Small component, big impact: Eight percent less heating energy 1 June 2018 Back to news index

New study confirms great savings with plastic spacer bars in insulating glass windows

Small component, big impact: Eight percent less heating energy

It is a small component with a big impact on the building's energy requirements: the spacer bar in heat insulating windows. It comes in metal or plastic. Now, a study by the independent German Passive House Institute has confirmed, with facts and figures, that plastic spacer bars make windows more energy efficient. The warm edge ensures lower energy consumption, CO2 emissions and heating costs.


The results for Frankfurt and Helsinki are representative for cool/moderate and cool climates, thus for the majority of Scandinavian and Baltic countries. The study compares aluminium, stainless steel and plastic spacer bars in windows in low-energy buildings which meet the German energy guidelines for new buildings from the 2016 Energy Saving Ordinance (EnEV). The results: if highly efficient plastic spacer bars are used instead of aluminium spacer bars, heating energy savings of 5.6 percent in the cool/moderate climate zone and 4.8 percent in the cool climate zone can be achieved in low energy-buildings with double glazing. In a low-energy building with triple glazing, the savings are 8.6 and 7.1 euro respectively.


This means less heating costs. For example, with a standard window of 1.23 x 1.48 m, savings of 135 euro are possible over 40 years of use. Building owners can save money even though a window with a warm edge costs slightly more.


If spacer bars have a high linear heat transmission coefficient, a lot of energy is lost to the outside – despite having an ultra-modern frame profile and insulating glass. There are also differences with plastic spacer bars. The highly efficient warm edge used in the study has a value of 0.14; stainless steel is 0.6 and aluminium spacer bars have a high level of 160 W/(mK). Plastic spacer bars also offer more comfort. They prevent the build-up of condensation at the edge of the glass, reduce the risk of mould and keep the temperature inside the window pleasant.


The study was commissioned by the warm edge manufacturer, SWISSPACER: “We wanted to provide reliable data from an independent institute,” stressed Managing Director, Andreas Geith. For more information, visit