Macro & Micro Climate Enclosures in Healthcare: How They Impact Infectious Control

The coronavirus pandemic serves as a sobering reminder of the ever-changing nature of health-related influences on our global community. In fact, research shows that plagues and pandemics have been a part of human history going back to prehistoric times. And, as the effects of this current virus continues, we can be certain that the past will repeat itself in future events.

It is typical, that in the aftermath of such disruptive events, industries and practices are influenced and, in some cases, improved. This is especially true if the experience severely impacts a broad population. Human evolution has consistently enhanced its state of being through continued improvements largely in comfort, practicality (ingenuity), and safety/health.


The exterior of a building, or what is typically referred to as the exterior building enclosure, is commonly designed to keep the outside out and the inside in. For example, the roof, exterior walls, and floors of an occupied building are designed to separate the conditioned interior from the exterior climate.  This is accomplished by providing continuous air, water, thermal and vapor control layers in the exterior enclosure. These control layers, or systems, also reduce the risk of toxins being transmitted or developed within the interior climate, such as mitigating against exterior airborne toxins and particulate matter, ground radon, mold, and other odors or pollutants. Appropriately sized and designed mechanical systems then supplement the interior climate by providing heat, cooling, and filtered fresh air make-up ventilation for indoor comfort and occupant health. The traditional exterior building enclosure may be considered a macroclimate separation.

To verify and confirm exterior enclosure integrity is achieved in a new building or modernization, a whole building air tightness standard with an allowable leakage rate is incorporated into the design and construction (for example the US Army Corps of Engineers allowable leakage rate for buildings is 0.25 CFM/sf at 75Pa.)   The building is then physically tested using high power fan systems that both pressurize and depressurize the building while incorporating leakage diagnostics with other equipment such as infrared thermography.


High power fans and infrared cameras are commonly used to verify and confirm whole building air tightness.

Another type of building enclosure focuses more at the microclimate level where rooms within a building need separation from the primary interior building climate. Such rooms typically require separate and different temperatures and humidity levels; or needs to manage the control of aerosolized movement of contaminants and pathogens. Examples of these types of microclimate environments include refrigerated warehouses, electrical enclosures, data centers, botanic grow operations, and to the bioscience or healthcare world, can include isolation rooms, barrier rooms and biosafety laboratory rooms.

In Mission Critical facilities, the enclosure requires performance at both the macroclimate building exterior and individual microclimate interior spaces, the latter of which is typically measured by Room Integrity Testing.

Airborne infection isolation rooms (AIIRs), as defined by the Center for Disease Control (CDC), “is a single-occupancy patient-care room used to isolate persons with a suspected or confirmed airborne infectious disease. Environmental factors are controlled in AIIRs to minimize the transmission of infectious agents that are usually transmitted from person to person by droplet nuclei associated with coughing or aerosolization of contaminated fluids.” In such mission critical type facilities, the enclosure requires performance at both the macroclimate building exterior and individual microclimate interior spaces, the latter of which is typically measured by Room Integrity Testing.


In healthcare facilities, Room Integrity Testing is a process for identifying, testing and proving acceptable ranges of air leakage into and out of mission critical spaces to mitigate the transmission of infectious diseases. For these mission critical spaces that require tight control, pressurization of the internal and external space is a key factor. These spaces, as defined by the National Institute of Health (NIH), “consist of the perimeter walls, floor, ceiling, doors, windows and other elements that surround and contain the space. They must be constructed, finished and sealed sufficiently to prevent leakage and infiltration. In addition, windows must be sealed and entrances and exits must be minimized and configured in vestibules with interlocking doors and directional airflow to maintain integrity of the barrier.” 


Room integrity testing of microclimate spaces provides a detailed process for mission critical roooms that require tight control.


For the past six years, Pie Consulting & Engineering has provided comprehensive Building Enclosure Commissioning (BECx) consulting services for a 1.1 Million Square Foot Hospital facility, which included Room Integrity Testing. As specified, the purpose of this test is to determine if the walls, floors, ceilings, penetrations, and other containment barrier features have adequate integrity to meet room integrity acceptance criteria. Biosafety Level (BSL-3) Spaces in the Hospital and Animal Biosafety Level (ABSL-2) space in the Clinical Investigation Building included exam rooms, laboratories, operating rooms, recovery rooms, patient rooms and nurseries. Typically, the rooms are tested after the HVAC testing and balancing activities have been completed, and the rooms are in normal operating conditions with doors closed.

Testing is accomplished in a multi-step process. In general, a smoke pencil is used to conduct air leakage and directional air flow testing. In addition, a digital manometer and gauge is used to conduct differential pressure and quantitative air leakage testing. An orifice blower door fan system is also installed within the room’s main entrance to conduct Quantitative Air Leakage testing.

Pressure monitors are then installed in each room and in adjacent rooms, so that accurate relative differential pressures can be obtained.  Lastly, a door force gauge is used to conduct door force testing by placing the gauge against the door, pressing and measuring the force, in pounds, to open the door.

Test Results

This data represents some of the results and findings from the room integrity and smoke pencil tests.


Although not a direct solution to mitigating the transmission of airborne contaminants, the value of a high-performance interior and exterior enclosure system cannot be overstated. The BECx program provided at the Hospital highlighted above, illustrates the value in providing a building enclosure quality assurance program. It informs responsible material selection and continuity during design, provides oversight for proper installation of materials during construction, and verifies system performance through a robust field testing and verification program. Moreover, the enclosure system positively influences mechanical systems, thereby creating healthy environments for patients, staff and visitors alike.

In the future, we cannot afford to return to business as usual without seriously considering the lessons learned in the wake of current events. They must inform the continuation and expansion of best practices for future preparedness. This includes mandating building enclosure requirements (both macroclimate and microclimate where needed), in project specifications as a key part of the commissioning process, not as an optional task, but as a critical component of responsible design.

For more information on BECx and field performance testing for Mission Critical facilities, contact Pie Consulting & Engineering today.


Pie Consulting & Engineering is a leading global provider of building and forensic science services who provides a comprehensive and diverse range of engineering, rehabilitative design, consulting, enclosure commissioning (BECx), construction management, and field performance testing services. As a new subsidiary of Lerch Bates, Inc. (, Pie services its development, design, construction, insurance/claims, and legal professional clients globally from our headquarters in Colorado and multiple regional offices strategically positioned throughout the nation. To learn more, visit