Passive House: Reduce Energy Consumption in Your Building

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Passive house is a concept used in construction to build energy-efficient, comfortable, and ecological buildings that are also affordable. It is a building standard that consists of a set of design principles that are used to achieve a precise level of energy efficiency within a specific level of comfort.

Passive houses make effective use of the sun, internal heat sources, and heat recovery, due to which typical heating systems are not required even during the coldest times of the year. They also make use of some cooling techniques like strategic shading during summer to keep the temperature within comfortable limits.

The concept and physics behind building a passive house is the same all over the world, but the specific elements require adaptation in accordance with the climate of the region.

Principles of Passive House Design

The following five principles are fundamental to passive house design and construction:

1. Insulation

Insulation in a building helps minimize the loss of heat during cold months and keep the house cool in warmer months. Insulation is needed in the ceiling, walls, and floors. The materials used in insulation create a barrier between the interior and exterior spaces. Insulation is crucial in both warm as well as in cold climates.

It leads to a significant decrease in the consumption of energy required by traditional heating and cooling systems and creates a comfortable temperature inside the building throughout the year. There are many types of insulation materials that can be used in the construction of a passive house. These include cellulose, cotton, sheep’s wool, fiberglass, polyurethane, mineral wool, etc.

2. High-Quality Doors and Windows

Doors and windows play an important role in passive house designs. It is necessary to use doors and windows of superior quality that have a low thermal conductivity and provide optimum insulation. Because doors and windows provide light and visibility, they cannot be insulated in the same manner as a wall and hence become weak spots in terms of thermal resistance. Therefore, it is crucial to use high-quality doors and windows which meet passive house standards.

3. Airtightness

While constructing a passive house, the building is made airtight to control any unwanted movement of air, thus preventing any leakage of warm air or infiltration of cold air. To be certified as a passive house, a building must attain the standard of 0.6 ach-1 @50 Pa. This means that there should be less than 0.6 cubic meters of air change per hour for every square meter of floor area when the difference in air pressure between the inside and outside of the house is 50 Pascals.

4. Thermal Bridge Free Detailing

Another principle used in the construction of passive houses is the minimization of thermal bridging. These are the meeting points of different architectural details in a building. For example, how a window is attached to the wall or how a wall is linked to a balcony, or how walls meet at the corners.

The aim is to avoid these thermal bridges, which can cause the heat to escape as well as cause an increase in the condensation risk by creating localized cold spots. There are a few different ways to avoid thermal bridging, like making changes in the typical architectural design or decreasing the direct conductive relationships between the interior and exterior. These measures establish the effectiveness of the insulation used in a passive house.

5. Heat Recovery Ventilation

A passive house requires considerable ventilation since it is airtight and superinsulated and uses a heat recovery ventilation unit for the same. This system aims to reduce energy consumption, carbon dioxide emissions, and overall heating costs. The heat recovery ventilation carries fresh cold air into the house and uses a heat exchanger to take the heat from the warm air inside the room and transfer it to cold air.

This ensures the circulation of fresh air inside the room while maintaining an ideal temperature. It is important to note that the fresh and stale air do not mix together so that the air coming into the house remains warm and fresh. These systems have a success rate of about 90% and some can even run on as little as 15 watts per hour.

Passive House Requirements

To be certified as a passive house, a building needs to meet certain standards set by the Passive House Institute. These are:

1. Space heating demand should not exceed 15 kWh/(m²a) per annum or 10 W/m² for heating load. In climates where cooling is required, the space cooling energy demand should match the heat demand requirements mentioned above, with an additional consideration for dehumidification.

2. Thermal comfort must be met for all living areas during summer as well as in winter, with not more than 10% of the hours in a year over 25°C.

3. Total primary energy consumption for hot water, heating, and electricity must be ≤ 120 kWh/m²

4. Airtightness is set at 0.6 ach (+/- 50 Pascals) and air permeability is set at 0.6m3/hr.m2 (+/- 50 Pascals) for larger buildings.

Benefits of Passive House

Though the concept of the passive house has been around for decades, it is recently getting considerable recognition in architectural projects because of the benefits associated with it. Some of the benefits of building a passive house are:

1. Energy Efficiency

A passive house is designed primarily to save energy. It uses significantly lesser energy, even up to 90% less energy than the usual consumption of a traditional building, while performing the same or even better functions.

2. Eco-Friendliness

In a passive house, traditional heating and cooling systems are no longer needed, even in the most demanding climates. It makes use of natural energy from the sun and wind without causing any damage to the environment or depleting any valuable energy resource.

3. Good Indoor Air Quality

Passive houses have specialized ventilation systems that draw out air from kitchens, bathrooms, and other rooms that produce moisture or odors and channel fresh air into bedrooms and other living spaces. This also helps control dust and keeps the air inside the house fresh, clean, and of good quality.

4. Affordability

While the construction cost of a passive house is typically 10% more than a traditional house, the working and maintenance costs are significantly lower. Without the use of typical heating and cooling systems, and with energy-efficient and clean power sources, the electricity bills in a passive house are significantly low.

5. Comfort

The design of a passive house allows unmatched comfort inside the house. Airtightness provides good sound quality inside the house, and insulation eliminates any cold corners and excessive heat losses, keeping the temperature even throughout the entire house. Thus the atmosphere inside a passive house remains pleasant and quiet.

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