diff --git a/cara/apps/calculator/model_generator.py b/cara/apps/calculator/model_generator.py
index 100b02da..ef4e74fa 100644
--- a/cara/apps/calculator/model_generator.py
+++ b/cara/apps/calculator/model_generator.py
@@ -1,4 +1,3 @@
-from cara.models import Model
 from dataclasses import dataclass
 import html
 import typing
@@ -46,7 +45,7 @@ class FormData:
     @classmethod
     def from_dict(cls, form_data: typing.Dict) -> "FormData":
 
-        valid_na_values = ['windows_open', 'ventilation_type', 'mechanical_ventilation_type']
+        valid_na_values = ['windows_open', 'mechanical_ventilation_type']
         for name in valid_na_values:
             if not form_data.get(name, ''):
                 form_data[name] = 'not-applicable'
@@ -113,10 +112,11 @@ class FormData:
             infected_finish=time_string_to_minutes(form_data['infected_finish']),
         )
 
-    def build_model(self) -> Model:
+    def build_model(self) -> models.Model:
         return model_from_form(self)
 
     def ventilation(self) -> models.Ventilation:
+        always_on = models.PeriodicInterval(period=120, duration=120)
         # Initializes a ventilation instance as a window if 'natural' is selected, or as a HEPA-filter otherwise
         if self.ventilation_type == 'natural':
             if self.windows_open == 'interval':
@@ -141,17 +141,17 @@ class FormData:
                                                inside_temp=inside_temp, outside_temp=outside_temp, cd_b=0.6,
                                                window_height=self.window_height,
                                                opening_length=self.opening_distance * self.windows_number)
+        elif self.ventilation_type == "no-ventilation":
+            ventilation = models.AirChange(active=always_on, air_exch=0.)
         else:
             if self.mechanical_ventilation_type == 'air_changes':
-                ventilation = models.AirChange(active=models.PeriodicInterval(period=120, duration=120),
-                                               air_exch=self.air_changes)
+                ventilation = models.AirChange(active=always_on, air_exch=self.air_changes)
             else:
-                ventilation = models.HVACMechanical(active=models.PeriodicInterval(period=120, duration=120),
-                                                    q_air_mech=self.air_supply)
+                ventilation = models.HVACMechanical(
+                    active=always_on, q_air_mech=self.air_supply)
 
         if self.hepa_option:
-            hepa = models.HEPAFilter(active=models.PeriodicInterval(period=120, duration=120),
-                                     q_air_mech=250.)
+            hepa = models.HEPAFilter(active=always_on, q_air_mech=250.)
             return models.MultipleVentilation((ventilation,hepa))
         else:
             return ventilation
@@ -269,7 +269,6 @@ def model_from_form(form: FormData) -> models.Model:
 def baseline_raw_form_data():
     # Note: This isn't a special "baseline". It can be updated as required.
     return {
-        'RADIO_ventilation_type': 'natural',
         'activity_finish': '18:00',
         'activity_start': '09:00',
         'activity_type': 'office',
@@ -296,7 +295,7 @@ def baseline_raw_form_data():
         'simulation_name': 'Test',
         'single_event_date': '',
         'total_people': '10',
-        'ventilation_type': '',
+        'ventilation_type': 'natural',
         'volume_type': 'room_volume',
         'window_height': '2',
         'window_width': '2',
@@ -309,7 +308,7 @@ ACTIVITY_TYPES = {'office', 'training', 'workshop'}
 EVENT_TYPES = {'single_event', 'recurrent_event'}
 MECHANICAL_VENTILATION_TYPES = {'air_changes', 'air_supply', 'not-applicable'}
 MASK_WEARING = {'continuous', 'removed'}
-VENTILATION_TYPES = {'natural', 'mechanical', 'not-applicable'}
+VENTILATION_TYPES = {'natural', 'mechanical', 'no-ventilation'}
 VOLUME_TYPES = {'room_volume', 'room_dimensions'}
 WINDOWS_OPEN = {'always', 'interval', 'breaks', 'not-applicable'}
 
diff --git a/cara/apps/calculator/static/form.html b/cara/apps/calculator/static/form.html
index 568466ff..98a3b23f 100644
--- a/cara/apps/calculator/static/form.html
+++ b/cara/apps/calculator/static/form.html
@@ -36,9 +36,9 @@ Beta v1.0.0 <span style="float:right; font-weight:bold">Please send feedback to
 
