diff --git a/IDEAS/BoundaryConditions/SimInfoManager.mo b/IDEAS/BoundaryConditions/SimInfoManager.mo
index d2ebd23916..e6a1c05b10 100644
--- a/IDEAS/BoundaryConditions/SimInfoManager.mo
+++ b/IDEAS/BoundaryConditions/SimInfoManager.mo
@@ -107,6 +107,43 @@ IDEAS uses TMY3 input files.
 The default weather file 'Brussels.mos' contains weather information from IWEC for the Brussels region.
 For detailed documentation see 
 <a href=\"modelica://IDEAS.BoundaryConditions.WeatherData.ReaderTMY3\">IDEAS.BoundaryConditions.WeatherData.ReaderTMY3</a>.
+<h4>Interzonal airflow</h4>
+<p>
+IDEAS supports several levels of detail for simulating interzonal airflow and air infiltration,
+which can be selected by setting the value of the parameter <code>interzonalAirFlowType</code>. 
+By default, <code>interzonalAirFlowType = None</code> and a fixed n50 value is assumed. 
+The corresponding <b>fixed</b> mass flow rate is pushed 
+into (with ambient properties) and extracted from each zone model.
+In practice, air infiltration however depends on the wind pressure 
+and occurs only for zones that have an exterior/outer wall
+or windows. 
+</p>
+<p>
+The other <code>interzonalAirFlowType</code> options model this effect in more detail.
+By default, the <code>OuterWall</code> and <code>Window</code> leakage coefficients are computed
+using the zone n50 values. The volume and n50 value of each zone are used to compute the total
+nominal air infiltration at 50 Pa pressure difference. The total exterior wall and window surface
+area are used to compute an average air leakage coefficient 
+(<code>q50</code> value) such that this total air infiltration
+is obtained at 50 Pa pressure difference. 
+Using these coefficients and the static wind pressures, 
+a flow network is configured that computes the mass flow rates through
+each wall and window.
+When a custom q50 value for a wall or window is known, it can be 
+assigned by the user using the parameters <code>use_custom_q50</code> and <code>custom_q50</code>.
+The algorithm considers these q50 values as known and recomputes all remaining q50 values
+such that the n50 value is reached.
+In a similar way, the total n50 value for one zone can be forced by using
+the zone parameters <code>use_custom_n50<code> and <code>n50</code>.
+In this case, only the remaining zones contribute to the total building
+air leakage, which is subsequently attributed to the surfaces of only those zones.
+</p>
+<p>
+In case <code>interzonalAirFlowType=OnePort</code> then one port is used to model the air exchange through each surface.
+When <code>interzonalAirFlowType=TwoPorts</code> two ports are used, 
+which adds a bit of detail at the cost of having to solve
+a more complex flow network.
+</p>
 </html>", revisions="<html>
 <ul>
 <li>
diff --git a/IDEAS/Buildings/Components/Interfaces/DummyConnection.mo b/IDEAS/Buildings/Components/Interfaces/DummyConnection.mo
index 19489756ff..99e1247bc5 100644
--- a/IDEAS/Buildings/Components/Interfaces/DummyConnection.mo
+++ b/IDEAS/Buildings/Components/Interfaces/DummyConnection.mo
@@ -126,8 +126,8 @@ equation
 
   connect(zero.y, zoneBus.v50) annotation (Line(points={{-59,-40},{100.1,-40},{100.1,
           -1.9}}, color={0,0,127}));
-  connect(custom_n50.y, zoneBus.custom_n50) annotation (Line(points={{-59,-90},{
-          100.1,-90},{100.1,-1.9}}, color={255,0,255}));
+  connect(custom_n50.y, zoneBus.use_custom_n50) annotation (Line(points={{-59,-90},
+          {100.1,-90},{100.1,-1.9}},color={255,0,255}));
   connect(q50_zone.y, zoneBus.q50_zone) annotation (Line(points={{-59,-70},{100.1,
           -70},{100.1,-1.9}}, color={0,0,127}));
   connect(custom_q50.y, zoneBus.use_custom_q50) annotation (Line(points={{-59,
diff --git a/IDEAS/Buildings/Components/Interfaces/PartialSurface.mo b/IDEAS/Buildings/Components/Interfaces/PartialSurface.mo
index b185ca46ce..b479e27ad7 100644
--- a/IDEAS/Buildings/Components/Interfaces/PartialSurface.mo
+++ b/IDEAS/Buildings/Components/Interfaces/PartialSurface.mo
@@ -47,7 +47,7 @@ partial model PartialSurface "Partial model for building envelope component"
   parameter Boolean use_custom_q50=false
     "set to true to disable the default q50 computation and to assign a custom q50 value"
     annotation (Dialog(tab="Airflow", group="Airtightness"), Evaluate=true);
-  parameter Real q50_val = 2
+  parameter Real custom_q50 = 2
     "Envelope air tightness"
     annotation (Dialog(enable=use_custom_q50,tab="Airflow", group="Airtightness"));
   final parameter Real q50_internal(fixed=false)
@@ -275,7 +275,7 @@ model Q50_parameterToConnector "Converts parameter values into connectors for pr
           fillPattern=FillPattern.Forward)}));
 end Q50_parameterToConnector;
 initial equation
-  q50_internal=if use_custom_q50 then q50_val else q50_zone.q50_zone;
+  q50_internal=if use_custom_q50 then custom_q50 else q50_zone.q50_zone;
 
