environmental impact assessment and thermal performances of

Environmental Engineering and Management Journal
September 2014, Vol.13, No. 9, 2363-2369
http://omicron.ch.tuiasi.ro/EEMJ/
“Gheorghe Asachi” Technical University of Iasi, Romania
ENVIRONMENTAL IMPACT ASSESSMENT AND THERMAL
PERFORMANCES OF MODERN EARTH SHELTERED HOUSES
Horia Tundrea1, Sebastian George Maxineasa1, Isabela Maria Simion3,
Nicolae Taranu1,2, Mihai Budescu1, Maria Gavrilescu2,3
1
“Gheorghe Asachi” Technical University of Iasi, Faculty of Civil Engineering,
43 Prof. Dr. docent Dimitrie Mangeron Street, Iasi 700050, Romania
2
Academy of Romanian Scientists, 54 Splaiul Independentei, RO-050094 Bucharest, Romania
3
“Gheorghe Asachi” Technical University of Iasi, Faculty of Chemical Engineering and Environmental Protection,
73 Prof. Dr. docent Dimitrie Mangeron Street, Iasi 700050, Romania
Abstract
The impact of modern structures on the environment during the building process and actual life-cycle becomes more and more of
a problem and needs to be minimized using unconventional architectural and building solutions, materials and overall
acknowledgement of the whole concept.
This study has the task of determining the feasibility of a modern earth sheltered house solution by comparing its thermal
performances and environmental impact to a conventional above-ground building solution. Although both models are studied
having the same dimensions, orientation and structure materials, the noticeable differences in the final measurements are due to
the fact that unconventional natural insulating and waterproofing materials were used in the case of the earth-sheltered house.
Also, the buried wall and green roof of this pilot underground house determine significant differences between the two sets of
results. The studies were conducted using the RDM 6 and the GaBi 6 software. The models were both virtual, with materials and
basic structure given by the earth-sheltered house that is already built but not completely finished.
This study highlights the better results of this unconventional alternative to building above ground in a region where the climate
and overall geographical context encourages its premises.
Due for completion in 2015, the house is the first to be built in Romania and is now under development in the northern region of
the country, near the town of Iasi, Iasi County.
Key words: earth sheltered houses, energy consumption, environmental impact, global warming potential
Received: February, 2014; Revised final: May, 2014; Accepted: May, 2014
1. Introduction. A modern approach towards an
ancient living solution
When looking for solutions regarding the
future of green and efficient building, we often look
for examples that turned out to be effective in the
past. Such is the case of simple logical solutions used
by our ancestors to satisfy basic yet vital sheltering
needs which often take advantage of natural
surroundings, site orientation and nearby building
resources to reduce costs and maximize efficiency in
a time when sustainability was not a requirement, but
a must-have logical result (Golany, 1983). Such is
the case of the earth-sheltered house.
Ever since American architect and eco-activist
Malcom Wells started to give attention to bringing
this concept back in the construction scene,
underground living has been struggling to outpace its
hippie, utopia stigmata. Now, the rest of the world is
eager to rediscover that “the Earth’s surface was
made for living plants, not industrial plants” (Wells,
1998), and architects of different cultures and
 Author to whom all correspondence should be addressed: e-mail: [email protected]
Tundrea et al./Environmental Engineering and Management Journal 13 (2014), 9, 2363-2369
nationalities take their own ancient examples of
successful energy saving living, respecting the
natural context and drawing design inspiration from
it. Approaches and overall image of interior and
exterior design differ from one culture to another,
depending on architectural heritage, climate and
fondness of new unconventional solutions to pressing
energy saving issues. Modern displays of earth
sheltered living structures come from civilizations
used to this type of housing, in either hot or cold
environments and lately in temperate continental
climates in regions that prove this unconventional
approach to be viable in the economical context we
live in (Eidt, 2013).
Our first modern underground building
example comes from Swiss architect Peter Vetsch of
Vetsch Architektur, a firm specialized in designing
uniquely tailored underground homes of various
sizes. The term he uses is Earth House (Fig. 1a) and
the general idea is to develop modern structures that
“don’t live under the ground but with it” (Wagner
and Schubert-Weller, 1994), shaping a sculptural and
highly customized space as a kind of “third skin” to
its owners and inhabitants. The organic image and
