to minimize risks and maximize the magnitude of value owners can get out of building upgrades:

  • Commercial Property Assessed Clean Energy (C-PACE) financing programs are currently active in 28 states, and 10 more have PACE-enabled legislation. C-PACE provides low-cost, long-term financing for energy efficiency upgrades and renewable energy systems in new construction and retrofit/renovation projects. Loans are repaid along with property tax bills, and transfer to new owners when properties are sold.
  •  Energy Efficiency as a Service (EEaaS), works similarly to a solar power purchase agreement, where a third-party investor or “energy tenant” pays for energy efficient upgrades to a new building or renovation, collects available energy tax credits and incentives, and recoups their investment over time from energy savings. The building owner avoids the capital cost premiums, and the building tenants get the benefits of occupying a green building with no extra costs. Overall, tenant utility bills stay the same for the term of the agreement, while the net energy cost savings go to repay the energy tenant’s upfront investment in upgrades. One example of this is the Metered Energy Efficiency Transaction Structure (MEETS) approach piloted in the Bullitt Center project in Seattle, WA.
  • In locations with Building Performance Standards coming online, look for incentives tied to these new regulations.

Strategies for IAQ and Energy Performance Improvement

The following is an overview of key strategies to improve IAQ and reduce energy use in buildings.

High-efficiency Filtration – Low-efficiency MERV 8 filters are commonly used in commercial HVAC systems and do little to remove small particles that are detrimental to human health. Maintaining healthier indoor air requires high-efficiency filtration of both the outside air supply and recirculated air to remove outdoor pollutants (pollen, automobile emissions, wildfire smoke, etc.) and indoor contaminants and allergens (dust, fungus, respiratory particles, etc.). However, there is a common misconception that high-efficiency filters (e.g., the MERV 13 filters promoted by LEED and WELL) are incompatible with older HVAC systems and can increase the energy used by air handlers. High efficiency filters are available in a huge variety of configurations and constructions, enabling very low pressure drop options for nearly every scenario. Properly selected replacement MERV 13 filters can therefore be installed in terminal units and air handling units with pressure drop and fan power well within a normal range.  Even for buildings that already have high-efficiency filters, reviewing filter selection is likely to reveal options for reducing pressure drop and saving energy.

Energy Recovery – Now commonly required by code for new construction, airside energy recovery eliminates the most significant energy issue with ventilation: heating and cooling outside air.  Energy recovery uses heat exchangers to move heat between air leaving the building and air coming in to preheat, precool, and in some cases (de)humidify the outside air. The heat exchange comes in a variety of different configurations that trade off practical concerns like size, freeze protection, and cross contamination with effectiveness of heat transfer. With energy recovery, the benefits of dramatically higher ventilation rates typically outweigh the energy impacts by a factor 150 times (Int. J. Environ. Res. Public Health 2015, 12(11), 14709-14722, While energy recovery is usually designed and installed as part of an integrated HVAC system in new construction and major renovation projects, it should also be considered in long-term capital improvement plans for existing buildings.

Dedicated Outside Air Systems – While theoretically a cost effective and efficient way to condition and ventilate buildings, real world experience is that most VAV systems are far too complicated to run well. Inevitable minor malfunctions or control mis-adjustments lead to operation far from optimal with simultaneous heating and cooling wasting huge amounts of energy and spaces being under-ventilated.

Alternatively, dedicated outside air systems (DOAS) provide ventilation independent of interior heating and cooling demands. Coupled with heat recovery, their simple operation is easy to understand, diagnose, and fix when things go wrong. These systems make it straightforward to confirm how much outside air is getting to each room in the building. DOAS systems have typically been sized to meet ASHRAE 62.1 minimums, but facilities seeking good indoor air quality will need substantially higher outdoor airflows. In existing buildings, DOAS should be considered in conjunction with heat recovery in capital improvement plans.

Heat Pumps – Heat pumps are a versatile technology for heating and cooling, offering high-efficiency and all-electric operation. While a single heat pump can theoretically send heat between a variety of sources and sinks, for the reliability of the equipment, and to achieve desired performance, it is critical to keep its operation as simple and consistent as possible. With currently available equipment, it is better to provide centralized heat pumps with dedicated functions than to switch modes between prioritizing heating and cooling. Distributed VRF or VRV heat pump systems offer a turnkey solution, but their substantial refrigerant charge and safety limitations warrant careful evaluation.

Fans – In any HVAC systems, fans do the work of moving air where it is needed and are a high value place to pursue energy savings and other benefits. Efficient fans move more air with less noise and less energy; often taking up less space. Looking at fans along with the air distribution network overall can create a “cascading effect” of improvement: Optimizing filters substantially reduces fan power, allowing smaller, quieter fans; quieter fans allow elimination of silencers, which further reduces system pressure, fan power and noise.

Running Buildings Smarter – "Smart” building solutions are most likely to succeed when they provide timely insight to operators. The highest value solutions are often coupled with automated building data analysis and expert review/coaching by real people. Key features to pursue include:

  • Allowing operators to readily track the outside airflow (to individual spaces and the whole HVAC system) against established minimum values.
  •  Enabling operators to track real-time energy use(s) against tailored predictions and helping to trouble-shoot discrepancies.
  • Refining system scheduling around actual building occupancy.

Looking into smart buildings is a great opportunity to provide benefits beyond HVAC operation, including:

  •  Reporting on portfolio or tenant sustainability metrics.
  •  Providing concierge and wayfinding services to occupants.
  •  Optimizing janitorial deployments.
  •  Negotiating billing for vertical transportation services.
  •  Encouraging healthy competition for occupants to do their part in improving building operation.

This is a rapidly evolving field loaded with great new ideas, including techno-fantasy and common DDC control features rebranded as breakthroughs. There are many new technologies that can be leveraged to expand the visibility of data on indoor environments and make new correlations between that data and human performance. By proceeding with an open mind and healthy sense of skepticism, we can optimize human health and energy performance in real time.

Additional Efficiency Upgrades – Independent of HVAC upgrades to improve ventilation, filtration, and energy performance, many existing buildings present opportunities for low-cost energy savings, including lighting retrofits, motor replacements, controls upgrades, and addressing component failures. Harvesting these savings can help to offset energy penalties from IAQ improvement strategies. For example, it is not uncommon to find that economizer dampers in air handling units have been manually closed. By reenabling economizer function, fresh air ventilation increases while also saving energy through free cooling.

Summary and Conclusion
In the last several years, we’ve seen change at an unprecedented rate. We’ve acted on the necessity of making decisions on compelling, but still incomplete, science. As we set expectations for a post-pandemic period, we have an opportunity to do better and live better.

Building owners and operators need specific guidance for their current operations, capital planning, and design standards. Based on current literature, and experience designing, commissioning, and testing, the authors recommend:

  •  Delivering at least 20 CFM/person of outdoor air in spaces for near term operations. This will provide more   consistently decent air quality than ASHRAE 62.1-2019.
  •  Targeting 35 CFM/person as the default for capital planning, renovations, and new construction. It is reasonable     to reduce this for particularly high-density spaces (<20sf/occupant).

More broadly, stepping beyond the dated assumption that IAQ and energy are at odds, we know that enhancing human health, comfort, and productivity while also increasing energy efficiency and reducing carbon emissions are vital and mutually achievable goals for existing buildings and the design of new facilities. We do not need to choose between them, as there are many available strategies and technologies to support both outcomes. The benefits are great, and the costs of inaction are high. A thoughtful approach to identifying, implementing, and verifying effective measures is a sound investment in human health and performance, operational cost reduction, and minimization of inevitable risks.