THERMAL AND ACOUSTIC COMFORT IN BUILDINGS
S. Monteiro da Silva, M. Guedes de Almeida
Affiliation: Department of Civil Engineering, University of Minho, Guimarães, Portugal
e-mail: sms@civil.uminho.pt; malmeida@civil.uminho.pt
Abstract
To achieve an adequate quality of buildings it is necessary to consider a set of aspects that
are interconnected and influence each other, not always in a favourable way. The selection
of the most suitable construction solution for the building elements must consider its
contribution to the thermal and acoustic comfort inside the buildings, the daylight conditions,
its energy efficiency and sustainability, and also the weight of the solution and its effect on
the structural project of the building.
In this work, the use of a multi-criteria analysis, to balance all these aspects on the design
phase, in order to assist the designer in the selection of construction solutions and materials,
will be presented. The selection of the most adequate construction solutions will increase the
buildings thermal and acoustic behaviour and also its energy performance and sustainability.
Keywords: Thermal behaviour, Acoustic performance, Energy efficiency, Sustainability,
Multi criteria analysis.
1 Introduction
Energy efficiency and sustainability of buildings are nowadays major concerns. Buildings
must guarantee a healthy and comfortable indoor climate as Men spend about 90% of their
time inside closed spaces. Thus, it is mandatory to control the energy consumption in the
building sector, while maintaining, or even improving, the indoor comfort conditions.
But, as buildings are complex systems, where all aspects are interconnected and influence
each other, an integrated and comprehensive approach to the buildings design that enhance
indoor health and comfort besides the energy savings and environmental sustainability,
should be followed. However, these goals are often in conflict and there is not a unique
criterion that describes the consequences of each alternative solution adequately and there
is not a single solution that optimizes all criteria simultaneously.
Therefore, heating, cooling, daylight availability, Indoor Air Quality, acoustic behaviour,
sustainability and energy reduction strategies should be meshed at an early stage with the
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other requirements to ensure the buildings overall comfort conditions and energy efficiency.
To do so, it is necessary to select the correct materials and construction solutions, on the
design phase, to improve the occupants overall comfort and, at the same time, reduce the
energy costs. Furthermore, to make a conscious selection of the possible alternatives, it is
necessary to balance the positive and negative aspects of each solution into the global
behaviour of the building.
Multi-criteria analysis is, in this way, an important tool in such problems, since it employs
mathematical models that evaluate alternative scenarios, in this case, materials and
construction solutions, fenestration strategies, etc., taking into account both their objective
characteristics (U-Value, acoustic insulation, embodied energy) and the preferences of the
decision makers regarding the objectives and constraints of each project.
The aim of this study was to investigate the viability of the use of multi-criteria analysis to
assist the designer in the selection of construction solutions and materials. A simple case
study was studied to demonstrate the feasibility of the approach using the multi-criteria
analysis method Electre III [1].
2 Methodology
To achieve an adequate behaviour of the buildings it is necessary to consider either the
overall comfort conditions (thermal, acoustic, visual and Indoor Air Quality) as well as
sustainability. It is then essential to optimize the building envelope, by improving construction
solutions and insulation levels, glazing type, optimizing the thermal and acoustic behaviour,
the natural ventilation and daylighting techniques through an appropriate design and
selecting materials with low embodied energy. But the solutions adopted in buildings, usually,
only optimize no more than one of the necessary comfort requirements. In many cases, the
best solutions to accomplish different comfort requirements are not compatible, especially in
what concerns natural ventilation and lighting strategies and the acoustic and thermal
performance. For instance, the type of window used can have a strong and opposite
influence on the thermal and acoustic performance of the building, just not to mention its
interference with the IAQ.
The design phase is the ideal moment to mesh and implement all these principals as it is still
possible to implement modifications on the project. So, it is during the design phase that the
sustainable, energy efficient and comfortable building concepts should be applied, by a
judicious selection of materials, technologies and construction methods to be used.
To test this integrated approach, two floors and four rooms, were studied, estimating the
thermal quality of the envelope (calculating the U-value), the acoustic behaviour of the
envelope (estimating the weighted normalized airborne sound insulation index of the façade
and walls and the weighted normalized airborne sound insulation index and the weighted
normalized impact insulation index of the floor), the weight, the embodied energy and the
thickness of the construction solution were also calculated.
