Does it cost more to build a passive building compared to a conventional equivalent?

In Australia, building energy standards are lower than in many parts of Europe, and it is relatively difficult to source some high quality components here. The extra cost will depend greatly upon design, size of project, quality of finishes and so forth, but typically a range of 10 – 20% should be prepared, assuming the builder has some experience and training in this type of construction. However, recent local social housing projects are suggesting very small additional costs. The more large-scale window and door manufacturers bring high-performance products to the Australian market, economies of scale will drive down costs. The cost is usually offset by the massive reduction in energy bills, and the elimination of heavy mechanical heating and cooling units. With increasing energy prices, the question to ask yourself is ‘Can I afford not to build a Passive House’!

Are Passive Houses a good investment to live in?

Absolutely, with a 90% reduction in annual heating/cooling fuel consumption the energy savings will cancel out much of the increased up-front investment cost of increased insulation, better-quality windows and ventilation systems. Building a significantly better quality, smart home is a hedge against rising energy prices in the future. Above and beyond the cost savings, a Passive House owner also enjoys better indoor air quality and overall comfort…a factor difficult to include in the good investment equation!

Can you build large buildings to the Passive House Standard?

Yes, any type of building can be built to the Passive House standard, including skyscrapers. In Europe there are Passive House schools, office buildings, supermarkets, retail centres, gymnasiums, health clubs, and thousands of Passive House apartment units. The largest current development is the 26 story Cornell University Campus in New York, which will house 520 people, built and certified to the Passive House Standard.

Does a Passive House have to follow a strict design style? Does it have to be modern?

With the right team in charge, passive design does not dictate aesthetics. A Passive House can be traditional or contemporary but the key to a Passive House is the simplicity in its plan. It is best (most efficient and cheapest to construct) to create a compact shape (two storey is more efficient than a bungalow) with optimal solar gain, but the Certified Passive House Designer should otherwise be free to create any bespoke design according to the Client’s needs. It is important that the Passive House concept can be adapted to local cultures, styles and building traditions.

Do I have to have lots of north facing windows for the Passive House to work?

Not necessarily. Sure enough, it is ideal to have north facing windows to harvest the free energy provided by the sun. However, it is also possible to achieve the Passive House standard if your site does not lend itself to maximising solar gain (but you will probably have to compensate for this with additional insulation). All designs have to be tested and verified in the Passive House Planning Package (PHPP) software. If you have a wonderful view from the southern side of your house, you needn’t deny yourself of this. The Passive House is not as rigid as many people think, particularly in the Australia’s moderate warm to temperate climate.

Is it necessary to have triple glazed windows in a Passive House in Australia?

It really depends on your location and thus the climate. All Passive House’s must be designed and tested using the specialist software PHPP and you might find, on occasion, that it is possible to use very high performance double glazing in some instances. If you do use double glazing, however, be aware that you will probably experience some thermal discomfort on very cold winter nights in mountainous regions whilst sitting close to such windows due to the temperature difference that will inevitably arise between the internal surface of the glass and the surrounding living space.

Does a Passive House have to have thick walls?

Generally, yes. A Passive House Building needs more insulation than a typical building, and this is generally achieved by having significantly thicker walls. The thickness of walls depends on the U-values required which in turn is greatly dependant on the performance of the insulation, the type of construction (whether concrete, timber frame, etc), overall design, orientation, compactness and so forth. You generally won’t notice the thick walls from the outside of the house, however, as the windows are placed in the insulation layer which is best placed towards the exterior of the building shell.

What is the best insulation to use for a Passive House?

There are no strict rules in this regard. The critical issue is to achieve the U-values (thermal performance) required as identified by the PHPP. Thereafter, you can use whichever insulation type you prefer or can afford, whether polystyrene, cellulose, polyisocyuranate, strawbale, sheep wool and so forth. Some insulation types are better performing than others, requiring thinner walls, whereas other are less efficient and will require thicker walls.

Do you need a special site type if considering building a Passive House Building?

No, generally not. Of course, it is ideal to be able to design the building to face north, and to avoid over-shadowing by coniferous trees or local buildings. However, if these conditions do not exist on your site, then don’t worry. Allowances can be made, and tested in the PHPP software, for any shortfall in terms of ideal orientation leading to reduced solar gain.

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