Buildings account for 35% of all worldwide energy usage, making them a substantial contributor to carbon emissions. Passivhaus is a tried-and-true solution that provides various proven techniques to offer net-zero-ready new and existing buildings that are enhanced for occupant health and wellbeing and optimised for a decarbonised grid, backed by more than 30 years of worldwide data. High levels of occupant comfort are provided by Passivhaus structures while requiring very minimal energy for heating and cooling.

The term “Passivhaus,” which translates to “passive home” in English, refers to structures built to exact energy-efficient design requirements to maintain a nearly constant temperature. The construction, insulation, and ventilation of Passivhaus buildings are so excellent that they retain heat from the sun and the actions of its residents, requiring minimal additional heating or cooling.

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Mayfield Passivhaus_©JamesGalpin

A voluntary energy efficiency requirement known as “passive house” (German: Passivhaus) lowers a building’s ecological impact. Facilities of ultra-low energy use less energy to heat or cool their interior spaces. Switzerland employs the MINERGIE-P standard, which is comparable. The measure has been used in constructing several office buildings, schools, kindergartens, supermarkets, and residential complexes. The design process integrates with architectural design rather than acting as an add-on or compliment. Although it is often used for new construction, it has also been used for renovations.

Passivhaus uses a whole-building strategy with precise quality assurance procedures, defined, measurable goals, and a focus on high-quality construction. For more information on why utilising an effective first strategy is crucial to achieving carbon reduction goals.

Origin and History

Bo Adamson of Lund University in Sweden and Wolfgang Feist of the Institut für Wohnen Und Umwelt in Darmstadt, Germany, had a discussion that led to the creation of the Passivhaus standard in May 1988. Later, with funding from the German state of Hessen, their idea was further refined through various research initiatives.

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Passive Solar Design Retrofits _©PrincetonsUniversity

Early “passive house” construction was heavily influenced by the work of North American builders in the 1970s, who tried to create homes with minimal to no energy use in reaction to the oil embargo. Large solar-gain windows utilised the sun as a heat source and were frequently featured in these designs. However, as seen by the Leger House in Pepperell, Massachusetts, and the Saskatchewan Conservation House (1977), super insulation ultimately won out (1977). The Saskatchewan Conservation house was a project of the Saskatchewan Research Council (SRC), which independently developed a heat recovery air exchanger (HRV), hot water recovery, and a blower-door apparatus to measure building air tightness. Of note, the house was created for the harsh -40C to +40C climate of the Canadian prairies.

Construction of Passivhaus

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Original Passivhaus, Darmstadt, in spring_©Passivhaus Institut

While some methods and tools, such as super insulation, were created especially for the “passive home” standard, the idea of passive solar building design has been around since antiquity. In addition to houses built following the strict energy rules of Sweden and Denmark, there were also older structures that met low-energy construction requirements, most notably the German Niedrigenergiehaus standard (low-energy home).

Passivhaus International Standard

According to the Passivhaus standard, the structure must meet the following criteria:

  • Use a peak heat load of 10 W/m2 (1.2 hp/1000 sq ft) of floor space, based on local climatic data, or a maximum of 15 kWh/m2 (4,755 BTU/sq foot; 5.017 MJ/sq ft) of floor area per year for heating and cooling.
  • Utilise primary energy at a maximum rate of 60 kWh/m2 (19,020 BTU/sq foot; 20.07 MJ/sq ft) annually (for heating, hot water and electricity).
  • Leak air up to 0.05 cubic feet per minute (1.4 l/min) per square foot of the enclosure’s surface area, or up to 0.6 times the house volume per hour (n50 0.6 / hour) at 50 Pa (0.0073 psi), as measured by a blower door.