The analysis considered the factors that have influence on the behaviour of the buildings,
such as glazing type, construction solutions and materials, weight (associated with thermal
inertia, acoustic insulation and to the building structure) and embodied energy.
2.1
Prediction Tools
The prediction of the building thermal behaviour was done using the U-value, determined
using the publication ITE50 – U-Values of Building Envelope Elements [2]. All the solutions
selected respect the minimum requirements defined in the Portuguese Thermal Regulation
[3]. The acoustic behaviour was considered estimating the weighted normalized airborne
sound insulation index of the façade, measured at 2m from them (D2m, nT, W), the weighted
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normalized airborne sound insulation index (DnT, W) for the walls and floors and the weighted
normalized impact sound insulation index (L’nT, W) for the floors, according the to the EN
12354 standard, using the Acoubat Sound Program [4, 5, 6]. The embodied energy was
assessed using Cumulative Energy Demand 1.04 [7].
2.2
Room Characteristics
To estimate the acoustic behaviour of the building, using Acoubat Sound Program, a geometry
with two floors and two rooms (3m x 4m x 2.5m) was defined. The window area, 1.2m x 1.2m,
was maintained constant. The area of the windows was defined to optimize the solar gains
during winter and the daylight availability and minimize the unwanted solar gains during
summer, according to the Illuminating Engineering Society of North America (IESNA)
recommendations, corresponding to a Window - Wall Ratio of about 20% (percentage that
results from dividing the glazed area of the wall by the total wall area) [8, 9].
2.3
Construction Solutions Characteristics
The construction solutions analyzed are shown in Figure 1, for the different types of elements
of the building. The construction solutions selected, single and double pane walls (hollow
concrete blocks, brick and hollow brick), concrete, hollow core concrete and beam and pot
slabs and materials (concrete, brick), cover a wide range of situations. The study was done for
two insulation materials (expanded extruded polystyrene, XPS, and mineral wool, MW). The
insulation could be placed in the exterior or in the interior of the single pane walls and in the air
cavity of the double pane walls (Figure 1).
Wood finishing
Polyethylene foam
Regularization layer
Concrete
Pre-strengthen beam
Ceramic pot
Plaster
Wood finishing
Polyethylene foam
Regularization layer
Regularization layer
Concrete
Wood finishing
Polyethylene foam
Concrete
Plaster
Plaster
Figure 1 – Vertical cross-section of the construction solutions of the walls and floors (external
and partition elements)
Different glazing types and frames were selected for the windows considering the existence
of PVC roller shutters or air inlets in the windows frames.
The air inlets were introduced to improve the air change rate and the indoor air quality. The
roller shutters were selected as they are the most used shading devices in Portugal and they
also allow controlling daylight. Roller shutters are also the most penalizing systems in what
concerns thermal and acoustic behaviour of the façade (when comparing with the venetian
blinds and shutters, for example) due to the existence of the roller shutters boxes.
2.4
Multi-criteria analysis
The multi-criteria decision analysis (MCDA) defines flexible approach models to help the
decision maker, and/or the design team, selecting the most adequate solutions among a
large number of options and possibilities. The problem of the decision maker is a
multi-objective optimization problem [10] characterized by the existence of multiple, and in
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several cases competitive, objectives that should be optimized, taking into account a set of
parameters (criteria) and constraints.
This kind of analysis is able to reflect the objectives and limitations of each one of the
alternatives to be studied, but it is necessary to be thorough on selecting the criteria that
should be exhaustive but not redundant (no more than 12) and must be coherent (which are
the criteria to be maximized and to be minimized) [11, 12].
The selection of the best options to optimize the sustainability and the comfort conditions of
buildings is a type of problem that fits the purposes of a multi-criteria analysis.
The multi-criteria methodology selected in this work to help the decision maker selecting the
most adequate solutions to optimize the building comfort and sustainability was the Electre III
model as it may be considered as a decision-aid technique suited to the appraisal of complex
civil engineering projects [13]. This method requires the definition of weights and thresholds,
which allows the decision maker to provide his scale of values, according to the objectives.
