Mann Construction

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Passive Housing » Introduction to Passive housing

Mann Construction
The 'Passive House' standard originated in Germany, and has become increasingly popular in Ireland and indeed all over the world. The main focus of the standard is to reduce the heat demand to such a level that conventional heating with radiators or underfloor heating is not required. In a Passive House, all the heat required can be supplied through a mechanical ventilation system. The other main feature of 'Passive House' dwellings is the use of solar energy. Large areas of highly efficient windows are installed on the south facing side of the dwelling in order to capture the free heating energy from the sun. In a Passive House, the heating demand is so small that the free 'passive' solar gains make up a huge proportion of the overall energy demand! Solar collectors are also used to provide �active� solar hot water and heat for the dwelling's remaining heat and hot water needs.

The overall aim is to build an energy efficient house, with low associated energy costs and low carbon emissions.
Whether you are aiming for an A-rated, a passive, or a low-carbon house, the following features should be a priority.
In no particular order :

  • High Levels of insulation - In the walls, floors and roof - U value 0.15
  • High performing windows and doors - U-value 0.74 - Minimise glazing on northern side of dwelling, maximise southerly glazing to capture free solar gains available. Doors and windows should be well sealed and have a low U-value (note : low U-value = high insulating ability)
  • Avoid thermal bridges - When insulation is interrupted by a material with a lower insulating ability , e.g. where an internal wall intersects with an external wall, and the insulation is discontinued as a result, an easy path for loss of heat to the outside can occur, this is known as a thermal bridge, and should be avoided.
  • High levels of airtightness - A major portion of a dwellings heat is lost through air infiltration. As well as sealing the building during construction, it is important to also remember vents, electrical outlets, pipework to exterior walls etc. as air can leak through these areas. Airtightness is achieved by careful application of approved membranes such as Siga. Minimum Airtightness of 0.6 changes per hour measured at a pressure of 50 Pascal: n50 0.6 1/h
  • Ventilation with heat recovery - A well insulated, airtight house has a low heat demand, but occupants still need good indoor air quality. Mechanical ventilation is therefore necessary in such a house. A 'heat-recovery' exchanger can also be added to the system to capture the waste heat from kitchens, bathrooms etc. that would otherwise be lost to outside.
  • Efficient DHW system with solar thermal - In a low-energy dwelling, because the heat demand is so low, energy required to produce hot water makes up a large proportion of the overall energy requirement. It is important, therefore, to install an efficient hot water system , and if suitable, use solar thermal collectors to provide a renewable contribution to hot water production. In a fully Passive House, where the heat demand is negligible, a solar collector installation can contribute significantly to the heating of the dwelling, which, as mentioned earlier, is provided entirely through the mechanical ventilation system.
  • Low energy lighting - Electricity from the grid is produced from a variety of sources, including fossil fuels. When we use one unit of electricity, approximately two and a half times that amount of energy is needed in order to produce this unit, and this unit is also responsible for over half a kilogram of CO2 emissions! The overall energy required is known as 'primary energy'. Using low energy lighting will reduce the primary energy use and reduce the resulting CO2 emissions....