Benefits Of Passive Home Design For Perth’s Climate

Living in Perth’s climate, you’ll be glad to know there are innovative ways to keep you comfortable all year around – without the cost of constantly running an air conditioner! Passive  home design can help create the perfect indoor climate and keep your energy bills down as well. 

Passive design homes are built with the local climate in mind and can reach a comfortable indoor temperature all year round to save you money long term. Using insulation, glass glazing, and advanced design practices, you can completely remove the need for central heating and cooling in your home. 

If you’re planning to build a new home in Perth or surrounds, you may want to consider this climate-friendly architectural method. There are also many elements of solar passive design that can be applied to a standard home build, without the hassle of passive home certification. 

When working with a Perth custom home builder, you can work with your residential designer to integrate some fantastic energy-efficient features. If you’re building a new house, why not make it climate-friendly from the beginning? It’s a great way to save money on your energy bills for years to come, as well as adding value to your property. 

Eager to learn more about passive design principles? We’ve put together this article to help you understand what passive houses are, how they work, and why these principles are perfect for Western Australia’s climate. 

If you want to know more about passive home designs, continue reading below.

What Is A Passive House?

A passive house design is a home building process that significantly reduces the heating or cooling needed in homes. This practice emphasises creating a comfortable, low-energy, indoor environment. 

The name “passive” has been given to this architectural style because of the little to no reliance these homes have on heaters and air conditioners to maintain a comfortable climate. Passive home design has exploded in popularity worldwide, especially in Australia. 

Passive homes achieve the right indoor climate by utilising free and renewable resources like the sun and wind to supply ventilation, heating, cooling, and lighting. Passive home designs have been shown to reduce temperature drops and peaks throughout the day and increase your home’s overall air quality. 

The ideal indoor comfort band is anywhere between 20° to 25°. This could be achieved by combining window placement, insulation, airtight designs, orientations, and the elimination of thermal bridges. Doing this will help create a comfortable, low energy indoor environment.

The way passive homes work revolves around reusing “free” heat within the home. This heat is generated by most, if not all, electrical and gas-powered appliances like fridges, ovens, computers, and light bulbs. To ensure the passive home works correctly and no heat is lost, the home must be insulated and airtight. 

What Qualifies As A Passive House?

A passive house is a home that is built with specific design principles in mind to create an ideal ambient temperature without needing air conditioners or heaters. 

The globally accepted definition is:

 “A Passive House is a building, for which thermal comfort (ISO 7730) can be achieved solely by post-heating or post-cooling of the fresh air mass, which is required to achieve sufficient indoor air quality conditions–without the need for additional recirculation of air.”

This definition is purely functional and is valid for any climate. According to the Passive House Institute (PHI), an independent research institute and the only internationally recognised, performance-based energy standard in construction, there are four criteria it must meet.

  1. The Space Heating Energy Demand should not exceed 15 kWh per square metre of the house’s net living space (treated floor area) per year, or 10W per square metre peak demand.
  2. The Renewable Primary Energy Demand; the total energy to be used for domestic applications in the house (which includes any kind of heating, domestic electricity, and hot water, among others) should not exceed 60 KWh per square metre of treated floor area per year.
  3. The structure’s Airtightness; a maximum of 0.6 air changes per hour at 50 Pascals pressure (ACH50), verified by an onsite pressure test (within both pressurised and unpressurised states).
  4. Thermal comfort shall be met for all living areas during winter and summer seasons, with not more than 10% of the hours in a given year reaching over 25°C.

These criteria are achieved through intelligent design and implementing the five principles of passive house designs. However, it is very possible to achieve similar results with an uncertified house that incorporates any or all of the principles of passive house designs.

A custom designed home can consider many of these variables, giving you more flexibility in which features you want to include, without needing to meet rigorous certification standards. 

The 5 Principles Of Passive House Designs

Passive houses are designed and built in accordance with five building principles: airtightness, thermal insulation, mechanical ventilation heat recovery, high-performance windows, and thermal bridge free construction.

