Passive houses will be Industry Norm - 39
IF you are building or renovating a house you will inevitably hear the term ‘passive house’ or ‘passivhaus’, the word ‘passiv’ with a Teutonic clip of its ‘e’. For the uninitiated, this term, and the cheery declaration of ‘passivhaus standard’ slapped on a range of energy-efficient products, can be confusing. Passivhaus standards, or an approximation, will increasingly become the industry norm for house building, as all new homes are constructed to be carbon neutral, emitting no harmful gases as we heat our rooms and water.
Turn up the body heat
For a house to be deemed passive, it must draw a minimal amount of active external energy, if any at all (excluding solar), to run its space and water heating and keep it cool, where needed. Passive houses are sometimes termed ‘body heat houses’, as the warmth emanating from the people who live there, and the passive heating coming through the windows, is enough to keep them cosy.
In their most developed forms, these sustainable houses can become very active, selling energy back to the national energy grid. If you want to find out more about energy-positive housing, Google ‘Villa Åkarp’, the first of a new league of super homes constructed in Malmø Sweden.
Setting the standard
The energy standard for the true Passivhaus, is set by the PassivHaus Institute in Germany, and despite its rigorous demands, it remains a building concept not a brand. The concept was developed by Professors Bo Adamson of Sweden, and Wolfgang Feist of Germany and the first Passivhaus dwellings were constructed in Darmstadt in 1991. The criteria for a passive House per m² living area include a maximum of 15 kWh/m²yr annual space-heat requirement and no more than 42 kWh/ m²yr annual total amount of energy input.
A semi-detached, two storey Irish house built in the mid 1970s before the introduction of thermal insulation standards would have a space heating requirement of over 200kWh/m²yr and have a total primary energy demand of over 400 kWh/ m²yr. In short the energy efficiency of the Passivhaus is 90% better.
Highly insulated
A passive house is highly insulated throughout every centimetre of the envelope, including walls, roof, floor slab, windows and doors, and has no ‘cold-bridging’ where heat jumps across one material to another. It’s air-tight to prevent thermal loss and uncontrolled air ingress. The ventilations is carefully managed through a mechanical and heat ventilations system, abbreviated as a MHRV (75% of the heat from exhaust air is transferred to the fresh air by means of a heat exchanger). In warm weather the Passivhaus will use passive cooling techniques, including strategic shading. A successful build means a comfortable temperature year round, healthy humidity, fresh, clean air, no draughts whatsoever and laughable fuel bills.