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If building products do not contain any dangerous/cancerous substance and their
chemical composition by manufacturer or third party is publicly declared, these products
contribute to the achievement of credit MR6.
In
EQ section
, the roof can give its contribution for earning until 4 points: 3 associated to
the credit EQ2
“Low-emitting Interiors”,
strictly closed to the credit MR4 and 1 associated
to the credit EQ8 “
Acoustic Performance
”.
The performed analysis highlighted that for both the LEED versions, the roofing system
could contribute to achieve the credit regarding the heat island effect, if the SRI
(Solar
Reflectance Index)
value of the titanium-zinc sheet is higher than 29.
In particular, for LEED Italia the credit is SS7.2
“Heat Island Effect: roof”
(1 point) and for
LEED v.4 the credit is SS6
“Heat Island Reduction”
(2 points). The sheet used in the
case study does not have a suitable value of SRI and for this reason is not able to meet
the credit requirements. Anyway there are on the market similar LEED compliant
products, with EPD certification and SRI value higher than 29. Using such kind of
products could increase the point contribution of the roof. In this way for LEED Italia the
point will be 32 and LEED v.4 33.
Concluding, the “optimal” stratigraphy of the roofing system for both LEED versions is
the configuration including cork insulation layers and a titanium-zinc sheet with a light
color surface (high SRI). It is important to remind that for LEED v.4, this stratigraphy
shall be verified with LCA and realized by using EPD certified products.
Despite the introduction of new categories and credits and the new point distribution, we
can affirm that the contribution of the roofing system in the two LEED versions is more or
less the same, in terms of points and in number of satisfy-able criteria. This means that
the importance of materials choice and construction yard management is still the same
from a qualitative point of view. What is really different is that with LEED v.4, earning the
same score level is more difficult because:
1. increased level of products quality:
o
LCA analysis,
o
EPD certificates,
o
more rigorous thresholds ,
o
more responsible materials provision,
2. increased products attributes:
o
chemical avoidance,
o
environmental, economic and social performance,
3. presence of combined credits:
o
non-structural materials and low-emitting interiors.
In LEED Italia the only parameter used for assessing materials sustainability is their
percentage related to the total materials cost. This approach is not so correct because in
this way the contribution of a building sub-assembly can vary proportionally to the
building size. For example, the same type of roof applied to a low-rise building or to a
high-rise building can have a very different incidence, because of the higher contribution
in terms of dimension and costs of the other building sub-assemblies (walls and floors).
Instead, in LEED v.4, the presence of LCA gives the possibility to consider sustainability
not only in terms of cost, but also in terms of impacts, whose values is cost independent.
The results of the LEED v.4 application to our case study are not definitive, since the
LEED v.4 version is still under development and open to public comments. Just few
credits are already well defined, while the major part of credits is continuously evolving.
Only when the final v.4 version will be launched, we could confirm or modify and
integrate our results.
