March 3, 2022

Sustainability in the Built Environment: How Can HVAC System Simulation Help Save Our Homes?

As the weather slowly shifts to winter, and following recommendations to avoid…
Charles Luzzato

As the weather slowly shifts to winter, and following recommendations to avoid entering the workplace amidst the COVID pandemic, I sit in my small home office drafting this blog post. The COP26 climate summit has recently concluded, and I’m reading opinionated articles criticizing the number of private jets used by politicians and billionaires around the world to join the event, one of them in the same breath claiming that we are “one minute to midnight” to prevent climate catastrophe.

All the while, I feel cold; no matter how warm the radiator next to me might be, no matter that my smart home tells me that 60% of my annual heating consumption is used in this tiny room alone, it’s always cold; perhaps the layout of the heating system was not well thought out.

Perspective and Focus: Building Industry Single Largest CO2 Emitter

Public opinion is quite content with pointing the finger solely at the automotive or aviation industry when it comes to emissions; but surely, others have had the misfortune of experiencing a similarly bitter temperature, from a similarly ineffective heating system, in a similarly old house. This must all contribute to energy waste. In fact, when we look at the numbers, it’s quite a lot…

The building industry is the single largest energy consumer and CO2 emitter; not to say that transport is irrelevant, but yes, it is more than transport. In 2020, the UN Global status report for buildings and construction found that the building industry was responsible for 35% or energy use, and 38% of emissions. In 2021, the numbers were just as bad, with building exploitation (which means everything happening after construction) accounting for 30% of the energy use across industries. Looking a little further back, the trend of the building industry, in its efforts to meet the 2015 Climate Targets set out in Paris, has been appalling: we have been moving in the wrong direction, further away from our 2050 goal. The situation is so dire that Architecture 2030 claims that “We must eliminate all CO2 emissions from the built environment by 2040 to meet the 1.5o Climate Targets.”, at least for new builds.

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Getting the Design Right Pays Off

Over 80% of overall building costs occur after construction completes, so one would think that dividing your Heating Ventilation and Air Conditioning (HVAC) energy costs by a factor 2 would be reason enough to renovate. Even with those incentives though, it is estimated that 75% of buildings in Europe have poor energy performance, and that the vast majority of these buildings will still be in use in a decade. As an answer this, and in an attempt to restart the economy after the COVID pandemic, the European Union is committing to the Renovation Wave. Armed with a budget of several hundreds of billions of Euros, and in the context of the European Green Deal fighting against climate change, they will provide grants and loans to member states to help renovate 35 million buildings by 2030. Their focus will be on energy efficiency, comfort and productivity, and healthy indoor environment. In the United States, the Leadership in Energy and Environmental Design also provides aid in the form of tax credits, rewarding developers who maintain a low energy consumption with high thermal, noise and light comfort, and good interior air quality. To be able to receive these grants and tax credits though, you better be quite sure of how well your building will perform before it is built.

must provide clear information allowing engineers to balance energy consumption, thermal and noise comfort, and indoor air quality, whilst remaining cost effective.

, we demonstrated an example of how multiscale and multiphysics simulation technologies could help design the cooling system of a building. The low-cost 1D system modeling approach provided an effective initial dimensioning of the HVAC system, and comfort indicators throughout the building. The speed of this solution allows users to obtain full-year energy consumption and comfort data in the span of a few hours. Further optimization of the components chosen, or the size and layout of the components, can be automated and synced with changes in layout in the 3D geometry. In this specific example, we considered the impact of air recirculation on energy consumption. Past legislation for air recirculation would have allowed large quantities of pre-cooled room air to be reused, and reinjected into the room, thus reducing the energy required in the cooling system. Learning from the effects of COVID though, these types of systems are being phased out, and replaced with architectures which leverage filters (increasing pressure drop and maintenance costs) or newer technologies such as adiabatic heat exchangers. In the example shown, the overall energy consumption of the building using these newer technologies is decreased by 51%, as predicted by the system modeling.


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