4 minute read
The lowdown on energy modelling
What is energy modelling and how does it impact HVAC?
HVAC keeps us cool in summer and warm in winter. However, it can use a large amount of energy. By simulating energy use based on a building’s features and systems, such as HVAC, energy modelling can help to find ways to use this energy more efficiently – cutting usage costs and reducing the impact on the environment.
With a Master’s degree in Building Performance and Sustainability, Sarah Daniell is an associate and ESD team lead at eCubed. She keeps up to date on the latest research and innovations in the sustainable built environment including indoor environmental quality considerations, integrated design processes, data science for the built environment, and smart building control systems.
Sarah is also a qualified Green Star Accredited Professional, Homestar assessor and NABERSNZ assessor and has worked on a range of engineering and sustainability projects, with experience in simulation and building modelling including thermal modelling, energy simulation, performance optimisation, daylight modelling, computational fluid dynamics and code compliance.
IRHACE sat down with Sarah to learn the ins and outs of energy modelling and how it can inform HVAC design.
What is energy modelling?
“Energy modelling is a tool that can be useful in different ways,” says Sarah. “One way is as a design tool where you can look at the building, predict how much energy it will use, and try to reduce that – starting with passive design strategies, then moving into more active strategies, then finally offsetting your energy use by looking at solar and other renewable energy options.”
This is where the best results can be achieved – by integrating energy modelling into a building’s design process as early as possible.
“The certification or verification side of energy modelling is when we use energy modelling for, for example, Green Star ratings or building code compliance, or anything else where we’re saying this is what the design is, and we’re going to assess how it performs against fixed standards.”
How can energy modelling inform HVAC design?
There are many ways energy modelling can be used when it comes to heating and cooling.
“The simplest way it can be used, if you’re just looking specifically at HVAC, is once you’ve got an energy model, you can use it at a very basic level for system sizing. This isn’t really an energy model, it’s more of a load model. But you can produce your heating and cooling loads using the same model, which is really useful,” says Sarah.
It can also be approached in a more dynamic way by looking at energy peaks and when and where in the building those peaks occur.
“You can look at different options from a system design perspective, in terms of where you’re putting your heating and cooling and what kind of systems you’re selecting.”
Another way of using energy modelling is by setting up complex modelling that demonstrates detailed ways of controlling a HVAC system. This allows different outcomes to be assessed in terms of fine-tuning mechanical control strategies during design.
Combining HVAC with other approaches to optimise performance is also an important part of energy modelling.
“In our practice, we also look at a lot of mixed mode buildings,” says Sarah. “We look at building control using things like automatic opening windows and automatic opening vents, night purge ventilation, or various ventilation strategies to reduce the amount of active cooling we’re doing in a building.”
Misconceptions around energy modelling
There can be a lack of awareness around energy modelling, including its benefits.
“It’s not just an extra cost, it can bring quite good savings – especially if you take a step back from energy modelling and look at load modelling and starting with passive building performance before you even get into the mechanical design.
“If we can optimise that early on during the concept design, we might end up spending a bit more on modelling, but then you can save money by reducing peak loads and having a more cost-effective mechanical system.”
