Larisa Brojan

PhD Candidate, Architecture

Measuring creep of straw bale wall assembly

Measuring creep of straw bale wall assembly

Larisa is a PhD student from the University of Ljubljana, Faculty of Architecture in Slovenia, Europe. She came to the lab as a visiting scholar from September ’12 to June ’13 to conduct her experimental work. Her research explores many facets of Strawbale construction including environmental, social, and economical aspects, as well as strawbale mechanical performance characteristics.

Project: Straw Bale Construction in Slovenia

Dissertation Abstract:

Larisa’s doctoral dissertation defends the basic thesis that building with straw, speci -
cally building with straw bales in Slovenia, has potential and is an appropriate building
material for the needs of the modern user. In the theoretical part of the thesis, we present
the use of straw in architecture, its morphology and life cycle. We found that
straw in architecture has tradition in Slovenian territory and is important in the context
of architectural heritage. By analyzing the statistical data, we found that the
amount of available straw on an annual basis is sufficient for building purposes with
straw bales, which is presently the most promising form of use of straw in construction.
In the main part of the dissertation, the analytical part, we are dealing with the
construction of straw bales from different perspectives which is directly related to building
and construction. The analytical work also presents the results of three surveys
that have been designed and carried out for the purposes of the dissertation. Using
the survey results, we determined the importance and order of the building criteria
for Slovenian and foreign builders. The ecological value, estimated by owners of straw
bale buildings, is the most important building criterion, as expected. Environmental
impacts of building with straw bales were also calculated and compared to the impact
of brick wall construction utilizing three factors (Primary Energy Input, Acidi cation
Potential and Global Warming Potential). Performance characteristics of straw bale
building (bale construction properties, structural systems design and implementation,
design features, etc.), in Slovenia and abroad, were reinforced by the survey results. By
presenting examples of good practice, we have shown the range of possibilities discussed
in terms of building construction, site construction, design options, and so on. Special
emphasis was also placed on the economic viability of straw bale construction, as it is
well known to be a cost efficient option. The extent of straw bale employed in any one
project naturally depends on user preference and standard of living as well as costs
of other materials. The fi nal amount of the investment is influenced by the level of
involvement of the investor in the entire building process. In the experimental part of
the thesis, three experiments were conducted to verify: 1) passage of moisture through
the wall of straw bales, 2) plain bale and plastered bale composite load capacity, and 3)
measured ow of air through the bales of straw and its composites and corresponding
criteria for air tightness of the house from straw bales. Values of moisture in the wall
and air-tightness were measured for various compositions and the impact of bale orientation
and plaster type on compressive strength were quanti fied. In the case of measuring
the air-tightness, it was found that plain straw bale performs poorly and that cracks in
the plaster have a large impact on the overall wall air-tightness. Importantly, we have
shown the shortcomings of the current guidelines for building with straw bales with
regards to air tightness. We conclude the dissertation with confi rmation of the thesis
title that building with straw bales in Slovenia has good potential.