Session 1 - Montefiore

398
2.2. Embodied energy and carbon: procedures and assumptions
The study is a cradle-to-gate study (A1 to A3 of [44]). It covers all
the production steps from raw materials “in the earth” (i.e. the
cradle) to finished products ready to be shipped from the factory.
The non-metallic materials databases are BEES database (http://
ws680.nist.gov/bees/) or preferably CRTI (Luxembourg Construction
portal, www.crtib.lu) database providing energy consumption
and equivalent CO2 emissions for a quite wide amount of
construction materials in Europe.
Transport to and from site (A4) is included in the present study
but is only slightly affecting the final results. For instance, if the
Ecoinvent database for impacts linked to transportation by trucks is
considered, the energy needs for transportation only attain 2% of
the embodied energy if a 50 kms distance is considered.
On-site processes (A5), such as the finishing of steel structures
(cutting, shot blasting, welding) is not included but, according to
steel producers, this step of the analysis is usually negligible [45].
Nevertheless, the net amount of products used for the construction
of the building is increased by 5% in order to take into account the
losses during construction, due to the vulnerability of products
during transport and handling or due to inadequate dimensions.
The end-of-life stages (deconstruction C1, transport C2, reuse
and recycling C3, disposal C4) are not included in the analysis for
non-metallic material (concrete, insulation, plaster, finishes). As
already mentioned for transport to the site, transport to the waste
treatment facility might also not have a strong influence on the
embodied impacts but are also taken into account. Transport
distances are 50 kms to the construction site for all the products
and 250 kms are considered between the site and the recycling
plant for steel (while only 20 kms are considered for non-metallic
materials).
The study includes the credits associated with the steel recycling
since it can have a strong influence on the final results [46,47].
Steel is produced using two process routes. The main one is the
blast furnace (BF) route (basic oxygen furnace), whereas secondary
steel production process uses the electric arc furnace (EAF) route.
Both processes recycle a certain amount of scrap that is melted in
the furnace making steel a recyclable material. The absolute recycling
potential of steel is 100% but, in reality, the net quantity of
scrap introduced in the furnace depends on the steel demand. One
important parameter of the analysis, especially for construction
steel, is the recovery rate that can attain 60% for rebar while, for
profiles, it can raise 100%. Nowadays, industries have resolutely
worked to influence the methodology and include the end-of-life
(EOL) treatment within the life cycle inventory data for steel.
Table 1
Total electricity use per country (source: iea.org, 2010).
B. Rossi et al. / Building and Environment 51 (2012) 395e401
Fig. 3. Steps of the life cycle analysis.
Those data are calculated for the BF route (based on iron ore and
steel scrap) and the EAF route (mainly based on steel scrap) on the
basis of World or European averages and can be obtained via the
Worldsteel facility. It is possible to specify the recovery rate (RR is
the percentage of steel that will be recovered at the end-of-life
stage) or use the average RR for the considered sector. In the
present study, an RR of 95% is considered. This parameter will be
discussed throughout this paper.
Replacement, refurbishment and repair of materials and products
(B1 to B5) is not taken into account specifically in the analysis.
However, the embodied carbon/energy are simply augmented by
5% every 10 years to take that into account. A 50-year service life
was considered in the analysis and is also one parameter that will
be further discussed.
2.3. Operational energy and carbon (B6 and B7): procedures and
assumptions
This part of the LCA concerns the Use phase (heating, hot water,
ventilation, cooling, lighting, building automation and control,
Operation in Fig. 3) in which no maintenance or repair is taken into
account (B1 to B5) a part from what is described in the previous
paragraph.
2.3.1. Space heating and cooling
The well-known heat loss factor (HLF) is provided in Equation
(1) below:
HLF ¼ X
½UiAiŠ (1)
i
where Ui ¼ heat transfer coefficient of wall i (W/m 2 K) and
Ai ¼ surface of wall I (m 2 ).
The heat transfer coefficient of the windows is calculated
differently. Depending on Uglass and Uprofile, the value of Uwindow is
evaluated for each window included in the building. The average
heat transfer coefficient permits the user to calculate the heat loss
through each window. This method leads to slightly overestimated
results.
Conduction of heat may occur through the walls either inwards
or outwards. This heat transfer depends on the temperature
difference between the warm and cold sides of the walls. In this
study, the energy demand for space heating evaluation takes into
account a scenario in which (a) each month is characterized by
a minimum and a maximum temperature lasting 12 h a day; (b) the
required indoor temperature is considered different during the
Belgium (GWh) % Portugal (GWh) % Sweden (GWh) %
Coal 7235 8.5 11196 24.4 2235 1.5
Oil 406 0.5 4148 9.0 873 0.6
Gas 24646 29.0 15199 33.1 603 0.4
Nuclear 45568 53.7 0 0.0 63889 42.6
Hydro 1757 2.1 7296 15.9 69211 46.1
Geothermic/wind/solar/other 5318 6.3 8130 17.7 13217 8.8
Total (in 2008) 84930 45969 150028