One of the cornerstones of energy efficient, healthy, sustainable building design, the PassivHaus standard aims to provide comfortable year round living conditions through minimal energy expenditure.

These aims are achieved through:

• An effective passive solar design that will provide the necessary heat gain (heating).
• To manage the heat gain:
• …very highly specified insulation,
• …near complete airtightness.
• Mechanical ventilation coupled with highly efficient heat recovery and ‘backup’ heating systems to manage the internal climate.

No additional heating systems are required.

The PassivHaus standard for buildings in Europe dictates that the building will consume no more energy than:

• Heating & Cooling: 15kWh per m2 floor area per annum.
• Total Primary Energy* Consumption: 120kWh per m2 floor area per annum for all appliances, domestic hot water and heating and cooling.

* Primary Energy is drawn from the national grid which is inherently inefficient, much energy being lost during distribution.

passivhaus.org.uk

Visit the BRE managed PassivHaus site for further details of the specification.

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A term often heard, but of rarely understood, just what does it mean?

Some definitions:

“within ten years every new home will be a zero-carbon home“

Gordon Brown, then Chancellor, in pre-budget report 2006.

When asked for further clarification, a zero-carbon home was defined as one that does not contribute to global warming - hardly a precise definition.

The zero carbon building produces no Carbon Dioxide and by combining all the available innovations can actually export carbon free energy back into the electricity grid.

http://www.applied-energy.com/ definition

Definitions can tend to ignore the CO2 emissions related to the sourcing of materials and the construction of the fabric of a building and in the initial provision of services and supporting infrastructure. A genuinely zero carbon building must be able to payback the carbon invested in its construction through generating and exporting zero carbon energy back into the national grid.

So where does that leave us. Personally, I am happy to use the catch-all zero carbon as an umbrella term incorporating both practical, real world low carbon design and an aspiration toward a truly zero carbon building lifecycle.

A zero carbon house is one that maintains ongoing CO2 emissions as near to zero as possible. The zero is currently aspirational.

Is the negative carbon house somewhere around the corner?

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One of those frequently occurring eco-building terms, thermal mass is often mentioned but rarely defined.

The thermal mass of a building is an assessment of the ability of its internal fabric to absorb and store thermal energy. Through absorption of heat, the temperature of a material increases - the amount of heat that must be absorbed to raise the temperature of a material by one degree varies by material. This ability to absorb heat is measured by the Specific Heat Capacity of the material (SHC). The SHC is a measure of the amount of heat energy required to raise 1KG of the material by 1 degree Celsius. Those materials that require most heat to increase in temperature have a high thermal capacity (also know as high volumetric heat capacity), such materials are typically dense in composition and ideal for storing thermal energy - these are materials such as brick, concrete and stone.

As a major element of our heating and cooling strategy, through passive solar design, we will seek to employ thermal mass in harnessing the energy of the sun during the day and releasing it during the night when it is needed.

In the Summer, the thermal mass will provide a buffer to over-heating, absorbing thermal energy and reducing the peak temperature whilst moving the time of the peak later into the evening.

In the Winter, high thermal mass buildings will take longer to initially heat up, but with regular occupation will retain the heat for longer and will reradiate heat comfortably overnight when it is required.

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Whilst a little late in the day for our barn (it was built 100+ years ago) the orientation of a building to the sun and the suns relationship with the buildings windows, doors and other openings are the focus of passive solar design.
Through effective passive solar design we seek to harness the power of [...]