How can air purification support building energy efficiency and carbon goals?

Key points

• Improving indoor air quality does not always require increasing outdoor air ventilation rates alone.
• Air cleaning can supplement ventilation by reducing indoor pollutant concentrations through cleaned recirculated air.
• In some buildings, this can reduce heating and cooling demand associated with conditioning large volumes of outdoor air.
• Energy outcomes depend on the building, climate, HVAC design, occupancy, and pollutant profile.
• Monitoring and verification matter: energy and indoor air quality should be assessed together rather than treated as separate objectives.
• Healthy Air Technology’s Smart Zero case study demonstrated measured building energy savings of up to 14% whilst maintaining indoor air quality targets.

Indoor air quality and energy efficiency are often presented as competing priorities.

On one side, building operators are under pressure to reduce operational carbon, HVAC energy use, and peak loads. On the other, expectations around ventilation, occupant wellbeing, and indoor air quality continue to rise.

Historically, improving indoor air quality often meant increasing outdoor air ventilation rates. Whilst ventilation remains essential, conditioning outdoor air can carry a significant energy penalty—particularly in buildings exposed to hot, cold, or humid climates.

This is why building strategies should focus on:

“How can buildings deliver enough clean air whilst minimising unnecessary energy demand?”

This article explains how air purification can support energy and carbon goals when integrated carefully into building ventilation strategies.

Why ventilation affects building energy use

Ventilation systems bring outdoor air into buildings to dilute indoor pollutants and manage CO₂ levels.

However, outdoor air rarely arrives at indoor comfort conditions.

Depending on the season and climate, HVAC systems may need to:

• heat outdoor air
• cool outdoor air
• dehumidify outdoor air
• humidify outdoor air
• filter outdoor pollutants

This conditioning process consumes energy.

In many commercial buildings, ventilation-related conditioning loads represent a substantial part of HVAC energy demand.

For example:

• winter ventilation increases heating demand
• summer ventilation can increase cooling and latent loads
• high outdoor pollution events may increase filtration resistance and fan energy

This creates a balancing challenge:

• buildings need clean indoor air
• but conditioning large outdoor air volumes has operational and carbon implications

Clean air is broader than outdoor air alone

One of the most important concepts in modern indoor air quality engineering is that “clean air” can come from more than one source.

In simplified terms:

Total clean air = outdoor ventilation air + cleaned recirculated air

Ventilation introduces fresh outdoor air.

Air cleaning removes pollutants from indoor air and recirculates it back into the occupied space.

From an engineering perspective, both contribute to pollutant reduction, although they are not interchangeable for every contaminant.

For example:

• outdoor air ventilation is essential for CO₂ control
• particle filtration can effectively reduce PM and bioaerosols without increasing outdoor air loads
• gas-phase filtration may help address VOCs and outdoor gaseous pollutants

This combined approach is increasingly important in buildings attempting to balance:

• indoor air quality
• thermal comfort
• energy efficiency
• operational carbon targets

How air purification can reduce HVAC energy demand

Air purification systems can support energy strategies in several ways.

1) Reducing dependence on high outdoor air rates for particle control

In many buildings, elevated outdoor air rates are partly used to dilute indoor particles and airborne contaminants.

High-efficiency air cleaning can supplement this process by removing pollutants directly from recirculated indoor air.

This may allow buildings to maintain indoor air quality targets with reduced dependence on very high outdoor air volumes in certain operating modes.

The result can be lower:

• heating demand
• cooling demand
• humidification/dehumidification loads
• associated carbon emissions

The exact outcome depends heavily on building operation and HVAC design.

2) Improving resilience during outdoor pollution events

Outdoor air is not always “clean air”.

Buildings near:

• traffic corridors
• industrial areas
• wildfire smoke events
• urban pollution sources

may experience periods where outdoor air quality deteriorates significantly.

During these periods, increasing outdoor air intake can sometimes worsen indoor particle or gaseous pollution loads whilst also increasing HVAC energy demand.

