Project Energy Assessment (PEH)

What is a Project Energy Assessment?

A Project Energy Assessment (Projektové energetické hodnotenie, or PEH) is a quantitative technical document that predicts the energy performance of a building or building component before it is constructed or renovated. It serves as the bridge between design intent and regulatory compliance, translating architectural and engineering decisions into measurable energy outcomes. In Slovakia, PEH is a mandatory deliverable under the Energy Performance of Buildings Directive (EPBD) and the national building act 25/2025 Z. z., which took effect on 1 April 2025.

The PEH assigns an Energy Performance Class (A through G, with A representing zero-energy performance and G the least efficient standard) and calculates primary energy demand in kWh per square metre per year. This makes it both a design tool and a compliance proof—architects and engineers use PEH data to iterate toward better efficiency, while regulators and funders use it to verify that projects meet statutory minimums.

Why is PEH mandatory in Slovakia?

Slovakia, as an EU member state, must implement the EPBD, which requires all new buildings and major renovations to undergo energy performance assessment before permitting. The practical effect is that no building permit is issued and no renovation subsidy is granted without a PEH. This is especially true for Obnov Dom (the Slovak government's residential renovation support scheme), where PEH is a gateway document—projects cannot enter the funding pipeline without demonstrated energy performance targets.

The requirement serves three overlapping goals: transparent communication of a building's efficiency to future owners (informational function), enforcement of minimum performance standards set by law (regulatory function), and documentation of environmental improvement in renovation projects (subsidy-eligibility function). Under the 2025 act, the thresholds and calculation methods have been harmonised more closely with other EU states to support cross-border design standardisation.

How is PEH calculated, and what does it measure?

PEH calculation follows standard methodologies defined in Slovak technical norms (STN 73 0540 series) and EU guidelines (EN ISO 52000 series). A certified professional—typically an architect, engineer, or energy specialist—models the building using approved software, inputting:

• Thermal properties: wall, roof, and foundation u-values; thermal bridge details
• Airtightness: airtightness rating and infiltration assumptions
• Systems: heating source type and efficiency, cooling strategy, domestic hot water method, lighting, and ventilation type (including whether it incorporates heat recovery ventilation)
• Climate data: Slovak regional climate profiles for degree-days and solar radiation
• Operating assumptions: occupancy patterns, internal gains, thermostat setpoints

The output is a predicted annual energy demand in kWh/m², broken down by end-use (heating, cooling, hot water, etc.). This figure is then normalized to generate the A–G class rating. The calculation is deterministic but based on simplified operating assumptions, so actual performance may vary by ±15–20% depending on occupant behaviour.

How does PEH differ from an Energy Audit?

Aspect	PEH (Project Energy Assessment)	Energy Audit
Timing	Pre-construction or pre-renovation (design phase)	Post-occupancy (existing building)
Data source	Design drawings, specifications, design assumptions	On-site inspection, utility bills, metering, thermal imaging
Purpose	Permit compliance, funding eligibility, performance forecasting	Understanding actual performance, identifying retrofit priorities
Accuracy	Predictive (±15–20% margin); assumes standard occupancy	Measured or calibrated; reflects real conditions
Regulatory role	Mandatory before permit issuance	Optional; required for certain retrofit grant schemes

In renovation projects, an energy audit often precedes the PEH: the audit identifies deficiencies and opportunities in the existing building, while the PEH models the impact of proposed improvements and confirms compliance with targets.

How does PEH influence design decisions?

PEH is a powerful iterative tool. Architects and engineers use it to test trade-offs: upgrading window u-values, adding insulation thickness, or incorporating a heat recovery ventilation system all show measurable energy impacts. This allows designers to optimize cost-benefit during the design phase and make evidence-based choices about which investments deliver the greatest efficiency gain per euro spent.

For passive-house or near-zero-energy projects, PEH becomes a continuous feedback loop—design iterations aim for lower and lower energy class ratings until the project meets its target (often A or B class). The document also clarifies where a building sits on the efficiency spectrum: a class D renovation may qualify for Obnov Dom but a class G design will not, so PEH provides architects with clear goalposts.

What are common misconceptions about PEH?

One frequent misunderstanding is that PEH guarantees actual energy consumption will match the predicted value. In reality, PEH assumes standardised occupancy and operation; real buildings are inhabited by diverse occupants with different heating setpoints, ventilation habits, and device use. A well-designed A-class building can consume more energy if inhabitants open windows in winter or set thermostats to 24°C continuously.

Another misconception is that PEH is only relevant for new construction. In fact, PEH is equally important (and often more impactful) in renovation: it quantifies the benefit of retrofit measures and is a prerequisite for subsidy eligibility. Without PEH, a renovation project lacks proof of compliance and loses access to most public funding.

A third myth is that PEH and Energy Performance Class are fixed once issued. In reality, they can change if the design is revised significantly, building systems are substituted, or (in occupied buildings) if actual consumption data warrants recalibration. PEH is a snapshot of design intent, not a perpetual certificate.

PEH and the 2025 Slovak Building Act

The new act 25/2025 Z. z. (effective 1 April 2025) maintains the mandatory PEH requirement but refines calculation methodologies and minimum performance standards. Notably, the act increases minimum u-value requirements for new builds and sets higher renovation targets for Obnov Dom eligibility. Any PEH prepared under the earlier 1976 act framework is no longer valid for new permits—practitioners must use the updated calculation norms and assumptions.

This transition has particular impact on renovation projects: buildings that might have qualified as 'adequately renovated' under the old regime now require higher energy class targets to access current subsidies. Architects should verify which building act applies to a given project timeline and ensure the PEH professional is working under the correct regulatory framework.

How does PEH relate to certification systems?

System	PEH relationship	Typical role in project
Passive House	PEH is one input; Passive House uses its own stricter calculation method	PEH establishes baseline; Passive House certification requires separate modeling
BREEAM	PEH satisfies BREEAM's energy-performance credit requirement	PEH data feeds into BREEAM energy score; BREEAM adds broader sustainability assessment
EU EPC (Energy Performance Certificate)	PEH becomes the EPC for new buildings; differs for existing buildings	PEH IS the regulatory compliance document; no separate EPC needed at permit stage

In practice, PEH often serves as the foundation for multi-label projects: a designer will produce a PEH for regulatory compliance, then use that data as a starting point for Passive House certification modelling or BREEAM environmental scoring. PEH is the mandatory common denominator; additional certifications layer on value and marketing differentiation.

Who prepares PEH, and what qualifications are required?

Under Slovak law, only a qualified professional can prepare PEH. Typically, this is an architect, engineer, or certified energy auditor registered with the relevant professional body and having completed training in Slovak energy calculation standards (STN 73 0540, EN ISO 52000 methods). Most architecture offices maintain in-house expertise or partner with specialist consultants.

The responsibility for accuracy rests with the professional who signs the document; they must declare compliance with current norms and take professional liability. As PEH is a legal precondition for permitting and funding, authorities audit PEH quality periodically, and calculation errors or outdated methodology can result in permit rejection or subsidy clawback.