A Passivhaus building employs a different technique than specific carbon-neutral structures, which use a mix of energy efficiency and sustainable energy generation to balance out any energy usage. By being well-sealed against the elements, a Passivhaus building strives to consume less energy overall. Passivhaus buildings will be built using a variety of techniques, but they will all share the following characteristics:

  • Much better insulation than ordinary UK homes.
  • Frames with triple glazing and insulation.
  • Impressive levels of airtightness (around 20x more than a standard build).
  • Mechanical ventilation with an integrated heat recovery system.

Design and Construction

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The Passivhaus uses a combination of low-energy building techniques and technologies_©MichkaB

A change in building design and construction methods is necessary to achieve the significant reduction in heating energy consumption needed by the standard. The “Passivhaus Planning Package” (PHPP), which uses specially crafted computer simulations, can help with the design.

The methods utilised to meet the standard are listed below-

  • Passive solar design and landscape

Energy-efficient landscaping and passive solar building design enhance passive home energy saving and may incorporate them into a community and environment. To enhance passive solar gain, passive solar building approaches recommend that buildings be compact in design to limit their surface area and have main windows pointed south in the northern hemisphere and north in the southern hemisphere. However, reducing the total energy needed for the house comes before using solar gain, particularly in areas with moderate climates. Brise soleil, trees, pergolas tied to buildings with climbing vines, vertical gardens, green roofs, and other techniques are used in environments and areas where it is necessary to prevent excessive summer passive solar heat gain, whether from direct or reflected sources.

The prevailing year-round ambient outside temperature determines the best exterior wall colour for reflection or absorption insolation qualities when the surface allows for a choice. Deciduous trees and trellised or self-attaching vines on walls can help in locations without dramatic temperature swings.

  • Superinsulation

Compared to traditional structures, Passivhaus buildings use superinsulation to considerably limit heat transmission through the walls, roof, and floor.  To achieve the needed high R-values (low U-values, generally in the 0.10 to 0.15 W/(m2K) range). Thermal bridges are removed with particular care.

The requirement for thicker wall insulation has the drawback that, unless the building’s external dimensions can be increased to make up for it, the interior floor space may be less than with traditional construction.

In Sweden, the insulation would need to be 33.5 centimetres (13.2 in) thick (0.10 W/(m2K)) and the roof 50 centimetres (20 in) wide (0.066 W/(m2K)) to meet passive house regulations.

  • Advanced window technology

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A Typical passive-house windows_©MichkaB

Windows are produced with incredibly high R-values (low U-values, often 0.85 to 0.45 W/(m2K) for the whole window, including the frame) to comply with the standards of the Passivhaus standard. The windows typically incorporate air-seals, specially designed thermal break window frames, and triple or quadruple-pane insulated glazing (with an appropriate solar heat-gain coefficient,[2][58] low-emissivity coatings, sealed argon or krypton gas-filled inter-pane voids, and “warm edge” insulating glass spacers).

Even in the middle of winter, the heat gains from the sun are typically more significant than the heat losses for unobstructed south-facing Passivhaus windows throughout Central Europe and the majority of the United States.

  • Airtightness

In contrast to traditional construction, the Passivhaus standard calls for very airtight building envelopes. Depending on the capacity of the building, they must either achieve 0.60 ACH50 (air changes per hour at 50 pascals) or 0.05 CFM50/SF (cubic feet per minute at 50 pascals per square foot of building enclosure surface area). To meet these criteria, the building air barrier enclosure should be tested with a blower door at some point during construction.

Uncontrolled air leaks should be avoided since “passive houses” are constructed with most air exchange. The external is done by controlled ventilation through a heat exchanger to reduce heat loss (or gain, depending on the region). Another factor is the substantial use of insulation in the passive home standard, which often necessitates careful management of moisture and dew points. Air barriers, thorough sealing of each construction connection in the building envelope, and sealing of all service penetrations are used to achieve this.

  • Ventilation

When the surrounding temperature is suitable, passive natural ventilation is a crucial part of passive house design. It can be achieved by single or cross ventilation, a simple aperture, or the stack effect of the smaller entrance with more enormous egress windows and clerestory-operable skylights.

