Ventilation, energy and environment

Ventilation is necessary for providing indoor air quality and thermal comfort in buildings, yet it significantly impacts energy and the environment. Efficient ventilation systems are essential for minimising energy usage and reducing carbon emissions.

Synergy and balance between ventilation, energy and environment

Ventilation, energy and the environment are deeply interlinked and intertwined in buildings and systems. The link is conceptual and practical.

There is a need for ventilation to create a good indoor environment, allowing people to live comfortably in buildings. Yet, efficient ventilation consumes energy to provide good indoor air quality, thus having a large impact on the environment.

Ventilation

The smarter the ventilation, the less energy is consumed.
Efficient ventilation delivers indoor environmental quality that influences people's health and productivity indoors.
Ventilation can enhance renewable energy strategies for the longevity of the environment.

Energy

Efficient energy → lower energy use → smaller environmental emissions.
Energy is the enabler that powers the environment.
Energy performance needs to align with sustainability goals.

Environment

Environmental goals, such as carbon neutrality and low embodied energy, depend on optimising both energy and ventilation.
Achieving a good environment through ventilation methods results in minimal environmental cost.
The longevity of the environment is a direct outcome of good ventilation methods and optimised energy consumption.

Synergy lies in balance → When ventilation, energy and environment strategies reinforce each other, the outcome is a balance of sustainability and resilience.

Means to achieve the balance

The relationship between ventilation, energy and environment is one of dynamic ballance - a continuous flow defined by the quality, efficiency and sustainability of buildings. When the three elements work together, it becomes an interplay between fullfilling human needs, technological efficiency and ecological responsibility.

The relationship between ventilation, energy, and environment is one of dynamic balance — a continuous flow defined by the quality, efficiency and sustainability of buildings. When the three elements work together, it becomes an interplay between fulfilling human needs, technological efficiency and ecological responsibility.

Smart-ready functionalities play a pivotal role in enabling ventilation systems to optimise occupant comfort while achieving energy efficiency in buildings - effectively connecting indoor environmental quality (IEQ) parameters directly to the energy performance of buildings.

The Energy Performance of Buildings Directive (EPBD) and the Smart Readiness Indicator (SRI) are means to help balance ventilation, energy and environment. By defining IEQ and emphasising indoor environment monitoring, the EPBD supports the notion that indoor environmental parameters - such as air quality, thermal comfort, lighting, and acoustics - are integral parts of ventilation effectiveness and energy performance in buildings.

Critically, the indoor environment and energy must always be treated as a duo, never separated, as comfort and efficiency are inseparable objectives. Leveraging everything that EPBD and SRI can make the environment visible, starting from indoor air quality and leading to outdoor surroundings.

Treating energy, ventilation and environment as inseparable ensures buildings are efficient, healthy, resilient and future-ready - benefiting building occupants and the planet as well.

Smart-ready functionalities help improve occupants' comfort and buildings' energy consumption

Smart buildings are about connection — interlinking and reacting to signals — thus satisfying building occupants' demands and achieving buildings' good energy performance. Smart buildings are responsive and can adapt operations. Here are a few examples of smart-ready functionalities.

Occupancy detection sensors help improve air quality and save energy.
Providing information to occupants about the energy consumption of each technical building system can stimulate responsible behaviours.
Fault detection systems can support the effective maintenance of building systems.
Heating, cooling, and domestic hot water systems can be operated based on signals from the grid to provide flexible services without decreasing occupant comfort.

The role of the EPBD and the SRI: How smart-ready buildings address people's needs and meet tomorrow's challenges

The smartness of a building refers to its ability to sense, interpret, communicate, and actively respond efficiently to changing conditions concerning the operation of technical building systems, the external environment, and building occupants' demands. The EPBD Recast, supported by the Smart Readiness Indicator (SRI), envisions smart buildings as integrated energy systems — capable of producing, using, and storing energy while providing a healthy and comfortable indoor environment for people through effective HVAC systems and other advanced building services.

Read our Update&Insight 'The role of the EPBD and the SRI: How smart-ready buildings address people's needs and meet tomorrow's challenges'

Definition of IEQ including its parameters and recognising the importance of indoor environment monitoring in the EPBD

"Indoor environmental quality means the result of an assessment of the conditions inside a building that influence the health and well-being of its occupants, based upon parameters such as those relating to the temperature, humidity, ventilation rate and presence of contaminants."

— The primary definition in Article 2, EPBD

"Member States shall set requirements for the implementation of adequate indoor environmental quality standards in buildings in order to maintain a healthy indoor climate."

"Member States shall require non-residential zero-emission buildings to be equipped with measuring and control devices for the monitoring and regulation of indoor air quality. In existing non-residential buildings, the installation of such devices shall be required, where technically and economically feasible, when a building undergoes a major renovation. Member States may require the installation of such devices in residential buildings."

"The building automation and control systems shall be capable of: (d) by 29 May 2026, monitoring of indoor environmental quality."

— Article 13 sets the requirements for controlling IEQ parameters.

