Four out of five houses in Germany need too much heating energy. Show the yellow areas on the thermograph, where the heat escapes. The recipe: Improve the insulation of the building envelope! We say, what's up.
The Hamburg energy consultant Hermann-Michael Hell puts it in a nutshell: “When I analyze old buildings, I find this again and again, that almost always with the help of heating renovations or investments in thermal insulation 50 percent energy could be saved.”
The savings potential of private households, the anyway 30 percent of German energy consumption, so it's huge. However, the experience of the past few years also shows, that hasty actions by thirsty do-it-yourselfers (or poorly executed measures by craftsmen) more harm than good. The problem: Mold in old buildings that have been thermally insulated. The cause: A change in building physics due to thermal insulation – this is particularly common, if only new thermal insulation windows were installed – and lack of ventilation. Before the refurbishment, the leaking windows ensured sufficient air exchange, thereafter condenses the humidity on the cold, uninsulated exterior walls. These are ideal conditions for mold. So let's insulate ourselves sick? The energy consultant disagrees: „Gesundheitsprobleme entstehen nicht durch die Wärmedämmung an sich, but because it was wrongly planned or executed. However, correct ventilation is important.” Unanimous opinion of hygienists, made of polystyrene, is attached to the underside of the basement ceiling and costs between 20 and 30 Euro pro qm. That's easy, because the insulation is just glued to the ceiling.
EXTERIOR WALLS
The outer skin of a house is exposed to temperature fluctuations and the effects of the weather. Is there a renovation going on here?, is it worth, think about insulation. A house loses a large part of its heat through its outer shell. These are the four most common methods:
The thermal insulation composite system (so-called perimeter insulation) consists of insulation boards, which are glued and dowelled directly to the existing exterior plaster. It is suitable for all plaster facades. The square meter price of this "thermal skin", from 14 cm thick panels made of mineral wool or hard foam panels (polystyrene) consists, is about between 100 and 125 Euro.
The rear-ventilated curtain wall consists of a substructure, which is attached directly to the wall, as well as from the actual insulating material in the gaps. The rear ventilation takes care of that, that moisture can dry off. Curtain walls are priced from 150 to 225 euros per square meter more expensive, but also enable interesting facade designs. The insulation should be drawn into the window reveal, to avoid thermal bridges, the insulation thickness should be at least 12 cm.
A backfilling of the air layer is recommended for double-leaf masonry, as is usual in Northern Germany. For example, "Perlite" is used for this, a mineral bulk material, which is blown between the two shells of the wall and thus fills the gap. This method does not quite achieve the thermal protection of a thermal skin, but is significantly cheaper (with an air layer of 6 cm thickness between 20 and 30 Euro pro qm). However, this procedure can only be carried out by specialist companies.
External wall insulation is out of the question on historical or listed external facades and on clinker brick buildings. In these cases, only the interior insulation remains. Their energy saving effect is still around 50 percent. However, a professional should do it here. Interior insulation leads to the so-called dew point shift, which can result in significant structural damage. A complete vapor barrier is important, which prevents during the cold months, that the humidity penetrates into the colder wall and then mold forms. The internal insulation of external walls with a thickness of 8 cm costs between 70 and 80 Euro pro qm.
ATTIC
It is well known that heat rises. Therefore, well sealed and thermally insulated roofs save a lot of expensive heating energy. If the attic is not inhabited, only used as storage, thermal insulation is particularly simple and inexpensive. Insulation thickness up to 20 cm can easily be laid on the top floor and covered with chipboard (30 Euro pro qm). This is particularly easy with insulating material, the, already covered with laying boards, Thermal insulation and walkable area can be created in one operation (for example "Kombirock" by Rockwool). Alternative for old buildings: There is usually a cavity under the floorboards of the wooden beam ceiling. At least this one has 6 cm depth, blowing in cellulose flakes is worthwhile (for example Isoflock).
ROOF SURFACES
So-called over-rafter insulation is the most effective, where the insulating layer lies between the rafters and the roof tiles. However, this is an expensive option, which is only worthwhile, if the roof has to be covered anyway. The "between-rafter insulation" is therefore more common, where insulating wedges are mounted between the rafters – a job, which is no problem for do-it-yourselfers. But beware: Not worked carefully, create thermal bridges, where the insulation layer can become wet. Equally important is the vapor barrier, which prevents the ingress of humidity. Price per square meter of insulated roof area: about between 75 and 100 Euro.
WINDOW
In old buildings, the windows are the biggest heat leak. And that doesn't just apply to single-pane glazing. Although already the usual double glazing 50 percent less heat, modern thermal insulation windows can reduce energy losses by another half. Thermal insulation glass has an inert gas filling in the space between the panes and an almost invisible metal vapor coating on the inner pane, which reflects the thermal radiation.
A common mistake when renovating old buildings is the removal of so-called casement windows. Inside window sashes used to be hung on the wooden reveal, which supplemented the outside windows during the heating period and formed an "air cushion". – effective thermal insulation.
Whether casement windows should actually be exchanged for new windows and which insulation measures make sense, It is best to have a professional energy consultant check it on site.