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Energy-efficient apartments

January 26, 2010

A new project in Freiburg's Weingarten district is making apartment living more energy-efficient. Now, the German federal government is lending financial support to this "passive house" project.

The high-rise on Bugginger Strasse is being converted into a "passive" apartment building
This rebuilt high-rise will feature 139 energy-efficient unitsImage: Christian Quiring

At eight in the morning, the rising sun illuminates a 50-meter structure on Bugginger Strasse in Freiburg's Weingarten district. As construction manager Josef Adrian stands amid the scaffolding on the job site, his thoughts are drawn to decades past.

Forty years ago, Adrian was part of a construction crew that built the high-rises next door. The apartments at 50 Bugginger Strasse became run-down over the years, but now they're getting an eco-friendly face-lift.

Adrian is part of a new project to transform this old residential building into an energy-efficient "passive house" - a building that consumes minimal energy for heating and cooling.

Total makeover

But before work can begin on this frigid January morning, Adrian and the foreman must troubleshoot the winter weather. Frosty conditions make it difficult for the 100-person crew to operate on-site machines, many of which require water.

Traces of the old apartment walls at the high-rise project in Freiburg
Few details from the old 1960s-era apartments are still visibleImage: Christian Quiring

The framework of the old 16-story building is still standing, but few traces of the 1960s-era apartments remain. Adrian's crew recently finished removing the old heating pipes and fixtures, as well as windows and doors - enough for three truckloads each day. Wood, concrete and an adhesive containing asbestos have been sorted according to contamination level.

The first step involves drilling some 3,000 holes, which will later be filled with concrete for the building's future walls. Some of the new balconies for the apartments, each weighing 7.5 tons, are already in place.

Passive living on display

The building crew has set up a model apartment on the third floor of the otherwise empty building. Here, Adrian shows families from the neighborhood, old tenants and prospective renters how the new "passive" units will utilize cutting-edge insulation methods to retain heat.

Apartment walls in the new building will be insulated with mineral fiber materials, and windows will be triple-glazed to guard against "cold bridges," tiny cracks around window frames.

Construction manager Josef Adrian talks with the building foreman
Transform high-rise apartments into a series of "passive" flatsImage: Christian Quiring

Better insulation will reduce heating consumption in the new units to a maximum of 15 kWh per square meter each year. The renovations will also decrease the building's yearly carbon footprint by 60 tons.

The "passive" project's goal is to help tenants reduce their oil and gas consumption by one-third over previous levels. A regulated ventilation system is another energy-efficient upgrade, which helps minimize heat loss.

Freiburg's municipal housing association has allocated more than €13 million for the renovation project. The cost of demolishing the building was estimated at €4 million, yet Adrian said restoring the building was a better option, particularly as blasting the structure wasn't feasible.

"There are residential and commercial buildings in the surrounding area," he said. "And since it was constructed in 1968 and is very, very unstable, the walls would have to be taken out one by one."

Federal assistance

Freiburg Mayor Dr. Dieter Salomon, a Green Party member, believes it will be particularly important to keep rents in the Weingarten district at affordable levels, even after renovations.

"We certainly have the obligation to renovate the apartments when they get run-down to the point of being unlivable," he said.

The German Federal Ministry of Economics and Technology provided nearly one million euros in grants for the passive apartment renovations. According to the city of Freiburg, the project will receive a total of €984,875 in yearly installments between 2010 and 2013 from the government's "Energy Efficient City" initiative.

The money will help fund further renovations of four- and eight-story apartments in the Weingarten district. This includes promoting the use of new building methods and materials like aerogel, a high-quality thermal insulator.

Long-term sustainability

Freiburg's municipal housing association, which owns the high-rises, developed a simple plan to recoup a portion of the renovation costs. The building's 100 large apartments are being subdivided into 139 smaller, two- to three-room units. Under this plan, the housing association can increase its overall revenue from rentals, while still keeping the costs for tenants down.

Tenants who don't mind the loss of space also stand to gain because they will require less heating.

The Freiburg-based Fraunhofer Institute for Solar Energy Systems (ISE) provided technical support for the passive apartment renovation initiative. Sebastian Herkel, director of the solar building group, hopes to present results of the Weingarten project at industry conferences, but he believes that architects aren't the only ones who stand to benefit from the new knowledge.

"The construction companies involved have also compiled "know-how" that they can use for future projects here in the region," Herkel said.

Construction manager Josef Adrian believes compact, high-rise apartments are particularly well-suited for passive house projects. The Bugginger Strasse building offers 625 square meters of living space with few exterior surfaces, making it "extremely cheap" to keep heat indoors.

Author: Christian Quiring / AP
Editor: Nathan Witkop

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