While the draft of the Buildings Energy Act (GEG) is currently going through the parliamentary process in the German Parliament and Federal Council, homeowners are pondering the right type of heating for the future. Heat pumps, biomass, or sustainably produced gas are top candidates. But could new types of insulation or green facades and roofs not also have what it takes to put the heating issue to bed?
Super thermal insulator made from the waste product of paper production
In Osnabrück, the start-up “aerogel-it” is working on an important step in precisely this direction. It wants to bring a new generation of aerogel super thermal insulation materials to market maturity. Aerogels are a highly porous solid, the volume of which consists of up to 99.98 percent pores. Generally speaking, aerogels are not unknown in the construction industry. Insulation manufacturers like to embed them in a matrix of gypsum or cement to increase strength and durability.
The special feature of the aerogel from Osnabrück is that it requires neither petroleum nor mineral raw materials. Instead, the material is based on lignin, a substance that makes up about 30 percent of the matter of the wood cell wall and is a waste product of paper production. The biopolymer is extremely light, consists almost entirely of microscopic air pores and is therefore extremely poor at one crucial thing: transporting heat. The start-up is currently working on testing the first prototypes of the insulating materials in specific applications.
The hope is to soon eliminate a substantial disadvantage of virtually all other common natural insulation materials: Such materials made from hemp, flax, sheep’s wool, or wood fiber are indeed ecologically sustainable. But they generally have noticeably lower insulating performance than synthetic materials.
Vacuum insulation panels: A thermos for the house wall
Manufacturers of vacuum insulation panels (VIP) have long since moved beyond tinkerer status. At their core, the panels consist of heat-stable powdered silicon oxide or glass fiber, for example, which are wrapped in multiple layers of airtight foils. The VIPs obtain their strength from the existing vacuum and the pressure on the gas-tight foils. The physical principle is similar to that of a thermos flask: Where no air can circulate, no heat can be transported. The striking advantage of VIPs is that they are only a few centimeters thick, making them ideal for use in renovations where space is limited.
A look at phase change materials (PCM) also shows that the high-tech sector has been involved in efficient insulation for a long time. PCMs are latent heat storage materials that are able to store heat and cold energy for a longer period of time and then release it again without any losses. The role of the storage medium is played by salts, fatty acids, or kerosenes. When they melt, they absorb heat; when they solidify, they release the heat again. Even when heat is applied for a long time – for example, when there is a lot of sunshine and solar heating is switched on – their temperature hardly rises.
At home, this means that if the liquid-solid phase transition is approximately at room temperature, the PCMs release the heat again as soon as the temperature falls below a certain value and the materials change to the solid phase. Compared to the heat storage capacity of building materials, such as gypsum, wood, cement, or stones, PCMs store many times more heat when they melt.
Building greener: How facade greening can replace air conditioning systems
Change of perspective to the southwest of the republic, to the Stuttgart basin. Especially in such topographies, flat roofs and facades heat up strongly in the summer sun. A good portion of the energy used for heating in winter now goes into cooling the buildings. The “Helix” nursery from nearby Kornwestheim specializes in vertical greening of building facades.
For good reason, explains “Helix” building architect Jonathan Müller. “The plants and underlying construction act like a second skin. This results in a certain additional insulation performance in winter.” But the focus with facade greening is a reverse effect in summer, he says: “On the one hand, the facade heats up less, simply because less sunlight gets through due to plant shading,” Müller explains. “On the other hand, the water develops a cooling effect as it evaporates.” Together, this quickly adds up to a 20 degree lower surface temperature on the facade. “The second skin acts like a wet sponge.”