Investigating and Improving Thermal Performance of Bhutanese Rammed Earth Dwellings

Abstract

Traditionally Bhutanese buildings are built with rammed earth. These buildings have low insulation values and lack thermal comfort resulting in sub-zero temperatures inside the homes in colder regions. Modern insulation materials in Bhutan are uncommon due to the lacking availability, and therefore, a local source of insulation material is needed to improve the living conditions. The worldwide use of natural and bio-based materials has increased over the past couple years, and the use of local natural materials has been investigated in this thesis to improve the insulation value and thermal comfort levels of Bhutanese rammed earth constructions. By adding the fibres straw, pine needles and rice husk, to the earth mixture in different percentages the thermal conductivity was decreased. The results of the different mixtures was used to quantify the improvement in operative temperature in unheated cases and energy use in heated cases.
The results of the Thermal Constants Analyser showed that the thermal conductivity was improved by 35 % by adding 8 % rice husk fibres to the earth mixture. However, the addition of fibres in an unheated case had insignificant impact on the operative temperature. In the heated cases the rammed earth wall construction only accounted for 5 % of the total energy loss and therefore the improvement in energy use of the building was also found insignificant.
When new buildings are constructed in Bhutan the following issues should be considered in order to build good buildings for the future:
1. Reduce infiltration;
2. Improve windows and doors;
3. Improve building materials.
In order to reach Western levels of indoor comfort, the rammed earth buildings need to be complemented with a proper insulation layer.

Popular Abstract

INVESTIGATING AND IMPROVING THERMAL PERFORMANCE OF BHUTANESE RAMMED EARTH DWELLINGS

In Bhutan traditional dwellings are built with rammed earth, these buildings have low insulation values, resulting in sub-zero internal temperatures during the cold seasons. By improving the insulation value of the rammed earth walls by addition of natural additives the thermal comfort ought to improve.

This thesis looked at improving the insulation value of rammed earth walls by adding, straw, pine needles and rice husk in different percentages, by weight, to the earth mixture. By doing this the density and, with it, the thermal conductivity decreased. However, the addition of additives also impacted the mechanical properties of the wall construction. Therefor the maximum amount of additive that can be added is dependent on the minimal mechanical requirements of the construction. During the study the mixability of the additives formed a large restriction, as thoroughly mixing the additives with earth would not produce homogenous samples. Knots formed in the mixture and by decreasing the length of the additive the homogeneity of the earth mix improved. The thermal conductivity of the samples was tested and a maximum improvement of the insulation value of 35 % was achieved. However, this improvement only impacted the transmission losses through the external wall construction. Resulting in a marginal improvement in overall energy use and in thermal comfort. The energy model showed that the majority of the energy dissipates through the roof construction and through infiltration. Improving the infiltration value had the largest impact on the energy use and thermal comfort levels.

The study showed that only improving the insulation value of the rammed earth wall construction has little impact on thermal comfort and energy use and the whole building needs to be improved. Furthermore, the 35% improvement of the insulation value of the rammed earth construction was not sufficient to reach western standards. A different solution with a proper insulation layer is needed to reach good western levels.

This thesis has been conducted to determine if the use of natural additives in the rammed earth was sufficient to improve the insulation value and, with it, the energy use and thermal comfort. This with respect to the traditional aesthetics of Bhutanese rammed earth buildings. The reason natural additives were used was due to their availability, and low impact on the environment and availability in comparison to the conventional insulation materials such as styrofoam and mineral wool.

• author: van Jaarsveld, Matthijs Pieter Bernard
• supervisor: Paulien Strandberg-de Bruijn
• organization: Division of Energy and Building Design; Department of Architecture and Built Environment
• course: AEBM01 20191
• year: 2019
• type: H2 - Master's Degree (Two Years)
• subject: Technology and Engineering
• keywords: Bhutan, Vernacular Architecture, Rammed Earth, Bio-based Materials, Additives, Material Properties, Thermal Conductivity, Mechanical Properties, Energy Performance, Thermal Comfort
• language: English
• id: 8998306
• date added to LUP: 2019-12-04 10:32:19
• date last changed: 2019-12-04 10:32:19