All things environmental

Musings about the environment and all it touches, from education to city planning

Renovating heritage brick buildings for energy efficiency

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One of the original buildings at Holstenkamp 119

How do you make a heritage building energy efficient? That’s a real problem in Europe, where many buildings that are old and in need of renovations also tend to be historic; you can’t just wrap the building in some kind of high-tech blanket – it has to retain its character.

Holstenkamp 119, a complex of eight brick buildings from the 1920’s, in Hamburg-Altona, is a case in point. The buildings, owned by the city, were originally designed as an old folks home. Over the years its function changed several times; it was last used as a residence for difficult teenagers, before becoming vacant. While the heritage structure itself was sound, the original doors were damaged and the windows, which were not original, were of poor quality. Because of that, the request for new doors and windows was accepted by the city’s heritage watchdog.  The wiring, in bad shape, was also completely redone.

But what could not be done was changing the structure’s exterior appearance. This meant, for instance, that no solar panels could be installed, since they would be visible on the sloping roof. The outside walls were insulated from the interior, an operation made easy from the fact that the building was vacant (in Hamburg, many appartment buildings get extra insulation using an external coating). Radiant or convective heaters were installed throughout, drawing power from a central heat and power plant. An air exchange system with heat recovery needed to be installed (otherwise, the thermal performance of the building would be poor), but where were the air intake and exhaust ducts to be installed? The designers found that the existing chimneys could be repurposed for that, in a clever use of the existing structure.

But as I’m reading about this particular project, I notice something unexpected. The problem stems from the use of insulation on the inside of the walls. This is the norm in Canada; and to avoid condensation in the walls, a vapor barrier is laid on top of the insulation, on the indoor side – end of story. Not so in Germany, it appears. The description of the renovations mentions the use of “internal capillary active insulation”. Huh, what? After a bit of searching I found a report from the Frauenhofer Institute that shed some light on the situation. Part of the issue is that brick is porous, and the walls need to breathe in order to dry out after a driving rain. So the choice of material is crucial to ensure that moisture circulates and condensation is minimized. The report also mentions that a special grant was made available in order to pay for the design of the system, and no wonder: the Frauenhofer article describes solving simultaneous partial differential equations to describe the diffusion of heat and moisture (these are the sort of thing that delights theoretical physicists and scares everybody else; see side box).

What you need to solve in order to figure out where the moisture goes in a brick wall...sheesh!

What you need to solve in order to figure out where moisture goes in a brick wall…sheesh!

The report also mentions that funding for the renovations came from both the city and a group of owners, as well as from Co2ol Bricks, an EU-funded group that specializes into renovations projects for heritage buildings in the Baltic countries. The total cost, for a heated floor area of 3300 square meters, was 174,000 Euros and the payback period is expected to be thirteen years, based on before-and-after calculations. (Co2ol Bricks has a website chuckfull of case studies of renovations of historic brick buildings in countries around the Baltic, well worth perusing for inspiration).

But then, when I do a search for this address, I notice that the complex is back in operation as an old folks home, yet it has multiple owners in partnership with the city. Is this a condominium-type system, where the elderly own their own appartments but have access to medical care? I still have so much to learn about the German system, and I continue to bejust as baffled now as when I arrived.

And then I read from the papers that the city has made some of the appartments available for a few refugees, some lucky ones among the thousands in the city. And the elderly owners of the other appartments are not happy about this. Sigh.

But at least everyone is housed in a comfortable, warm, energy efficient building.

Technical details:
Floors insulated with 15 cm polystyrene (U value of 0.35 W/m2K)
Ceiling insulated with 24 cm fiber (U value of of 0.035 W/m2K)
Walls insulated with 3 cm Klimasan insulation plaster or 5 cm Ytong Multipor (U values of 0.078 and 0.045 W/m2K, respectively)
Doors and windows with U values between 1.2 to 2.0 0.35 W/m2K
Heating energy use before renovations: calculated at 387 kWh/m2a
Heating energy use after: 48 kWh/m2a, for an energy saving of 86%


Written by enviropaul

December 27, 2015 at 12:55 pm

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