Per the Passive House Institute and the Australian Passive House Association:

Airtight Construction

The building envelope should be as airtight as possible and have a low air leakage rating. This is considered the first principle in achieving energy efficiency, affordability, and comfort in passive houses. It will involve the construction of highly insulated exterior walls, windows, roofs, and floor slabs.

In Australia, this principle can feel like one of the most challenging, but air leakage accounts for about 15% – 25% of loss in winter heat and summer cooling in houses. Part of our culture and climate is having our doors and windows open to let fresh air into our homes. Contrary to what you might think, passive home designs won’t have you sitting in an airtight box full of stale air. 

An airtight construction will prevent moist or humid air from penetrating the house, affecting the quality and temperature of the air inside. The principle allows you to retain any warmth or coolness generated within the house. 

Thermal Insulation

Insulation in the right places will provide thermal separation between the indoor climate and the exterior environment. Insulation that is properly done will create a highly efficient building envelope that will improve indoor comfort and reduce the risk of condensation.

For the most part, passive houses are wrapped in what could be called a blanket of insulation. Insulation can be found within walls, floors, and ceilings. In conjunction with an airtight construction, heavy insulation will serve as a barrier against heat flow and keep the house either cool or warm in summer or winter.

Heat Recovery Ventilation

A Heat Recovery Ventilation (HRV) system, also known as a Mechanical Ventilation with Heat Recovery (MVHR), refers to the process that improves the house’s indoor air quality without opening any window or door. It doesn’t stop you from opening doors and windows, but rather, it removes the need to open them for fresh air.

This principle controls indoor air quality and doesn’t primarily tackle a passive house’s cooling or heating aspect. However, as the name implies, MVHR systems can recover warm and cool air that would have been wasted in its absence. This is nowhere near the level or temperature regulation that insulation or airtightness provides but should be used in conjunction with airtight construction.

HRV systems flush out stale air, clean indoor air from pollution, and replace it with a constant supply of fresh, temperature-controlled, filtered air. These systems ensure that 85% – 90% of the energy in the house is kept in the house. In warmer climates, an Energy Recovery Ventilation (ERV) system is used and achieves similar results as HRVs but with the added benefit of humidity balance.

High-Quality Door And Window Glazing

It may not seem like it, but windows play a vital role in a passive house design. Superior grade windows and window glazing will allow solar radiation to warm up the indoor climate during winter and minimise radiation in the summer. Window frames in passive houses should be airtight, well insulated, and fitted with double/ triple glazing or low-emissivity glass.

Low-emissivity Glass – Low-emissivity glass is glass that comes with a very thin coating that reflects heat. This is useful for blocking out the Sun’s heat in warmer climates but may compromise winter heat gain when used on north-facing windows in solar-passive houses.

Glass Glazing – This refers to the number of panes that sit within the window frame. Single glazing refers to one pane of glass, double is two panes, and triple has three. Although double glazing will usually suffice, some Australian homes will require triple glazing.

On average, double-glazed windows will only transmit 16% of the heat compared to a single-glazed window. Some higher quality windows use Low-emissivity glass and are filled with Argon gas that can prevent heat loss by as much as 70% and heat gain by as much as 77%.

Eliminating Thermal Bridges

High-quality insulation must be continuous; otherwise, it’s not worth doing. As such, eliminating thermal bridges will keep penetrations through the insulation to a minimum, and where it cannot be avoided. This can be achieved by using low or non-conducting materials.

The primary aim is to avoid thermal bridges along which heat can escape, as they can also increase the risk of condensation.

Thermal Bridging refers to physical pathways within a building shell that conduct heat or cold faster than the rest of the structure. Thermal bridges will compromise the overall performance of the house’s insulation.

