Everyone is looking for ways to cut down on their energy consumption. Some of the best steps you can take towards saving energy is through the design of the building itself. One of the more popular variants of efficient building design is passive house design. You may have heard of passive house design, but what is it exactly? In today’s article, we’re taking a closer look at passive house designs.
What is passive house design?
Let’s start with a definition of what exactly passive house design is. Passive house design is a layout that aims to maximise thermal comfort through minimal heating and cooling demands. This is achieved through design choices such as insulation, appropriate window and door choice, airtightness, and ventilation.
The original concept originated in Germany during the 1990s (though they call it Passivhaus buildings), to find innovative construction techniques that would reduce a house’s energy usage. The Germans were clearly on to something as this idea has since spread around the world, including in Australia. There was some scepticism about passive house designs in Australia, as it appeared to better suit the colder European Climates, however, this has long ago been dispelled. With rising energy prices and concerns regarding the environment, it’s no wonder passive house buildings have become a staple in the construction industry.
What are the key principles that define Passive House Design?
Like any construction concept, there are a few key elements that help define exactly what passive house design is. Meeting the below requirements is essential if you want your home to be accredited as a passive house design. Here are the key principles behind passive house designs.
Airtightness
For accreditation, your house needs to have a low air leakage performance. This means your house has to have less than 0.6 air changes per hour.
While that may seem a little technical, the basic point is that air tightness is the first line of defence in improving a design’s energy efficiency, thermal insulation and overall affordability of living costs.
This may seem like an odd concept in this country, as it is a very Australian strategy to fling open the windows on a hot summer’s day, hopeful of catching a cool breeze. Passive house design isn’t all about locking yourself in your home. However, when you do close your doors and windows, warm or cool air won’t escape as easily, meaning your house will remain at a more comfortable temperature for longer.
Thermal insulation
Insulation is a key component when it comes to controlling the temperature of your home and acting as a barrier to heat flow. The right insulation choice for your home will depend greatly on the environment you’re building in. For example, somewhere in North Queensland will have completely different insulation requirements than a building in Hobart.
Thermal insulation is a topic big enough to have its own article, and that’s just what we’ve done!
Mechanical Ventilation systems with heat recovery (MVHR)
Mechanical ventilation with heat recovery is about improving air quality within the house without having to open the doors or windows. This doesn’t mean you can’t open the windows, just that air quality won’t suffer if you don’t.
It’s important to note MVHR isn’t about heating and cooling your home so much as improving the air quality. However, it can recover hot or cool air that would otherwise go to waste. It also helps keep your home more comfortable while other elements of the passive house take care of maintaining the temperature.
High-Performance Windows
Windows aren’t just for making the most of the view; they serve a vital role in the energy efficiency of your home. Ideally, your windows will allow solar radiation into your house during the winter while minimising this same effect during the summer. Most modern windows achieve this through placement, a focus on air tightness, and being either double or triple-glazed. Along with controlling the thermal insulation, it’ll help reduce outside noise.
Thermal Bridges and thermal bridge-free construction.
No matter how good the insulation material you buy, it won’t be much use if it’s installed improperly. Well-installed insulation keeps any gaps or penetrations to an absolute minimum. Along with letting heat and cool air escape, thermal bridges can lead to an increase in moisture and condensation, both of which can lead to water damage and mould.
What are thermal bridges?
Thermal bridges are any potential weak spots in your insulation where heat transfer is more likely. This occurs when a specific area is more conducive to energy than the surrounding materials. Common building materials that can create thermal bridges include concrete, aluminium and steel.
How does Passive House Design optimise energy efficiency?
Passive house design improves energy efficiency by improving the thermal comfort of your home through careful design choices. Through this, you’ll be less likely to require air-conditioning and heating. When you do require either of these, your house is much more likely to maintain the temperature, thereby reducing how long you need to leave the heating and cooling on.
How does passive house design influence site selection & orientation?
The position of your house and the direction it faces on your block play a crucial part in how effective your passive home design will be. When we talk about orientation, we’re talking about how your house design faces in relation to the sun’s path during both summer and winter. Taking this into account will help keep your home cool during the hotter months and warm during cold winter nights. Your builder should be taking this into account anyway, but it’s worth bringing up to make sure your house orientation is correct.
How much does it cost to build a passive house design?
When it comes to construction costs, it can vary a lot depending on who you’re building with and just as importantly, where. Not only do certain areas cost more to build in, but certain climates will be easier to build a passive house in. For example, in an area where summers aren’t too hot and winters aren’t too cold will be easier to make a passive more often than a hot one that experiences more extreme temperatures.
How do insulation and thermal mass contribute to the energy performance of a Passive House?
Thermal comfort is a key goal for any passive house residents and insulation plays a huge role in this. The more thermal comfort that can be achieved through the insulation, the closer you’ll be to having a low-energy house. There are a variety of insulation options on the market, with some being much more eco-friendly than others. Check out our guide to find out more.
What considerations are taken into account for windows and doors in a Passive House?
The placement of your windows and doors can have a huge impact of the thermal performance of your home. Allowing sun into your house will warm it up and natural sunlight also reduces your need to use lighting.
Installing double or triple-glazed windows will help your home hold heat during winter and keep it out during summer.
What certifications and standards exist for Passive House Design, and why are they important?
Passivhaus building certification (passive house certification) is available to ensure your home does indeed meet the requirements and building standards of a passive house. This ensures that you’ve gotten what you’ve paid for and having a certified passive house could potentially increase your home’s value. Your home will need to meet other legislation and regulations such as the National Construction Code.
How does Passive House Design adapt to different climate zones?
Passive house design can adapt in a variety of ways depending on the climate. Something as simple as the colour of your house can have an impact on the thermal capacity of your home. In Queensland, you’ll notice more lighter colour roofs on existing buildings as this helps reduce heat gains.
What are the advantages of Passive house designs?
- When done well, passive house design can greatly reduce the need for additional heating and cooling. Considering how hot the summer heat can be in Australia, you’ll still probably need fans/air-conditioning on particularly scorching days.
- It’ll make your home more comfortable to live in.
- They’re well-ventilated, providing your home with better air quality.
- Improve the sustainability of your home.
- Can be a selling point if you’re looking to move down the track. Sustainable house designs are only going to become more popular in the future, so it’s a wise investment.
What challenges are associated with Passive House Design?
- Australia is a country with extreme weather conditions. Sometimes it’s scorching hot, other times it’s bucketing down and other times it’s freezing (in some places, this can all happen in one day). This means passive housing is unlikely to completely remove the need for additional cooling and heating fixtures.
- Passive house construction can cost more depending on the passive house components you require.
- Knowing the exact steps to take to create a low-energy building can be challenging. Talk to builders or a passive house designer who knows and understands passive house standards.
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