overall concept is disrupted solely by the materials
used in engineering the structure of this monolith
concrete inhabitable sculpture, reinforced concrete
being a heavy artificial material crucial in assuring
the modern space quality and durability in the
harshest of natural contexts (Vetsch, 1993),
resembling the catacomb-like structure of the early
Berber dwellings (Anselm, 2012; Golany, 1988).
Another modern underground living example
comes from Portugal, where the architect Luis
Pereira Miguel of Lisbon-based Pereira Miguel
Arquitectos interpreted the earth sheltered house
concept in creating a beautiful minimalistic beach
house. The concept of “creating your own sand
dune” (Perreira, 2009) is translated into a fairly
moderate dimensioned holiday retreat in Grandola,
Portugal.
Casa Monte na Comporta (Fig. 1b) is
incorporated beneath two crescent-shaped artificial
dunes. Despite its modern choice of expression, the
dune house looks like it has been there forever,
enriching its modern simplicity with natural materials
borrowed from the nearby beach and vegetation. Due
to the wind and sand that covers all the nearby area
as well as the roof, the house will eventually look
like a sand dune, a sheltered environment that
provides a cool refuge from the hot Portuguese
summers.
The last example depicts a similar image
regarding the ancient Romanian Pit House
(Bucurescu, 2013; Camilar, 2002; Farwell, 1981),
half buried and half bermed from the ground
revealing itself through glazed surfaces that drown
the interior space in natural light, making it look a lot
bigger than it really is. Dutch architects
Denieuwegeneratie develop the Dutch Mountain
House (Fig. 1c), a small open plan building
embedded in the moorland and its lovely
surroundings, artfully concealed among the trees and
forest and partly buried in the landscape. The house
replaces the timber structural frame with light metal
structural elements, allowing the considerable span
between structural poles and the overall highly
customizable interior spaces that grows and evolves
with its inhabitants and their way of life (Laylin,
2012).
The earth sheltered house proves to be a
viable alternative to conventional modern houses and
deserves a closer look in terms of actual
sustainability factors as well as energy efficiency, as
these are the main pros when using earth as the main
insulating material and thus integrating the whole
structure and allowing it to resonate with its natural
surroundings (UM, 1979).
A green flat-roofed variation of this category
is the subject of our analysis, a pilot project that is
due for completion in 2015 in the Bârnova region,
near Iași County, Romania. This project adopts the
bermed solution as the most viable one in this region,
taking full advantage of its surroundings while
remaining as non-intrusive as a concrete/ceramic
block structure can be. The berming house has a
green roof that blends into the landscape, two out of
four walls buried into the ground and one exposed
glazed side towards which all interior spaces are
oriented. Placed on a south or west facing hillside,
this house becomes extremely energy efficient while
providing modern living standards with healthy
ventilated rooms and well lit spaces (Snodgrass and
McIntyre, 2010).
Fig. 1. Examples of modern Earth sheltered houses: a. Earth House Estate Lättenstrasse (Vetsch, 1993); b. Casa Monte na
Comporta, Grandola, Portugal (Pereirra, 2009); c. Dutch Mountain House, Dutch natural reserve (Laylin, 2012)
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Environmental impact assessment and thermal performances of modern sheltered houses
2. Determination of the thermal characteristics for
the earth sheltered house
In order to further examine the particular case
of the earth sheltered house, the study will
concentrate in analysing the two main distinctive
features that recommend this solution as an
unconventional one: the north-east buried wall and
earth covered roof (Fig. 2b) Applying the same
physical proprieties, dimensions and structural
materials, a virtual duplicate of the earth sheltered
house was created, a conventional terrace roof house
built above ground and insulated using conventional
materials and solutions. The constant comparison
between the two will help to determine the
advantages and disadvantages of the studied project.
The following tables reveal the measured
thermal transmittance of both case studies. According
to the C107-2005 normative, the buried wall of the
earth sheltered house is not measured by the same
formulae applied in Table 1, as there is no need for
R’ calculation.
Fig. 2. Studied cross section of characteristic elements: a. Above ground case study; b. Earth-sheltered case study
Table 1. Thermal transmittance of wall (above ground case study)
Thickness (d)
[m]
Layers
M5 Interior plaster
G.V.P
Polystyrene
M5 Exterior plaster
0.02
0.24
0.1
0.02
Thermal conductivity (λ)
W

