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Urban Energy Systems
Bauhaus-Institute for
Infrastructure Solutions
Faculty of Civil Engineering
Bauhaus-Universität Weimar


Coudraystrasse 7
99423 Weimar

+49 (0) 36 43 / 58 46 32

+49 (0) 36 43 / 58 46 39

mark.jentsch @ uni-weimar.de

SusTherm - Collaborative Research Project with Partners in Bhutan
Project Details
Project title:
SusTherm - Scoping study for sustainable thermal insulation of buildings under the alpine climate conditions of Bhutan (Potentialstudie zur nachhaltigen Wärmedämmung von Gebäuden unter den alpinen Klimabedingungen Bhutans)

Funding body:
Federal Ministry of Education and Research (BMBF)

Project duration:
01.02.2015 - 31.12.2016

Principal investigator:
Assoc. Prof. Dr. Mark Jentsch

Project partners:
Tenzin (director of department) & Karma Namgyel (chief engineer), Engineering Adaptation and Risk Reduction Division (EARRD), Department of Engineering Services (DES), Ministry of Works and Human Settlement (MoWHS)

People involved in the project:
Bauhaus-Universität Weimar: Assoc. Prof. Dr. Mark Jentsch, Dipl.-Ing. Christoph Kulle, Dr. Torsten Seiffarth, Dr. Thomas Haupt, Tobias Bode, Toni Pauer
Department of Eneering Services: Tenzin, Karma Namgyel, Karma Euthra, Jamyang Dukjey, Karma Tenzin

Project Outline
Most existing buildings in Bhutan lack thermal insulation and are characterised by high infiltration rates through poorly sealed windows and doors. The SusTherm project aims at investigating the feasibility of improving air tightness and using thermal insulation materials in Bhutan, looking at solutions that are rooted in the local resource base and know-how. The project encompasses preliminary building monitoring studies in Bhutan in order to obtain an indication of the current thermal performance of the existing building stock in Bhutan. This is complemented by laboratory work on Bhutanese construction materials in Germany as well as training of Bhutanese early career researchers on the use of building performance assessment equipment. The outcomes of the research collaboration will be worked up in a scoping study report that will serve as a dissemination document for the workshops held within the framework of the project. The key focus of this project is to lay the scientific foundations for a lasting collaboration which aims at developing sustainable thermal insulation materials and to demonstrate their viability through long term monitoring of case study buildings.

Project Background
In developed countries thermal insulation has been the focus of a large amount of research over the past decades. This could lead to the conclusion that, apart from advanced materials research, there is no scientific need for further investigation. However, this falls short of the reality in developing nations which lack the technical capacity, skills base and financial resources for manufacturing and implementing high end solutions such as mineral wool or polystyrene / polyurethane foam, not to mention the facilities to appropriately dispose off such materials at the end of their useful life. In the setting of a developing country an individual review of the locally available resources and skills base is required in order to produce environmentally, economically and socially viable solutions for thermally improving buildings. This is the starting point of the research collaboration between the Bauhaus-Universität Weimar and the Department of Engineering Services in Thimphu.

As highlighted by Figure 1 for Paro in comparison to Erfurt, the central areas of Bhutan experience external winter temperatures at levels that make the consideration of thermal insulation a viable option. Traditionally, buildings in the western parts of Bhutan were constructed of rammed earth and in central and eastern areas of the country with solid stone walls [1]. Over recent decades construction methods in urban areas have changed to uninsulated reinforced concrete frame structures with single brick filling rendered with cement plaster [1,2]. As highlighted in Figures 2 and 3, this shift in construction has resulted in slimmer walls as compared to the traditional construction methods, also losing some of the traditional constructions’ benefits such as thermal mass providing climate moderation on hot sunny days and cool nights [3]. Whilst some research has been conducted examining improvement options for traditional rammed earth constructions in Bhutan to meet modern code of practice standards [3] as well as the seismic performance of modern reinforced concrete frame buildings in Bhutan [4], thermal insulation and air infiltration have, to date, not received any detailed investigations.

The SusTherm project intends to address this issue by providing a scoping study on the general feasibility of improving airtightness and using thermal insulation materials based on local resources and skills in Bhutan. It serves as starting point for the development of a more comprehensive research scheme with respect to material development, testing and extended monitoring of case study buildings.

Work to Date
The collaboration between the Bauhaus-Universität Weimar and the Engineering Adaptation and Risk Reduction Division (EARRD) is characterised by joint workshops and an exchange of early career researchers. The first workshop took place in Weimar in April 2015 (Figure 4). It served to develop a catalogue of research questions and to define the requirements for building performance investigations in Bhutan. If was agreed that the main target for the scoping study is to investigate and assess the thermal properties of individual building elements, focussing mainly on walls and windows. Further to this the equipment to be used for the building monitoring in Bhutan was demonstrated and first joint tests conducted in order to familiarise the partners with the devices.