2.4.1 The Electre III method
Electre III is a multi-criteria decision analysis method [1] that takes into account the
uncertainty and imprecision, which are usually inherent in data produced by predictions and
estimations. The construction of an outranking relation amounts at validating or invalidating,
for any pair of alternatives (a, b), the assertion "a is at least as good as b". This comparison
is grounded on the evaluation vectors of both alternatives and on additional information
concerning the decision maker's preferences, accounting for two conditions: concordance
and non-discordance.
The Electre III method is based on the axiom of partial comparability according to which
preferences are simulated with the use of four binary relations: I, indifference; P, heavy
preference; Q, light preference and R, non-comparability. Furthermore, the thresholds of
preference (p), indifference (q) and veto (v) have been introduced, so that relations are not
expressed mistakenly due to differences that are less important [1].
The model permits a general ordering of alternatives, even when individual pairs of options
remain incomparable where there is insufficient information to distinguish between them.
Also, the technique is capable of dealing with the use of different units, the mix of both
quantitative and qualitative information and when some aspects are “the higher the better”
and others are “the lower the better”, as occurs within an engineering project appraisal.
The rank of a building in a series does not change much when the weights given to the
various criteria or the threshold levels for veto, preference or indifference are changed within
a realistic range [12, 14].
The Electre III method does not allow for compensation, which may occur when using
methodologies based on performance indexes, due to the use of the veto threshold.
Compensation occurs when a criterion with poor rating according to one parameter is
compensated by fair results on several other parameters. Using this method, a building
which shows too poor results in one criterion cannot be ranked in a higher position [12, 14].
3 Results
In the study performed, the Electre III method was applied to the evaluation of several
alternative solutions for the façade walls, for the walls separating dwellings and separating
dwellings from common circulation zones and for the floors, on the basis of five criteria:
thermal and acoustic insulation, embodied energy, weight and thickness. Table 1 lists the
different criteria, thresholds and weights that are needed to use the Electre III method. The
weights and thresholds presented here are just an example. These values must be defined
by the design team according to the objectives and constraints of the project.
The criteria selected are related to the sustainability of the buildings and to the most
important characteristics of the IEQ, the thermal and acoustic comfort. These criteria were
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also selected because it is possible to define them in a non subjective way, they are possible
to predict in the design phase and are under the designer scope. The minimum thermal and
acoustic insulation values are also defined in the Portuguese thermal and acoustic regulation
and are mandatory. The weight and the thickness of the solutions are also relevant as they
affect the structural design of the building and their useful area.
Table 1 – Criteria, weights and thresholds (criteria to: ↓ - minimize; ↑ - maximize).
Category
(Criteria)
Thermal Insulation
(U-Value)
Acoustic Insulation
(D 2m, nT, W, D nT, W, L’nT, W)
Embodied Energy (EE)
Weight
Thickness
Units
Weight
Threshold
Preference Indifference
Veto
W/(m2ºC)
↓
25
0.25
0.10
0.50
dB
↑/↓
25
5
2
10
MJ/m2
kg/m2
cm
↓
↓
↓
20
15
15
220
80
7
80
30
3
460
160
15
The weight and the thickness are criteria to be minimized to reduce the weight of the building
and to increase the useful area available. The U-Value and the L’nT,W are criteria that should
be minimized and the D 2m, nT, W and the D nT, W are criteria that should be maximized.
The weights were defined taking into account the relative importance of each criteria. The
weights established for the thermal and acoustic insulation criteria, associated to the thermal
and acoustic comfort, were defined according to the relative importance of each one to the
occupants based on studies performed in Portugal and according to literature [15, 16, 17].
These studies showed that the thermal comfort is the most valued criterion, followed by the
acoustic comfort. The thresholds were defined according to the criteria characteristics, for
example a 2 dB difference is not perceptible to the human ear, but 5 dB is a significant
difference. Differences in the embodied energy and in the weight of about 10% are not
significant, differences of about 25% are relevant and if the difference is higher than 50% the
options are not comparable.
Several alternatives were selected for the walls and for the floors, based on different
construction solutions (single and double pane walls) and materials (concrete, brick, mineral
wool, MW and expanded extruded polystyrene, XPS). All the options fulfil the Portuguese
Thermal and Acoustic regulation.
