Energy Performance Regulation for Buildings

The Ordinance No. 138-I/2021, of 1 July marks a structural milestone in the evolution of energy efficiency in buildings in Portugal. This decree establishes, for the first time in an integrated and systematic way, the minimum energy performance requirements applicable both to the building envelope and to the installed technical systems, promoting a more rational use of energy and contributing to the environmental sustainability of the national building stock.

Single-family dwelling with good energy performance, view of the living area

Context and Application

This Ordinance was issued in implementation of Decree-Law No. 101-D/2020, of 7 December, which regulates the Energy Certification System for Buildings (SCE). Its main objective is to ensure that new and renovated buildings in Portugal meet high energy performance standards, reducing energy consumption and carbon emissions. The Ordinance applies to:

• Residential buildings

• Commercial and service buildings

• New or renovated buildings

• Technical systems installed or renewed in buildings

Ordinance Structure: Two Fundamental Pillars

The regulation is organized into two complementary annexes defining technical requirements:

Annex I: Building Envelope

Sets requirements for building elements that separate the interior from the exterior or unconditioned spaces:

• Opaque envelope (walls, roofs, floors)

• Glazed envelope (windows, glazed doors, skylights)

Annex II: Technical Systems

Defines performance obligations for all installed systems:

• Ventilation systems

• HVAC systems

• Domestic hot water systems (DHW)

• Lighting systems

• Electricity generation systems

• Automation and control systems (BMS)

• Elevators, escalators, and moving walkways

• Electric vehicle charging infrastructures

Building Envelope Requirements

Opaque Envelope: Insulation and Thermal Protection

The Ordinance sets maximum thermal transmittance coefficients for walls, roofs, and floors, varying by climate zone (I1, I2, I3) and geographic location (Mainland Portugal, Madeira, Azores).

Example for residential buildings in Mainland Portugal (zone I3):

• Exterior vertical walls: U≤0.35 W/(m2⋅°C)U≤0.35W/(m2⋅°C)

• Exterior horizontal roofs: U≤0.30 W/(m2⋅°C)U≤0.30W/(m2⋅°C)

• Vertical thermal bridges: U≤0.90 W/(m2⋅°C)U≤0.90W/(m2⋅°C)Key points:

• All building elements must have documented technical characterization

• CE marking and declaration of conformity mandatory

• Possible exemptions if adequate thermal comfort is demonstrated

• Alternative solutions allowed in case of technical or functional constraints

Glazed Envelope: Solar Control and Thermal Losses

Glazed openings must meet two types of requirements:

• Maximum thermal transmittance coefficients:

  • Residential buildings (Mainland Portugal, zone I3): Uw≤2.20 W/(m2⋅°C)Uw≤2.20W/(m2⋅°C)

  • Commercial and service buildings: Uw≤3.30 W/(m2⋅°C)Uw≤3.30W/(m2⋅°C)

• Solar gain control:

  • Maximum solar factors vary by climate zone and thermal inertia

  • Specific requirements for shading and solar protection

  • Limitation on glazed area depending on solar exposure

Technical Systems: Efficiency and Quality

Ventilation Systems

Prioridades:

• Priority for natural ventilation whenever possible

• Ensure adequate indoor air renewal

• Minimum airflows defined by space typology

Examples of minimum airflows (commercial and service buildings):

Tipo de atividade	Caudal mínimo (m³/h por ocupante)
Sleeping	16
Resting	20
Sedentary (offices)	24
Moderate (labs)	35
High (sports halls)	98

Technical obligations:

• Installation of appropriate filters in mechanical systems

• Minimum safety distances for fresh air intake

• Energy recovery in systems > 80 kW

• Airtightness and adjustment testing

  
  

HVAC Systems

Separate temperature control per space or thermal zone

• Rigorous thermal insulation of all distribution networks

• Use of free-cooling devices when supply airflow > 10,000 m³/h

• Minimum 50% energy recovery efficiency

• Power limitations:

  • Electric heating ≤ 5% of total thermal power (max 25 kW per unit)

  • Terminal reheating ≤ 10% of cooling power

• Monitoring and control:

  • Energy meters mandatory for centralized systems

  • Integration into energy management systems (power ≥ 50 kW)

