Conservatories – good for the indoor climate, bad for the global climate? – District of Munich

From time to time the sun can still be seen in November. Nevertheless, it is rather uncomfortable on the terrace when the autumn storm is sweeping around the house at the same time. A winter garden would be just right now, thinks some property owners and dreams of a light-flooded living space extension. The employees in town halls regularly get building applications for such glazed extensions on the table. Usually it is about the exemption from the development plan, if this does not provide for winter gardens. In the municipality of Unterhaching, which has set itself the ambitious goal of being climate-neutral by 2030, the municipal councils are now addressing the problem of building limits that have been exceeded: Are conservatories actually energetically justifiable?

“That cannot be said in general terms. It depends on the individual case,” says Anna Lambrecht from the climate protection department in Unterhachingen town hall. Because not all winter gardens are the same. More precisely, there are cold winter gardens and residential winter gardens. At the latest when the sun no longer heats the winter garden to a comfortable temperature, the owner thinks about whether he is content with just cooling his beer in his attached glass house in winter and wintering plants that are sensitive to frost, or whether he needs a heater. If you want to reach a comfortable 20 degrees so that you can sit down at the dining table without a thick jacket even in February, the winter garden must be connected to the heating system in the house or you can even have your own heating system installed. But then, it is said from the Unterhachingen town hall, a winter garden is not a good thing for climate protection.

Because a winter garden consists mostly of glass. “The heat loss through the panes at cold temperatures is of course greater than with normal masonry,” write the experts on the online portal Fensterbau-Ratgeber.de. In the heating phase, the heating requirement of the winter garden is about three to four times that of the house. The Bundesverband Wintergarten also confirms on its website: “If there is too little direct sunlight or too little scattered light, the winter garden needs a higher heating output than compact buildings because of the still better thermal insulation of massive walls and roofs.” However, the federal association also describes the glass extensions as a “highly effective solar system with solar energy gains in the kilowatt-hour range”.

Can also be used in our latitudes for 220 to 270 days

During the heating season, they would drastically reduce the fuel required for heating this and the adjacent room, in some cases even make it superfluous. The window construction guide also emphasizes that the heat input into the winter garden is significantly higher on sunny days than in a normal living space. On 220 to 270 days in our latitudes, pleasant temperatures in the winter garden prevailed even without heating. Thus, the energy requirement of a winter garden, including the solar gains, does not differ significantly from that of a normal living space. However, this also depends on the orientation.

The cold winter gardens find the benevolence of the climate protection department in Unterhachingen town hall, as they act as a climate buffer for the building itself and thus as an energy saver. This is also confirmed by Ruth Jürgensen, energy advisor at the Ebersberg-Munich energy agency. “If, on the other hand, they are heated, they would be seen as an extension of the thermal envelope,” she explains the difference. As a rule, house walls insulated better than panes of glass, although very good glazing is available nowadays with regard to thermal insulation. If it is an extension to a very old existing building, it could also happen that the modern glazing insulates better than the old masonry.

Anna Lamprecht from the Unterhachingen town hall has other points that have to be taken into account when building a winter garden if you want to do something not only for your own well-being, but also for climate and environmental protection: if the extension is to be built on an existing terrace and no additional area has to be sealed, if it is even to be used for growing vegetables, one could definitely collect plus points in Unterhaching with a building application in the future. Town hall spokesman Simon Hötzl assumes that such criteria will play a decisive role when it comes to exemption from the development plan.