3.1
Façade Wall
The construction solutions analyzed for the façade walls are listed in Table 2, where F stands
for façade wall, S for single wall with insulation on the outside and D for double pane wall
with insulation placed in the air cavity. Several options were defined for the opaque part of
the façades walls and for the windows (frame and glazing type) and the existence, or not, of
roller shutter box and air inlets. Table 3 lists the results of the prediction of the façade walls
behaviour according to the five criteria selected to outrank the design alternatives. The
acoustic requirements of façade walls are D2m, nT, W ≥ 28dB for sensitive zones (residential
areas, areas with schools, hospitals and leisure areas), and D2m, nT, W ≥ 33dB for the other
zones (named as mixed zones) [4].
The U-Value, embodied energy and the weight of the solution are weighted averaged values
taking into account the opaque, the glazing part of the façade and the roller shutter box.
The results of the outranking using Electre III method are presented in Table 4. The single
pane hollow concrete block wall, option FS2, was ranked as the best action, this solution has
the second higher acoustic insulation. The double wall with hollow brick with 11cm and
hollow concrete block with 12cm was ranked second. The best ranked options are the one
with lower embodied energy.
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Table 2 – Construction solutions studied for the façade.
Option
Wall
FS1
Single pane concrete wall with 20cm with 4cm of
XPS
Single pane hollow concrete block wall, 20cm,
with 4cm of XPS
Single pane hollow brick wall with 22cm with 4cm
of XPS
Double pane wall, concrete wall with 20cm and
plasterboard wall with 1.3cm with 6cm of MW
Double pane wall, hollow brick with 11cm and
hollow concrete block with 12cm with 5cm of MW
Double pane wall, hollow brick with 15cm and
hollow brick with 11cm with 6cm of MW
Double pane wall, hollow brick with 11cm and
hollow brick with 11cm with 6cm of MW
Double pane wall, brick with 15cm and hollow
brick with 15cm with 6cm of MW
Double pane wall, brick with 11cm and hollow
brick with 15cm with 6cm of MW
Ventilated wall, stone with 5cm and concrete wall
with 22cm with 6cm of MW
FS2
FS3
FD4
FD5
FD6
FD7
FD8
FD9
FD10
Frame
Glazing
Aluminium 6+12+4
Roller box Air inlets
No
Yes
4+12+4
No
No
Aluminium 4+12+6
Yes
Yes
wood
PVC
4+12+6
No
Yes
Wood
6+8+6
No
Yes
PVC
4+8+6
Yes
Yes
Wood
6+12+6
Yes
No
Aluminium 4+12+4
Yes
No
4+12+4
No
No
Aluminium 4+12+6
No
Yes
PVC
Table 3 – Criteria for the different design alternatives studied for the façade.
Thermal insulation Acoustic insulation Embodied Energy Weight Thickness
U-Value [W/(m2ºC)]
D 2m, nT, W, [dB]
EE [MJ/m2]
[kg/m2]
[cm]
Options
FS1
FS2
FS3
FD4
FD5
FD6
FD7
FD8
FD9
FD10
1.21
1.02
1.11
1.07
0.96
0.78
0.82
0.84
0.86
1.24
39
42
34
34
34
34
40
44
42
41
1768
699
1864
1378
907
1534
1004
2850
2162
3360
464
265
208
395
355
227
226
268
296
489
27.5
27.5
29.5
29.3
32.5
35.5
31.5
33.5
37.5
38.5
Table 4 – Credibility degrees matrix for the alternative solutions selected for the façade walls.