When the surrounding climate is unfavourable, mechanical heat recovery ventilation systems are used to maintain air quality and recover enough heat from doing away with a traditional central heating system. Because passively designed buildings are airtight, the air change rate can be optimised and carefully controlled at about 0.4 air changes per hour. Every ventilation duct is insulated and leak-proofed.

Particular Passivhaus designers promote earth-warming tubes. The lines usually have a diameter of 200 millimetres (7.9 in), measure 40 metres (130 ft) in length, and are 1.5 metres deep (4.9 ft). They serve as earth-to-air heat exchangers and pre-warm (or pre-cool) the intake air for the ventilation system by being buried in the ground. The warmed air also stops ice from forming in the heat recovery system’s heat exchanger during cold weather. Condensation and mould issues have raised questions about this method in various areas. 

An alternative is to utilise a liquid circuit with a heat exchanger (battery) on the supply air for an earth-to-air heat exchanger instead of an air circuit.

  • Space Heating

Image 6_ the heat exchanger (centre), a micro-heat pump extracts heat from the exhaust air (left), and hot water heats the ventilation air (right)Passivhaus Institut

In addition to passive solar gain, Passivhaus structures make extensive use of their intrinsic heat from internal sources, such as waste heat from lighting, white goods (large appliances), and other electrical devices (but not dedicated heaters), as well as body heat from occupants and other animals. This is because, on average, each person emits heat equal to 100 watts of thermal energy.

This implies that a traditional central heating system is optional, even if they are occasionally installed owing to clients’ mistrust. This goes hand in hand with the extensive energy-saving measures used.

The supply air duct of the ventilation system may occasionally be combined with a dual-purpose 800 to 1,500-watt heating and cooling element used during the coldest days. The need that all essential heat be carried by the typical minimal air volume needed for ventilation is vital to the design. To prevent any potential scorching odour from dust that escapes the system’s filters, a maximum air temperature of 50 °C (122 °F) is enforced.

A tiny heat pump, annualised geothermal energy, direct sun thermal energy, or a simple natural gas or oil burner can all be used to heat the air-heating element. In certain instances, a micro-heat pump is employed to draw out more heat from the exhaust ventilation air and use it to warm the incoming air or the hot water storage tank. Small wood stoves can also heat the water tank, but caution must be taken to prevent overheating in the room where the stove is placed.

  • Lighting and electrical appliances

The various passive and active daylighting approaches should be used as the initial daytime solution to reduce primary energy use. It is possible to utilise innovative, sustainable lighting designs with low-energy sources on low-light days, in areas that are not naturally lit by the sun, and at night. ‘Low voltage’ electrical filament-Incandescent light bulbs, compact metal halide, xenon, and halogen lamps, solid-state lighting with LED lamps, organic light-emitting diodes, PLED – polymer light-emitting diodes, and compact fluorescent lamps are examples of low-energy sources.

For gardens and outdoor purposes, solar-powered exterior circulation, security, and landscape lighting with photovoltaic cells on each fixture or linking to a central solar panel system are offered. Low voltage systems allow for more independent or regulated lighting while consuming less power than standard fixtures and lights. For a Passivhaus environment, timers, motion detectors, and natural light operation sensors further decrease energy use and light pollution.

Appliance consumer items should be used in passive homes if they pass independent energy efficiency testing, have Ecolabel certification markings for decreased electrical-‘natural-gas’ usage, and have carbon emission labels on them during production. Examples include Energy Star and EKOenergy’s eco-label certification markings.

Advantages of Passivhaus construction

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The illustration on Renewable passive housing_©NearbyEngineers

Imagine residing in a structure with no chilly draughts and year-round, consistent temperatures throughout. Healthy interior conditions are produced through passive home building, resulting in low heating and cooling costs.

  • Recent advancements in green technology can be leveraged to significantly lower household energy expenses.
  • Modern insulation materials come in a large variety, and mechanical systems always get better.