Most houses have common thermal bridges, such as the cracks under the doors, poorly insulated walls, and inefficient windows. Designing a structure with a passive house design in mind will ensure the removal of these ‘weak spots’ and create a more comfortable climate. 

What Are The Benefits Of A Passive House?

The fact that passive homes save money by not needing central heating and cooling is one of the many benefits of passive homes. The long list of benefits this architectural style has is why it has blown up in popularity in the last decade and will continue to influence how we build homes and buildings in the future. 

Key benefits of passive home design include: 

Low Monthly Energy Use 

The most enticing upside to a passive house design is that it does not need an air conditioner or a heating system, which leads to lower energy costs. Winter and summer months typically see a rise in energy costs for most homes due to the frequent use of temperature regulating systems. So a house that practically heats and cools itself is very energy efficient.

High Indoor Air Quality

It’s not common for structures of homes to be very airtight. Modern architecture typically doesn’t place much importance on keeping the house sealed. As a result, homeowners generally can not control the house’s ventilation. This means toxins can be blown into the cracks in your home and pollute the air inside. The air circulation and exchange of a passive house ensure that indoor air is filtered for almost the entire day.

Less Cleaning Required

The ventilation system of a passive house will also filter out allergens such as pollen or dust. This makes passive house designs very attractive for those who are allergic to common allergens or those who are very prone to seasonal hay fever.

A Quieter Living Environment

You won’t need soundproofing panels or walls as the house blocks a large portion, if not all, of the sound around outside. Having a passive house in a busy neighbourhood won’t be a problem because you’ll go through your day barely hearing your neighbours and cars driving past. One of the biggest noisemakers within your home is the air conditioner, which won’t be a problem for a passive home.

Building Material Flexibility 

Passive home standards are performance-based, which means you may opt to use materials that are otherwise not possible with a traditional home. This could be anything from reclaimed wood for walls to recycled denim for insulation. So long as the performance standard is met, a homeowner has the liberty to select the building materials.

Future-Proofing 

Residential building codes typically improve over time. And although nobody knows when these will change, building codes are only going to incorporate more energy efficiency elements over time. By building a passive home, you can rest easy knowing that the odds of your house will likely remain compliant for decades to come.

Learn more about Perth’s residential building codes (R-Codes).

How Do You Get A Passive House Certified?

To certify a passive house, it should undergo a rigorous testing process to ensure compliance with the Passive House Institute’s (PHI) certification criteria and standards. It is recommended to have a passive house certifier on board early in the planning process to identify any problems with its certification.

As a rule, any relevant energy planning documents and technical data of construction materials should be submitted before the construction of the house even begins. This will allow the certifier to provide information about any necessary changes/ modifications. It is best to use construction products with a “Certified Passive House Components” certificate.

The certification process has to go through three “teams” that have roles in pushing a passive house certification forward:

Design and Construction Team 

  1. Develop Building Form Options
  2. Choose Form, Identity, Construction, and Select Products
  3. Build, Test, and Commission

Passive House Consultant

  1. Basic PHPP Analysis
  2. Detailed PHPP Analysis to Optimise/ Finalise Design

Passive House Certifier

  1. Initial Check
  2. Final Assessment
  3. Certification Processing

Is A Passive House Cheaper To Run In Perth?

Yes. Passive houses are cheaper to run because of the long-term savings found in an energy-efficient house. Although the construction of a passive house costs a little more due to the extra insulation materials, you won’t have to worry about energy price hikes or usage surges during the peaks of winter and summer.

It is possible to save costs by implementing solar passive principles without paying a premium for a certified passive home builder. Some Perth building contractors, such as Central Avenue Homes, can incorporate the solar passive design principles of a passive home into a custom home build. 

Do Passive Houses Have Less Dust?

Because of their airtight construction, passive homes have less dust in them. Passive home design keeps dust from outside from entering the house and things like sand, mould spores, and airborne bacteria. This will inevitably lead to better indoor air quality and a healthier indoor environment. 

