Civil Engineering Reference
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building (LC-ZEB). The refurbishment option that will get closer to this LC-ZEB
will be those that have the lowest sum of operational and embodied energy and
therefore the best life cycle energy performance.
The AEE is always above zero in a refurbishment project when we need to add
new products and systems, but ideally the added embodied energy should be as
low as possible to ensure that large life cycle energy savings are achieved. When
we refurbish a building towards 'zero-energy' use in operation, or even to be an
'energy-positive' building, this requires the installation of some form of renewable
energy systems. However, the renewable energy systems must be considered as
any other building component and so their additional embodied energy is also
annualized and enters the equation as a part of the AEE. Therefore, when including
renewable energy installations in a building refurbishment and trying to optimize
life cycle energy performance, installations with a high environmental perfor-
mance and high 'net energy' input, which is a large ratio of energy produced to
their embodied energy, would be part of an optimum refurbishment solution.
Oversizing of building components or renewable energy systems with the sole
intention of bringing the annual energy use to zero could result in a high increase
in AEE, meaning that the total life cycle energy savings might not be significantly
reduced or could even increase.
The life cycle energy performance calculation presented here can serve as an
indicator of the true value of the efforts to minimize energy use in the built
environment, taking into account the frequently hidden or indirect energy uses
attributed to products and systems. As it will be explained in the next section, this
perspective can help to improve life cycle energy performance of a refurbishment
project. However, for the life cycle energy optimization presented in the following
section, it has to be taken into account that we are in all cases discussing strictly
and solely the life cycle energy performance perspective of a refurbishment pro-
ject, without addressing all other social, economic and environmental issues
potentially associated with the project.
3.4 Life Cycle Energy Optimization
The building industry's advance towards zero energy means a probable increasing
integration of additional energy saving and renewable energy products in refur-
bishment projects. The main advantage of the methodology presented here is that it
allows carrying out comparative analysis of the life cycle relevance of design
decisions in refurbishment projects, in relation to building envelope design, mate-
rials, HVAC and renewable energy systems. All such components can be included in
the analysis through the analysis of their impact on annual energy use and AEE.
Historically, this approach has not been considered in very low energy building
design. There could arise situations where systems or building components are