Non-Dom
Options
FS1
FS2
FS3
FD4
FD5
FD6
FD7
FD8
FD9
FD10
FS1
0.77
0.98
0.93
0.68
0.42
0.00
0.00
0.13
0.00
FS2
0.00
0.00
0.00
0.59
0.00
0.00
0.00
0.00
0.00
FS3
0.00
0.67
0.00
0.53
0.64
0.00
0.00
0.00
0.00
FD4
0.22
0.75
0.00
0.98
0.52
0.00
0.00
0.00
0.00
FD5
0.00
0.75
0.00
0.00
0.00
0.00
0.00
0.00
0.00
FD6
0.00
0.73
0.80
0.00
0.85
0.00
0.00
0.00
0.00
FD7
0.00
0.97
1.00
0.00
0.85
0.96
0.80
0.77
0.00
FD8
0.00
1.00
1.00
0.85
0.85
1.00
0.00
0.96
0.00
6
FD9
0.00
1.00
1.00
0.85
0.91
1.00
0.00
0.00
0.00
FD10
1.00
0.8
0.95
0.88
0.75
0.48
0.00
0.67
0.75
-
A
FS1
FS2
FS3
FD4
FD5
FD6
FD7
FD8
FD9
FD10
Ranking
Options
µ(A)
0.02
FS2
1.16
FD5
0.33
FS3
0.02
FD6
0.84
FD4
0.15
FS1
0 FD10, FD9, FD8, FD7
0
0
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INTERNOISE 2010 │ JUNE 13-16 │ LISBON │ PORTUGAL
3.2
Walls Separating Dwellings and Separating Dwellings and Common
Circulation Zones
The solutions studied for the walls separating dwellings and separating dwellings from
common circulation zones are listed on Table 5, where I stands for internal wall, S for single
and D for double pane wall, MW for mineral wool (placed in the air cavity) and EPS for
expanded polystyrene. All the walls are finished with 1.5cm of plaster on both sides except
the concrete walls that have plaster only in one side.
The values obtained for the different criteria are also listed on Table 5. Some of the solutions
do not fulfil the requirements established on the Portuguese Acoustic Regulation for
elements separating dwellings, but all can be used as walls separating the dwellings and the
common circulation zones (elevator shaft, staircase and the common hall) (DnT, W ≥ 48dB,
DnT, W ≥ 40dB if the source room is the staircase and the building have an elevator or DnT, W ≥
50dB if the source room is a garage) [4].
Table 5 – Criteria for the different design alternatives for the walls separating dwellings and
common circulation zones.
U-Value
[W/(m2ºC)]
Single concrete wall with 20cm with 2cm of EPS (IS1)
1.16
Single concrete wall with 25cm with 2cm of EPS (IS2)
1.13
Single pane hollow concrete block wall with 20cm (IS3)
1.71
Single pane hollow brick wall with 20cm (IS4)
1.25
Double pane wall, hollow brick with 7cm and hollow
0.50
brick with 11cm with 5cm of MW (ID5)
Double pane wall, hollow brick with 7cm and hollow
0.47
brick with 15cm with 5cm of MW (ID6)
Double pane wall, hollow brick with 11cm and hollow
0.50
concrete block with 12cm with 5cm of MW (ID7)
Double pane wall, hollow brick with 11cm and hollow
0.48
brick with 11cm with 5cm of MW (ID8)
Double pane wall, hollow brick with 11cm and hollow
0.46
brick with 15cm with 5cm of MW (ID9)
Double pane wall, hollow brick with 15cm and hollow
0.43
brick with 15cm with 5cm of MW (ID10)
Options
DnT, W
EE
Weight Thickness
[dB] [MJ/m2] [kg/m2]
[cm]
52
710
470
20
55
865
595
25
48
625
275
23
43
830
210
23
45
969
220
26
46
1052
250
30
50
885
440
31
45
1006
240
30
46
1183
280
34
47
1172
310
38
The results of the outranking using Electre III method are presented in Table 6 and in Table
7.
Table 6 – Credibility degrees matrix for the different design alternatives for walls separating
dwellings and common circulation zones.
