The Ins and Outs of Passive Houses
Passive Houses are continuing to rise in popularity, as more and more Australians come to appreciate and understand the benefits of building a functional and environmentally friendly home. The design standard, which originated in Germany, sees innovative insulation and ventilation techniques used to achieve a comfortable home year round, with minimal artificial heating and cooling requirements. If you are looking to build a future-proof home that has a minimal impact on the environment, it’s a great option to consider!
As a qualified Passive House builder in the Gippsland area, the Olsson team have all the know-how to help you bring your home to life. Here is what you need to know if you are considering this eco-friendly option.
What is a Passive House?
‘Passive House’ is a world-leading design standard that ensures comfortable and efficient homes through energy-efficient construction. Their aim is to reduce the need for heating and cooling and protect the building structure so that the home can be occupied for years to come.
Building a Passive House isn’t an afterthought, it is woven into the very fabric and structure of the building itself. This ‘fabric first’ approach has a focus on ensuring the thermal envelope, the layer that separates the inside of your home from the exterior, is optimised for an ideal indoor environment.
This means a Passive House will have:
· Appropriate insulation
· An airtight envelope
· Appropriate and high-quality windows (often double or triple glazed) and doors
· No thermal bridges
· Reliable ventilation systems that can recover heat
To achieve certification, a Passive House must satisfy a number of requirements. However, it is also possible to introduce Passive House elements into your home without reaching for the standard.
The Passive House Standard
To obtain an official ‘Certified Passive House’ qualification, a home must meet the following criteria:
Internal temperatures remain consistent throughout the year, with a 20°C minimum during winter and summer. No more than 10% of hours in a given year should be over 25°C (this can be adjusted in areas of extreme climate)
Energy used for heating or cooling must not exceed 15kWh per square metre per year (or 10W per square metre of living space). In humid areas, the cooling allowance may be adjusted to allow for dehumidification.
There must be a maximum of 0.6 air changes per hour at 50 Pascals pressure (ACH50). This can be achieved through airtightness, but does mean that ventilation with heat recovery is required to bring in fresh air and maintain air quality inside.
The total energy for all appliances, including heaters, lighting and hot water must not be more than 60 kWh per square metre per year.
Elements of Passive House Design
Even if you aren’t looking to obtain official Passive House certification, there is merit in incorporating key features into your home design as it will result in an energy-efficient home. The following design features of Passive Houses can be incorporated into any build.
Insulation
Without insulation, there’s no way to control heat loss and gain – think very hot homes in summer, and very cold homes in winter! Heat loss through walls, roofs and floors are responsible for more than 70% of the total heat loss in buildings, making insulation a key part of energy-efficient design.
Thick and continuous insulation is required in order to achieve thermal comfort, providing an established layer between the outdoor conditions and your living spaces. This includes the entire thermal envelope around your home – walls, ceilings and floors. In some climates, this may even extend under a concrete slab.
Elimination of thermal bridges
A bucket with holes is much less effective at holding water than a bucket with no holes – the same principle applies to insulation. It’s essential to keep gaps where heat could escape to an absolute minimum – these gaps are known as thermal bridges.
Thermal bridges can not only cause cold spots, but also encourage condensation, increasing the risk of mould. In a Passive House they must be eliminated, or at least adjusted, for so that there is no risk of condensation, mould or excessive heat changes.
Traditionally, the most common places for thermal bridges occur are aluminium framed windows, steel beams and uninsulated concrete slab edges. Gaps around doors and windows, unsealed vents, skylights or exhaust fans, and gaps between floorboards and wall openings can also be key points where heat can escape or enter the home.
Ventilation
An airtight home means only controlled sources of fresh air will reach inside your home (i.e opening doors or windows). When this isn’t possible, or won’t help maintain a consistent temperature, ventilation really comes into play as it ensures an ongoing flow of fresh and clean air into your home.
Passive Houses use heat recovery ventilation - this draws outdoor air through a filter into your living spaces and bedrooms, while removing stale air from bathrooms and kitchens. This removes moisture, smells, dust and pollutants from your indoor spaces, resulting in healthier and cleaner air.
Windows and doors
Windows are often the largest source of heat loss and gain in any building. When building a Passive House, it’s important to install either double-glazed or triple-glazed windows with high-quality insulated frames that seal tight to prevent thermal bridges. This can reduce the heat transmission to just one-sixth of a typical window.
The placement of windows is also important – they must have appropriate shading to control the amount of heat that filters through in both winter and summer.
Airtightness
Airtightness is a key component in achieving true energy efficiency, even if you aren’t looking for official Passive House accreditation. It can often be seen as a challenge in Australian climates, but airtightness doesn’t mean you can never open doors and windows! It relates to what happens when you close all windows and doors – thanks to highly insulated walls, windows, roof and floor slab, there should be no gaps for air to escape, helping to maintain a comfortable environment.
Eliminating all gaps also restricts excess moisture and pollutants from entering your home, reducing the chance of mould and moisture damage.
Thinking about incorporating some Passive House elements into your next build, or even going for full certification? Whichever option you choose, building with Passive House design elements in mind will be beneficial for years to come. So, when you’re ready to start your Passive House journey with a certified Passive House builder, contact Olsson.