It is probably because of their similar names that these two ‘passive’ systems often get confused. However, passive solar design and passive house (or passivhaus) are two completely different systems.
Solar passive design is more known in Australia while passive house is quite a new concept here and has only been taking off in the last few years. You can google the difference between those two systems but I am going to give you a quick explanation.
What is a solar passive house?
Passive solar design minimizes the energy requirements of a building by making best use of natural factors. The buildings have a dominant solar strategy (highly glazed north façade), usually combined with a high level of thermal mass – designed to smooth out indoor temperature. Commonly these buildings are also designed with a natural “cross flow” ventilation strategy.
However, the success of this approach is highly reliant upon the building orientation and occupant’s intervention. In addition to this, heat can be lost in winter or gained in summer through excessive air infiltration or thermal bridging, leading to overheating during summer, and coldness in winter when the thermal mass is not isolated from outside.
So, in a plain language – poorly insulated house with drafty windows and doors will mainly ‘benefit’ from too much heat in summer and excessive heating requirements in winter.
What’s a passive house?
Passive House, or Passivhaus as it is known in Europe, is a standard of construction that sets limits on energy consumption and air leakage. In reality Passive house isn’t really passive as they have active ventilation systems. It confuses everyone who has known about passive solar design since the seventies. Passive house is achieved through five key factors:
- An optimal level of thermal insulation
- High quality windows, usually triple glazed with insulated frames
- “thermal bridge” free construction (thermal bridges are weaknesses in the building envelopes that allow more heat to pass through than might be expected, e.g poorly insulated slab)
- An airtight building envelope, to reduce heat loss
- Mechanical ventilation with heat recovery
The result is a building that takes very little energy to heat or cool. The standard was developed as a way of saving energy, but there is a very desirable side-effect: It’s comfortable.
The Passive House Standard has its critics – some say that the standard is too rigid, requires unjustifiable amounts of insulation, and doesn’t take climate variations into account.
At ecokit, rather than to take one of those roads, we have chosen to combine them and to take the best of both worlds. Properly adhered to our instructions, the ecokit home incorporates all the benefits of the best of passive solar design, plus additional science-based efficiency approaches using technology and latest products to drive the building’s energy consumption to exceptionally low levels.
Here is our final take on marrying those two systems:
A big part of building high quality, passive energy home is creating an airtight envelope. There’s a lot of confusion about what ‘airtightness’ actually is. Think of it as control. It’s not about being in a hermetically sealed box, not being allowed to open your door or window. Airtight construction means that when you close the doors and windows, the house is actually closed. Not leaky.
Ecokit features large corner sliding door that can be opened for that ‘indoor-outdoor flow’ when the conditions suit, but having an airtight envelope is the only way to really ensure you achieve maximum passive energy efficiency when it’s time to close up and keep the warmth in. The limited solar passive design and our super insulated building fabric radically reduce heating and cooling energy.
The only way to achieve low energy buildings is to ensure a high level of airtightness is attained. That means designing and installing a continuous seal around the external envelope to eliminate unwanted drafts. Once the airtight vapour check is in place and sealed with durable and flexible tapes and seals, it ensures that the insulation functions to its optimum performance, saving energy and drastically reducing carbon emissions for the lifetime of the building. The airtight vapour check also ensures that condensation risk is minimized, ensuring no structural damage from moisture, mould, rot and damp.
Less windows but enough daylight
As always, our first design aim is reduce the amount of energy you need to use in the first place. So high ceilings and tall windows maximize light in all spaces, deceasing or negating the need for lighting during the day.
Heat / Energy recovery ventilation
Mechanical ventilation is crucial in a house with airtight envelope. Human body produces heat and humidity, so does our cooking and hot showers. Mechanical ventilation takes care of the humidity and stale air. Heat Recovery Ventilation (HRV) systems are even more advanced – they remove the stale air and bring in the fresh air – without losing most of the heat. They are the ideal choice for cooler climates such as southern Australia where humidity is not an issue and heating is essential. HRVs can recover up to 90% of the heat from out going exhaust air. For more humid areas such as Queensland or Northern Territory, Energy Recovery Systems are more suitable as they can also de-humidify the air. All units provide high-quality filtration to improve air quality.
Hot water systems
Solar thermal is a great proven technology and has been a rational cost decision if you plan to live in your house for more than five years, plus the Tractile Roof tile integrates the solar hot water system seamlessly with the PV system. We look to boost solar performance with Heat Pumps that are now getting efficient enough to consider.
We believe buildings should be designed around occupants. That’s who they are for! They should be comfortable, full of light, grand or quaint, they should resonate with our souls. Certified Passivhaus can satisfy the architect’s need for checking boxes, and the energy nerd’s obsession with btu’s, but it might fail the occupant. Solar passive design is more natural approach but extensive solar gain in summer can overrun the benefits of a minimal solar gain throughout the winter.
We partly embrace the Passive House approach because it reliably succeeds in delivering highly energy-efficient buildings. The low remaining energy demand can be met by using renewable energy sources on a long-term basis.
If you’re looking to build a healthy, energy efficient home, then you might have just found one.