ASHRAE Column
ENCOURAGING
NET-ZERO CONSTRUCTION
By Chilufya Lombe, ASHRAE simulations committee chair
The ASHRAE simulations committee is
made up of professionals in the building
industry (predominantly mechanical
engineers) that work mostly on buildings
simulations and optimisation.
What is net-zero carbon? Basically, a building needs to generate as
much energy as it consumes over a year. This does not necessarily
mean it is off grid, grid feedback and other offsets can be used.
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www.hvacronline.co.za
Energy Efficiency: Typically, however, there is a big difference
between what a building uses and what can be generated. A high
level of energy efficiency is needed to make the two the same. Net-
zero is about energy efficiency, not just renewable energy.
HVAC is a large consumer of energy in buildings and requires a
step change in energy use, i.e. reducing energy by two or three
times rather than a few percent at a time. This will be a significant
challenge for mechanical engineers.Â
RACA Journal I May 2020
uilding simulation has come a long way in South Africa,
from the first certified green building in 2009 to several
hundreds today. There is however no central body that brings
professionals in the field together and this is the mandate of
the simulations committee.
In a new era of sustainability, particular focus will be on
mechanical engineers to take up the challenge of being the
focal point in the pursuit of net-zero carbon buildings. Net-zero
carbon buildings are the latest effort at addressing climate
change and are being adopted at a rapid pace all over the
world. In South Africa for instance, the grid is predominantly
coal-based, which means there is a lot of carbon generated by
electricity use in a building. Offsetting the carbon generated to
power a building is what net zero carbon is all about.
In simple terms, a net-zero building is one that offsets all
the carbon related to the building operation over a one-year
period. The offsets are generally done via renewable energy,
namely electricity production via solar photovoltaics. This
does not necessarily mean the building is off grid, buildings are
allowed to feed energy back into the grid.
So why a challenge for mechanical engineers? Although the
final offset is via renewable energy, net-zero carbon is really about
highly energy efficient buildings. There is often a finite amount
of renewable energy that can be generated on a site so often
lowering energy use substantially is the only way to achieve net
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