Archive for October, 2009

Quite frankly, it is not to much effort. Building technology has developed to a great extent since the passivhaus standard came into existence, and it is quite a bit easier to build a passive house now than it was 10 years ago. Most of the building material that you require are easily available. Passive houses are as comfortable to live in as any other homes and in fact are healthier and safer because of the building design.

Passive houses are more expensive to build than conventional homes because of the materials required between five and ten percent depending on size. However, over the long run, they have proven to be much cheaper. When you look at how much a conventional home costs in terms of heating, cooling, ventilating, electricity, and air conditioning – a passive house turns out to be a cheaper bargain.

Passive homes are not that uncommon either. Although it is difficult to find a completely passive house in the US – they’re common in the UK and across Europe. Closer to home, we have green homes that make use of some of the principles of passivhaus and add their own two bits to create an energy efficient green home. In Washington DC, we have architect and green builder Travis Price’s four story green home, just about 10 minutes from the White House. His house was featured on the Discovery channel’s World’s Greenest Homes – which, by the way, is a great show to see how much and how easily people can build green homes for themselves.

4. Ventilation: Ventilation is properly controlled in a passive house, by means of a mechanical heat recovery ventilator. Although HRV are used in most houses, passive homes use an extremely efficient one, since no other heating or cooling device is used in the house. Most passive houses use both – air to air and earth to air heat recovery systems – depending in the size of the house and climate.

5. Air-tightness: Air-tightness is an extension of the ventilation requirements. Passive houses don’t make use of any HVAC systems – only a HRV system. Thus, it becomes very important that air doesn’t pass through the house in any other way, otherwise, the HRV systems will not be able to perform optimally. Passive houses are therefore super air-tight, much more than conventional houses. The building envelope is sealed thoroughly, and so are any service components that go through it.

6. Space Heating: This is a pretty novel concept in the passivhaus technique. When all the previous measures are not enough to heat a particular house, passive houses use heat generated within the house due to electrical appliances, lights, human beings and animals to heat it. Other than this, some houses install a small or heating device (running on renewable energy) that is integrated with the ventilation system. Some houses also use a micro heat pump that can recover heat from the air escaping through the ventilation system. Together, all these ideas make a conventional heating system quite unnecessary.

7. Electrical Appliances: Passive house use low wattage electrical appliances, CFLs and intelligent installation to minimize the use of electricity.

By using certain principles for building aspects. The passivhaus technique achieves its standards by improving on many aspects of designing and building, particularly:

1. Passive Solar Design: This entails using naturally available sunlight, the suns’ daily and annual cycles to maintain a comfortably warm home without using other heating and ventilation system. This is done by building compact structures, window orientation, using lightweight materials and other techniques.

2. Superinsulation: The walls, floor and roof of a passive house are highly thermal insulated to prevent heat from escaping. Most houses have some form of insulation, however, they will depend on traditional temperature control devices to maintain constant temperatures throughout the house. Passive houses are superinsulated, such that the walls themselves are made up of insulating materials. Because of this, there are no thermal bridges, and there needs to be no external insulation of any kind.

3. Advanced Window Technology: Windows play an important role in designing passive houses. Window placement, size, alignment, material and design help to increase natural lighting in the house without adding to the heat or using electricity. Windows for passivhaus are differently manufactured and are made with extremely thermal resistant. The glass also is generally filled with argon or krypton gas which reduces heat transfer either ways and absorbs UV rays.

In order to be called as a ‘passive house’ a house must be built with certain standards in mind. These standards were created in Europe and hence apply to homes built in the European countries, but are used more or less in the same manner throughout the world:

1. The house should not consume more than 15kWh/m2 in a year for heating and cooling requirements.
2. Its total energy consumption in a year must not be more than 42kWh/m2

In the US, these standards change a little in the following manner:

A house to be called a passive house must be designed in such a way that it consumes 1 btu per square foot per heating degree day for space heating purposes, compared to traditional homes which use anywhere between 5 to 15 btu. Your contractor should be able to explain better what standards he expects to achieve.

Along with these there are also standards for insulation and air-tightness. The structure should not leak air any more than 0.6 times the volume of the house.

Standards of this type make most people think that achieving them will be rather expensive. However, in the long run, the energy consumption of a passive house is less than 25% than that of a normal house. Plus, the overall cost of building, installing and operating a regular house and a passive house are almost the same.

Passivhaus – The Origin

It might surprise you to know that Passivhaus is not a latest trend in green building. IT’s been around for quite some time, since 1988, to be precise. However, green building, sustainability and the environmental awareness is a relatively new concept, which is why many are hearing about Passive Houses only lately.

The technique and principles actually emerged in Sweden in 1988 and the first ‘passive house’ was built in Germany 2 years later and 6 years after that, the Passivahus-Institut was founded in Germany. After that, over 15,000 houses have been built, largely in Europe and particularly in Scandinavia using the passivhaus technique. Closer home, the first passive house was constructed in Illinois in 2003. In the US, passivhaus is looked at as a relatively new concept, but one that architects and builders will be quick to embrace, given its potential and possibilities.

The first principles of passivhaus required homes to have a space heating requirement which was 90% less than other houses. To this, other engineers, builders, and architects added their own innovations which made achieving this standard easier and economical. Eventually, building products like construction materials, window and door frames, glass came to be designed specifically for passive houses. Of special mention is a software program called the Passivhaus Planning Package developed and sold by the Passivhaus-Institut that helps architects design and create passive houses. The European Union in 2008 called for a binding requirement that from 2011, all houses built requiring heating and cooling should be built by the passivhaus standard.