 equation
   connect(prescribedHeatFlowE.port, propsBusInt.E);
@@ -338,7 +338,7 @@ equation
           -43},{79.4,-44},{56.09,-44},{56.09,19.91}}, color={0,0,127}));
   connect(q50_zone.using_custom_q50, propsBusInt.use_custom_q50) annotation (Line(points={{79,-52},
           {56.09,-52},{56.09,19.91}},      color={0,0,127}));
-  connect(setArea.custom_n50, propsBusInt.custom_n50) annotation (Line(points={{79.4,
+  connect(setArea.use_custom_n50, propsBusInt.use_custom_n50) annotation (Line(points={{79.4,
           -91},{79.4,-90.5},{56.09,-90.5},{56.09,19.91}},      color={255,0,255}));
   connect(setArea.v50, propsBus_a.v50) annotation (Line(points={{79.4,-83.2},{
           79.4,-82},{56,-82},{56,0},{100.1,0},{100.1,19.9}}, color={0,0,127}));
diff --git a/IDEAS/Buildings/Components/Interfaces/PartialZone.mo b/IDEAS/Buildings/Components/Interfaces/PartialZone.mo
index 44f69e479f..c0aa713c39 100644
--- a/IDEAS/Buildings/Components/Interfaces/PartialZone.mo
+++ b/IDEAS/Buildings/Components/Interfaces/PartialZone.mo
@@ -10,17 +10,17 @@ model PartialZone "Building zone model"
     replaceable package Medium =
     Modelica.Media.Interfaces.PartialMedium "Medium in the component"
       annotation (choicesAllMatching = true);
-  parameter Boolean custom_n50=sim.interZonalAirFlowType==IDEAS.BoundaryConditions.Types.InterZonalAirFlow.None and not sim.useN50BuildingComputation
+  parameter Boolean use_custom_n50=sim.interZonalAirFlowType==IDEAS.BoundaryConditions.Types.InterZonalAirFlow.None and not sim.useN50BuildingComputation
     "if true, a custom n50 value is used instead of a globally computed n50 value" annotation(Dialog(tab="Airflow", group="Airtightness"));
 
   parameter Real n50(unit="1/h",min=0.01)= sim.n50 "Optional n50 input"
    annotation(Dialog(tab="Airflow", group="Airtightness"));
-  final parameter Real n50_computed(unit="1/h",min=0.01) = if custom_n50 and not setq50.allSurfacesCustom then n50 else n50_int "Computed n50 value";
+  final parameter Real n50_computed(unit="1/h",min=0.01) = if use_custom_n50 and not setq50.allSurfacesCustom then n50 else n50_int "Computed n50 value";
 
 protected
   parameter Real n50_int(unit="1/h",min=0.01,fixed= false)
     "n50 value cfr airtightness, i.e. the ACH at a pressure diffence of 50 Pa"
-    annotation(Dialog(enable=custom_n50,tab="Airflow", group="Airtightness"));
+    annotation(Dialog(enable=use_custom_n50,tab="Airflow", group="Airtightness"));
 
 public
   parameter Boolean allowFlowReversal=true
@@ -228,7 +228,7 @@ protected
     n50=n50_int,
     V=V,
     q50_corr=sim.q50_def,
-    use_custom_n50=custom_n50)
+    use_custom_n50=use_custom_n50)
     annotation (Placement(transformation(extent={{-60,-100},{-40,-80}})));
 
