Innovative solution for heat recovery of ventilation air in older apartment buildings - with low intervention affecting the residents

Buildings today account for 40% of the world’s primary energy use and 24% of the greenhouse gas emissions. Reducing the energy use in buildings is an important measures to reduce energy dependency and greenhouse gas emissions. In Sweden, there are roughly 2 500 000 dwellings in multifamily houses and single family houses. There is a need to address the energy use within the existing dwellings; especially within multifamily buildings constructed 1960-1975, which accounts for almost one million dwellings or roughly 40 % of the dwelling stock in Sweden. There are good examples of energy renovations of buildings, reducing the energy use by more than 50 %. To reach the energy savings; balanced ventilation with heat recovery was a necessary measure in all projects. However, in all projects; loss of ceiling height in parts of the apartments is a consequence of the measure. Furthermore, it required the residents to temporary move during installment in the majority of the projects. The purpose of this study is to investigate the potential of using a heat exchanger, suitable for natural ventilation, exhaust air ventilation and hybrid ventilation, for installment in the existing building stock in Sweden. A qualitative and quantitative comparison is carried out; comparing mechanical exhaust air ventilation, balanced mechanical ventilation with heat recovery and the heat exchanger suitable for natural ventilation, exhaust air ventilation and hybrid ventilation. The qualitative analysis compares the advantages and disadvantages of the different ventilation system. The quantitative part investigates the potential energy savings and a potential quantity of dwellings where heat recovery may be installed. By installing heat recovery, energy used for space heating may be reduced by roughly 25%. Combining installment of heat recovery with improvement of the building envelope may reduce the energy demand for heating by roughly 75 %. Heat recovery should be able to install in roughly 80 % of the dwellings in the existing dwelling stock, built before 1980