Saving energy with heat protection windows
Heat-insulating windows are not comparable to conventional insulating glass. They insulate up to three times better than conventional double glazing.
Special features of heat protection windows
Insulating glass consists of glass panes, between which air is trapped. This layer of air is insulating. Heat-insulating glass additionally uses the heat of the sun to heat the rooms.
The panes are invisibly coated with metal towards the room. Light and heat pass the glass towards the room. The thin metal layer reflects the heat of the room and prevents it from penetrating the glass.
Furthermore, there is rare gas between the panes, which conducts heat less well than air. The edge seal of the glazing is made up of stretchable gaskets that securely trap the inert gas between the panes.
The window frames used to be the weakest point in the system. With modern thermal insulation glazing, the frames are also insulated. In addition, seals along the frame prevent the ingress of cold air.
Characteristics of windows
Two values provide information on how well insulated a building material is. The U-value (heat transfer coefficient) indicates which thermal energy in watts (W) per square meter and degree of temperature difference in Kelvin (K) penetrates a medium. Modern windows let only a tenth of the heat through the window like single-pane glass. Compared to double-glazed windows, you reduce the passage to one-third.
According to the 2009 Energy Saving Ordinance (EnEV), a maximum of 1.3 W / (sqm K) is allowed for windows. The lower the value, the better the window is insulated.
The g (total energy transmittance) value indicates how much heat enters the room from the outside through the window. A g-value of 0.5 means 50 percent of the existing heat energy passes through the window.
If a manufacturer increases the U-value, he simultaneously lowers the g-value. That is physically inevitable. If a house is in a sunny location, it makes sense to buy windows with a high g-value, although this means a higher U-value.
It's worth taking advantage of the outdoor heat. If the windows are in the shade, a low U-value is important. A U-value of less than 0.9 W / (sqm K) and g-values of 70 percent are technically feasible today.
The installation of heat-insulating windows may be deducted from tax. KfW receives funding from anyone who builds energy-efficiently or renovates it energetically. Cheap loans or subsidies are possible, both can be requested from the house bank.
Installing windows: what does it cost?more
We answer these and many other questions on our topic page about working with windows!
What to Consider When Installing
Planning is in the hands of an energy consultant. The insulation of the windows must match the walls. Anyone who has well-insulated windows installed in poorly insulated walls risks damaging themselves through moisture and mildew.
For this reason, installation must be carried out by a qualified specialist for window construction. This prevents thermal bridges that occur due to incorrect installation. In addition, a certificate of rehabilitation by a specialist firm is required to obtain funding.
A heat protection window of one square meter costs between 150 and 400 euros. The costs for the installation depend, among other things, on the masonry. Plastic windows are the cheapest. They cost on average with installation 500 euros. Aluminum windows are the most expensive with an average of 800 euros.