With stone walls measuring more than a metre thick, the medieval churches on the Island of Gotland in Sweden were certainly built to last. Unfortunately for parishioners and tourists who continue to admire them, this meant that indoor temperatures barely rose above the freezing point for many months of the year.
With rising heating costs and the potential for interior decorations, artifacts, paintings, wood fixtures and fittings to deteriorate overtime due to moisture related problems by cause of poor indoor climates, finding a sustainable way to heat churches while preserving the inventories inside them is about as challenging and complex as energy projects get.
Energy Solutions for Historical Buildings
The work undertaken falls under the framework of Sweden’s National Research Program for Energy Efficiency in Historic Buildings, which was established in 2006 by the Swedish Energy Agency and supported by the National Heritage Board and the Church of Sweden. The Program’s objective was to create a sustainable national research infrastructure and to develop competencies by developing methods and technical solutions for energy efficiency and preservation of cultural and historical valuable buildings.
Phase one of the Program involved 15 projects, including the Save and Preserve Project – Energy Efficiency Improvements in Historically Valuable Buildings. It comprised the development of appropriate criteria for good indoor climate, strategies and technical solutions for climate control, calculation models and guidelines for climate measurements, methodologies for risk analysis, and implementation and demonstration. It also targeted in-depth knowledge on how energy efficiency improvements can be adapted to facilitate preventive conservation and energy efficiency in historically valuable buildings.
A Beneficial Approach
WSP’s goal was to present a heating and energy efficient strategy where a local area of thermal comfort could be provided to people, while leaving the natural climate environment unchanged in the rest of the church.
In cooperation with Uppsala University Campus Gotland (now Gotland University) and the Church of Sweden, WSP’s Department of Building Physics in Stockholm’s Environmental Division took an ingenious approach of using local heating, namely, warming the air around the congregation with radiant heat, rather than attempting to centrally heat the whole building.
Since local heating diffuses minute amounts of heat, it was deemed more beneficial for non-energy efficient historical buildings as it addressed the issues of heat loss, energy efficiency, preservation of church inventories, as well as enhanced parishioners comfort level while leaving the environment as is.
Producing a comfortable environment required much calculation and original research. Today, the solution has been retrofitted in two of churches in Gotland.
The team has tested similar systems in ruined cathedrals and castles elsewhere in Sweden.