By Nick Martin and Abhishek Ajansondkar, Contributing Writers

Ambulatory care facilities are subject to a range of requirements that do not always align with inpatient care engineering design approaches. Occupancy classifications, local code application and engineering strategies for HVAC, emergency power, life safety systems, medical gases and system redundancy also can vary significantly depending on the program. 

In designing these facilities, an engineer’s challenge is to realize project goals in the context of firm budgets, aggressive development schedules and thoughtful system sizing that clearly aligns with performance requirements, system reliability and the level of care being delivered. 

Avoid overdesign 

An ambulatory care center is an outpatient facility that provides non-emergency, non-surgical services such as preventive care, chronic disease management, diagnostics and routine treatments. Urgent care facilities, imaging centers and specialty clinics fall within this broad category. These services are provided in primary care clinics, specialty care centers, outpatient clinics, urgent care centers, retail clinics, diagnostic imaging centers and ambulatory surgery centers. 

While these facilities serve patients with lower acuity than traditional inpatient hospitals, project engineering designs can often drift towards hospital-grade application. But applying inpatient hospital standards across an entire ambulatory facility often leads to overdesign and unnecessary cost escalation without proportional benefit. 

Overdesign is a common challenge in outpatient projects. It can be avoided by communicating with organizations’ leaders about operational and scheduling expectations and coordinating with the architect to establish the appropriate occupancy classification. Costs can be further mitigated by designing for high-grade equipment, system redundancy and resilience only when required for critical programs such as operating rooms, sterile processing departments and compounding pharmacies. 

Design and program alignment 

Ambulatory care centers and ambulatory surgery centers serve different clinical functions and therefore require distinct engineering approaches. This variety of services and applicable codes can lead to uncertainty and result in overdesign of engineering systems. 

System design elements that can prevent unnecessary costs while maintaining patient comfort and code compliance include: 

• airflow, filtration and other environmental requirements as dictated by local mechanical codes rather than healthcare-specific standards 
• standard commercial-grade HVAC systems, such as DX packaged rooftop units 
• basic temperature control without active humidity control 
• limited pressurization requirements, typically only for specialty spaces, such as labs 
• reduced ductwork through plenum returns air strategies 
• portable cylinders rather than central or manifolded medical gas systems 
• emergency power limited to life-safety systems 
• limited application of mechanical, electrical and plumbing (MEP) system redundancy strategies. 

Ambulatory surgery centers are licensed medical facilities where same-day surgical procedures are performed. These facilities require sterile environments, anesthesia delivery, post-operative recovery spaces and advanced medical equipment. While scaled for smaller programs and non-24/7 operations, ambulatory surgery center engineering systems more closely resemble hospital surgical departments. Key system considerations include: 

• compliance with ASHRAE 170 or the equivalent local code for outpatient healthcare ventilation 
• centralized MEP equipment, often located in mechanical penthouses for access and maintenance 
• strict temperature and humidity control in operating rooms, sometimes requiring low-temperature chillers or desiccant dehumidification 
• specialized spaces, such as operating rooms, sterile processing, labs and pharmacies requiring specific air change rates, pressure relationships and continuous monitoring 
• enhanced filtration requirements for operating rooms, including MERV-16 or HEPA filtration, depending on procedure type 
• dedicated exhaust systems for hazardous compounding pharmacies, sterile processing or nuclear medicine spaces 
• central medical gas systems with medical air and vacuum compressor skids 
• thoughtful redundancy and emergency power strategies based on operational expectations during utility outages. 

Designing for redundancy, fuel storage and emergency power in an ambulatory surgery center can be an individual decision. In some locations, extreme weather that might cause an outage is predicted, and surgeries can be postponed. In most cases, the design anticipates completing ongoing operating room activity while all other patients are evacuated. 

Challenges of adaptive reuse 

Adaptive reuse of existing buildings for ambulatory care facilities can be an appealing alternative to new construction. But buildings not designed for healthcare might have systems that are not suitable for adaptive reuse. An early engineering evaluation that assesses existing building attributes can help validate the needs of this development approach. 

Facilities designed for other uses might have HVAC and electrical systems that are undersized or noncompliant with current codes, as well as insufficient structural capacity to support the ambulatory care program and MEP systems. Buildings also can present space and fit challenges due to existing floor-to-floor heights never intended to support healthcare-focused systems. 

Older facilities also often lack the thermal performance of modern construction and require envelope enhancement and increased HVAC system sizing. 

Pursuing excellence and performance 

Ambulatory care facilities sit in a sweet spot. They require clinical-grade systems but offer greater flexibility than inpatient hospitals, which makes them ideal candidates for high-performance, low-carbon designs. The following strategies offer a blend of sustainability, resilience, high performance and patient-centered design: 

• Occupancy-based scheduling and setbacks can be leveraged in HVAC designs to account for predictable peak times, allowing systems to ramp down during off-hours. 
• Low-energy HVAC deployment accounts for spaces with Group B occupancies, which have less stringent HVAC requirements and offer opportunities for higher-performing air delivery systems. 
• Separation of high-ventilation zones — e.g., procedure rooms — from low-intensity zones — e.g., administrative areas — avoids over-conditioning. 
• All-electric design through the avoidance of gas-supplied heating and domestic hot water supports decarbonization. 
• Water conservation measures, made possible by ambulatory care facilities’ lower water use intensity, reduce operational costs and environmental impact. 
• Building envelopes with enhancements, such as high-performance glazing and insulation, amplify MEP system performance. 

Designing cost-effective engineering systems for ambulatory care facilities is not about minimizing investment but about investing strategically. Successful projects align system reliability with patient acuity, prioritize comfort and avoid applying inpatient hospital standards where they are not warranted. 

Close collaboration among designers and facility owners and engineers is essential to define operational expectations and explain the way engineering systems support those goals. When system planning is grounded in program understanding, adaptive reuse challenges are addressed early and performance requirements are right-sized, ambulatory care facilities can achieve high reliability, flexibility, sustainability and patient satisfaction while remaining within budget constraints. 

Nick Martin, P.E., is principal and healthcare market leader with Affiliated Engineers. Abhishek Ajansondkar is project manager and healthcare market leader with the firm.