Indoor carbon dioxide (CO2) has long been a topic of discussion in the context of ventilation and indoor air quality (IAQ). Over the centuries, these discussions have evolved to encompass various aspects, including using CO2 as an IAQ metric, estimating ventilation rates through CO2 as a tracer gas, adjusting outdoor air ventilation based on CO2 concentrations, and understanding how CO2 impacts building occupants.


The American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) has issued a Position Document concerning indoor carbon dioxide in non-industrial indoor environments meant for human occupancy, such as homes, offices, schools, and transportation spaces.

ASHRAE takes the following positions:

  • 1. CO2 as an IAQ Metric: Indoor CO2 concentrations alone do not provide a comprehensive indication of IAQ.
  • 2. Health and Well-being: The direct impacts of CO2 on health, well-being, learning outcomes, and work
    performance at typical indoor concentrations lack consistency.
  • 3. Ventilation Standards: Current indoor CO2 levels do not warrant alterations to ventilation and IAQ standards, regulations, or guidelines.

Using CO2 for Ventilation Evaluation:

Distinguishing between indoor and outdoor CO2 concentrations can be a useful method for assessing ventilation rates and air distribution. This can be achieved through established tracer gas measurement techniques, but accuracy relies on the validity of assumptions and input values.

Critical Factors for Accurate Measurement:

To draw meaningful conclusions from indoor CO2 concentrations, sensor accuracy, proper sensor placement, and regular calibration are crucial considerations.

Air-Cleaning Technologies:

Air-cleaning technologies that exclusively target CO2 removal may not necessarily enhance overall IAQ and could potentially interfere with systems utilizing CO2 for ventilation control or IAQ monitoring.

Research Areas for Better Understanding:

ASHRAE identifies a range of research topics aimed at gaining a deeper understanding of CO2’s role in IAQ.


Indoor CO2 plays a multifaceted role in discussions surrounding IAQ. While it has been considered an IAQ metric and a basis for ventilation evaluation, ASHRAE’s positions suggest that its direct impacts on health and the need for changes in standards are not clear-cut. Further research is needed to comprehensively comprehend the role of CO2 in overall IAQ.
Source: ASHRAE Position Document on Indoor Carbon Dioxide (2022)


As energy professionals, we are often faced with a critical decision when recommending energy efficiency measures. Should we prioritize energy savings or consider the broader context of emissions reduction? To make the right choice, we need to delve into the intricacies of regional electrical grids and their varying emission intensities, a factor that can significantly impact our recommendations.


In 2020, Canada witnessed notable variations in emission factors across provinces, underscoring the complexity of our energy landscape. Emission factors ranged from a mere 0.04 tonnes/MWh in Ontario to 0.30 tonnes/MWh in New Brunswick and a striking 0.66 tonnes/MWh in Alberta (Source: Environment and Climate Change Canada). These disparities emphasize the importance of tailoring energy management solutions to the unique characteristics of each location.

Understanding the Local Grid’s Impact

The key insight is that energy savings do not operate in isolation; they are intricately linked to the GHG emissions produced by the local grid’s power source. Whether it’s high-emission coal, clean hydro, or renewable energy, the emissions associated with the power generation source vary significantly by region.

Beyond Financial Viability: A Holistic Approach

While financial viability is a crucial consideration, it offers only a one-dimensional view of energy management decisions. To make informed choices, we must adopt a multi-dimensional approach that factors in both economic feasibility and grid emissions intensities. In some cases, it may be financially prudent for certain provinces to prioritize natural gas savings over electricity savings, but the broader implications on emissions cannot be ignored.

Leveraging Comprehensive Decision Tools

To guide clients toward informed decisions, it’s essential to employ sophisticated decision tools such as life cycle GHG and costing analyses. These tools provide a more comprehensive perspective than traditional cost-only metrics, allowing us to articulate the benefits of our energy and GHG management strategies effectively.

