Rooftop units

A rooftop air conditioning unit can cool a building by taking heat from the air. Like the domestic air conditioner, it can be reversible and thus cover the heating requirement of the building. Unlike air conditioners, the rooftop unit is a single unit and is installed on the roof of a building.

Working principle

A rooftop unit can be described as an air conditioner that can use:

  • outdoor (fresh) air or a mixture of outdoor air / exhaust air
  • recycled air (indoor air) or a mixture of recycled air / outdoor air

A rooftop unit consists of 2 parts:

  1. - A first compartment for air handling and renewal. It is similar to an air handling unit for mixing outdoor (fresh) air / recycled air.
  2. - A second compartment comprising the air conditioning function (and heating mode by inversion of the thermodynamic cycle) consisting of a refrigerant, an evaporator, one or more compressors, an expansion valve and a condenser.

An additional back-up heater or gas burner may also be integrated into the rooftop unit.

Air ventilation is done with or without outdoor air. The ratio of fresh air / recycled air is controlled by a mixing box: this ratio may vary depending on the occupancy of the building.

The rooftop unit also has a “free-cooling” function, which, when conditions permit, uses outdoor fresh air (e.g. during the night) to meet the cooling demand of the room. The thermodynamic cycle does not work during the free-cooling mode.

Thus, the rooftop unit can operate with 100% fresh air as well as with 100% recycled air, depending on the need of the building and the season.

The different certified technologies

Rooftop units can be in “cold only” or “reversible” mode. The term “reversible” means that the air conditioner can produce heat (heating mode) and cold (cooling mode).

Rooftop units draw/release their calories from/into the air, but some models can also be installed on a water loop.

Advantages of a rooftop unit

A rooftop unit can cool, heat and ventilate very large areas. It is therefore particularly well suited to large volumes for industrial or commercial use such as warehouses, shops or supermarkets. The floor area is never cluttered since the unit is installed on the roof.

When the “free-cooling” function is activated, the system is truly energy efficient since the compressor is not operational.

Compare to make the right choice

It is very easy to make the right choice: just compare the products. But when product performance is not certified, this becomes impossible.

Certification makes it possible to compare objectively.

  • The product performance is evaluated according to the same criteria, and the results are expressed in the same unit of measurement, regardless of the country where the products are manufactured or marketed.
  • A certified product has its performance verified by an impartial, independent and competent accredited body.
  • Certified products comply with standards.
  • A product whose performance is certified will work according to the specifications stated by the manufacturer.

The performances we certify

Following new European regulations promoting the sale of high-performance cooling and heating equipment, the performance of rooftop units is changing: their efficiency long characterised by an instantaneous efficiency called COP (coefficient of performance) or EER (energy efficiency ratio), will be characterised from 1st June 2018 by a performance that reflects the efficiency of the rooftop unit throughout the year.

This is known as:

  • SEER (seasonal energy efficiency ratio) or ηsc for cooling mode
  • SCOP (seasonal coefficient of performance) or ηsh for heating mode.
  • Cooling capacity
  • Heating capacity
  • EER ( energy efficiency ratio)
  • COP (coefficient of performance)
  • Sound power level

From 1st June 2018

  • Seasonal energy efficiency in hot mode (SCOP, ηsh)
  • Seasonal energy efficiency in cold mode (SEER, ηsc)

Related technical insights

Thermal comfort for buildings

Certified brands