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Building Envelope

Low heating power requires low heat losses. Energy-efficient passive house suits for ventilation heating.
Building envelope’s thermal properties need to be accurate for heating system design

Design requirements
A passive House is defined with performance requirements for heating energy consumption, heating power demand, and total primary energy consumption. To accomplish the power demand requirement, energy designer needs to be sure of the building envelope characteristics. On the other hand, in the concept design phase, the energy designer may need to set requirements for building envelope characteristics, for to be able to limit the energy and power demand.

The heating power demand of a Passive House is only 10W/m2 or less. Therefore the peak demand calculation for each room needs to be accurate. Oversized heating system makes the control more difficult and thus they consume more energy. They are also an extra cost.

Design co-operation between architectural, energy, and structural design is required. Energy designer can guide architecture not to place windows into difficult structural locations where air circulation may be limited. As there are no heat sources underneath the windows, condensation may occur even with high-performance windows.

Envelope properties

  • Wall 0,1 – 0,15 W/m2K
  • Floor 0,09 – 0,15 W/m2K
  • Roof 0,08 – 0,15 W/m2K
  • Window < 0,8 - 1,0 W/m2K
  • Door < 0,4 – 0,8 W/m2K

Good air tightness of a Passive house refers to n50 < 0,6 air changes per hour at 50 Pa pressure difference. This also means that heat losses through infiltration are low. The Passive House certification scheme requires air tightness tests to be carried out for a finished building, increasing thus the reliability of building envelope characteristics.

It is essential to design simple and easy to use systems. Also easy use of control systems is important. It should be kept in mind that no special attitude is needed to live in a passive house. However, energy performance and systems of a Passive House should be made clear to the occupants