 (m  K) 
0.87
0.75
0.044
0.87
2
External surface resistance – Rse=0.042  m  K

Internal surface resistance – Rsi=0.125 m2  K

U=
1
=0.356
R

W 
d m2  K 
W 
λ 
0.023
0.32
2.272
0.023
Thermal resistance (R)
 m2  K 

W 
2.805

W 


W 2

m
K

 
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Tundrea et al./Environmental Engineering and Management Journal 13 (2014), 9, 2363-2369
Table 2. Thermal transmittance of roof slab (above ground case study)
Thermal conductivity (λ)
Thickness (d)
[m]
Layers
M5 Interior plaster
Equivalent layer*
Insulation
Concrete equalisation layer
Waterproofing
Waterproofing protection
W

 (m  K) 
0.02
0.25
0.25
0.05
0.02
0.02
0.87
1.02
0.044
1.74
0.17
0.87
External surface resistance – Rse=0.042  m  K

W 
Internal surface resistance – Rsi=0.125  m

W 
2


U=
1
=0.16
R
2
K
d m2  K 
W 
λ 
0.023
0.245
5.682
0.029
0.118
0.023
Thermal resistance (R)
 m2  K 

W 
6.287


W 2

  m  K  
* - thermal properties of the Porotherm ceramic floor system (17 cm ceramic floor+8 cm reinforced concrete slab)
Table 3. Thermal transmittance of roof slab (earth sheltered case study)
Layers
M5 interior plaster
Equivalent layer*
Cork boards
PVC protective layer
Gravel
Geotextile
Gravel
Soil growth medium
Thickness (d)
[m]
Thermal conductivity (λ)
W

 (m  K) 
0.02
0.25
0.25
0.025
0.05
0.008
0.05
0.40
0.87
1.02
0.043
0.38
0.7
0.1
0.7
2
2
External surface resistance – Rse=0.042  m  K 
W

d m2  K 
W 
λ 
0.023
0.245
5.814
0.066
0.071
0.08
0.071
0.2
Thermal resistance (R)
m2  K 
W 

6.737
2
Internal surface resistance – Rsi=0.125  m  K 
W

U=
1
=0.15
R


W 2

  m  K  
* - thermal properties of the Porotherm ceramic floor system (17 cm ceramic floor+8 cm reinforced concrete slab)
The numeric values of the analysed thermal
bridges were obtained using the results generated by
the RDM software regarding the thermal flux, as well
as applying the formulae in the C 107-2005
Romanian code. The analysed thermal bridges are
presented in Fig. 3 (RC, 2005). As previously stated,
the thermal bridges of the earth sheltered house’s
buried wall represent a special case.
According to the C107 normative, the height
of the buried wall is divided in 7 segments, each one
with its own thermal bridge, as shown in Fig. 3f,
being Ψ1 to 7. The values are presented in Table 4 (RC,
2005). Using these results, the U’ values for the
analysed building elements were calculated with the
formulae in the C 107-2005 Romanian standard
normative. The resulting values are presented in
Table 5.
According to Romanian C 107-2005 standard
Normative, in the case of new houses, the maximum
accepted values for the corrected thermal
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transmittance U’ of the analysed envelope
construction elements are (RC, 2005):
- above ground case study – 0.56  W m 2  K  for
the wall and 0.20  W m 2  K  for the slab;
- earth-sheltered case study – 0.35  W m 2  K  for
the wall and 0.20  W m 2  K  for the slab.
The results clearly state an improvement in
the way the earth sheltered case study preserves its
energy, both structures having been tested using the
Romanian climate parameters for the northern region
(climate zone III with -18˚C specific exterior
temperature and 20˚C interior temperature). This
unconventional solution deals with heat transfer
better than the conventional one, even without taking
into consideration the immense thermal mass of the
earth which further improves this aspect, making it
easier to bring interior temperature to optimal
comfort parameters.
Environmental impact assessment and thermal performances of modern sheltered houses
Fig. 3. Studied thermal bridges: a. attic horizontal thermal bridges; b. interior to exterior wall vertical thermal bridge; c. exterior
wall thermal bridge; d. exterior corner wall intersection vertical thermal bridge; e. floor slab horizontal thermal bridge; f. earth
sheltered thermal bridges
Table 4. Linear thermal transmittance
Linear thermal transmittance (ψ)
Ψ1a
Ψ2a
Ψ1b
Ψ1c
Ψ2c
Ψ1d
Ψ2d
Ψ1e
Ψ1f
Ψ2f
Ψ3f
Ψ4f
Ψ5f
Ψ6f
Ψ7f
Ψ8f
W

