Sustainable buildings are designed to be efficient, resource-efficient, and durable. But in everyday life, there is another factor that determines how a building is truly perceived: the indoor climate.
People don't experience buildings through certificates or technical documentation, but through temperature, humidity, CO₂ levels, odors, particulates and overall air quality. Since people spend up to 90% of their time indoors, this factor is becoming increasingly important. A building can be perfect on paper and still feel “off” in the long run.
The Quality Seal for Sustainable Buildings (QNG) plays a central role in this context. It defines requirements for sustainable construction and serves as a guide for building owners, designers, and certification experts. At the same time, there is growing interest in solutions that demonstrate how buildings perform in actual operation.
After all, there is often a difference between sustainable planning and a healthy indoor environment.
Sustainable Building Quality Certification: What are the QNG requirements?
The QNG label evaluates buildings not merely as individual products or technical components, but as an integrated system throughout their entire life cycle. The goal is to make sustainable quality measurable, comparable, and transparent.
The QNG takes various quality aspects into account:
- environmental quality
- economic quality
- technical quality
- Process quality
- sociocultural and functional quality
The sociocultural and functional quality of a building is particularly important for its future use. This includes, among other things, user comfort, health, accessibility, and indoor air quality.
In addition, the QNG defines what are known as “special requirements.” These address issues of particular social importance and enhance the sustainability impact of buildings. They include, among other things:
- Climate Protection and Resource Conservation
- Prevention of Hazardous Substances in Construction Products and Materials
- Space efficiency
- Comfort and quality of stay
- interiors that are safe for health
This makes it clear that sustainability, as defined by the QNG, does not stop at energy performance indicators or building materials, but also encompasses very specific aspects of the building’s future use.
Indoor air quality as part of the QNG requirements
One area of the QNG requirements that is particularly relevant in practice is indoor air quality.
This is because even with careful planning and high-quality materials, indoor air quality can change over time. This is due not only to building materials, but primarily to how the space is used, its occupancy, and the technical conditions of daily life.
Typical influencing factors include:
- High CO₂ levels due to high occupancy
- inadequate or improperly adjusted ventilation
- Emissions from furniture and interior finishes (VOCs)
- particulates particulate pollution
- Humidity and dry air
- Odors caused by use and cleaning
These factors are crucial to users’ comfort, health, and productivity. This is precisely why indoor air quality is increasingly viewed as a measurable standard in the context of sustainable buildings, rather than merely a design target.
QNG Plus Seal and QNG Premium: What's the difference?
In addition to standard QNG, there are various quality levels, including QNG-Plus and QNG-Premium.
These levels differ in terms of the stringency of the requirements and the depth of the sustainability criteria considered. Simply put, as the level increases, so do the requirements for quality, sustainability, and overall building performance.
While QNG serves as the basic standard, QNG-Plus and QNG-Premium set higher standards, particularly with regard to:
- Energy Efficiency and Resource Use
- Material and health considerations
- Overall quality of the building
This also highlights the importance of how a building is actually used. After all, the higher the sustainability standards, the more important it becomes to consider how a building performs in everyday use.
QNG evaluates buildings. The air-Q measures actual indoor air quality
The QNG evaluates the sustainable quality of a building as a whole system. Individual products or sensors are not certified separately.
The air-Q is therefore not an official component of the QNG certification and does not replace formal documentation in the certification process.
However, this is not a contradiction, but rather a clear division of responsibilities.
QNG answers the question: Does the building meet defined sustainability and quality requirements?
air-Q answers the question: How good is indoor air quality in real-world conditions?
In practice, it is clear that even certified and well-designed buildings can present challenges once they are in operation. Typical problems include:
- elevated CO₂ levels in crowded rooms
- inadequate air exchange
- dry or excessively humid air
- VOC exposure following renovation or furnishing
- particulates and particulate pollution
- Rumors and Stagnant Air
These effects do not arise during the planning phase, but rather during operation. This is precisely where continuous monitoring comes into play.
From Planning to Building Operations: Why Monitoring Is Crucial
Sustainability doesn't end with the completion of a building. Its true value is realized during its ongoing operation.
After all, it is only when people use a building on a daily basis that it becomes clear whether comfort, health, and functionality truly go hand in hand.
air-Q supports exactly this transition:
- Continuous measurement of indoor air quality
- Real-time analysis of CO₂, VOCs, particulates other parameters
- Data-driven evaluation of ventilation designs
- Early detection of indoor air quality issues
- Optimizing comfort and interior quality
This makes indoor air quality data a key component of sustainable building operations.
Relevance for WELL, DGNB, LEED, and RESET
In addition to QNG, other standards also play an important role in the assessment of sustainable and healthy buildings.
The WELL Building Standard places a strong emphasis on occupant health. The DGNB incorporates indoor environmental quality as a key component of its building certification. Ventilation, air quality, and monitoring are also key evaluation criteria under LEED. The RESET places particular emphasis on continuous indoor air quality data.
In all of these systems, a building’s actual performance is becoming increasingly important. This is precisely where indoor air quality data provides the necessary transparency.
Sustainable buildings need more than just certifications
Certifications such as the QNG establish standards, provide guidance, and enable comparability. They are an important part of modern construction and planning processes.
The key difference, however, becomes apparent in everyday life.
That is when it becomes clear whether buildings have been designed not only to be sustainable, but also to be healthy, comfortable, and functional.
The air-Q supports this transition from planning to implementation. It is not intended to replace certifications, but rather to serve as a tool for making better operational decisions.
After all, sustainable buildings shouldn't just look good on paper—they should also feel good in everyday life.
