Designing Buildings from Operation Backwards

Keywords: Building automation; EN ISO 52120-1:2022; EPBD; Smart Readiness Indicator; hydronic balancing; data-driven operation; HVAC distribution systems; building performance; demand response; asset value

Future-ready buildings protect asset value by combining comfort, energy efficiency, regulatory compliance, and verifiable operational performance. This requires planning from operation backwards: starting with future operational, reporting, and investment requirements, and translating them into building automation, HVAC functionality, and dynamically balanced water and air distribution systems.

Future-ready buildings are operational assets

Building projects are increasingly expected to deliver not only carbon- and energy-efficient construction, but also long-term operational performance, adaptability and regulatory compliance. This shifts attention from the completion of a building towards its performance throughout its entire lifecycle.

For many years, buildings have been planned mainly around static assumptions: fixed-usage profiles, peak loads, standard operating schedules, and conventional system sizing. This logic may be sufficient to complete and hand over a building. However, it is no longer sufficient to ensure that the building remains valuable, efficient, compliant, and attractive throughout its life cycle.

The use phase of buildings is becoming increasingly dynamic: occupancy patterns change during the day, internal and external loads fluctuate, and spaces may be repurposed several times over a building’s lifetime. At the same time, energy prices are becoming more volatile, grid interaction and demand response are gaining importance, reporting obligations are increasing, and users expect comfortable, transparent, and flexible indoor conditions. As a result, buildings must continuously adapt to changing operational requirements.

This changes the strategic role of HVAC systems and building automation and control systems (BACS). They are no longer only technical infrastructure; they are essential enablers of asset value, operational performance, compliance documentation, and data-driven operation.

From asset value to technical functionality

A building is future-ready not just because it was built efficiently, but because it can be operated, measured, adapted, and optimized effectively.

Future requirements point in this direction. The Energy Performance of Buildings Directive (EPBD) strengthens the role of technical building systems, BACS, monitoring, and indoor environmental quality. In Article 15 and Annex IV, the EPBD establishes the framework for assessing the smart readiness of buildings, including their ability to respond to occupants, technical systems, and the energy grid [1]. In EPBD, Article 15, the Smart Readiness Indicator assesses whether a building can adapt its operation to the needs of occupants, technical systems, and the energy grid. EU sustainability reporting and building-policy instruments increasingly require reliable, traceable, and verifiable building performance data.

This creates a new planning logic: asset value depends on operational performance; performance must be measured; measurement requires reliable building data; building data enables monitoring, reporting, and benchmarking; and these capabilities depend on building automation and HVAC systems designed for dynamic, load-driven operation.

In other words, long-term value starts in the use phase, but it must already be considered in the design phase. Figure 1 illustrates this planning logic.

Figure 1. Future-ready buildings can be designed by working backwards from operational goals: from asset value, performance, reporting, and flexibility to building automation and control systems, HVAC functionality, and dynamic distribution systems.

Future requirements for non-residential buildings

Future-ready buildings should be able to meet several requirements simultaneously. Table 1 summarizes the operational relevance and technical consequences of these requirements.

Table 1. Future requirements for non-residential buildings and their technical consequences.

EN ISO 52120-1 as a functional bridge

It is recommended to define the BACS already in the design phase of a building project, as it is a critical and essential performance part of the infrastructure, not a late-stage add-on. BACS defines whether a building can monitor, control, analyze, and optimize its technical systems in real operation.

Figure 2. Cover of the REHVA/eu.bac brochure on EN ISO 52120-1, linking building automation with energy-efficient and sustainable buildings.

EN ISO 52120-1:2022 provides a practical framework for specifying and assessing building automation, control, and technical building management functions [2]. The eu.bac / REHVA brochure describes the standard as a functional bridge between sustainability and building performance [3]. It provides a harmonized methodology to assess the influence of BACS and building management on energy performance and functionality. It also creates clarity for stakeholders and enables verification that building systems perform as intended.

For building owners, facility managers, planners, engineers, and ESG teams, the standard offers three major benefits: clear and verifiable performance requirements, measurable improvements in energy efficiency and indoor climate, and reliable data for ESG reporting and compliance.

