Interactive nature of double facade building

Riga's newest office and retail center comes wrapped in cellophane.

Located on the corner of Gertrudes and Baznica streets, the Gertrudes Centrs looks onto the elegant square facing Old Gertrudes Church.

Completed in December 2002, Gertrudes Centrs introduces to Riga the concept of a "double facade" building - in which a protective wall of glass paneling extends about one meter from the building's exterior, encapsulating the structure in glass.

This kind of facade serves several functions, according to architect Andris Kronbergs, director of the design firm Arhis Ltd. and lead architect on the project. Key among them is the building's energy savings potential.

Originally the idea of the double facade derives from problems encountered with the modern high-rise skyscraper. Essentially a hermetically sealed box, the skyscraper has its own independent and self-contained heating, cooling and ventilation systems. Windows are designed not to open not only to maintain internal environment control, but to control the dynamics of wind pressure acting on the building's structure. The result is that high demands are placed on control systems. In other words, skyscrapers have high rates of wear and tear.

By adding an extra wall of glass to the exterior the complexities of wind pressure are altered. Importantly, the extra wall creates a column of air in the space between the surfaces that acts as a kind of chimney.

As air in the column is warmed by sunlight, the hot air rises, creating a draft. As long as there is an opening at the bottom and top of the column, cool, fresh air will be pulled in at the bottom and the hot air exhausted through the top. Windows facing this space can then be opened to regulate indoor temperatures naturally, with very little or no use of electricity.

New York-based architects Richard Dattner & Partners point out that total life-cycle costs of the building are factors considered here by both designers and building owners, as the focus should not be just on the short-term initial construction costs.

Kronbergs' inspiration originated from several sources. First among them was the central location in the city and respect for Old Gertrudes Church. He stresses that the composition should work with and maintain the "perimetry" of the square, and that the block shape promotes neutrality and balance in view of surrounding architectural elements.

Granted, the project was somewhat complicated by a small wooden UNESCO-protected house sitting at one corner of the site. The solution was to incorporate the historical facade into the overall structure. This led to extending wooden paneling to the entire six story structure.

The idea of the glass skin followed, serving to protect the overall building facade from inclement weather. It also helps to reduce street level noise - even with windows open - and to keep the building's surface clean.

Gertrudes Centrs marked the completion of a two part project, begun in 1997, the first phase being the earlier completion of the adjoining indoor parking garage. This was the first planned combination office and parking garage development in Riga.

The building's foundation sits on a poured concrete slab 3 meters below grade, and the structure continues upward in reinforced concrete - poured on site. Construction took eight months, though some detailing and interior finishing remains. Communication lines, elevators and plumbing for all floors are concentrated against one outer wall, leaving virtually each entire floor open for maximum flexibility. Only 11 percent of total space is taken by common areas.

It was agreed with city planners to compensate for lost outdoor space by creating a "green roof" for tenants' leisure.

The American investment fund NCH Baltic is the owner of the project, with daughter company Domuss acting as property manager and leasing agent.

Andris Kupcis, director of Domuss, cited a greater than 90 percent occupancy rate based on signed leases and prelease agreements. Office rents are competitive starting at $12.60 per square meter plus utilities and common expenses, tied to 5 years and higher terms.

Current tenants include the Canadian Embassy, Unilever and Hoffman-La Roche.

Retail space ranges from $20 to $30 per square meter per month.

Project realization costs for the office building totaled over $3 million, though costs when including the parking garage reach $4.5 million. No loan financing was used, and the investor group expects returns of 12 percent.

Whether the building achieves its targeted energy efficiency levels depends upon the education of the tenant in understanding its interactive nature. What is once again evident, though, is that interesting and innovative design will attract customers, and with almost full occupancy Gertrudes Centrs should be considered a success in Riga's crowded office space market.