Technical procurement of of heat recovery systems in existing apartment blocks in Sweden

The installation of heat recovery systems is one of the most important measures to save energy in existing apartment blocks and presents a technical potential of up to 5 TWh savings per year in Sweden. Today, most apartment blocks built before 1975 are ventilated by natural ventilation or mechanical exhaust ventilation, while heat recovery is seldom used. Components and systems exist, but require development and adaptation if they are to be suitable for widespread use in rebuilding projects. In addition, rational methods need to be developed to cover ordering, design, rebuilding and administration.

In order to help to start a market for heat recovery systems, five local housing companies in Sweden, in conjunction with SABO (Swedish Association of Public Housing Companies) and the Swedish Energy Agency, announced a technical procurement project for exhaust air heat recovery systems. The purpose of the project is to kick-start development and market availability of energy-efficient system solutions for such systems in the run-up to the coming extensive rebuilding of apartment blocks.

A technical specification has been produced with a call for tenders for installation of systems in seven demonstration blocks. Two nominated bids have been taken forward. An efficient air-to-air heat exchanger-based system with an visually acceptable duct system that is easy to install in the apartments. The other bid uses a heat pump to recover heat from the exhaust air, which efficiency is improved by a condenser.

Preliminary results show that it is possible to produce effective solutions for heat recovery from ventilation exhaust air in existing apartment buildings, and that it will be possible to reduce costs. Designs and methods have been developed that enable such systems to be installed in apartments with a minimum of disturbance for the tenant. The start of a market range of heat recovery systems in refurbishment seems to be established in near future.

Written By: Åsa Wahlström, CIT Energy Management, Tomas Berggren, Swedish Energy Agency and Therese Rydstedt, SABO