Everything to know about passive house

The passive house is a concept invented by the German physicist Wolfgang Feist, originally popular abroad but growing in popularity within Canada. These projects are recognized as low-energy housing, and therefore green-friendly, as the construction of these houses relates back to the way they are built and the materials they use.

In order to understand the implications behind the construction of a passive house, you'll first need to understand relevant information about the concept!

The passive house: a German concept

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The insulation of a passive house

The use of heavy and dense materials such as terracotta, brick or stone allows us to take advantage of the thermal inertia. Thus, the preservation of internal heat during the winter, as well as freshness in the summer is assured. These materials minimize thermal bridging, allowing for the correct temperatures inside the home, no matter the season.

Note that great care must be taken during the construction process to ensure maximum water-tightness. as to avoid the presence of entry points around the home's foundation. As a result, the risk of heat loss and mould growth as a consequence of high humidity are eliminated. As for the walls, they usually contain three times more insulating materials than the average home.

Ventilation

In order to ensure adequate ventilation in the house, passive houses benefit from natural ventilation during the summer season. Further, they benefit from air circulation, which is especially true if the home has more than one level. This is because allowing cooler air to enter the home through the ground floor window overnight works to push warm air from the house to upper floors.

Thus, the fresh air cools the interior of the house so as to avoid starting the day in sweltering heat. Passive houses are also equipped with a heat recovery ventilator that allows heat recovery alongside evacuation. The fresh air entering the home is warmed by the exhaust air that is expelled!

Since fresh air circulates constantly, there won’t be a cold breeze causing inconvenience to the occupants. In addition, because the system allows for heat recovery and reuse, it increases the energy efficiency of the home, with heat recovery reaching around 95%. Not only does the HRV offer an excellent performance, but it is particularly fast at getting the job done, as the air in the home will be renewed in three hours. Further, it should be noted that the HRV is warmed by the circulation of water through its system, which justifies the low cost of its use. The performance of the system should provide a renewal of air equivalent to 30 cubic meters per hour per person.

The fenestration of a passive house

In order to increase the heat input into the house, the front of a passive house should always face south. This will allow you to maximize natural light due to the optimization of the sun’s rays from this angle. As an indication, south-facing windows must occupy 6% to 12% of the total floor area and be equivalent to approximately 60% of the total windows of the house. 

Evidently, the type of window valued in a passive house is generally characterized by its high energy performance. These windows are often equipped with a glaze that has a high degree of transparency, as this works to capture the most sunlight while still allowing natural light into the home. Triple-glazed windows filled with argon are recommended because of their attractive insulating properties. 

Although windows with high energy efficiency have undeniable advantages, they may tend to block the sun’s rays to a great extent. To avoid this situation, the standard set by the passive house suggests a minimum heat coefficient of 50%.

Heating in a passive house

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With regard to the building's heating, a passive house takes advantage of the heat coming from the occupants and the operation of the various apparatus which it contains. As mentioned in the previous section, passive fenestration also plays a big role in bringing heat into the house.

On another note, it should be emphasized that a passive house can greatly reduce heating costs.  Savings of around 85% are expected as compared to the Novoclimat standard and around 90% as compared with a traditional house.  In order to obtain the passive house authentification, it is imperative that the home requires no more than 15 to 20 kilowatt/hours per square metre of living space. For oil, a maximum of 1.5 litres per square metre per year should not be exceeded.

Regarding the total energy consumption as relative to the daily operation of the home, a maximum of 120-kilowatt hours per square meter per year should not be exceeded, which is surprising considering that 100-kilowatt hours per square meter are necessary to ensure the heating of a conventional home.

Passive houses: are they profitable?

Of course, even if the attributes of a passive house are numerous, the question of its profitability still arises when it comes time to make a purchase. Although it is necessary to resort to more expensive materials, it seems that these additional costs may be offset by:

• Savings in heating and electricity;

• The lack of expensive air conditioning and heating systems required to achieve that same performance;

• The savings made on the living space.

Finally, the total costs generated by the construction would be only 5 to 10% higher than a traditional house. Based on the aforementioned criteria, there is no fear for the long-term profitability of the home.

The room layout

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Although the choice of materials is of paramount importance, the way the rooms are laid out is also an essential aspect. As fenestration to the north provides less heat input, rooms that do not require much heat such as the laundry room or bathroom should ideally be positioned in these places. This will leave space in the north section of the home for rooms which require a greater heat input.

In order for the rooms facing south to be able to receive the expected heat input, it is necessary to limit the presence of divisions. This will allow for the heat to spread more evenly around the home. Regarding the bedrooms, they should be located on the eastern side of the home so as to avoid overheating during the summer months.

Solarium: an interesting source of heat

Since heat generation is essential, installing a solarium is a worthy option. Indeed, a solarium is a room that is excellent for capturing heat. The heat stored there can then be redistributed throughout the rest of the home by simply opening the door. However, be careful not to leave this door open at night, because the cool air from the night will also be redistributed in the house. Unless the day is hot, the cooling of the house may lead to discomfort.

Other aspects of a passive house to consider

Due to the fact that every aspect of a passive house is given special attention, the colour of the floors is no exception. Select flooring of a darker colour to improve the absorption of solar energy. Keep in mind the selection of materials that will have a great ability to retain heat during the winter. One example of this is concrete, as it will limit its absorption during the summer.

Bear in mind that planting hardwood trees on the south side of the home will allow for shading that is generated by the foliage. This will help to monitor and avoid too much heat finding its way into the home. During the winter, the sun passing through the bare branches will offer the same amount of warmth to heat your home. Conifers placed to the northeast or northwest will adequately protect the house from winter winds.

Although heat is the central concept in a passive house, it should be kept at bay. Thus, the installation of awnings works to avoid direct entry of sunlight into the rooms of the home. As pointed out by Adele Breton in her easy about passive houses and their characteristics “to limit cooling in the winter, a roof slope should follow the direction of the prevailing winds, which are generally northwestern winds in Quebec.”

The shape of a home is rarely a concern when buying or building a new home. Yet, in the case of a passive house, this decision is not to be taken lightly. Indeed, it will be important to choose a house whose shape is that of an east-west rectangle and whose structure will be as long as possible.