>> more information on the Workshop in Weimar (in German)

The second workshop was held in Thimphu, Bhutan in October 2015. This workshop dealt with refining the monitoring programme for the on-site building physics measurements devised at the first workshop in Weimar. Various buildings in the Thimphu area were identified for this purpose, making sure, that a wide range of typical historic and modern construction types were covered, looking at both dwellings and offices. Further to this the workshop included visits to a concrete stabilised earth block production facility and a local window manufacturer.

As part of the workshop the complete team of Bhutanese and German researchers undertook a first joint assessment of a building constructed with compressed stabilised earth blocks. This investigation which is shown in Figures 5 to 7 aimed at testing the equipment that was sent from Germany as well as to verify and refine the methods that were devised for the monitoring. Besides looking at wall U-values, the indoor room climate, thermal bridges and capillary water absorption of the walls, airtightness tests were conducted and the properties of building materials, windows and joints of the test buildings documented.

This assessment formed the basis for the building monitoring programme in the month following the workshop which was conducted by the two German MSc students involved in the project and the three Bhutanese early career researchers. Looking at in total 10 different buildings it was shown that both current and historic wall constructions have rather high U-values of typically about 1.0 to 1.5 W/m²K. The air tightness tests revealed that present buildings possess air infiltration rates of up to 5 air changes per hour which is mainly due to poor joints and seals of windows and doors. Furthermore a room climate moderating effect of historic constructions with rammed earth walls as compared to modern built forms was demonstrated. Overall, the assessments which are currently being worked up for a scientific journal publication revealed a number of potentials for improvement which the research partners are hoping to be able to address in a follow-on project.

>> more information on the research stay in Bhutan (in German)

The three Bhutanese early career researchers already involved in the building monitoring programme in Bhutan came to Germany for a two-week research stay in April 2016. In the first week of their stay they conducted further training in the use of airtightness testing equipment as well as thermal transmittance and indoor comfort measurements. This was a preparation for being able to independently conduct such tests in buildings in Bhutan. This was, in the second week, followed by laboratory tests looking at the water absorption, compressive and tensile bending strength and the particle size distribution of Bhutanese compressed stabilized earth blocks, as these were identified as a centre point of interest for future joint research (Figure 8). The third workshop in Weimar, which followed the research stay of the Bhutanese early career researchers in Germany, served to evaluate the data gathered during the research stays and to prepare a scoping study report brochure which will represent the final output of the joint workshops and is aimed at being published by the end of 2016.

>> news article on the university's website (in German)

[1] Nock D (1995), The Architecture of Bhutan, The Architectural Review, 198 (1186): 78-81.
[2] Lang DH, Sing Y, Namgyel K (2013), Building Classification Scheme for Bhutan, EQRisk project report, Report no. 13–006, Kjeller – Roorkee – Thimphu, August 2013
[3] Sethna Z (2008), A Sustainability Approach to Standards for Rammed Earth Construction in Bhutan, Fourth-year Undergraduate Project, University of Cambridge
[4] Dorji J (2009), Seismic Performance of Brick Infilled RC Frame Structures in Low and Medium Rise Buildings in Bhutan, MSc Thesis, Queensland University of Technology
Fig. 1 - Comparison of the climatic conditions in Erfurt and Paro: annual temperature variation (Data sources: Erfurt - Meteonorm 7, Thimphu - WMO World Weather Information Service, data provided by Department of Hydromet Services (DHMS), Bhutan)
Fig. 2 - Traditional building (bottom right) with new build dwellings around it (Photo: Jigme Choden)
Fig. 3 - View of a construction site for a new build dwelling with reinforced concrete frame and imported brickwork, including a construction detail of a door opening (Photos: Jigme Choden)
Fig. 4 - Discussion about construction details at the first project workshop in Weimar
CSEB building Thimphu
Fig. 5 - South facade of the investigated building in compressed stabilised earth block construction
CSEB building building physics tests
Fig. 6 - Left: Pressure difference testing for determining the air tightness of the building, Right: Set-up of the equipment for monitoring the room climate in the building
CSEB water absorption testing
Fig. 7 - Capillary water absorption measurements on 10 day /
1 year old compressed stabilised earth blocks
Bhutanese researchers in materials lab
Fig. 8 - Bhutanese early career researchers working in the materials lab in Weimar