The study of the Passive House Institute: Information for architects and builders
According to the study, homeowners and tenants in Germany save 8.6 percent of the total heating energy annually if highly efficient spacers made of plastic - instead of aluminum spacers - are used in the windows of a low-energy house commonly built today. This shows: The spacer is a small component with a big effect. The "warm edge" increases the energy efficiency of buildings.
Important component in the energy-saving window
The spacer is located at the edge of the insulating glass and keeps the panes at a distance. It creates a gap that is usually filled with the inert gas argon for a better insulating effect. Spacers are available on the market in aluminum, stainless steel and plastic. The highly efficient plastic spacers are also known as "warm edge" spacers. The spacer is now rightly coming into focus. The study makes it clear that, in addition to the glass and the frame, the spacer is the third key component for energy performance in modern thermal insulation windows.
Lower heating costs with warm edge
According to the study, plastic spacers ensure that homeowners and tenants pay less heating costs than aluminum spacers - and this over the entire period of use. For example, in the case of the low-energy house studied in Frankfurt with triple glazing, this amounts to 2463 euros over 40 years of use. Thermal insulation windows with highly efficient plastic spacers are slightly more expensive to buy. The figures show that homeowners and tenants save money on balance.
More living comfort and less risk of mold
Plastic spacers in windows provide more living comfort: the temperatures inside the window remain comfortable even in winter. In addition, the warm edge prevents condensation on the edge of the glass and reduces the risk of mold there. High-quality plastic spacers increase the quality of living and the value of a building.
If a building requires less energy, this saves CO2 emissions. The results of the study make it clear that anyone can make a surprisingly large contribution to the energy turnaround with the right choice of a small, efficient building component.
It makes the difference: the heat transfer coefficient
If the spacer has a poor - i.e. high - heat transfer coefficient, a lot of heat is lost to the outside - despite a very good frame and high-tech glass. However, even with plastic spacers, there are big differences in performance values. A high-efficiency warm edge, like the one in the study, has a linear thermal conductivity of 0.14 W/(mK). For stainless steel, the value is 0.6, and for the aluminum spacer - as the clear taillight - it is a high 160 W/(mK).
More design freedom in window planning
Because less energy is lost through windows with efficient plastic spacers, larger window areas can be realized on the east and west sides of buildings. On the south side, according to the study, they allow "heating energy requirements to drop even to full glazing."