A Sustainable Future: Prioritizing GHG Emissions

In conclusion, I urge my fellow energy professionals to shift their focus and prioritize GHG emissions when crafting energy management strategies. By striking a balance between energy savings and emissions reduction, we not only ensure long-term sustainability but also play a significant role in the global fight against climate change.
Originally published at:

Addressing Challenges in the Penetration of Distributed Energy Resources (DERs) for a More Equitable Energy Future

The adoption of Distributed Energy Resources (DERs) in the United States faces significant challenges, including high upfront and financing costs. This issue is exacerbated by disparities in adoption rates, particularly among low-income households, those with low credit scores, and renters. Furthermore, installation hurdles in certain areas hinder the deployment of DERs such as level 2 EV chargers and solar and storage systems. A multi-faceted approach is necessary to address these challenges and promote equitable access to DERs.

Challenge 1: Low Adoption Rates and Equity Concerns

1.1 Low Adoption Rates: DER adoption rates are relatively low across various technologies. For example, heat pump water heaters represent only 2% of water heater replacements annually, while distributed solar arrays are utilized by just 3.7% of single-family households as of 2020. Additionally, smart thermostats are installed in fewer than 20% of single-family homes.
1.2 Equity Concerns: Low- to moderate-income households and those with low credit scores face barriers to adopting DERs. They often struggle to cover upfront costs, while high-cost financing options, like credit cards, diminish the energy savings potential of these technologies. This disparity has significant energy justice implications.

Challenge 2: Installation Hurdles

2.1 Installation Delays: Consumers in certain areas encounter delays in installing DERs due to several factors. These include a shortage of electricians, protracted building permitting processes, overloaded electrical feeders preventing interconnection, and other logistical challenges.

Potential Solutions

Solution 1: Financial Assistance for DER Adoption

1.1 Low-Cost Financing: Private and public financial institutions, such as community development financial institutions and green banks, can offer low-cost financing options for DERs. These institutions should be supported by industry groups and consumer advocates who can educate the public on the benefits of DERs and assist in crafting effective financial assistance strategies.
1.2 Rebates and Tax Incentives: State and local organizations should promote DER adoption by offering rebates and tax credits, leveraging initiatives like the Inflation Reduction Act. Consumer education and support should be provided to ensure accessibility to these incentives.
1.3 Utility Programs: Utilities can enhance DER adoption through on-bill financing with lower interest rates, technology-specific rebates, leasing options for solar-plus-storage systems, and education and technical assistance for consumers.
1.4 Building Weatherization: Governments and organizations can support weatherization and insulation programs, particularly in disadvantaged communities. This reduces the strain on the grid when HVAC systems are time-shifted, improving the value of homes as thermal batteries.
1.5 Consumer Protection: Consumer advocate organizations and the Consumer Financial Protection Bureau should engage in ensuring that DER finance and loan agreements align with consumer interests.

Solution 2: Workforce Development

2.1 Partnerships with Trades: Utilities, DER manufacturers, and VPP platforms can partner with trade organizations like the International Brotherhood of Electrical Workers and the National Electrical Contractors Association to promote workforce development for DER installation and maintenance.
2.2 Building Codes: State and local governments can revise building codes to encourage VPP-enabled DER adoption, and bolster permitting agencies’ personnel capacity as needed.
2.3 Education for Safety: State energy offices, regional energy efficiency organizations, and industry groups can provide education to permitting agencies to enhance their understanding of the safety and benefits of DER technologies.

Solution 3: Equitable Benefits Allocation from VPPs

3.1 Prioritizing Equity: Utilities, regulators, and state policymakers should ensure equitable distribution of VPP benefits, including cost savings, job creation, resilience improvements, and air quality enhancements, focusing on disadvantaged communities.
By implementing these solutions, we can overcome the challenges hindering the penetration of DERs, promote energy equity, and foster a more sustainable and accessible energy future for all.