Supply air and exhaust air systems ensure controlled air exchange in buildings. Exhaust air systems remove humid and stale air from rooms such as bathrooms, WCs or kitchens to the outside, while supply air systems introduce fresh outside air into living and occupied spaces. The interaction between supply air and exhaust air creates a continuous airflow within the building, reducing humidity, odours and pollutants and supporting a stable indoor climate.
Fans without heat recovery (HRV) are primarily used wherever a simple and cost-effective ventilation solution is required – for example in wet rooms, internal rooms without windows or renovation projects. Decentralised supply and exhaust air units can often be integrated flexibly into existing buildings and enable targeted ventilation of individual rooms.
What are fans without heat recovery (HRV)?
In many buildings, ventilation is based on the interaction between exhaust air systems and supply air systems. While exhaust fans transport humid air from bathrooms, WCs or kitchens to the outside, supply air systems ensure a continuous fresh air supply in living and occupied spaces. This enables a predictable air exchange within the building, reducing humidity and improving air quality.
Functional principle: supply air and exhaust air interaction
Supply air and exhaust air systems work together to create a controlled airflow within an apartment or house. Supply air systems introduce fresh outside air into occupied rooms, while exhaust air systems remove stale and humid air from wet rooms.
In many ventilation concepts, the airflow follows a clear principle:
Supply air → living spaces → wet rooms → exhaust air
Fresh outside air first enters living spaces such as living rooms or bedrooms via supply air systems. From there, the air flows into rooms with higher humidity loads, such as bathrooms or kitchens. There, the stale air is transported outside via exhaust fans.
This principle enables targeted airflow routing within the apartment or house and ensures continuous air exchange.
Exhaust air systems – removal of humid and stale air
Exhaust air systems transport humid or stale air from indoor spaces to the outside. They are mainly used in rooms with high humidity or odour loads. Whether showering, cooking or washing – humidity and odours are generated that must be reliably removed.
Typical application areas for exhaust air systems are:
- Bathrooms
- Toilet rooms
- Kitchens
- Utility rooms
Mechanical exhaust air is particularly important in internal rooms without windows.
Supply air systems – controlled fresh air supply
Supply air systems ensure the controlled supply of fresh outside air into indoor spaces. They provide air supply within the residential unit or building and enable the air supply required for exhaust air systems by directing outside air into living or occupied spaces.
Typical rooms for supply air are:
- Bedrooms
- Living rooms
- Offices
- Occupied spaces
From there, the air is distributed within the apartment or house and then flows further into rooms with exhaust air.
Exhaust air systems for bathrooms, WCs and wet rooms
Humidity is mainly generated in everyday life during showering, bathing or cooking. If this air is not removed, it can accumulate in the room or building structure. Exhaust air systems ensure continuous ventilation and support moisture protection within the building.
Exhaust air in bathrooms
Bathrooms regularly generate large amounts of humidity. Exhaust air systems transport this air outside and help prevent moisture build-up. This reduces the risk of mould growth and improves air quality in the room.
Ventilation for internal rooms without windows
Internal bathrooms or toilet rooms without windows often require mechanical ventilation. Exhaust air systems ensure continuous air extraction and enable reliable ventilation.
Exhaust air solutions in riser ducts
In multi-storey residential buildings, exhaust air systems are often implemented via vertical riser ducts. Exhaust air from multiple units – typically bathrooms, WCs and kitchens – is routed outside via shared duct systems.
This design enables space-saving exhaust air routing across multiple floors and is a well-established solution in multi-storey residential construction. The system typically operates via fan-assisted exhaust air, while the fresh air supply must be ensured separately, for example via passive airflow supply (system) (PAS) units or mechanical supply air fans.
Supply air systems for living and occupied spaces
Supply air systems ensure the controlled supply of fresh outside air into living and occupied spaces and enable a stable air supply within the building.
In living spaces, continuous fresh air supply is important to reduce stale air, odours and pollutants and to support air exchange within the building.
Fresh air supply in bedrooms
In bedrooms, supply air ensures a continuous supply of fresh air and supports a comfortable indoor climate during use.
Supply air solutions for living spaces and offices
In living spaces and offices, controlled fresh air supply contributes to stable air quality. Supply air systems enable predictable air supply.
Air supply within the ventilation concept
For exhaust air systems to function continuously, sufficient outside air must be supplied. This air supply can be ensured either via fan-assisted supply air systems or via passive airflow supply (system) (PAS) units and is an essential component of ventilation concepts according to DIN 1946-6.
While supply air systems actively and demand-based introduce fresh air into the building, PAS units enable pressure-dependent air supply. In combination with exhaust air systems, both solutions ensure defined airflow routing within the building and guarantee proper system operation.