This makes EN ISO 52120-1 more than just a technical standard; it provides a method for making performance requirements specific, achievable, and verifiable.

Dynamic buildings require adaptive systems

Building operation is becoming more dynamic as occupancy patterns, thermal loads, energy prices, and grid conditions change over time. Technical building systems must therefore respond flexibly to changing operational conditions.

Static balancing and fixed operating assumptions are generally less suited to environments characterized by continuously varying demand. Systems designed primarily for peak-load conditions may result in oversized equipment, reduced operational stability, elevated return temperatures, increased pump and fan energy use, comfort-related issues, and suboptimal integration of renewable energy systems.

This is particularly relevant for heating and cooling water distribution systems as well as air distribution systems. In water-based systems, dynamic hydronic balancing supports the delivery of heating or cooling based on actual demand. It contributes to stable flow conditions, improved temperature differentials, reduced pumping energy, and more efficient operation of heat pumps and chillers.

Similarly, demand-controlled ventilation and zone-based airflow control align air supply with occupancy levels and indoor air quality requirements rather than fixed operating schedules. Figure 3 illustrates the difference between static design assumptions and the dynamic conditions encountered during building operation.

The functional requirements described in EN ISO 52120-1 reflect this perspective. As outlined in the eu.bac / REHVA brochure on EN ISO 52120-1 Class A includes adaptive hydronic balancing and demand-based zone ventilation control using CO₂ or air-quality sensors. Class B includes simpler static balancing and occupancy-based ventilation control, while Class C is associated with manual control or fixed-schedule operation [3].

This distinction is important. Software alone is generally insufficient to achieve smart building functionality without appropriate field-level capabilities. Smart readiness depends on field-level capabilities: sensors, actuators, valves, controllers, data points, trend logs, and control strategies. Without controllable and measurable distribution systems, BACS cannot deliver real performance.

Figure 3. Buildings are often designed according to static assumptions, while real operation is dynamic. This creates the need for dynamic balancing, demand-based control, and continuous monitoring.

The hidden cost of oversizing

One of the largest cost blocks in building technology is generation equipment: heat pumps, chillers, boilers, air handling units, and related infrastructure. These systems are often sized on static design assumptions and safety margins. If real demand is not properly understood, and if distribution systems are not balanced and monitored, installed capacity may exceed what is actually required in operation.

Oversizing can have several implications. It may increase capital expenditure, reduce part-load efficiency and contribute to cycling behavior, unstable operating conditions and shortened equipment lifetime. In addition, oversized systems can increase the cost and complexity of the transition to renewable heat supply.

Thinking from operation backwards requires a different perspective when evaluating the replacement or sizing of HVAC equipment: What is the real demand of the building, and can the distribution system deliver this demand efficiently and dynamically?

Only after these questions have been assessed can HVAC capacity be sized on the basis of effective operational demand.

Case study: GW St. Pölten

The GW St. Pölten project in Austria provides a practical example of this approach [4,5]. GW St. Pölten Integrative Betriebe GmbH operates an industrial campus of four buildings with a total floor area of 17,500 m², including production, workshop, and office facilities with varying occupancy patterns and operational requirements. The existing heating system consisted of four gas boilers with a combined output of 1 MW. At the start of the project, there was no systematic monitoring of energy flows, and the heating distribution system had not been hydronically balanced.

Instead of replacing the existing boiler capacity on a like-for-like basis, the project team first installed measurement points for energy-flow diagnostics and online monitoring. This created a data-based understanding of actual heating demand, revealed operational inefficiencies, and provided the basis for system redesign.

The diagnostic data showed inefficient system behavior, including frequent cycling and unstable supply and return temperatures. Based on this data, hydronic balancing was implemented using pressure-independent control valves. The optimized distribution system improved operational stability and enabled smaller valve dimensions, resulting in reported investment savings of approximately 15% for the distribution system.

The improved understanding of real demand and the optimized hydronic system allowed the future heat pump system to be downsized from 1 MW to 500 kW, saving approximately EUR 200,000 in investment costs for heat generation equipment [5].

The hydronic optimization and distribution measures also delivered substantial environmental and economic benefits. The reported carbon saving attributed to distribution and hydronics was 1,088 tCO₂e over the project lifetime [5], with cost savings of 158,000 CHF.

