Net Zero Energy ≠ Net Zero Carbon: Does it matter for a healthy indoor environment?

Introduction

“Net Zero” is everywhere in building discourse, but two versions often get conflated: Net Zero Energy (NZE)—balancing annual energy use with on-site renewables—and Net Zero Carbon (NZC)—eliminating or offsetting all greenhouse-gas emissions across a building’s life cycle. The distinction matters not just for climate targets, but for indoor environmental quality (IEQ) and occupant health.

Why the difference impacts health

An NZE building can still draw power from a fossil-heavy grid when on-site generation isn’t sufficient. Combustion upstream contributes to outdoor air pollution that infiltrates indoors and drives disease burden. Global electricity remains far from fully renewable, so energy balance doesn’t guarantee low-pollution operation. The World Health Organization attributes millions of premature deaths each year to air pollution exposure, and the built environment is a major driver through energy use and heating fuels. Indoors, the U.S. Environmental Protection Agency reports pollutant levels often 2–5× higher than outdoors, especially where airtight envelopes are not paired with robust filtration and ventilation.

Airtightness, ventilation, and cognitive performance

High-performance envelopes are a hallmark of NZE projects, improving thermal stability and reducing energy use. However, airtightness can trap CO₂, VOCs, and PM2.5. Research synthesized by the Harvard Healthy Buildings Program shows that higher ventilation rates and low-VOC environments can boost cognitive function scores by 60–100% compared with conventional baselines—underscoring that energy strategies must be integrated with health-centric IAQ design.

Materials, embodied carbon, and indoor chemistry

NZC frameworks go beyond operations to address embodied carbon in cement, steel, glass, and insulation—responsible for a significant share of building-sector emissions. Lower-carbon specifications (supplementary cementitious materials, recycled steel, low-carbon aluminum) reduce climate impacts that worsen heat, wildfire smoke, and pollen seasons—each a growing indoor air challenge. Crucially, many low-carbon procurement pathways also encourage low-emitting materials, reducing formaldehyde and VOC off-gassing that contribute to headaches, asthma, and irritant symptoms.

Thermal and visual comfort—health co-benefits

NZE and NZC design often leverage passive strategies—solar control, high-performance glazing, and daylighting. These can cut lighting energy dramatically while supporting circadian health, sleep quality, and mood. Maintaining indoor temperatures within recommended ranges and relative humidity around 40–60% reduces respiratory irritation and limits mold growth—key to a healthier indoor microbiome.

Equity and resilience

Aligning with NZC typically accelerates electrification of heating and cooking, eliminating indoor combustion byproducts (NOₓ, CO) and improving health equity for sensitive groups. Weatherization plus filtration makes homes more resilient to outdoor smoke and heat. In short, NZC aligns climate action with everyday indoor health protection; NZE alone may not.

Bottom line

Not all “net zeros” safeguard occupants equally. Net Zero Energy is a vital efficiency milestone, but Net Zero Carbonbetter captures the strategies that protect indoor health: clean energy, non-combustion systems, material transparency, effective ventilation/filtration, and resilient envelopes. For truly healthy buildings, zero must mean zero emissions and zero compromises on indoor environmental quality.

References

• World Health Organization (WHO) – Air pollution and housing/health guidance

• U.S. Environmental Protection Agency (EPA) – Indoor Air Quality (IAQ) reports

• United Nations Environment Programme (UNEP) – Global Status Report for Buildings and Construction

• International Energy Agency (IEA) – Net-zero pathways and building energy analyses

• World Green Building Council (WGBC) – Health, Well-Being & Productivity in Green Buildings; embodied-carbon guidance

• Harvard T.H. Chan School of Public Health – Healthy Buildings Program – Ventilation, VOCs, and cognitive performance findings