When constructing and refurbishing residential properties , comfort and cosiness play an important role for the occupants . For the right feel-good climate , the relationship between temperature and air humidity also has to be right from a construction physics perspective . The impact that the quality of the windows and the choice of spacer bar has on comfort is shown by a new study of the Passive House Institute ( PHI ).

windows are , as a general rule , still the weakest elements in the _building

In its study “ Living Comfort ”, the Passive House Institute in Darmstadt , Germany , dealt with the question of how comfort and hygiene criteria can be defined and met for windows in different climate zones . “ The windows are , as a general rule , still the weakest elements in the building in thermal terms ,” explains Prof . Dr . Benjamin Krick , managing director of the Passive House Institute . “ Also important for how they perform in terms of thermal comfort are the location of the building and its climatic environment .” The study differentiates between Arctic , cold , cool-temperate , warm-temperate and warm climates . The investigation is based on various plastic windows with double , triple or quadruple glazing . Spacer bars made from aluminium and stainless steel as well as the highly energy-efficient Warm Edge spacer bar SWISSPACER Ultimate were also used .

Comfort and cosiness

People perceive a space as being thermally comfortable when it has a certain “ operational temperature ”. This comprises the average value of the air temperature and the surrounding surfaces . Large temperature differences between air and surfaces give rise to the unpleasant impression of draughts . In the case of cold air draughts , the air falls onto cold surfaces , causing uncomfortable air movements . It has been proved that a pleasant feeling arises when the temperature difference between the indoor air and the surrounding surfaces , such as external walls , ceilings , floors or windows , is less than 4.2 Kelvin .

From these underlying conditions , the Passive House Institute has calculated the so-called “ Passive House comfort criterion ” for various climate zones . For the cool-temperate climate that prevails in Germany , for example , the derived U-value is 0.85 W ( m2 / K ). For this , the team in Darmstadt assumes an operational room temperature of 22 ° C and an outside temperature of -16 ° C . If this characteristic value is not reached , a heat source is needed under the window to avoid the unpleasant sinking of cold air .

Avoiding condensation and mould formation

An important factor where comfort and health are concerned is the avoidance of condensation and mould . Moisture gathers at the coldest point in the room – which is frequently around the edge of the glass . However , mould starts growing above the dew point temperature . Surface temperatures must therefore be above

the “ mould temperature ” to effectively protect a building ’ s structure and the health of its occupants . “ The temperature factor fRsi has become established as an indicator for the hygiene-related conditions on the edge of the glass . If this value is at least 0.7 in a cool-temperate climate , it can be assumed that no mould will grow at normal levels of indoor humidity ,” says Krick . An effective solution :

increase the temperature at the edge of the glass . “ The temperature at the edge of the glass depends on the spacer bar , on the thickness of the glazing unit and on the installation of the pane in the window ,” Krick explains . That is why the most meaningful solution is the combination of high-quality thermal spacer bar , triple glazing with the widest possible gap between the panes , and a well-insulated window frame .

The PHI study shows that the choice of spacer bar has an important effect on the window ’ s thermal quality . From the warm-temperate climate and cooler , the general recommendation is to use triple glazing in combination with highly energy-efficient spacer bars such as the SWISSPACER Ultimate .

The values required for comfort and hygiene could

then be achieved even with the uninsulated window frames widely found in these regions . With well insulated window frames , the requirements for warm-temperate and cool-temperate climates can be met both with stainless steel spacer bars and with the premium space bar from SWISSPACER . The requirements of the Arctic climate necessitate the use of the SWISSPACER Ultimate in conjunction with a particularly well insulated frame . The study was commissioned by SWISSPACER . For years , the Passive House Institute in Darmstadt and SWISSPACER have been working together on studies that provide fundamental information for the market .

More information at en . swisspacer . com / studies / study-living-comfort