 model Setq50 "q50 computation for zones"
@@ -260,7 +260,7 @@ model Setq50 "q50 computation for zones"
   Modelica.Blocks.Interfaces.RealInput Area[nSurf]
     "Surface areas"
    annotation (Placement(transformation(extent={{-126,-6},{-86,34}})));
-  Modelica.Blocks.Interfaces.BooleanOutput custom_n50s[nSurf]
+  Modelica.Blocks.Interfaces.BooleanOutput use_custom_n50s[nSurf]
     "Equals true if the surfaces connected to this zone should use the custom q50 value"
    annotation (Placement(transformation(extent={{-98,-38},{-118,-18}})));
   Modelica.Blocks.Interfaces.RealOutput q50_zone[nSurf]
@@ -276,7 +276,7 @@ initial equation
   allSurfacesCustom = max(Modelica.Constants.small, sum(defaultArea)) <= Modelica.Constants.small;
 
 equation
-  custom_n50s=fill(use_custom_n50,nSurf);
+  use_custom_n50s=fill(use_custom_n50,nSurf);
 
   if use_custom_n50 then
     q50_zone=fill((((n50*V) - sum(v50_custom))/max(Modelica.Constants.small, sum(defaultArea))), nSurf);
@@ -295,7 +295,7 @@ end Setq50;
 initial equation
 
 
-  n50_int = if custom_n50 and not setq50.allSurfacesCustom then n50 else sum(propsBusInt.v50)/V;
+  n50_int = if use_custom_n50 and not setq50.allSurfacesCustom then n50 else sum(propsBusInt.v50)/V;
 
   Q_design=QInf_design+QRH_design+QTra_design; //Total design load for zone (additional ventilation losses are calculated in the ventilation system)
 
@@ -496,8 +496,8 @@ end for;
   connect(setq50.use_custom_q50, propsBusInt.use_custom_q50) annotation (Line(points={{-60.6,
           -82},{-80,-82},{-80,39.9},{-80.1,39.9}},
                                               color={0,0,127}));
-  connect(setq50.custom_n50s, propsBusInt.custom_n50) annotation (Line(points={{-60.8,
-          -92.8},{-60,-92.8},{-60,-92},{-80.1,-92},{-80.1,39.9}},       color={
+  connect(setq50.use_custom_n50s, propsBusInt.use_custom_n50) annotation (Line(points={{-60.8,
+          -92.8},{-60,-92.8},{-60,-92},{-80,-92},{-80,40}},             color={
           255,0,255}));
   annotation (Placement(transformation(extent={{
             140,48},{100,88}})),
diff --git a/IDEAS/Buildings/Components/Interfaces/SetArea.mo b/IDEAS/Buildings/Components/Interfaces/SetArea.mo
index 28483851dd..a0a8f74b75 100644
--- a/IDEAS/Buildings/Components/Interfaces/SetArea.mo
+++ b/IDEAS/Buildings/Components/Interfaces/SetArea.mo
@@ -11,7 +11,7 @@ model SetArea "Block for communicating the surface area of the surface to the Si
   Modelica.Blocks.Interfaces.RealInput v50
     "v50 value"
      annotation (Placement(transformation(extent={{-126,48},{-86,88}})));
-  Modelica.Blocks.Interfaces.BooleanInput custom_n50
+  Modelica.Blocks.Interfaces.BooleanInput use_custom_n50
     "Is the zones n50 custom?"
      annotation (Placement(transformation(extent={{-126,-30},{-86,10}})));
 
@@ -21,7 +21,7 @@ protected
   parameter Modelica.SIunits.Area A_def_q50 = if use_custom_q50 then 0 else A;
 
 initial equation
-  if not use_custom_q50 and not custom_n50 then
+  if not use_custom_q50 and not use_custom_n50 then
     v50_custom=0;
   else
     v50_custom=v50;
@@ -30,7 +30,7 @@ initial equation
 
 equation
   areaPort.A = A;
-  areaPort.A_def = (if custom_n50 then 0 else A_def_q50); // if surface is not custom, then the area is communicated, else 0
+  areaPort.A_def = (if use_custom_n50 then 0 else A_def_q50); // if surface is not custom, then the area is communicated, else 0
   areaPort.v50 = v50_custom;
 