  • Monitoring points for temperature, consumption, and efficiency

Domestic Hot Water Systems

Priority for equipment using renewable energy

• Strict thermal insulation of pipes and tanks

• Installation of certified solar thermal systems

• Water efficiency and waste minimization

• Certification by accredited laboratories mandatory

• Mixing valves for temperature control

• Sizing for 50% to 75% of annual needs

• Freeze and overpressure protection

Lighting Systems

Power density limits (W/m² per 100 lux) vary by space type:

• Offices and classrooms: 1.8 W/(m²·100 lux)

• Corridors and staircases: 2.3 W/(m²·100 lux)

• Parking areas: 2.1 W/(m²·100 lux)

• Mandatory control systems:

  • Presence detection and daylight harvesting

  • Light intensity regulation

  • Integration into energy management

  • Timers and schedules

Automation and Control Systems (BMS)

Application by installed power:

Total Rated Power	System Type
100 kW ≤ PC < 290 kW	Technical Management System (TMS)
PC ≥ 290 kW	Centralised Technical Management System (CTMS)

Minimum functionalities:

• Continuous consumption monitoring and logging

• Energy efficiency comparative analysis

• Detection of efficiency losses

• Communication with technical systems via standard protocols

• Individual meters per system

• Historical data archive (minimum 6 years)

Energy efficiency class targets:

• Until 2025: Class B (EN 15232)

• From 2025 onwards: Class A

Elevators and Vertical Mobility

Energy efficiency requirements:

• Elevators: Class B (ISO 25745-2)

• Hydraulic elevators: Class C

• Escalators and moving walkways: Class A (ISO 25745-3)

Electric Vehicle Charging Infrastructure

New residential buildings:

• Provision for future infrastructure in all parking spaces

• Prepared ducts and cable paths

  
  

New commercial and service buildings:

• Provision in one out of every five spaces

• Minimum installation of two charging points

• Integration into technical energy management system

Single-family dwelling with good energy performance, view of kitchen and dining area

Constraints and Flexibility

The Ordinance acknowledges exceptional situations and provides flexibility mechanisms:

Types of constraints:

• Technical or functional: inability to comply due to specific regulation or impairment of function

• Economic: proven impossibility in certified buildings

Alternative solutions:

• The project author must precisely identify and justify constraints

• Propose alternative solutions that minimise impacts

• Promote improved energy performance and comfort

• Document all options in the project

Installation, Testing and Adjustment

• Installation by duly qualified entities

• Supervision by qualified technicians (where applicable)

• Compliance with legislation, standards, and project

Mandatory Tests

The Ordinance establishes stringent verification procedures:

Ventilation systems (airflow ≥ 3,000 m³/h):

• Duct network airtightness

• Airflow measurement at terminals

• Electrical protections verification

• Cleaning and functionality checks

HVAC systems (power > 30 kW):

• Hydraulic network tightness

• Network balancing

• Combustion efficiency

• Electrical consumption measurement

Lighting systems (≥ 25% of area):

• Illuminance level measurements

• Control system calibration

• Energy consumption

Reports and Documentation

• Execution report validated by owner

• Operation manuals

• Final diagrams (Telas Finais)

• Technical catalogues and conformity certificates

• Maintenance procedures

Practical Advice for Developers and Owners

• Plan ahead: Integrate energy requirements from design phase

• Choose qualified professionals: Ensure designers and installers have specific energy efficiency training

• Invest in envelope: Thermal insulation and efficient glazing provide guaranteed medium-term returns

• Prioritise renewables: Solar thermal and heat pump systems reduce operating costs

• Do not neglect ventilation: Indoor air quality is essential for occupant health and comfort

• Prefer control systems: Automation optimises consumption without compromising comfort

• Document thoroughly: Keep records of tests, certificates and maintenance manuals

• Consult specialists: Seek expert technical support for constraint situations to find suitable solutions

Impacts and Benefits

Implementing Ordinance No. 138-I/2021 provides multiple benefits:

• Environmental:

  • Significant reduction in energy consumption

  • Decrease in greenhouse gas emissions

  • Contribution to national and European climate goals

• Economic:

  • Lower energy costs over building lifecycle

  • Increased property value

  • Reduced external energy dependence

• Social:

  • Improved thermal comfort and indoor air quality

  • Reduction of energy poverty

  • Promotion of qualified employment in the sector

Reflection

Ordinance No. 138-I/2021 represents a qualitative leap in building energy regulation in Portugal, aligning the country with best European practices. Beyond a legal obligation, it is an opportunity to rethink how buildings are designed, constructed and managed, promoting environmental sustainability, economic efficiency and quality of life simultaneously.