The case illustrates the management relevance of operation-based planning: measure first, optimize distribution, then size generation capacity and invest.

Figure 4. At GW St. Pölten, early diagnostics, monitoring, and hydronic balancing enabled the heat pump system to be downsized from 1 MW to 500 kW, saving approximately EUR 200,000 in investment costs.

Data-Driven Operation starts in design

Effective Data Driven Operation depends on design decisions made during the planning phase. If the required sensors, data points, control functions, and system architecture are not specified early in the project, the ability to support advanced operational functions may be limited.

Functions such as predictive maintenance, fault detection, demand response, benchmarking, ESG reporting, and digital building logbooks rely on the availability of high-quality operational data. Data quality is closely linked to what is measured, while the availability of measurements depends on how systems are planned, installed, commissioned, and maintained throughout their lifecycle.

Consequently, the planning process should consider future operational requirements from an early stage, including questions such as: Which performance indicators must be reported? Which systems must be monitored? Which rooms or zones require indoor climate data? Which loads can be shifted? Which equipment should be maintained predictively? Which benchmarks are needed at the portfolio level? Which data must be available for compliance, ESG reporting, or SRI assessment?

The answers to these questions can provide the basis for defining the required automation functions, monitoring capabilities, and HVAC system requirements.

In this context, designing from operation backwards means using future operational, reporting and performance requirements as inputs for system design and specification.

Poor data availability limits the ability of owners and operators to demonstrate compliance, benchmark performance, and identify optimization opportunities. As reporting requirements evolve, data quality is becoming a strategic asset rather than a purely technical consideration.

Implications for HVAC and BACS planners

For HVAC and BACS planners, this approach has several implications.

First, the use phase should be considered a central design criterion. Planning should address not only how peak loads can be covered, but also how the building is expected to perform under changing part-load conditions.

Second, distribution systems can increasingly be regarded as active performance systems rather than passive infrastructure.

Heating water, cooling water and air distribution systems play an important role in linking energy supply, indoor environmental quality, occupant comfort, and operational data.

Third, BACS requirements should be defined early in the project and described in functional terms.

EN ISO 52120-1 can support this by defining the desired automation class and the corresponding functions for heating, cooling, ventilation, lighting, monitoring and optimization.

Fourth, commissioning processes should verify operational functionality in addition to the correct installation of system components.

From an operational perspective, the key consideration is whether the building is able to effectively monitor, control, and optimize performance under real operating conditions.

Finally, future adaptability should be considered during system design and specification. Building use, tenant requirements, operational processes, comfort expectations, energy markets, and regulatory frameworks are likely to evolve over time. Technical systems can therefore benefit from a level of flexibility that allows adaptation to changing requirements without extensive redesign or replacement.

Conclusion

Future-ready buildings are not created by oversized generation equipment, but by dynamic, measurable, and controllable systems that can adapt to real operation. Operational performance protects long-term asset value, and this performance is enabled by design decisions made early in the project.

The GW St. Pölten case demonstrates this logic in practice. Early diagnostics, monitoring, and hydronic balancing enabled more informed investment decisions, reduced required generation capacity, and improved both economic and environmental performance.

The key takeaway is clear: measure first, optimize distribution, size capacity based on real demand, and only then invest. In short, long-term building value is realized in operation, but it is created in design.

References

[1]     European Parliament and Council. Directive (EU) 2024/1275 of 24 April 2024 on the energy performance of buildings (recast).

[2]     CEN: EN ISO 52120-1:2022 Energy performance of buildings - Contribution of building automation, controls and building management - Part 1: General framework and procedures.

[3]     eu.bac / REHVA. Building Automation for Energy-Efficient & Sustainable Buildings – EN ISO 52120-1. 2026.

[4]     Belimo Climate Foundation. Annual Report 2024. “How an Industrial Building Gets a Climate-Friendly Concept: The Decarbonization Journey of GW St. Pölten”AS, pp.15-20.

[5]     eubac.org. “Decarbonising an Industrial Campus: The GW St. Pölten Case Study.” 9 June 2026.