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Passive house details should be designed without thermal bridges. Building form emphasizes detailed design
Ventilation unit with efficient heat recovery together with storage tank of a solar assisted heating system.
In mild or moderate climates a ventilation heating package can incorporate cooling as well through earth to air heat exchanger. In a passive house auxiliary cooling energy is not needed. (Figure: Fraunhofer Institute for Building Physics)

Building envelope
The energy conservation refers to thick insulation layers. A wall thickness including thermal insulation may range from 300 up to 600 mm depending on the load-bearing structure and climate.

Roof insulation thickness may be up to 600 mm. Floor insulation in ventilated floors can be up to 500 mm, and slab-on-ground floors to 250 – 300 mm. In cold climates the frost insulation to prevent frost heave of foundations needs to be designed accordingly, as the floor heat loss does not contribute for defrosting of the ground. In moderate climates the insulation thicknesses are lower.

In principle, a ventilation heating system is enough for a Passive House. The size of the unit should come from the required air flow rate for better efficiency and noise control.

Ventilation noise is sometimes a problem. The noise from ventilation comes either through ducts or through the device’s envelope. When the ventilation rate is high due to heat supply, the noise level rises accordingly. A separate technical room for the installations and extra noise dampers may be required.

Short air duct routes from the technical room are an optimum. This is not only a requirement for a Passive House but for a good quality building.

  • Small apartments with a floor area less than 50 m2: Ø = 125 mm
  • Detached houses or apartments with a floor area less than 125 m2: Ø = 160 mm
  • Detached houses apartments with a floor area more than 125 m2: Ø = 200 mm

Terminal units for air distribution to rooms may locate on inner walls.

Heating and cooling
Ventilation heating system can be an integrated system serving for ventilation, heating, hot water, and cooling. In addition, hot water can be supplied partly from solar collectors. In summer solar collectors can supply all the heat for hot water, but obviously in winter extra heat source is needed. Roughly 50% of the total hot water energy demand can be supplied by solar energy. Typically hot water collectors are placed on the roof, and the needed collector area is about 3 - 5 m2 and water tank volume 200 - 500 litres for a house. Additional heat can be supplied in a traditional way, e.g., from electrical, gas or pellet boiler, or ground heat.