When More Ventilation Isn’t Always Better: The Emerging Case for Outside Air Reduction

Learn why outside air reduction is reshaping building operations. Balance indoor air quality, energy savings, and ASHRAE standards in the post-COVID era.

Ava Montini

Sep 12, 2025

Written by

Published on

Why Reduce Outside Air? What Are the Trade-Offs

To see why reducing outside air is resurfacing, it's helpful to walk through what the costs are and what the benefits might be of dialling things back.

The Costs of Too Much Outside Air

Energy Use
- Heating and cooling costs skyrocket when you have to condition large volumes of outdoor air, especially in extreme climates. In summer, bringing in hot, humid air means your cooling system works harder; in winter, cold air needs heating.
- Beyond simply heating/cooling, there’s also fan energy. More outside air often means more airflow through dampers, larger pressure differentials, etc.
Visual Comfort / Thermal Discomfort
- Cold drafts in winter; humid, sweaty feelings in summer if moist outdoor air isn’t adequately dehumidified.
- Inconsistent thermal zones due to mixing outside air with return or recirculated air.
Mechanical Wear & Maintenance
- Outside air includes particulates, pollutants, and moisture. Therefore filters, coils, ducts, and dampers need more maintenance.
- When outside air brings in pollutants or high humidity, it can cause corrosion, mold, or damage to finish materials.
Indoor Air Quality Considerations
- Ironically, bringing in outside air isn’t always “cleaner”; if outdoor air is polluted (e.g. wildfire smoke, high PM2.5, industrial pollution), ventilation could degrade indoor air quality.

The Benefits of Reducing Outside Air (When Done Right)

Energy Savings
- Reduced heating/cooling loads → lower utility bills.
- In some ASHRAE Standard 90.1 addenda / code changes, reducing outdoor air intake is explicitly a path toward improved energy efficiency. For example, changes made in standard 90.1-2019 (and later) allow reduced outside air intake in central systems and reduced minimum flows in VAV (variable air volume) boxes. Energy Codes
- Buildings with moderated outside air approaches (versus maximum outside air strategy) can often hit much better energy performance, especially in climates with extreme temperatures.
Comfort and Building Stability
- More stable indoor temperatures, less risk of humidity spikes or condensation issues.
- Better ability to maintain indoor comfort metrics, which improves occupant satisfaction.
Cost Predictability & Maintenance Savings
- Less strain on HVAC equipment.
- Lower maintenance cost due to fewer introduced contaminants, less filter load, etc.
Health / IAQ Still Possible
- By using strategies such as proper filtration (appropriately rated filters), UVGI, good air distribution, and periodic flushing, you can maintain healthy indoor air even with more controlled outside air.
- ASHRAE guidance, post-COVID, suggests that ventilation + filtration + other engineering controls together are the path—not merely “open all dampers.” ASHRAE

How ASHRAE & Codes Are Shifting

The push to balance ventilation, energy and comfort is finding formal expression in updated standards and codes. Some key threads:

ASHRAE Standard 62.1 (Ventilation for Acceptable Indoor Air Quality) has been the go-to for minimum ventilation. But recent addenda adjust how outside air rates are calculated, especially in Variable Air Volume (VAV) systems, enabling more dynamic or performance-based approaches. Energy Codes
ASHRAE Standard 90.1 (Energy Standard for Buildings Except Low-Rise Residential Buildings) is increasingly recognizing that “more outside air” is not always the optimal path for energy efficiency. The 2019 to 2022 versions include addenda that allow for reduced outdoor air intake in some scenarios and model outside air intake more precisely. Energy Codes
Post-COVID Guidance from the Epidemic Task Force and other committees acknowledges that increased ventilation is helpful for infectious disease mitigation—but also warns about the cost, feasibility, and trade-offs. ASHRAE’s filtration & disinfection guidance, for instance, emphasizes that filters should be sealed well, systems should be maintained, and energy impacts considered. ASHRAE
There is growing interest in “ventilation efficiency” (i.e. how well the outdoor air being brought in actually participates in diluting contaminant levels) vs simply “bringing in more air.” That opens doors for smarter design: placement of supply/exhaust, air distribution patterns, possibly recirculation with clean filtration, and technology like UVGI in ducts. arXiv

What Building Owners / Managers Should Do

If you’re in charge of managing indoor air quality, HVAC systems, or the budget, here are some practical steps, questions, and strategies to move toward smart outside air reduction without compromising health or compliance.

