Passive house: Environmentally conscious and comfortable

Buildings account for over 40% of energy consumption in the European Union, and also the United States, even more than either transport or industry.  If insulation in buildings is poor for example, then more energy is required to keep rooms warm, and increasing energy usage and costs for households and businesses, as well as carbon dioxide (CO₂) emissions. By making buildings as energy efficient as possible we reduce energy consumption drastically, along with CO₂ emissions, and this will help to make a big difference.

Thermogram showing a flat built to Passivhaus
standards losing very little heat, and the
traditional flat losing a lot more heat

Original image source: Passivhaus-Institut

There is a standard of buildings which is extremely efficient in terms of heat insulation, but at the same time keeps the house well ventilated, and requires very little energy for either heating or cooling.  This building is called the Passivhaus (Passive house in English) standard, which is a strict but voluntary standard, and applies for all possible types of building such as houses, flats, supermarkets, offices, and factories.  The organisation which devises and maintains the Passivhaus standard is the Passivhaus-Institut.

The Passivhaus standard is adjusted for the local area, so what would apply in temperate regions such as Central Europe and Western Europe, would need to be adjusted for colder climates such as Scandinavia, Eastern Europe, Russia, Canada, or the Northern United States, and for warmer climates such as the Mediterranean, India, Australia, South Africa, Brazil, or the Southern and Southwestern United States for example.  The Passivhaus-Institut has simulator software to determine the required parameters for the local environment to assist in designing the passive house.

For Europe within a 40° - 60° latitude, the Passivhaus criteria is satisfied if:

• Total energy demand for space heating is less than 15 kWh/m²/yr (54 MJ/m²/yr)
• The total primary energy use for all appliances, domestic hot water and space heating and cooling is less than 120 kWh/m²/yr (432 MJ/m²/yr).

Note that 1 kWh = 3.6 MJ.

As well as these requirements, a passive house has to have the following design characteristics and principles:

• Superinsulation to reduce heat lost through walls, roof, and floor, using a combination of materials to achieve low thermal transmittance ("U-value") of no more than 0.15 W/m²K.  At the same time thermal bridges (where poor insulators meet and conduct heat away from the building) are eliminated.
• Extremely energy efficient windows with high solar heat gain.  The glazing would be triple glazed and argon or krypton filled, and both glazing and frames must have a thermal transmittance (U-value) of no more than 0.8 W/m²K.
  
• Extremely airtight construction compared to normal construction, to minimise the air passing through the building structure.  Air exchange is handled by a ventilation system mentioned below.
  
• Usage of mechanical heat ventilation systems, with a heat recovery of over 80% and high efficiency electronically commutated motors.  Air freshness is also maintained at 0.4 times per hour.
  
• Well thought out usage of solar and internal heat gains through direction of windows for example. 
• Although solar panels are optional for passive houses, I would always recommend them.
• One still needs to choose low energy lightbulbs and high efficiency electrical appliances to help further reduce energy consumption.

Diagram showing the cross-section of a passive house.
This illustrates the overall design of the house.

Original image source: Passivhaus-Institut

With all these design characteristics in place, passive houses ensure excellent comfort throughout the year, with warm temperatures inside the house, very little if any temperature variation throughout the year, so no cold feet inside the house even in winter.  The air-tightness ensures that there are no draughts.  The ventilation is also excellent and the air is very fresh.  With air exchanged regularly, and with so much heat recovered by the ventilation system, this eliminates the need for both an active heating system and air conditioning.  Although the air in passive houses is relatively dry, I believe this is a good thing as it helps to prevent mould and mildew buildup in the house for example.  Occupants of the buildings are very likely to be healthier and happier as a result.

As shown here, there is the potential of big reductions in energy consumptions and CO₂. To take an example, it is estimated that UK dwellings constructed to the Passivhaus standard only requires 32% primary energy use compared to an existing dwelling, which is a staggering reduction in energy requirements. Passive houses also only require 41% primary energy usage and 23% energy usage for space heating compared to a standard new build. In addition to that the energy consumption to produce hot water is also reduced by 50%. 

