The passive house design theory originates in Europe around 30 years ago. In 1988, German physicist Wolfgang Feist and Swedish structural engineer Bo Adamson developed this theory.
It relies upon the concept in which, by carefully designing around some key principles, it is possible to create a building that can self-maintain a dry, healthy and comfortable indoor air quality and temperature, with a little-to-no requirement for heating or cooling. In such houses, new elements replace the standard HVAC components like ventilators, air conditioners, etc.
The structural design and construction of a Passive House follow the below ten core principles:
1. Airtightness
A vital factor in the durability and performance of a Passive House is creating an airtight layer – a virtually impenetrable barrier. Such a barrier prevents air from penetrating through to the inside.
Designers make airtight layers by using a combination of sheet and fluid-applied membranes, sealants, and tapes, This layer facilitates the uninterrupted transition between the building’s structural elements. A blower door test is then used to verify the proper function of the layer, confirming the quality of the construction.
2. Continuous insulation
A continuous layer of thick insulation is wrapped around a Passive House design. Its function is to keep them optimally cool in summer and warm in the winter months. Not only does this improve the year-round thermal comfort of the space, but it also helps to reduce the incidence of condensation inside the building.
3. Heat recovery
Passive House design incorporates the delivery of fresh, filtered air with the addition of heat recovery to ensure that the building can maintain improved air quality indoors without the need to open any doors or windows. Balanced ventilation components are installed to supply a continuous indoor fresh air stream, whilst simultaneously removing odors, stale air, and other indoor pollutants from the bathrooms and kitchen spaces. These components are Heat Recovery Ventilators (HRVs) and Energy Recovery Ventilators (ERVs).
Within these devices, a heat exchanger enables the outgoing heat energy to warm the incoming air as the two streams of air continually mix within the unit. Conversely, in the summer months, the coolness of the outgoing air brings the temperature of the incoming air down. The units contain filters for removing pollutants and pollen.
4. High-performance doors and windows
The performance quality of doors and windows plays a pivotal role in the success of a Passive House design. The addition of windows and doors essentially interrupt the advanced wall assembly including the insulative, airtight layers that have been installed. Therefore, their performance is critical to maintaining the integrity of the design.
Passive House windows and doors need to allow solar radiation to effectively warm the interior air during winter months, yet also minimize this heat radiation from the outside in summer months. They are therefore designed to be airtight and are usually double or even triple-glazed for maximum insulation capabilities.
5. Thermal bridge-free construction
Good insulation is of little effectiveness if it faces interruption. A thermal bridge refers to any element of a building that enables air temperatures to bypass the thermal barrier otherwise created for the building. Examples include a poorly constructed/installed window frame, or a concrete floor that runs from the inside to the outside of the building.
As well as keeping insulation penetrations to a minimum, the impact of thermal bridges is minimized by introducing thermal breaks, which are insulative elements that prevent any thermal energy from flowing through an assembly.
6. Maximizing solar gain effectiveness
Natural daylight provides a passive solar gain that essentially creates free heating to a Passive House building. That said, for others, they can become a liability when the existing internal heat gains are already significant and need management.
Passive house designers must work to optimize the use of the available passive solar gains in keeping with the climate, and consider orientation, layout, shading, and all other factors to determine how best to utilize this free commodity within the design.
According to Buttonwood, a Toronto Property Management Company, a large number of landlords are now deciding to invest in passive homes for these eco-friendly benefits which are also attracting more residents.
7. Adequate shading
The cooler months may benefit greatly from the solar gains coming from the outside. However, this direct heat energy must also be efficiently managed to equally suit the warmer seasons. A great solution for this is to introduce deciduous trees to the external landscape, as their full summer branches provide shade, while their bare winter branches allow more sunlight to flow into the building.
Other design elements include window screens and shades, as well as retractable overhangs. They can also assist in controlling the direct solar energy exposure seasonally.
8. Efficient heating and distribution of water
The first step is to make sure Passive House design has successfully reduced heating/cooling related-energy consumption. The next culprit to focus on is the heating and distribution of domestic water. By installing an ultra-efficient water heater and making the distribution lines well insulated, smaller, and, where possible, shorter, it is possible to minimize the energy consumption in keeping with the goal of a Passive House design.
9. Building form and orientation
How easy or difficult it will be to achieve a successful Passive House design? This will depend largely upon the initial fundamental decisions around the proposed building’s form and orientation.
The orientation of the building is also a highly important matter. It has a high impact on the optimization of solar gains for optimal energy performance. Additionally, the more simple the overall form of the building, the easier it will be to ensure continuous insulations. It also helps to minimize thermal bridge interruptions.
10. Managing moisture
Different climates will alter the way that heat and moisture behave within building designs. Therefore, passive house designers must understand how to create plans that best manage these relationships. They need this to avoid the risks of water intrusions and condensation build-up.
Final thoughts
The principles of Passive House design allow for a careful balance between different factors. These factors include occupant use, heat emissions, and climate, etc. Such balance helps to optimize the energy efficiency of the building.
When successfully carried out, a Passive House should successfully keep the interior at a consistently comfortable temperature year-round. With a little-to-no requirement, it also minimizes any additional heating or cooling. Additionally, the continuous ventilation creates a superior 24/7 indoor air quality. As a result, the long-term comfort, health, and energy efficiency benefits to Passive House design are significant
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