Step	What to Do	Key Questions & Considerations
1. Audit your current system	Measure how much outside air is being brought in currently. Identify how often dampers are fully open, what settings for minimum outside air are. Document past energy bills, thermal comfort complaints.	Do you really need to run at 100 % outdoor air all the time? What’s the outside-air fraction during non-peak periods? How often are you using demand-controlled ventilation?
2. Model / simulate	Use energy modelling (or vendor/engineering consultants) to simulate what energy & comfort impact you’d see from reducing outside air to code minimum vs current levels vs maximum “pandemic level.” Include local climate, outdoor pollutant levels.	What’s your climate? How extreme are winters / summers? What are outdoor pollution or humidity challenges? Can your HVAC system handle variable loads well?
3. Filter & clean	If you reduce outside air, you’re inherently relying more on “recirculation / indoor air cleaning” to maintain IAQ. Ensure your filters are appropriate efficiency, well sealed, replaced regularly. Consider supplementary measures (UV, air cleaners, HEPA, etc.).	What is the MERV rating you’re using? Can your fan/coil handle higher efficiencies without losing capacity? How about maintenance cycles?
4. Design flexibility & control	Make systems adjustable—both in terms of outdoor air intake (dampers, controls) and monitoring (CO₂, PM2.5, VOCs). This allows ramping up when needed, and reducing when risk is low or when conditions are unfavorable.	Do you have sensors to detect indoor air quality? Do your controls allow override or programmed changes? Are occupants/management aware and aligned with policy?
5. Engage stakeholders	Staff, occupants, board members often worry that reducing outside air means compromising health. Transparency helps: show them energy/comfort data, IAQ readings, trade-offs. Sometimes policies (e.g. open windows during good outdoor air, closed when it’s bad) help.	What are occupant expectations? Do you have health policies in place? Who signs off on trade-offs (e.g. budget vs comfort)?
6. Monitor & adjust	After changes, monitor indoor environment (temperature, humidity, CO₂, pollutant levels), energy, comfort complaints. Be ready to adjust. Outside air isn’t a static setting; it’s dynamic.	How often will you review? What thresholds trigger change? For example: high CO₂ or PM2.5, or outdoor air pollution alerts, might warrant reducing outside air.

What This Means for Policy, Standards, & the Future

Energy codes & carbon targets

As jurisdictions push toward net zero or carbon reduction, the HVAC energy penalty of over-ventilating becomes a liability. Efficient outdoor air management helps reduce energy use, which helps reduce emissions. ASHRAE 90.1’s newer addenda are already projecting energy savings from smarter outside air settings. Energy Codes

Health & resilience

Pandemics have taught us that buildings need flexibility—not fixed, extreme settings. Systems that can adapt: e.g., crank up ventilation when risk is high, pull back otherwise—are more resilient. Outdoor air reduction is part of enabling that flexibility.

Indoor air quality (IAQ) & occupant wellness

People increasingly expect buildings (schools, offices, public spaces) to deliver both clean air and comfort without extreme energy waste. Outside air reduction done thoughtfully helps spread the benefits: lower energy bills, better comfort, less waste.

Cost pressures

Energy costs are volatile. Running massive outside air loads just to “play it safe” all the time may no longer be financially justified, especially in regions with high energy costs or challenging climates.

Getting Outside Air Right, Not Just More

After so many years where the message was “more outside air, more safety,” we’re entering a more mature phase—one where how outside air is managed, rather than just how much, becomes the critical question.

Reducing outside air (when it can be done safely) doesn’t mean lowering standards or compromising on health. It means using all the tools: ventilation, filtration, controls and monitoring, to deliver indoor air quality that is healthy, comfortable, sustainable and cost-effective.

If you’re managing buildings, this is the moment to rethink your default settings. Push for audits, invest in systems and sensors, communicate clearly with occupants. Because the buildings that get this right will be healthier, more resilient, and much more efficient in the long run.

How to Understand and Manage Wildfire Risks: A Comprehensive Guide for Consumers and Businesses

Jennifer Crowley
Jun 28, 2024
3 min read

Updated: Jul 15, 2024

Man in PPE vest holds a caution sign amidst forest brush on fire — As climate change continues to impact our environment, it’s crucial to understand wildfire risks and take proactive steps to manage them.

Wildfires are becoming a more frequent and severe threat across North America, posing significant risks to both homes and businesses. As climate change continues to impact our environment, it’s crucial to understand wildfire risks and take proactive steps to manage them. At Blade Air, we are committed to providing the knowledge and tools necessary to protect your property and health from the adverse effects of wildfires.

Understanding Wildfire Risks

Wildfires can ignite due to various reasons, including human activities and natural causes like lightning. Understanding the dynamics and risks of wildfires is essential for effective management.

