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Helping Engineers Harness Natural Ventilation’s Potential

Helping Engineers Harness Natural Ventilation’s Potential

From ASHRAE Journal Newsletter, June 30, 2021

Natural ventilation has the potential to decrease a building’s energy use and increase thermal comfort, but design engineers need more information to achieve these goals.

“Many in the industry can see the appeal of natural ventilation for environmental stewardship concerns; however, there appears to exist some reticence in application and confusion over the interpretation of the current standards,” said Erin McConahey, P.E., HBDP, Fellow ASHRAE, and Peter Simmonds, Ph.D., Fellow/Life Member ASHRAE.

To help, the ASHRAE Design Guide for Natural Ventilation, written by McConahey and Simmonds, assists owners, architects, engineers, facilities personnel and building design professionals to explore the feasibility of natural ventilation for their project during the early phases of design. The guide details how natural ventilation designs can comply with prominent ASHRAE standards such as ANSI/ASHRAE, Standard 55, Thermal Environmental Conditions for Human Occupancy, ANSI/ASHRAE Standard 62.1, Ventilation for Acceptable Indoor Air Quality, and ANSI/ASHRAE/IES Standard 90.1, Energy Standard for Buildings Except Low-Rise Residential Buildings.

McConahey and Simmonds talked with ASHRAE Journal about the design guide and natural ventilation’s potential and barriers.

What are the biggest barriers to mass adoption of natural ventilation?

There are limitations on application arising from outdoor climate as well as those related to cultural expectations around dress, comfort and communal control of windows. The social acceptability of a natural ventilation scheme is as important to its success as its technical feasibility. Once the client has agreed that indoor conditions under a natural ventilation scheme would be acceptable, that the target tenants would have enough personal freedom to adjust devices and clothing, and that the cost of ownership is manageable, then the conversation of comfort versus energy use can be further explored in greater detail beyond a risk-benefit comparison alone.

While social consciousness and reputational benefits may be a factor in the decision to pursue natural ventilation, clients will typically need evidence specific to the scale of their own projects to make a credible argument for a tangible benefit before invoking that support. They deserve to understand the benefits and risks of natural ventilation as an asset-embedded investment, so that they can judge its efficacy against other priorities for funding. There always needs to be a project-level understanding of the value of the benefit versus its first cost. This guide is intended to normalize expectations regarding the minimum steps and analyses necessary to facilitate key decision-making conversations with the stakeholders.

Also, there is more research to be done in the industry related to resolving the question of health and productivity benefits associated with natural ventilation.

Where do you hope to see natural ventilation adoption/usage in the future? 

We hope that with greater clarity on design paths, the practitioner and research community will be able to invest in quantifying the benefits beyond energy savings and that it can be more widely considered as a valuable, yet functionally beneficial, amenity when provided in a hybrid “mixed-mode” approach with air-conditioning systems.

Why is it important to explore this topic now?

With the Architecture 2030 challenge and the move towards net zero carbon design, natural ventilation is a measure often considered by design teams to reduce energy use in a building. This obviously needs to be balanced with the likelihood of global warming and the comfort of the occupants.

The ASHRAE Design Guide for Natural Ventilation is meant to assist owners, architects, engineers, facilities personnel and building design professionals to explore the feasibility of natural ventilation for their project during the early phases of design, taking into account such considerations.

What do you want engineers to know about natural ventilation?

Natural ventilation takes a wider amount of dialogue with the design team, ownership team and stakeholders to ensure its long-term success, especially in a world with greater weather extremes.

The progress of a design team from conception to fruition for a natural ventilation scheme is one of collaborative review of critical analysis results. Natural ventilation is reliant on a variable source of air movement and cooling capacity. Owners and tenants must be aware not only of the average expected results, but also the frequency of the extreme conditions for the current day and in a future climate-changed condition.

What lessons, facts and/or guidance can an engineer working in the field take away from this guide?

The design guide is organized in the order of milestone gateway decisions that will help design teams to decide whether to continue investing in exploring the feasibility of natural ventilation. For example, if a design team cannot confirm that the outside environmental conditions can support natural ventilation for a reasonable number of hours, then it makes no sense to engage in building design to support it.