Options (IS1) (IS2)
(IS1)
0.92
(IS2)
0.67
0.00 0.00
(IS3)
(IS4)
0.45 0.00
(ID5)
0.44 0.00
(ID6)
0.33 0.22
(ID7)
0.71 0.64
(ID8)
0.40 0.00
0.00 0.13
(ID9)
(ID10) 0.00 0.22
(IS3)
0.00
0.00
0.57
0.72
0.26
0.00
0.43
0.00
0.00
(IS4)
0.00
0.00
0.29
0.92
0.62
0.00
0.71
0.50
0.11
(ID5)
0.00
0.00
0.00
0.00
0.96
0.00
0.96
0.57
0.49
(ID6)
0.00
0.00
0.00
0.00
1.00
0.00
1.00
0.89
0.70
(ID7)
0.00
0.00
0.00
0.00
0.74
0.71
0.69
0.63
0.57
7
(ID8)
0.00
0.00
0.00
0.00
1.00
1.00
0.00
0.79
0.61
Non-Dom Ranking
(ID9) (ID10)
A
µ(A) Options
0.00 0.00 (IS1) 0.29
ID5
0.00 0.00 (IS2) 0.36
ID8
0.00 0.00 (IS3) 0.28
ID6
0.00 0.00 (IS4) 0.08
ID9
1.00 1.00 (IS5) 1.00
ID10
1.00 1.00 (IS6) 0.96
IS2
0.00 0.85 (IS7) 0.26
IS1
1.00 1.00 (IS8) 0.96
IS3
1.00 (ID9) 0.57
ID7
0.96
(ID10) 0.49
IS4
INTERNOISE 2010 │ JUNE 13-16 │ LISBON │ PORTUGAL
The Double pane wall, brick with 7cm and hollow brick with 11cm with 5cm of mineral wool in
plates placed in the air cavity, option ID5, was ranked as the best option for walls separating
dwellings and common circulation zones, according to the weights and thresholds defined.
This option was not the one that had the best performance on the different criteria, the best
behaviour was when considering the weight and the thickness, that are the less valued
criteria.
The double pane wall, with brick with 11cm and hollow concrete block with 12cm and with
5cm of mineral wool in plates placed in the air cavity (ID7) was the wall separating dwellings
that was best ranked, as Table 7 shows. This option was one of the worst ranked for the
walls separating dwellings and common circulation zones. So it is important to rank the
options according to the requirements.
Table 7 – Credibility degrees matrix for the design alternatives for walls separating dwellings.
Non-Dom Ranking
Options (IS1) (IS2) (ID7)
A
µ(A) Options
(IS1)
0.32 0.00 (IS1) 0.29
(ID7)
0.00 (IS2) 0.36
(IS2)
0.67
(IS2)
(ID7)
0.71 0.64
(ID7) 1.64
(IS1)
3.3
Floors
The solutions studied for the floors and other data obtained for the different criteria are listed
on Table 8, where F stands for floor. The floors between dwellings do not have thermal
requirements and have acoustic requirements regarding airborne and impact insulation
(DnT, W ≥ 50dB and L’nT, W ≥ 60dB) [4]. As, in general, the floors have the worst performance
related to the impact insulation this index was selected to represent the acoustic insulation.
All the floors have 0.8cm of wood as top surface finishing, and 1.5cm of plaster as inferior
surface finishing, except floor F2 that have a suspended ceiling with a plasterboard.
Table 8 – Criteria for the different design alternatives for the floors.
2.10
DnT, W /
EE Weight Thickness
L’nT, W
[cm]
[MJ/m2] [kg/m2]
[dB]
50 / 60 1325
390
17.8
0.64
55 / 51
1430
410
34.1
1.00
1.90
0.94
53 / 58
55 / 55
57 / 56
1526
1480
1680
470
555
596
23.8
22.8
28.8
1.43
50 / 60
1089
320
32.8
0.62
53 / 56
1290
415
38.8
1.52
53 / 58
1505
346
32.8
0.65
54 / 57
1706
440
38.8
1.46
53 / 55
1182
430
25.3
U-Value
[W/m2ºC]
Options
Concrete with 15cm, 0.5cm of polyethylene foam (F1)
Concrete with 15cm, 0.5cm of polyethylene foam and
a suspended ceiling with 5cm of mineral wool, 1.3cm
plasterboard (F2)
Concrete with 15cm, 2.5cm of cork, 4cm concrete (F3)
Concrete with 20cm, 0.5cm of polyethylene foam (F4)
Concrete with 20cm, 2.5cm of cork, 4cm concrete (F5)
Pre-stressed concrete “T” beams, 25cm hollow brick
pots, 5cm regularization layer, 0.5cm of polyethylene
foam (F6)
Pre-stressed concrete “T” beams, 25cm hollow brick
pots, 5cm regularization layer, 2.5cm of cork (F7)
Pre-stressed concrete “T” beams, 25cm hollow
concrete pots, 5cm regularization layer, 0.5cm of
polyethylene foam (F8)
Pre-stressed concrete “T” beams, 25cm hollow
concrete pots, 5cm regularization layer, 2.5cm of cork
(F9)
Hollow core concrete slab with 20 cm, 4cm
regularization layer, 0.5cm of polyethylene foam (F10)
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INTERNOISE 2010 │ JUNE 13-16 │ LISBON │ PORTUGAL
The results of the outranking of the floor solutions using Electre III method are presented in
Table 9. The concrete floor with 15cm and with polyethylene foam as resilient layer, option
F1, was the solution best ranked. This option is the lighter and thinner and also one of the
solutions with less embodied energy, but has the worst performance according to the thermal
and acoustic insulation. The hollow core concrete slab (F10) that is one of the floors with
best acoustic performance was ranked second. The slabs with floating layer of concrete, F3,
F5, F7 and F9, that are the thicker and have the higher embodied energy are the worst
ranked.
