Using quality materials is critical to building an energy efficient home, but materials are only part of the equation. That’s because it’s just as important to make data-driven choices about how and where to invest your money within the design.
Data lets us predict in advance how a building will perform and how changing individual variables will affect the design’s overall performance. We call this process energy modelling.
In New Zealand, many homeowners know all too well the frigid battle of trying to heat a cold home in winter, while others are sweltering in summer while struggling to cool their overheating townhouse. But life at home won’t be this way if you leverage energy modelling.
Keep reading as we explore more and explain why energy modelling is one of the most effective tools for maximising both the liveability and ROI of a home.
What is energy modelling for homes?
Energy modelling uses a combination of specialist expertise, tools and software to simulate a building’s thermal envelope relative to its climate, and predict requirements for heating/cooling, lighting, ventilation and more. Using this information, the specialist can appropriately determine the capabilities of equipment needed for these processes.
Having your building energy modelled makes it simple to make informed design changes and improvements to your home.
This could include increasing or decreasing the number of windows, and deciding where you should and should not use external shading devices or verandahs. You can also consider wall, roof and floor construction options, window/glass selections, and do quick cost-benefit analyses with data to support your decision.
As part of the energy modelling process, we consider a broad variety of factors including local climate and seasonal temperature shifts, house orientation, shading from nearby buildings, vegetation or topography, the intended utilisation of rooms, window placement and more.
Using energy modelling to understand heat demand and overheating potential
Two of the key variables measured when we create an energy model are the heat demand, which is the amount of heat energy your building requires to keep warm, and the overheating potential, which is the percentage of the year that the building is going to overheat.
Heat demand and overheating potential are inversely proportional – one increases as the other decreases – meaning the more energy efficient your home is, the more susceptible it will be to overheating if energy modelling is not done correctly.
The importance of energy modelling a new or existing building
A building’s energy requirement or operational energy is the biggest contributor to its carbon footprint when measured as part of a Life Cycle Assessment (LCA).
Energy modelling tools are essential to decarbonising buildings because the software reveals the most impactful design changes you can make to increase efficiency. It also shows which changes will maximise ROI when considering how to spend your budget.
In addition to the sustainability benefits and reduction in ongoing costs, energy modelling reduces the risk of condensation and mould, helping to ensure your building will be warm, healthy and comfortable.
While we recommend energy modelling as part of all new builds, the analysis can also be performed on existing buildings to improve performance.
Here are some of the benefits for new and existing builds:
Energy modelling for new builds
Energy modelling a new build gives a roadmap for achieving optimal energy efficiency and aligns the design with sustainability goals. Benefits can include best ROI for capital spend, lower energy costs, enhanced comfort, and a reduced carbon footprint. This all contributes positively to long-term ROI.
Energy modelling for existing buildings
For existing builds, we use energy modelling as a diagnostic tool to uncover inefficiencies and provide targeted solutions. These could include upgrading insulation, improving ventilation, retrofitting windows, or adding exterior shading. The insights gained will help in transforming even an energy-hungry home into a model of efficiency.
Hothouses: the overheating issue in modern townhouses
Ongoing updates to Clause H1 of the Building Code are resulting in more energy efficient buildings, which is fantastic. However, there are potential downsides to creating a home that retains more heat – overheating being perhaps the most concerning.
The most effective way to avoid an overheating building is to perform energy modelling, and here’s why.
There are design rules of thumb concerning overheating, such as:
Exterior shading cuts out at least four times the heat versus interior blinds
East and west windows require moveable screens or exterior blinds to keep lower elevation sun out
The north elevation should have a verandah or overhang to prevent the high summer sun entering the building.
However, our experience in modelling a variety of buildings has shown us there are no universally applicable rules.
In some cases, it may be optimal to let heat in rather than keep it out, whereas another house may have excessive heat accruing and in this case, reducing the ingress of heat is essential.
When energy modelling is not performed, the designer is blind to a buildings thermal comfort. It can lead to a variety of issues such as the overheating that’s increasingly afflicting city townhouses in New Zealand.
Sleepless in the suburbs: when townhouses become ovens
Recently, Team Green provided commentary for 1News, to discuss modern Auckland townhouses featuring glazed west elevations — these homes are becoming unbearably hot in summer as a result of poor design choices. In the bedroom of one such home, at 9pm, internal temperatures of 30 degrees were recorded, while at the same time, the outdoor temperature was just 26 degrees! This is totally unsustainable.
As cooling requires more energy than heating, it’s both difficult and expensive to cool down a home in which this level of heat is entering through glazing.
This case and others like it could easily be avoided with energy modelling and the use of appropriate external shading — were the property developers to implement these measures.
Tips for building a home that’s in harmony with your location
Creating a home that’s in harmony with its surroundings requires a mix of design techniques, technology, and environmental awareness. Here are some factors to consider:
Tailor your design to the site conditions: A home’s design should consider factors like sun path and wind patterns. Windows should be strategically placed to strike a balance between capturing maximum sunlight and avoiding excessive heat ingress.
Use appropriate materials: A “fabric first” approach to building ensures less requirement for services by creating the best thermal envelope. Careful selection of materials at the start is the best overall investment in your building and in the environment. Your building should have appropriate amounts of insulation, avoid thermal bridging, and use optimal windows paired with appropriate shading.
Leverage natural ventilation: A combination of natural and mechanical ventilation is key to thermal comfort and fresh air. Cross-ventilation encourages air flow throughout your home and reduces the need for mechanical cooling.
Invest in energy modelling at the outset: This will allow you to proactively solve potential overheating issues and build a home that’s beautifully comfortable all year round.
Final thoughts
By 2050 it is predicted that up to 50% of greenhouse gases will be due to cooling of buildings. So, it is essential that we knock society's over-reliance on mechanical cooling on the head.
With New Zealand’s Building Code becoming increasingly stringent due to ongoing updates, and the government’s emissions reduction plan (which states that by 2025, embodied carbon in all buildings will need to be accounted for at the consenting stage), it is becoming increasingly important to accurately predict your building’s energy usage.
Team Green Architects specialises in designing homes that seamlessly and thoughtfully match your locale, with energy efficiency at the forefront.
Enquire now to learn more about our energy modelling service, for cost-saving insights into your building's energy efficiency.
