P&K KFA (VDI 3781 part 4)



The form is used to define global settings for the project.

Project Title

The project title will be included in the output of graphics and reports.

Buildingblocks (Expert Mode)

The directive stipulates in chapter the consideration of closed building groups when determining the recirculation zone of upstream buildings. P&K KFA integrates a general block analysis of the surrounding development.

The program automatically adds to the list of recirculation zones of the upstream buildings the recirculation zones of the virtual block buildings. These blocks will be generated from those buildings in the relevant neighborhood of the exhaust house, which meet the following criteria:

  1. The buildings must exceed a height: Default higher than half the height of the exhaust house.
  2. The distance between buildings must be below a minimum distance: Default less than 4m.

A block is a flat roof building that encloses all the buildings integrated into it. In addition to the recirculation zones of all individual buildings, blocks are also taken into account in the determination of the height of the exhaust gas discharge system.

The two criteria for blocking can be adjusted as follows:

  1. For the minimum height:
    1. Height is not relevant. All surrounding buildings are included
    2. same height as the exhaust house
    3. half height of the exhaust house
    4. third height of the exhaust house
    5. quarter height of the exhaust house
  2. For the maximum building distance: 1m to 15m

Recirculation zone according guideline

When calculating the recirculation zone, the guideline distinguishes between the course over the emitting building and the course outside the building. Above the building, the recirculation rises to the maximum height (H2) and outside the building the recirculation zone at the building edge always starts with the height H2. This leads to a discontinuity at the building edge, especially in the case of propagation in the direction of the ridge. Placement of the discharge device on the ridge thereby results in significantly lower height than placement slightly outside the ridge.

P&K KFA offers the possibility to calculate width:

The default is the policy compliant option. Program parameters can be used to switch to the alternative calculation mode.

Note: The expert mode can be activated under Preferences.