Table 9 – Credibility degrees matrix for the different design alternatives for the floors.
Options
(F1)
(F2)
(F3)
(F4)
(F5)
(F6)
(F7)
(F8)
(F9)
(F10)
(F1)
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
(F2)
0.60
0.64
0.40
0.00
0.60
0.69
0.75
0.49
0.83
(F3)
1.00
0.60
0.85
0.67
0.85
0.00
0.85
0.00
1.00
(F4)
0.75
0.00
0.00
0.00
0.06
0.00
0.51
0.00
0.72
(F5)
0.83
0.66
1.00
1.00
0.80
0.60
0.96
0.60
1.00
(F6)
0.68
0.00
0.06
0.00
0.00
0.00
0.73
0.00
0.83
(F7)
0.83
0.91
0.72
0.56
0.00
0.83
0.81
0.73
1.00
(F8)
0.96
0.00
0.00
0.00
0.00
1.00
0.00
0.00
0.85
Non-Dom
Ranking
(F9) (F10)
A
Options
µ)Α(
0.92 0.66 (F1) 1.60
F1
1.00 0.00 (F2) 0.17
F10
1.00 0.12 (F3) 0.00
F6
0.85 0.65 (F4) 0.25
F4
0.28 0.00 (F5) 0.00
F2
0.92 0.60 (F6) 0.32
F8
1.00 0.00 (F7) 0.00 F9, F7,F5,F3
1.00 0.57 (F8) 0.04
0.00 (F9) 0.00
1.00
(F10) 0.34
The best ranked options for the floors were not the ones that had the best performance in the
criteria with highest weights. This example shows that applying this methodology, due to the
use of weights and thresholds, the best action is not the one associated to the highest
weight, even if it is the one that has the best performance in that criterion.
4 Conclusion
This methodology allows, in an easy and quick way, to outrank construction solutions options
according to a set of criteria pre-established and based on weights and thresholds assigned
to each one. The design team has the possibility to change the criteria, weights and
thresholds according to the objectives and constraints of the project which enable the use of
this methodology to a vast set of possibilities (selection of design alternatives, etc.).
Using this methodology, the design team can compare materials, construction solutions or
design alternatives based on different criteria, for example, the U-value, acoustic insulation,
thickness, weight, embodied energy, just to name a few, select and compare design
alternatives, considering, for example the useful area, glazing area, etc..
The disadvantages of the methodology are the need to compare a large set of alternatives,
to be able to select the best one, the necessity to determine the different solutions
characteristics (thermal and acoustic insulation, embodied energy, etc.) and also the time
needed to perform such detailed analysis.
The example here presented allows a robust analysis of the building elements as it comprise
a broad study of each alternative through a detailed analysis of the main factors that affect
the IEQ and also the sustainability, based on the thermal and acoustic insulation levels and
the embodied energy of the construction solutions.
Throughout the multi-criteria analysis performed, it was possible to verify that there are a
large number of construction solutions that, when adequately used, will assure the all the
needs, being only necessary to integrate the exigencies of all the different requirements.
9
INTERNOISE 2010 │ JUNE 13-16 │ LISBON │ PORTUGAL
The proposed multi-criteria method, which can easily be applied, allows construction
solutions to be rated according to their performance and may be used in the design phase or
to evaluate rehabilitation or retrofitting scenarios. Using the Electre III method, buildings,
design alternatives, construction solutions and materials or retrofit scenarios can be ranked
according to several criteria and weights representing the preferences of the decision maker.
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