Air cleaning strategies can help buildings maintain cleaner indoor air whilst reducing reliance on large increases in untreated outdoor air intake during short-term pollution events.

3) Supporting retrofit strategies in existing buildings

Many older buildings cannot easily expand HVAC ventilation capacity without major infrastructure work.

In these cases, portable or integrated air cleaning systems may help improve indoor air quality without requiring:

• major ductwork changes
• larger chillers or boilers
• extensive HVAC replacement

This is particularly relevant in:

• older commercial buildings
• schools
• healthcare environments
• heritage buildings

where energy retrofits and indoor air quality improvements often need to happen simultaneously.

The Smart Zero case study: measured energy outcomes

Healthy Air Technology’s Smart Zero case study explored how air purification could contribute to indoor air quality targets whilst reducing building energy demand.

The project focused on combining air cleaning with optimisation of HVAC operation rather than treating ventilation and air purification as isolated systems.

The reported outcome was:

• measured building energy savings of up to 14%

The important point is not simply the percentage itself, but how the savings were achieved.

The strategy involved:

• reducing unnecessary conditioning of outdoor air
• using air cleaning to support indoor air quality objectives
• optimising HVAC operating conditions
• monitoring system performance over time

This reflects a broader shift occurring across building engineering:

the move from “maximum ventilation at all times” toward “measured clean-air delivery with operational optimisation”.

Importantly, the case study does not suggest that ventilation becomes unnecessary. Rather, it demonstrates that intelligently combining ventilation and air cleaning can alter the energy balance of a building.

For readers interested in airflow and clean-air metrics, this links closely to:

• What is air changes per hour (ACH)?
• What is Clean Air Delivery Rate (CADR)?

Why verification matters

Energy claims around indoor air quality systems should always be interpreted carefully.

Real building performance depends on many variables, including:

• occupancy
• climate
• HVAC control strategy
• fan energy
• filtration pressure drop
• maintenance
• outdoor pollution levels

That is why measurement and verification matter.

Good projects monitor both:

Indoor air quality indicators

such as:

• PM₂.₅
• PM₁₀
• CO₂
• VOC trends

and

Building performance indicators

such as:

• HVAC energy use
• heating/cooling demand
• fan energy
• operational runtime

Without measurement, it becomes difficult to separate genuine performance improvements from assumptions.

Air cleaning and carbon reduction

The relationship between air cleaning and carbon is indirect but increasingly important.

Operational carbon reductions may occur if air cleaning allows:

• reduced heating and cooling loads
• more efficient HVAC operation
• lower peak energy demand
• better use of recirculated air

At the same time, air cleaning systems themselves consume energy and require maintenance.

This means the question is not:

“Does air purification use energy?”

It clearly does.

The better question is:

“Can the combined building system operate more efficiently overall whilst maintaining indoor air quality targets?”

In some buildings, the answer may be yes—particularly where outdoor air conditioning loads are high.

Why integrated design matters

Air purification works best when treated as part of a broader building strategy rather than as a standalone add-on.

That broader strategy may include:

• ventilation optimisation
• filtration upgrades
• sensor-driven controls
• occupancy-aware HVAC operation
• source control
• monitoring and commissioning

This systems-based approach is increasingly relevant as buildings attempt to meet:

• net-zero targets
• energy efficiency regulations
• occupant wellbeing expectations
• resilience goals

simultaneously.

Summary

Indoor air quality and energy efficiency do not need to be opposing objectives.

Ventilation remains essential, particularly for CO₂ management and dilution of indoor pollutants. However, conditioning outdoor air carries an energy cost that can become significant in modern buildings.

Air purification can support building energy and carbon goals by contributing additional clean-air delivery through filtered or treated recirculated air. When integrated carefully into HVAC strategies, this may reduce heating and cooling demand associated with outdoor air conditioning.

Healthy Air Technology’s Smart Zero case study demonstrated measured building energy savings of up to 14% through this type of integrated approach.

The wider lesson is not that air cleaning replaces ventilation, but that buildings increasingly benefit from treating clean air, energy performance, and carbon reduction as interconnected engineering problems rather than separate ones.