Passive House has steadily evolved over the years to become the go to standard when it comes to constructing energy efficient buildings. When you think of the main elements that are part of the Passive House standard, it becomes clear as day that buildings that make use of the Passive House principles are being designed with one goal in mind, to limit as much as possible the need for energy.
In essence, a Passive House is designed to achieve four main things: energy efficiency, comfort, affordability, and sustainability. What sets a Passive House apart from, let’s say, a Passive Solar house is that it not only uses the energy from the sun, it also makes air quality (via heat recovery ventilation) a requirement. By doing so, the interior climate is kept at a comfortable and healthy level without the need for active cooling and heating systems.
The main areas of focus for the Passive House standard when it comes to achieving energy efficiency can be classed as follows:
Minimising loss of energy around windows, while using solar gains
Mechanical ventilation combined with a heat recovery mechanism
As a practical way to illustrate how you can become energy efficient by putting the Passive House rules into practice, we thought it best to make use of two completely opposite case studies. One will focus on presenting the residential viewpoint, while the other will be a more theoretical approach. The focus here being to present how a hospital can become more energy efficient if the Passive House standard is used.
Energy Efficient Passive Housing – a Residential Case Study
With our first case study, we wanted to put things into an Australian context. It is well documented that Passive Houses from Europe have been thoroughly researched, and their measurements in terms of energy performance have been diligently looked into.
The same cannot be said about certified Passive Houses in Australia, for example. For this reason, we decided to present the energy efficiency outcomes of a three-bedroom, single storey detached Passive House from the suburb of Chifley in Canberra.
The Issue of Insulation
As expected, the building fabric of the house has been highly insulated. The insulating layer needed to be continuous and impede air movement. Any deviation from the process and a reduction in energy performance would follow suit.
A thermal bridge modelling software was employed to reduce the thermal bridging factor of the insulating layer. In terms of protecting the insulation from air movement, vapour permeable wind tight building wraps were used externally while on the inside air tight building wraps were put in place.
In terms of the prefabricated walls and roof panels, rigid foam was the desired material of choice to act as insulation.
After a consultation with the Passive House Planning Package, dark or tinted glass was discounted as an option to protect the interior from the summer heat. Instead, the preferred method was to go for operable external shading devices, which offered higher heat gains in winter and the opposite in summer.
Airtightness is particularly emphasised in the Passive House approach as it is an essential factor in ensuring comfort and reducing energy losses.
In this particular case, to ensure the building envelope is airtight, all surfaces and junctions, in particular, were carefully designed with airtight membranes, tapes, and grommets.
Rigorous blower door tests were carried out during and after construction to make sure the house falls under the Passive House airtightness parameters (0.6 ACH).
The result of all this precision work is that the house performs 150 times better than the average new build in terms of air changes per hour.
Ventilation, Heating, and Cooling
Because of the airtightness factor, mechanical ventilation with heat recovery needs to be installed in order to provide the house with fresh filtered air without losing any heat during the exchange. In this particular case, the only heaters used in the house were a 1.2 kW electric heater for the ducting of the mechanical ventilation with heat recovery system, and a 100W towel rail heater. No cooling devices were needed and hot water was provided by a standard heat pump.
Now that we got the technical vernacular out the way, it is time to look at specific results and see how energy efficiency has been achieved in this particular case:
Average energy consumption was 13.0 kWh per day
This represents a 64% reduction compared to other houses of this size in Canberra
Compared to Melbourne, the statistics show a 62% reduction in energy consumption
An energy rating of 9 stars was achieved under the national rating scheme
Energy Efficient Passive House Principles in a Non-Residential Context
With Passive House being a quality standard, it lends itself to any kind of construction. This means that when you think Passive House, residential shouldn’t be the only thing that comes to mind. This is what we want to change with the second case study. The focus will be purely theoretical and will try to demonstrate how the Passive House principles can be used to reduce energy consumption in a hospital.
Statistics show that hospitals are rated among the public buildings that consume the most energy, be it for electricity or heating. However, in order to implement the Passive House standard in a hospital, certain aspects need to be given extra care:
Areas with sensitive hygiene requirements will need to be addressed accordingly
Increased comfort requirements for the elderly and recovering patients
The amount of energy used will differ in accordance with a clinic’s specific focus. For example, consumption will differ if a clinic is sterilising its own equipment, has a cafeteria, does laundry in-house, and offers medical imaging as well.
Research shows that it is worthwhile to check use-specific energy applications normally not taken into consideration with conventional energy balances. What we are trying to say here, is that with improved processes and today’s energy efficient devices, a reduction in energy consumption of more than 30% can be achieved. This can be viewed as a major accomplishment considering that medical devices have not received the same attention as household appliances when it comes to energy efficiency.
The first instinct can be to say that it is impossible to achieve energy efficiency when it comes to heating a building the size of a hospital. However, it is precisely because hospitals are most commonly large and compact buildings, that the Passive House principles can be easily implemented to achieve significant reductions in energy usage.
For instance, if we go back to the issue of insulation, if it is done properly, heat distribution will no longer matter as much. Surface heating systems can also be put in place in order for ventilation and heat to run separately. This should address the more unique energy requirements of a hospital.
Co-generation can also be considered as a solution to be more energy efficient as it addresses the constant demand for hot drinking water and electricity.
With the increasing need, due to climate change, for us to be more mindful when it comes to our energy usage, we hope that this article has shown it can be possible through the use of the Passive House method.