Regular builds can also incorporate airtight construction in parts of the home to decrease dust. When building a custom designed home, you have more flexibility to specify the benefits you’d prefer. 

Does A Passive Home Work In Perth?

Yes, a passive home works in Perth! It all depends on the designer and builder you work with. The house should also be well-executed on-site by certified and experienced tradespeople, and use quality materials. 

If building a certified passive home sounds too complex, with all the rules and regulations required to qualify, it is still possible to apply some principles of a passive home to a regular build. Solar passive principles work brilliantly for new home builds in Perth, and really help make the most of the block’s features. 

When you work with a custom home designer and builder, they can integrate your preferred passive design features. This means you can choose which items are a priority for your comfort at home, and which you’d prefer not to spend extra money on. 

The results will not be as ‘textbook effective’ as a full passive house planning package, but this process is cheaper and more flexible. You’ll still enjoy many lifestyle benefits in your new Perth home and keep your energy bills down with solar passive heating. 

To find out more, speak to the experts at Central Avenue Homes

How Much Does It Cost To Build A Passive House In Australia?

Depending on the contractor you speak with, a passive house can cost anywhere from $2000 – $4000 per square metre. However, there is no specific ‘cost’ for building a passive house, since designs and materials vary considerably. 

Australia is still in the early stages of utilising passive homes, and a lot of trial and error is being done in search of the most effective building methods. The primary factors that will ultimately affect the price are;

  • Size
  • Site access
  • Complexity of the design
  • Level of finishes and materials
  • Project location
  • Construction materials
  • The individual builder

The most unpredictable factor when building a passive home is the builder, since highly experienced and established builders will charge more than those who are not. These are factors that are difficult or even impossible to influence or predict.

However, there are some ways in which you can influence the cost-effectiveness of passive house construction.

  • Come up with a compact floor plan that minimises circulation space
  • Have a simple but elegant build form, with a simple roof structure to minimise cost for complex elements
  • Use off-the-shelf colours and materials
  • Use simple but efficient construction materials
  • Get a builder on board very early in the process, one that will explore options to build the house in a cost-effective way
  • Avoid “reinventing the wheel” too much if any at all. Stick to standard construction details and certified passive house components to make the design and build easy, simple, and cost-effective.

If you want to enjoy the benefits of a passive home but can’t afford the high costs of a certified passive home builder, other experienced builders may be able to implement certain passive home designs. Discuss your plans with a more affordable custom home builder and identify what elements of a passive home they can include in your standard build. 

Can A Passive House Have Air Conditioning?

A passive home doesn’t have an air conditioner because it doesn’t need it. Instead of conventional air conditioning systems, passive houses use a Mechanical Ventilation with Heat Recovery (MVHR) system. 

This system provides fresh air for the home and ensures a comfortable indoor climate by dramatically reducing space heating and cooling requirements.

A passive house design will generally not require any additional temperature regulating machines, provided that it is constructed in accordance with established passive house standards and certifications. Having said this, there are still options for other systems such as night bypass cooling and heating and cooling through a heat pump.

Who Builds Passive Homes In Perth?

Passive homes are still a relatively new concept in Australia, so finding a reliable builder who builds passive homes can be challenging and expensive. However, local builders Central Avenue Homes can integrate many solar passive design principles into their custom home designs. 

So while a completely passive house may not be cost-effective Perth, working with a builder such as Central Avenue Homes will put you ahead of the curve by incorporating some passive home elements into modern homes. 

To find out more about reducing your energy costs on a new Perth home build, contact Central Avenue Homes

Disclaimer:

This article is published in good faith and for general informational purposes only. It does not take into consideration your individual circumstances and does not constitute an estimate for any specific project. Central Avenue Homes does not make any warranties about the ongoing completeness, reliability and accuracy of this information. Construction costs and other financial details vary and you should always seek a specific quote. 

Share This Post

Share on facebook
Share on linkedin
Share on twitter
Share on email

More To Explore