Mechanical cooling of indoor air requires careful planning and the right conditions

Hot summers are increasing the demand for mechanical cooling and presenting new challenges for property owners. Dive into the technical aspects of building technology and learn how indoor air is cooled mechanically in SATOhomes, as well as why controlling the temperature in a rental apartment can be challenging during the summer. Expert insight is provided by SATO’s Building Technology Manager, Jussi Sormunen.

What kinds of mechanical cooling systems are used in SATOhomes?

Some SATO buildings are equipped with mechanical cooling solutions. In a few buildings, cold air produced by a water chiller is used to cool incoming air or individual apartments via fan convector units. In certain buildings, energy providers supply district cooling, which works in conjunction with apartment-specific fan convector units.

In many new or recently renovated buildings heated by geothermal energy, the cooling of incoming air is carried out using the geothermal system’s circulation loop. Additionally, there are some air source heat pumps in apartments and communal areas, which are exclusively used for cooling.

What is a fan convector unit?

A fan convector unit is a device used for heating or cooling spaces. It typically consists of a heat exchanger and a fan. The air within the unit’s range is circulated through the heat exchanger by the fan, causing it to either cool or heat. When used for cooling, moisture in the air condenses on the heat exchanger, reducing the relative humidity and making the air feel fresher. In apartments, fan convector units are usually only utilised for cooling.

Why doesn’t every SATO building have mechanical cooling for incoming air?

As the number of hot summer days increases, so does the need for cooling. SATO ensures that all new and renovated buildings include at least incoming air cooling wherever possible and reasonable.

However, installing incoming air cooling in existing buildings can be very challenging or costly.

There may not be enough space for cooling coils or other required equipment, and constructing pipe routes for apartment-specific fan convector units can be labour-intensive. Additionally, existing air ducts might lack condensation insulation, which is necessary to prevent moisture in the air from condensing on the surface of the ducts.

The installation of air source heat pumps often presents challenges such as electrical requirements, condensate drainage, or finding a suitable location for the outdoor unit.

Why is my home still warm even though my building has mechanical cooling?

With mechanical cooling for incoming air, it is not possible to generate enough cooling power at the prescribed air flow rates to prevent indoor temperatures from rising during prolonged heatwaves. Instead, incoming air cooling slows down the rise in temperature and improves indoor air quality by reducing humidity. Increasing the airflow excessively to enhance cooling would likely result in noisy ventilation equipment.

If your apartment is cooled with an air source heat pump, the layout of the property may limit its effectiveness to the room where the indoor unit is located.

Can I influence how well mechanical cooling works in my home?

Residents can help optimise cooling performance by keeping ventilation outlets clean and blocking direct sunlight with curtains or blinds.

For air source heat pumps, it’s advisable to clean the indoor unit’s filter every few weeks and to regularly remove debris from the outdoor unit’s surfaces. If the pump’s efficiency decreases despite being clean and otherwise functioning properly, it likely needs maintenance. However, this should only be performed by a professional approved by the Finnish Safety and Chemicals Agency (TUKES).

Can I install my own cooling devices at home?

Installing an air source heat pump in a rental apartment always requires the property owner’s permission. It’s also worth noting that air source heat pumps are generally not allowed to be used for heating, as the outdoor unit may generate condensate water that freezes during the winter.

Portable cooling devices can be used if desired, if the condensate water tank is emptied regularly.

How does mechanical cooling affect a home’s energy consumption?

The energy consumption of a single air source heat pump used for cooling is relatively low. For instance, in my own home, the electricity costs during a hot summer were less than €100, even with frequent use of the pump.

Water chillers are more powerful than individual air source heat pumps, but since the cooling is distributed across multiple apartments, the energy consumption per apartment is not significantly higher.

A geothermal system’s circulation loop collects solar energy stored in the ground and transfers it to a heat pump. Cooling with this method—whether for incoming air or through fan convector units—has minimal energy consumption per apartment. This is because it only requires energy to operate the circulation pumps and any fans in the cooling equipment.

Geothermal cooling is also energy-efficient because the heat removed during cooling can be stored and reused in the next heating season.