Solar panels are optional in the Passivhaus standard, but I would recommend solar panels to be installed on all houses.  Furthermore, passive houses can also be Zero Energy Buildings at the same time.  In a Zero Energy Building, all heating and electricity needs are met on site, by sustainable and renewable energy such as solar and wind energy, and the key is to ensure that the net energy consumption for the building is zero. 

Passivhaus and ZEB can complement each other, and I believe that the house should be constructed to the Passivhaus standard in the first instance, and can incorporate ZEB features by producing energy on site.  Electrical and electronic appliances, can have their power requirements met with renewable energies, such as solar and wind energy, with (or without if not required) power from the electricity grid as backup.

Imagine a zero-energy passive house in the UK with wind vanes on every corner, solar panels or even solar tiles. If every building on the planet was constructed to the local passive house standard   and had its energy needs met by renewable energy available locally, our energy needs and CO₂ emissions can be significantly reduced and many, if not all, of these houses would be self-sufficient in energy.  They can still be connected to the electricity grid (National Grid in the UK) if desired, and export energy to the grid in the event of any surplus, that option is available.

One of the first passive houses, Darmstadt, Germany.

Original image source: Passivhaus-Institut

It only costs slightly more to build a new Passivhaus than it would for a standard new building, €14,000 (£12,000) is one estimate and 14% higher is another, although it could be very expensive to construct at a higher latitude than 60° (e.g. Siberia, Sweden, or Norway) due to the extra insulation required there.  I would not call this a cost though, I would call this an investment, and in addition more passive houses means more jobs are created. In addition, homes and other buildings can be retrofitted to meet the Passivhaus standard.  Passive houses have extremely low running costs even if they are not ZEB, but the investment in a passive house with ZEB features means zero long term running costs for the house.  More details on the short-term costs and long-term benefits can be found here.

Around 15,000-20,000 buildings worldwide are built to the Passivhaus standard, with the German-speaking countries and Scandinavia by far the biggest adopters to date.  In Switzerland there is a also similar standard called MINERGIE.  In January 2008, the European Parliament called on the European Commission to propose a binding requirement that all new buildings needing to be heated and/or cooled are constructed to Passivhaus or equivalent non-residential standards from 2011, and a requirement to use passive heating and cooling solutions from 2008.

Very few buildings are built to the Passivhaus standard in the UK, the first building was the Canolfan Hyddgen training and education centre (source: PassivHaus UK).  However, some houses are being built to the Passivhaus standard, for example a passive house in Denby Dale in West Yorkshire by the Green Building Company.  There is also a pilot scheme to convert old houses in North East London (Hackney), Stoke-on-Trent, and Powys to Passivhaus standards as well, and I believe this scheme will be successful because in Germany for example, old buildings already have been converted to Passivhaus standards.  For those of you who wish to build your own passive house, it is worth searching on the Internet to look for companies that build (or convert) passive houses as part of self-builds for your initial research.

Within the UK, England is only committing to new homes being ZEB for all new homes by 2016, and Wales aim to achieve this by 2012 (according to Wikipedia).  This is a start, but not enough unless the houses are passive houses as standard. In the UK which has very few passive houses, the government really needs to set a lead and require all buildings (new or otherwise) to meet the Passivhaus standard, and work in conjunction with, and support the building trade in achieving this. Passive houses have an important role to play in helping the UK in reducing its greenhouse gas emissions by 80% by 2050.

In every country, not just the UK, all buildings need to be passive houses at least. The benefits are well worth the investment, including lower or zero energy bills for the owners, a significant reduction in CO₂ emissions, drastic reduction in energy consumption reduces pressure on the electricity grid, and we can all still be really comfortable and cosy in such buildings. Making a passive house a ZEB at the same time can also make the house self-sufficient in energy.