Multiapartment buildings

Centralized and decentralized ventilation systems both have their advantages and are chosen depending on the building's size, usage, and energy efficiency.

Centralized ventilation with heat recovery

In centrally placed ventilation system one air handling unit serves supply and extract air for multiple apartments via a duct network. The heat recovery exchanger transfers energy from exhaust air to incoming fresh air. System can consist of one air handling unit covering all the apartments in a building or several units each serving several apartments in the same floor/corridor.

Advantages

High energy efficiency
Often most cost efficient installation in large buildings
Easy to maintain in one location and therefore creates less maintenance costs over lifetime
Quiet operation when designed correctly

To consider

Requires significant duct space
Higher installation complexity
Not as indivually adjustable - adjustments affect multiple apartments if not zoned properly
May require fire sections
Risk of transferral between flat

Read more:
CENTRAL SYSTEMS

Apartment-specific ventilation with heat recovery

In apartment-specific ventilation system each apartment has it's own individual air handling unit that serves supply and extract for that specific apartment via a duct network. The heat recovery exchanger transfers energy from exhaust air to incoming fresh air. The air handling unit can be installed in the bathroom, storage room, or kitchen area or in suspended ceiling.

Advantages

High energy efficiency
Each apartment controls their own indoor climate
Individual adjustable to each residents needs
No risk of transferal odors
Less vertical and horisontal shafts required
With wall outlets/inlets for fresh and exahaust air even less ducting required
No need for fire blocks

To consider

More units to maintain
Space for the unit needed inside each apartment
Service access inside apartments

Read more:
APARTMENT-SPECIFIC SYSTEMS

Centrally placed apartment-specific ventilation with heat recovery

A unique residential solution that combines the best qualities of central and decentral ventilation. Each apartment has it's own individual air handling unit that serves supply and extract for that specific apartment with all the units located outside the apartmnet in the roof and connected to the apartments via a duct network. The heat recovery exchanger transfers energy from exhaust air to incoming fresh air.

Advantages

A gapless continuous isolation of building and heat exchangers
Higher energy efficiency for the building
Roof placed unit saves space in the living area
Maintenance and repair is possible without accesing the apartment
Quick installation
Lower investment costs due to quick mounting and less ducting required

Disadvantages

Optimal for lower buildings (up to 5 stories)
Shafts and installation needs to be taken into consideration early in the building design

Read more:
APARTMENT-SPECIFIC ROOF PLACED SYSTEM

Wall placed ductless ventilation with heat recovery

These compact heat recovery ventilation units are installed directly through external walls. Therefore they don't require any ducting for suply air, but a separate extract duct from bathroom can be connected. Simple ductless installation makes these units ideal for renovation.

Advantages

Minimises needed ductwork
Simplified planning and installation
Suitable for renovations

To consider

Potential for increased noise
Limited airflow performance
Larger apartments may require several units to meet airlow requiremenets

Exhaust only

Exhaust ventilation is a traditional ventilation method that is used in many older buildings. In exhaust ventilation used indoor air is being extracted with a fan unit and fresh replacement air enters through inlets in the wall.

Pros