 end SetArea;
diff --git a/IDEAS/Buildings/Components/Interfaces/ZoneBus.mo b/IDEAS/Buildings/Components/Interfaces/ZoneBus.mo
index d35e84540b..e9c3b7b703 100644
--- a/IDEAS/Buildings/Components/Interfaces/ZoneBus.mo
+++ b/IDEAS/Buildings/Components/Interfaces/ZoneBus.mo
@@ -48,7 +48,7 @@ connector ZoneBus
   IDEAS.Buildings.Components.Interfaces.RealConnector v50(final unit="m3/h") "v50 if the surface has a custome q50 value" annotation ();
   IDEAS.Buildings.Components.Interfaces.RealConnector q50_zone(final unit="m3/(h.m2)") "v50 of the surface" annotation ();
   IDEAS.Buildings.Components.Interfaces.BooleanConnector use_custom_q50 "true if custome q50 value is assigned to surface" annotation ();
-  IDEAS.Buildings.Components.Interfaces.BooleanConnector custom_n50 "true if the zone n50 is a custom value";
+  IDEAS.Buildings.Components.Interfaces.BooleanConnector use_custom_n50 "true if the zone n50 is a custom value";
   annotation (Documentation(info="<html>
 <p>
 Connector that contains a weather bus and further
diff --git a/IDEAS/Buildings/Components/Interfaces/ZoneBusVarMultiplicator.mo b/IDEAS/Buildings/Components/Interfaces/ZoneBusVarMultiplicator.mo
index 79e7834970..08d172a174 100644
--- a/IDEAS/Buildings/Components/Interfaces/ZoneBusVarMultiplicator.mo
+++ b/IDEAS/Buildings/Components/Interfaces/ZoneBusVarMultiplicator.mo
@@ -28,7 +28,7 @@ model ZoneBusVarMultiplicator "Component to scale all flows from the zone propsB
   outer BoundaryConditions.SimInfoManager       sim
     "Simulation information manager for climate data"
     annotation (Placement(transformation(extent={{72,122},{92,142}})));
-  Modelica.Blocks.Routing.BooleanPassThrough custom_n50
+  Modelica.Blocks.Routing.BooleanPassThrough use_custom_n50
     annotation (Placement(transformation(extent={{8,-324},{-12,-304}})));
 protected
   IDEAS.Fluid.BaseClasses.MassFlowRateMultiplier massFlowRateMultiplier2(
@@ -157,9 +157,9 @@ equation
   connect(use_custom_q50.y, propsBus_b.use_custom_q50) annotation (Line(points={{9,-286},
           {100,-286},{100,-0.1},{100.1,-0.1}},
                                           color={0,0,127}));
-  connect(custom_n50.u, propsBus_b.custom_n50) annotation (Line(points={{10,-314},
+  connect(use_custom_n50.u, propsBus_b.use_custom_n50) annotation (Line(points={{10,-314},
           {100.1,-314},{100.1,-0.1}},color={255,0,255}));
-  connect(custom_n50.y, propsBus_a.custom_n50) annotation (Line(points={{-13,
+  connect(use_custom_n50.y, propsBus_a.use_custom_n50) annotation (Line(points={{-13,
           -314},{-100,-314},{-100,0.1},{-100.1,0.1}},
                                                 color={255,0,255}));
   annotation (Icon(coordinateSystem(preserveAspectRatio=false, extent={{-100,-180},
diff --git a/IDEAS/Buildings/Components/InternalWall.mo b/IDEAS/Buildings/Components/InternalWall.mo
index 624059d801..0aefc3c20a 100644
--- a/IDEAS/Buildings/Components/InternalWall.mo
+++ b/IDEAS/Buildings/Components/InternalWall.mo
@@ -2,7 +2,7 @@ within IDEAS.Buildings.Components;
 model InternalWall "interior opaque wall between two zones"
   extends IDEAS.Buildings.Components.Interfaces.PartialOpaqueSurface(
     final use_custom_q50=true,
-    final q50_val=2,
+    final custom_q50=2,
     final nWin=1,
     dT_nominal_a=1,
     E(y=if sim.computeConservationOfEnergy then layMul.E else 0),
diff --git a/IDEAS/Buildings/Components/SlabOnGround.mo b/IDEAS/Buildings/Components/SlabOnGround.mo
index 5037094918..44a7e26760 100644
--- a/IDEAS/Buildings/Components/SlabOnGround.mo
+++ b/IDEAS/Buildings/Components/SlabOnGround.mo
@@ -1,7 +1,7 @@
 within IDEAS.Buildings.Components;
 model SlabOnGround "opaque floor on ground slab"
   extends IDEAS.Buildings.Components.Interfaces.PartialOpaqueSurface(
-    final q50_val=0,
+    final custom_q50=0,
     final use_custom_q50=true,
     final nWin=1,
     QTra_design=UEqui*A*(273.15 + 21 - sim.Tdes),