Geographic and Environmental Factors

Climate and Weather Patterns: Dry, hot, and windy conditions significantly increase wildfire risks.
Vegetation: Dense forests, woodlands, and areas with dry grass are more susceptible to wildfires.
Topography: Fires spread more quickly uphill due to rising heat. Steep terrain can also complicate firefighting efforts.

Human Factors

Urban-Wildland Interface: Areas where human development meets undeveloped wildlands are particularly vulnerable.
Fire Management Practices: Poor land management, such as the accumulation of dead vegetation, can escalate fire risks.

Steps to Manage Wildfire Risks

Both consumers and businesses can take proactive measures to mitigate wildfire risks and protect their properties. Here are comprehensive steps to consider:

Before Wildfire Season

Assess Your Risk:
1. Use tools like CAL FIRE’s Fire Hazard Severity Zone maps (USA) and the Canadian Wildland Fire Information System (Canada) to understand your risk.
2. Evaluate factors such as building materials, landscaping, and proximity to vegetation.
Create a Defensible Space:
1. Clear flammable vegetation within 30-100 feet of your property.
2. Use fire-resistant landscaping and maintain a well-watered lawn.
3. Ensure trees and shrubs are well-spaced and pruned.
Prepare Your Property:
1. Use fire-resistant building materials like metal or tile roofing and dual-pane windows.
2. Remove combustible materials from decks and nearby structures.
3. Keep gutters and roofs clear of dry leaves and debris.
4. Install spark arrestors on chimneys.
5. Ensure hoses and fire extinguishers are readily accessible.

Develop an Emergency Plan

Create an Evacuation Plan:
1. Identify multiple evacuation routes from your neighbourhood or business location.
2. Designate a meeting place and an out-of-area contact for family members and employees.
3. Practice evacuation drills regularly.
Assemble an Emergency Kit:
1. Include a 3-day supply of non-perishable food and water (4 litres per person per day).
2. Pack a first aid kit, sanitation supplies, a battery-operated radio, flashlights, and extra batteries.
3. Keep important documents (ID, insurance policies, medical records) in a fireproof and portable container.
4. Include prescription medications, eyeglasses, cash, and a manual can opener.

During Wildfire Season

Monitor Conditions:
1. Stay informed through local news, radio, and emergency alert systems.
2. Keep track of air quality through websites like AirNow.gov (USA) and AirHealth.ca (Canada).
Protect Indoor Air Quality:
1. Create a “clean air room” using high-efficiency air purifiers with true HEPA filters.
2. Ensure HVAC filters are replaced as needed
3. Seal windows and doors and use weatherstripping to minimize smoke infiltration.
4. Avoid indoor activities that generate pollutants, such as smoking or burning candles.
Be Ready to Evacuate:
1. Keep your emergency kit and important items in an easily accessible location.
2. Park vehicles facing outward with a full tank of gas.
3. Follow evacuation orders promptly. Do not delay leaving if you feel unsafe.

After a Wildfire

Inspect and Repair:
1. Check your property for damage, including roofs, exterior walls, and HVAC systems.
2. Contact your insurance company to report losses and begin the claims process.
3. Replace all air filters.
Maintain Indoor Air Quality:
1. Continue using air purifiers until outdoor air quality returns to safe levels.
2. Replace filters in all air purification systems and HVAC units exposed to smoke and ash.
Update Your Plan:
1. Reflect on your emergency response and update your wildfire preparedness plan accordingly.
2. Replenish any used supplies in your emergency kit.
3. Schedule an air quality consultation to optimize your indoor environment for future fires.

You can learn more using our comprehensive ebook "The Ultimate Guide to Indoor Air Quality During Wildfires".

Blade Air: Partnering in Fire Risk Management

Blade Air’s commitment to innovation and sustainability extends to our wildfire preparedness solutions. Our advanced air purification systems, such as the HCFM-1 Portable HEPA Purifier, Pro Filter with Advanced Electromagnetic Filtration, and HEPA+ Filter, provide unmatched protection against wildfire smoke and other airborne contaminants.

Benefits of partnering with Blade Air:

High-Efficiency Filtration: True HEPA, activated carbon filters and electromagnetic filtration ensure clean indoor air during wildfire events.
Energy Efficiency: Our designs reduce energy consumption, making our purifiers both effective and environmentally friendly.
Comprehensive Coverage: Suitable for both residential and commercial spaces, ensuring wide-ranging protection.

Understanding and managing wildfire risks requires a proactive approach, blending knowledge and practical steps. By following these guidelines and utilizing Blade Air’s advanced solutions, you can safeguard your health and property from the impacts of wildfires.

Breathe innovation. Breathe sustainability. Breathe easy with Blade Air.

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