Connecting IEQ parameters directly with energy performance

IEQ is finally included in the EPBD legislation – securing the energy performance of buildings without compromising on indoor climate. As of 2025, IEQ is firmly established in the European legislative agenda for improved energy efficiency, promoting a healthy, comfortable, and productive indoor environment for all.

Here is the "equation": The level of IEQ has a direct impact on the energy performance of a building. At the same time, the energy performance of a building cannot be evaluated without IEQ. A good IEQ cannot be reached in poorly performing buildings.

IEQ must encompass indoor air quality, thermal comfort, lighting and acoustics.

Minimum IEQ requirements should be based on cost-benefit analysis, depending on building type, for example:

workplaces → higher productivity,
schools → better learning
and homes → improved health, rest and recuperation.

It is essential to understand these changes and report IEQ parameters, such as thermal comfort, air exchange, carbon dioxide, indoor pollutants, relative humidity, and external pollutants, as well as lighting levels, acoustic levels, and external noise pollution.

Key thoughts and learnings about IEQ in buildings using the EPBD

IEQ, energy, and health cannot be considered in isolation – comfort aspects for the people in the building and energy economics aspects also need to be taken into account.
The concept of indoor air quality is central to understanding the dynamics behind IEQ in indoor environments, and it is a good starting point for setting strategies.
HVAC systems in buildings are designed to provide comfort indoors and maintain acceptable indoor air quality (IAQ), all while operating in an energy-efficient manner.
All the strategies in the EPBD share the same basic goal – to implement IEQ in an energy-efficient manner for a building, safely and healthily for the building occupant, and in the long-term, sustainably for the future – but the means to achieve this differ, and all methods have their pros and cons.
What we need now is a solution for the present, and in time, we will learn from policy implementation, actual testing and key lessons. Preferably, all should be easily adopted.

IEQ is embedded in the EPBD in multiple places

The EPBD establishes a framework for reducing energy consumption and greenhouse gas emissions associated with the built environment, thereby contributing to the EU's overall climate goals of achieving a carbon-neutral economy by 2050. There is a need for establishing the IEQ definition and IEQ parameters, and tied it into energy performance, monitoring, certificates, etc. This is far more comprehensive than earlier versions of the Directive.

The definition lists several IEQ factors as the basis for minimum monitoring for national standards. However, these parameters are not comprehensive, and the definition needs to be further reinforced by the national guidelines. To ensure optimal indoor environments, guidelines like EN 16798-1 and other European frameworks for sustainable buildings recommend monitoring specific IEQ parameters, defined as temperature, ventilation rates, relative humidity, CO2 levels, VOCs, particulate matter PM2.5, lighting and daylight illuminance, and acoustics with sound pressure and reverberation time.

At least ten different Articles in the EPBD recast explicitly address IEQ, ventilation and/or indoor environmental quality (Articles 1, 2, 5, 7, 8, 13, 15, 19, 20, 23), and even more Articles address the energy performance of buildings. Some Articles are focusing on defining a scope or set a definition (Article 1&2), others are aiming at setting minimum design/performance requirements (5), ensuring IEQ in relation to new buildings and renovations (7, 8). Others are zooming in on monitoring and controls, systems and regulations (13), smart readiness of buildings (15), and, last but not least, some are focusing on information and certifications (19, 20, 23).

Why IEQ and energy as a duo must never be split, and forever must be treated as equals.

IEQ can majorly affect a building's energy performance.
Energy performance cannot be defined without also setting the required IEQ level.
A good IEQ cannot be achieved in a poorly performing building.
When assessing building energy performance, IEQ as a key input must be explicitly included.
Using cost-benefit analysis, minimum IEQ levels can provide the best environment for increased productivity, enhanced learning and improved health.
Reporting IEQ parameters is directly connected to energy results.
Without reporting actual IEQ parameters achieved in buildings, the energy balance and performance comparability cannot be assessed correctly.
Energy performance and indoor environmental quality only become apparent and visible through the achieved results.
Indoor environmental quality and energy-efficient solutions directly contribute to the resilience of buildings against the impacts of climate change.

"Using the EPBD and SRI to make indoor climate visible and valued by everyone is a step in the right direction. Today, defined methodologies exist to monetise energy savings and flexibility services in buildings and for people.

However, there is still a clear challenge in standardising the translation of improving indoor environmental quality (IEQ) into economic value. SRI makes the indoor climate more visible by prioritising user needs, with its scoring system rewarding buildings that enhance health, wellbeing, accessibility, comfort and convenience for people.

The missing link lies in translating these features into financial terms. While the SRI emphasises responsiveness to user needs and includes indoor climate as one of its three key functionalities, connecting these benefits to economic metrics is still critical. Doing so would ensure that IEQ improvements are not only visible but also demanded and valued by all stakeholders in the building sector."

— Statement from Pablo Carnero Melero, Technical and EU Project Officer at REHVA

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Watch: Short video summary of making indoor climate visible using EPBD & SRI

Pablo Carnero Melero & Mikael Börjesson

Experts on making indoor climate visible and demanded by everybody using EPBD & SRI.

Short video from Swegon Air Academy, 2024.

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More about standards

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It is time for a sustainable energy policy which puts people, the environment, human health and peace first.

Dennis Kucinich, an American politician

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