 (m  K) 
0.23
0.16
0.0026
-0.38
-0.38
0.082
0.082
0.18
0.17
0.18
0.15
0.14
0.13
0.15
0.10
0.20
Table 5. Corrected thermal transmittance U’
Building
types
Above ground
Earthsheltered


U 'wall  W 2

  m  K  
0.49


U 'floor  W 2

  m  K  
0.19
0.27
0.16
3. Environmental impact of the studied building
elements
The environmental impact can be assessed
using a couple of software tools (Simion et al.,
2013a, b). In this study, the environmental aspect of
the sustainability concept was assessed using the
GaBi 6 software. A cradle-to-gate Life Cycle
Assessment type of study has been conducted,
analysing the following life cycle stages (Fig. 4)
(Dumitrescu et al., 2014):
- extracting the raw materials;
- processing the raw materials;
- fabrication of the construction materials;
- transportation of the construction materials from
the factory to the building site;
- actual building process and completion of the
houses to the final usable stage.
For the transportation of the materials needed
to build the sheltered house, a Euro 3 diesel truck
with 3.3 t payload capacity was used. Depending on
the material type, the distance is different, as it can
be observed from Table 6.
In the earth-sheltered case, the environmental
impact of the actual digging process was also taken
into account by considering the excavation process of
652.392 m3 of earth (later used to cover the house).
Fig. 4. Analysed Life Cycle for the case studies (Maxineasa et al., 2013)
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Tundrea et al./Environmental Engineering and Management Journal 13 (2014), 9, 2363-2369
Table 6. Distance for each component
Material
Concrete
Ceramic bloc
Cement
Lime
Sand
Bitumen sheets
PVC roofing
Geotextile
Gravel
Cork board
Distance (km)
60
25
25
25
60
25
25
25
60
25
The Environmental Impact is expressed
accurately through the calculation of the Global
Warming Potential (GWP); the results being obtained
by using the CML 2001–Apr. 2013 methodology.
The obtained results are presented in Fig. 5.
Fig. 5. Global Warming Potential
Building a structure that will hold up below
ground is certainly not easy, but the results clearly
state the advantages when using the right materials,
local, easy to find solution for most cases that
minimize the overall impact of the building process.
The choice is non-intrusive, all construction
processes being at a small scale, without any
unnecessary actions (the dug-out earth is later used
and stays on site). Finally, a significant difference
(the above ground solution has a result that is almost
double than the earth sheltered one) between the two
environmental impact results is achieved through the
understanding and trusting of the unconventional
natural materials, like the earth or cork.
The environmental impact that a new building
has on the natural site is ultimately a fact rarely taken
into consideration when building structures that use
conventional materials. The idea behind the earth
sheltered solution is that a low environmental impact
can be achieved even when using high energy
consumption materials like concrete, steel
reinforcement and masonry. These materials are a
must when dealing with heavy terrain loads and
charges, so the difference is made by the insulation
materials and waterproofing. The team’s choice was
cork, a natural renewable material with extraordinary
2368
insulation and waterproofing proprieties as well as a
near indefinite life span. The use of this
unconventional, but quite logical alternative to
classic bitumen sheets led to the considerable
difference in the final results, without affecting the
heat transfer principles on which this type of earthshelter house functions.
4. Conclusions
The thermal transmittance and overall impact
on the natural environment are greatly diminished
when building below ground, and the result is a
house that is more environmentally friendly than a
conventional above ground solution, with better life
quality, better protection against natural hazards,
better climate integration, lower maintenance costs
and almost perfect site integration. However, greater
caution is necessary when embracing such a concept,
as the construction of the hidden/buried elements
must be done flawlessly, carefully making sure that
every necessary layer is in optimal parameters before
covering it with earth. Taking a greater toll on the
planning and building states, this house becomes
efficient during the usage period, thus accomplishing
its purpose in providing the comfortable modern
shelter the inhabitants need.
This paper shows that the earth-sheltered
house has a lower environmental impact compared
with the above-ground case and smaller thermal
transmittance for the studied construction elements.
Thus, the below ground house can be considered as a
sustainable solution in the construction sector.
Acknowledgements
This paper was elaborated with the support of a grant of the
Romanian National Authority for Scientific Research,
CNCS – UEFISCDI, project number PN-II-ID-PCE-20113-0559, Contract 265/2011 and PN-II-Capacitati-PC7,
Contract 264EU/30.06.2014.
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