Session 1 - Montefiore

Table 3
Distribution of the steel weight within the walls.
Wall designation % of steel
Roof 43
Floor 21
External walls 27
Internal walls 9
aggregates concrete mainly because of transportation. In fact, even
if, in an LCA, the original concrete is produced with recycled
aggregates, the production of cement is the main contributor to all
studied impact categories. It causes approximately 77% of the total
energy use and 88% of the total GWP. The main reason for such
a situation is a large CO2 emission during the calcinations process in
the clinker production and the fossil fuel usage. The contribution of
the aggregate and concrete production and demolition is very
small. The same conclusions are drawn in [9]. At this stage, it is
important to note that the transportation related to the end-of-life
is taken into account with a higher distance for metallic materials
than for non-metallic materials. Even though, the preliminary
conclusion is still the same.
3.2. Comparative analysis in three different locations
3.2.1. Introduction
To be able to draw general conclusions, it is necessary to conduct
a sensitivity analysis of the results to chosen parameters to truly
understand their influence on the final values. Herein, the goal is to
compare the LCA results of a building located in three different
towns and to assess the influence of climate and energy mix. The
following parameters (inputs) are thus not included in the sensitivity
analysis seen the fact that they don’t change the conclusion of
the comparative analysis, although having (for some of them)
a strong influence on the final results:
(1) Transportation modes and distances could differ from one
town to another but as it is only slightly affecting the results, it
is thus not considered in the sensitivity analysis;
(2) The energy mix: different energy mixes for electricity
production will be considered for the three climates but, in one
country, the energy mix will not be modified;
(3) The scenario and envelope composition: naturally, if the
occupation scenario, demanded temperature or insulation type
are modified, the indicators change consequently. Herein those
parameters will be kept constant but the interested reader can
refer to [10] and [11] for more information;
(4) The house configuration, the percentage of windows, the house
plan, the envelope composition and orientation are of course of
Table 4
Manual calculations e Masonry house versus steel house (kWh/m 2 yr).
Masonry Steel
Building Electricity (including cooling
and double flux ventilation)
20.97 21.97
User Electricity 18.79 18.79
Total electricity demand 39.76 40.75
Space heating 44.85 32.38
Ventilation 12.07 12.07
Hot water 5.57 5.57
Total heating demand 62.50 50.02
Heat recovery (double flux ventilation) 9.05 9.05
Total bought energy for heating 53.44 40.97
Total energy demand 102.26 90.77
Total bought energy 93.20 81.72
Without user electricity 74.42 62.93
B. Rossi et al. / Building and Environment 51 (2012) 402e407 405
Fig. 3. Manual calculations e Share of eachbuilding part in theEmbodied carbon e Masonry
house versus steel house.
great influence on the final results. They will remain unchanged
in the present sensitivity analysis;
(5) The presence of local heat/electricity production or energy
saving equipment was not investigated in the present paper,
although ventilation heat recovery is taken into account
because it is becoming a common measure in new built house.
Nevertheless, its influence will be briefly discussed;
(6) The carbon payback will be indicated on the next graphs and,
naturally, a modification of the lifespan (50 years until now)
will influence it.
The influence of two important parameters was so therefore
assessed since they might have an influence on the main conclusion
stated before:
(1) The database: The quality (precision, completeness, representativeness)
of the data used can have a significant impact on the
results of an LCA. The existence of uncertainties in input data
and modelling is often mentioned as a crucial drawback to
a clear interpretation of LCA results. First of all, it can be seen
that Equer database (EcoInvent) and the databases used in our
manual calculations provide similar results for the masonry
house (see the companion paper). The uncertainties in the
database yield to tolerable differences as far as these impacts
are concerned. Secondly, the steel embodied emissions initially
taken as EcoInvent ones in Equer, were replaced by the
Worldsteel database (IISI 2002) taking into account the recycling
of steel at the end of its life in our manual calculations
([12] and [13]) It was shown that the end-of-life credits have
a strong influence on the Embodied carbon/energy of the steel
house.
(2) The design of the steel house: It was shown that the quantity of
steel used per HFA, that was initially evaluated as 64 kg/m 2 , can
be increased to approximately 25% of its value, and that, in
order to reach the Embodied carbon of the masonry house.
Similarly, if the design is modified and the steel quantity
increased, the Embodied carbon will increase subsequently in
all climates. It is thus concluded that the design of the house
presented in this analysis does not affect the final conclusion of
the paper.
On top of these considerations, the main conclusions are
provided in the next paragraph which highlight the influence of the
energy mix and climate.