External Wall Insulation and the PassivHaus standard
The Passive House (Passiv Haus) standard is an ultra-low energy building design system. It uses extremely efficient building envelopes to significantly reduce energy consumption. This means great insulation and airtightness. The standard is completely voluntary but does have an extremely rigorous set of requirements that must be met in order to be classified as a "Passive House" by the Passiv Haus Institute. In future it is probable that Irish Building regulations will be updated to incorporate the concepts of Passiv Haus.
With Passive Houses there is no need for a “special heating system”. The heat from the lights, fridge etc coupled with the people living there is enough to keep the house warm. (People, on average, emit heat energy equivalent to 100 Watt per person.)
Typically we don’t consider people to be heat sources because in general there is such a huge heat loss from Irish homes that body heat becomes insignificant. With Passive Houses however, the temperature changes only very slowly. With ventilation and heating systems switched off, a passive house typically loses less than 0.5 °C (1 °F) per day in winter.
For householders who want to retrofit their home with External Insulation to a very high standard, we can exceed the SEAI (Sustainable Energy Authority of Ireland) standard of a U value of < 0.27. If required, we can use a thicker insulant layer and meet the Passive House standard of a U value < 0.15. This would future-proof your home and ensure that you will exceed the national specification for many years. For illustration a house built to Passive House standards will use 85% less energy than a house built to the 2002 standards and will reduce CO2 emissions by 94%. Source
To be considered a Passive House, it is not enough simply to insulate the walls. The entire building must meet the following criteria:
- The building must not use more than 15 kWh/m² per year (4746 btu/ft²) in heating energy.
- With the building de-pressurized to 50 Pa (N/m²) below atmospheric pressure by a blower door, the building must not leak more air than 0.6 times the house volume per hour.
- Total primary energy consumption must not be more than 120 kWh/m² per year.
- The specific heat load for the heating source at design temperature is recommended, but not required, to be less than 10 W/m².
See the PassivHaus primer for more information
This is all well and good for new houses but in Ireland there is however the issue of what to do with our existing homes. It is estimated that 930,000 houses were built before the first ever building regulations in 1991, with approximately 1,000,0000 built before the 1996 building regulations. To put that in context (shockingly): 350,000 houses have no wall insulation and 200,000 houses have no roof insulation. Source
To upgrade the existing poor quality housing stock in Ireland will be a mammoth task, taking many years. But one key aspect is Wall Insulation. According to the Passiv Haus Institute you can use 16 metres of concrete or just 300 mm of external insulation to bring your home to Passive House standards. Source
The External Wall Insulation such as the Aval and PowerWall Systems we provide are used widely on Continental Europe as a technique to upgrade existing buildings to the Passive House Standard. Source http://www.sei.ie/retrophguidelines Page 25. This system has proved extremely popular and highly successful in reducing the energy consumption of homes.