Many older buildings have insufficient insulation and inefficient heating and cooling systems compared to modern HVAC technology. Energy savings of more than 75% are possible when these structures are updated using passive house principles.

In passive home designs, energy recovery ventilation is employed to maximise efficiency. Air supply and exhaust exchange heat and humidity, lowering cooling expenses in the summer and heating expenditures in the winter. An ERV system may maintain cosy indoor temperatures at a low energy cost when used in conjunction with intelligent ventilation controls:

  • When occupancy is low, the ventilation rate decreases to conserve fan power.
  • The exhaust removes the heat from the fresh air intake throughout the summer.
  • On the other side, the exhaust air warms air intake in the winter.

A passive home has better indoor air quality and more consistent temperatures. Energy efficiency results in long-term savings, and mechanical systems are more compact because of reduced design capacities.

Even though passive home building demands a high-performance level, the approach provides design flexibility to accommodate the owner’s preferences. For instance, if a homeowner desires a large window area, they may install triple-pane coated glass and offer more insulation to the nearby walls. However, it is advised to engage with a skilled contractor to prevent design choices that will harm energy performance.

Disadvantages of Passivhaus construction

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The illustration on High-costing passive housing_©NearbyEngineers

In general, the green building movement faces significant obstacles, and passive home construction is no exception. Many projects are created to lower building costs, even when doing so eventually results in substantially higher energy expenditures.

On average, the upfront expenditures of a passive home project are 10–30% greater than those of a conventional building. Also, building a passive house might be difficult in areas with frigid winters or scorching summers.

  • To keep below the threshold of 15 kWh/m2/year, builders might need to use a lot of insulation and backup heating and cooling systems.
  • The needed energy performance may restrict a window’s size, and any windows that are utilised must have triple glazing and low-E coating.

The choice to construct a passive house project can be seen from a financial perspective. Over 90% of energy can be saved, but it can be costly to fulfil the Passivhaus criteria in regions with extreme temperatures. Owners must assess the return on investment by comparing utility cost reductions to building expenses.

Working with a skilled contractor is crucial when building a passive house. Buildings frequently experience thermal bridging, which occurs when insulating layers are displaced and creates a significant heat loss area. This might significantly affect how energy-efficient Passivhaus projects are.

Passivhaus construction cost

The illustration of Green building_©NearbyEngineers

The money saved by doing away with the traditional heating system may be utilised to update the building envelope and the heat recovery ventilation system in Passivhaus structures. In Germany, it is currently possible to build buildings for the exact cost as those made to usual German building standards, as was done with the Passivhaus apartments at Vauban, Freiburg, thanks to careful design and growing competition in the supply of the specially designed Passivhaus building products. According to reports, passive homes often cost more upfront than conventional structures by 5% to 8% in Germany, 8% to 10% in the UK, and 5% to 10% in the USA.

Studies have shown that, although it is technically feasible when building in Northern Europe above 60° latitude, the expenses of complying with the Passivhaus standard rise dramatically. Cities in Europe that are roughly 60° include Bergen, Norway, and Helsinki, Finland. Moscow is at 55°, whereas London is at 51°.

References:

  • Wikipedia.com (2020) last edited 5 November 2022 [Online] Available at- 

https://en.wikipedia.org/wiki/Passive_house

  • Passivhaustrust.org.uk (2021) [Online]

Available at- 

https://www.Passivhaustrust.org.uk/what_is_Passivhaus.php 

  • Energysavingtrust.org.uk (2022) [Online]

Available at-

https://energysavingtrust.org.uk/Passivhaus-what-you-need-know/ 

  • Nearbyengineers.com (2016) [Online]

https://www.ny-engineers.com/blog/green-building-trends-pros-cons-of-passive-house-construction 

Author

Ayushi Samarth is a freshly graduate architect. Reading, understanding and writing upon the analysis made have always been the keen interests of Ayushi. She has always been curious in understanding the impact of social issues on architecture and design. Dealing with the theory of user and context interaction with architecture and narrating the story of architecture always has her attention.

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