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Warmer than in the days of Napoleon


Modern floor insulation in a historical timber-frame house

It is an astounding 210 years old, this timber-frame house whose floor slab is now being insulated with Styrodur® C, BASF’s green, extruded polystyrene rigid foam (XPS). The builder is using Styrodur C 5000 CS, which stands out for its very high compressive strength, on the 90 square-meter floor space. The Styrodur C panels fulfill a pressure and load dissipating function, in other words, they are very good at absorbing the compressive load exerted by the external walls. As a result, the ground floor can be designed with few columns. The foundation slab is free of thermal bridges because the ground floor’s columns were removed while the insulation panels were laid. The two-storey home in Babenhausen, Germany, is the oldest building to be restored within the scope of the nationwide model project “Low-energy houses in the housing stock” by the German Energy Agency (Deutsche Energie-Agentur, dena). For the Babenhausen single-family house, the objective of the project is to consume 87 percent less primary energy than a newly-built house that complies with all of the stipulations of the German Energy Conservation Regulations (EnEV).

Compression-resistant insulation for floors under heavy loads
The timber-frame house without basement has a horizontal roof structure so that the load of the roof can be fully dissipated downwards through the external walls. This is why the floor slab can be covered with concrete within the foundation walls, without any need for additional footing for pressure loads and without the formation of thermal bridges. The perimeter insulation of the floor slab is joined without transitions to the interior insulation of the walls. In order to insulate the floor, 10cm thick Styrodur C panels are laid, a vapor-barrier film is placed over them and then they are covered with concrete. The advantages in comparison to the original compacted and damp floor of the timber-frame construction: owing to their closed-cell structure, Styrodur C thermal-insulating panels are impervious to moisture, they are dimensionally stable, durable, flame-resistant and do not rot.

Historical preservation and living comfort
“Since Styrodur C provides reliable insulation over a long time, I can preserve this historical building while restoring it in a cost-effective manner. The Styrodur floor insulating panels are pressure-resistant and easy to lay, so that I can design the house the way I visualize it, combining historical preservation with living comfort,” explains Carsten Herbert, homeowner and construction engineer, who is renovating the house according to his own plans. All the thermal-insulating measures – the insulation for the roof and masonry, heating and ventilation – help the timber-frame house get by on a requirement of primary energy of just 14.6 kilowatt-hours per square meter per year. In terms of the transmission heat loss (0.368 W/m2*K), the values for the old construction are even 30 percent lower than those for a newly-built house. All in all, this translates into a heating-oil consumption of less than seven liters per square meter per year. For the sake of comparison: an unrefurbished timber-frame house consumes between 25 and 30 liters of heating oil. The yearly CO2 savings in Babenhausen amount to 40.9 tons per year – also thanks to the thermal insulation with Styrodur C which, on top of it all, is free of CFC, HCFC, HFC since it contains air as cell gas.

The future lies in our housing stock
Approximately three-fourths of all residential buildings in Germany were built before 1979. Many of these old houses are inadequately or not at all insulated. The mere installation of proper thermal insulation and modern technical building systems would be sufficient to considerably lower the energy requirements. With support from the German Federal Ministry of Construction, the dena model project “Low-energy houses in the housing stock” has modernized 143 residential housing units since 2003. On the average, they exhibit energy values that are twice as good as that of newly built houses. The Babenhausen house was built in 1796 and has 197 square meters of living space. It is expected to be ready by March 2007, following one year of renovation work.

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