Juanqinzhai, Quinlong Garden Complex

The Qianlong Emperor (reign 1735–1796), the fourth emperor of the Qing Dynasty (1644–1912), was a well-known patron of arts and crafts. He ordered the construction of Qianlong Garden (1771–1776)—a retirement complex of palaces and gardens consisting of twenty-seven structures in the northeast section of the Forbidden City, China. Among these structures is Juanqinzhai or the Studio of Exhaustion from Diligent Service, a building unique in the quality and diversity of the arts and crafts used in its construction, decoration, and furnishings.

This relatively simple east-west aligned structure (224m² floor area and 1200m³ volume), was built with the traditional method of post and beam assembly with masonry infill and limited architectural features. Its rich interior is divided into two halves,—reception rooms and a private theatrical performance area—each with a unique decorative scheme and features. The reception area contains framing of polished ironwood, casement windows covered with double-sided embroidered silk, geometric pattern surface decoration in extruded bamboo thread marquetry with carved jade insets, and naturalistic scenes carved in low relief and covered with bamboo veneers. In addition, these rooms have landscape paintings and works of calligraphy mounted directly on the wallpapered walls. The theater side contains a roofed stage with a dramatic two-story viewing area, mural paintings on silk covering entire the walls and ceiling, and wooden surfaces painted to resemble a special bamboo. It also contains unique and exquisite silk trompe l'oeil paintings on the ceiling and walls. After the decline of the Qing Empire, the building was abandoned and its interior features were left exposed to the elements.

Because of its expertise in alternative climate control strategies, the GCI was invited to assist with the design and to oversee installation of a climate control system for Juanqinzhai. This work was undertaken as part of a larger effort spearheaded by the World Monuments Fund to restore the Qianlong Garden complex . The initial system would serve as a model to guide the environmental management of similar structures in the garden complex.

Beijing's weather cycle consists of a cold, dry winter and hot, humid summer. The outdoor temperature can fall to -17°C in January and reach 41°C in August. High concentrations of airborne particulates and gaseous pollutants are also problematic. This large annual climate variation as well as air pollution provide a major challenge to preserving both the building and the collections in historic buildings.

A minimally intrusive and conservation-focused climate control strategy was developed and successfully implemented in Juanqinzhai in November 2008. The building envelope was tightened to significantly reduce the infiltration of outside air, and large glass windows were double-glazed to improve thermal insulation. A mechanical system installed in the attic was designed primarily to limit relative humidity to less than 60% for conservation of the historic interior using dehumidification while allowing for variations of temperature. The combination of air tightening the building envelope and operating the high-performance filter system now successfully controls the dust problem. This climate control strategy has successfully reduced the annual variation of relative humidity from 90% to only 15% and has completely eliminated the spatial variation of the climate. The system has maintained the intended conservation climate of 40–60% relative humidity in the building during its first year of operation.

An article in the Spring 2007 issue of Conservation, the GCI Newsletter describes the project. Details of the project were presented at the 10th World Congress of Federation of European HVAC Associations (REHVA), Antalya, Turkey in May 2010.

Page updated: December 2010