     <!-- Ventilation Options -->
     Ventilation type:
-    <input type="hidden" id="ventilation_type" name="ventilation_type" value=""/>
-    <input type="radio" id="mechanical" name="RADIO_ventilation_type" value="mechanical" data-enables="DIVmechanical_ventilation">Mechanical</input>
-    <input type="radio" id="natural" name="RADIO_ventilation_type" value="natural" data-enables="DIVnatural_ventilation">Natural</input><br>
+    <input type="radio" id="no-ventilation" name="ventilation_type" value="no-ventilation" checked>No ventilation</input>
+    <input type="radio" id="mechanical" name="ventilation_type" value="mechanical" data-enables="DIVmechanical_ventilation">Mechanical</input>
+    <input type="radio" id="natural" name="ventilation_type" value="natural" data-enables="DIVnatural_ventilation">Natural</input><br>
 
     <div id="DIVmechanical_ventilation" style="display:none">
         <input type="radio" id="air_type_supply" name="mechanical_ventilation_type" value="air_supply" onclick="require_fields(this)">
diff --git a/cara/apps/calculator/static/js/form.js b/cara/apps/calculator/static/js/form.js
index 22436fe9..6dbc57c2 100644
--- a/cara/apps/calculator/static/js/form.js
+++ b/cara/apps/calculator/static/js/form.js
@@ -1,29 +1,16 @@
-/* -------Show/Hide DIVs------- */
-function show(show, var_id, obj) {
-  var show = document.getElementById(show);
-  if (show.style.display === "none") {
-    show.style.display = "block";
-    document.getElementById(var_id).value = 1;
-  } else {
-    show.style.display = "none";
-    document.getElementById(var_id).value = 0; 
-  }
-  require_fields(obj);
-}
-
-
 function on_ventilation_type_change(){
-    ventilation_types = $('input[type=radio][name=RADIO_ventilation_type]');
+    ventilation_types = $('input[type=radio][name=ventilation_type]');
     ventilation_types.each(function( index ) {
       if (this.checked) {
         getChildElement($(this)).show();
         require_fields(this);
-        $('input[name=ventilation_type]').val(this.id);
       } else {
         getChildElement($(this)).hide();
         unrequire_fields(this);
         // Clear the inputs for this newly hidden child element.
-        getChildElement($(this)).find('input').val('');
+        getChildElement($(this)).find('input').not('input[type=radio]').val('');
+        getChildElement($(this)).find('input[type=radio]').prop("checked", false);
+        getChildElement($(this)).find('input').prop("required", false);
       }
     });
 }
@@ -34,11 +21,6 @@ function getChildElement(elem) {
   return $("#" + elem.data("enables"));
 }
 
-function update_windows_open(obj) {
-  var windows_open = document.getElementById("windows_open");
-  windows_open.value = obj.id;
-}
-
 
 /* -------Required fields------- */
 function require_fields(obj){
@@ -124,17 +106,11 @@ function require_natural_ventilation(option) {
 
 function require_air_changes(option) {
   $("#air_changes").prop('required',option);
-  if (option) {
-    var mechanical_ventilation_type = document.getElementById("mechanical_ventilation_type");
-    mechanical_ventilation_type.value = "air_changes";
-} }
+}
 
 function require_air_supply(option) {
   $("#air_supply").prop('required',option);
-  if (option) {
-    var mechanical_ventilation_type = document.getElementById("mechanical_ventilation_type");
-    mechanical_ventilation_type.value = "air_supply";
-} }
+}
 
 function require_single_event(option) {
   $("#single_event_date").prop('required',option);
@@ -238,11 +214,15 @@ $( document ).ready(function() {
 
   // When the ventilation_type changes we want to make its respective
   // children show/hide.
-  ventilation_types = $('input[type=radio][name=RADIO_ventilation_type]');
+  ventilation_types = $("input[type=radio][name=ventilation_type]");
   ventilation_types.change(on_ventilation_type_change);
   // Call the function now to handle forward/back button presses in the browser.
   on_ventilation_type_change();
 
+  $("input[name=mechanical_ventilation_type]").change(function(){
+    console.log('Changed!');
+  })
+
   // Setup the maximum number of people at page load (to handle back/forward),
   // and update it when total people is changed.
   setMaxInfectedPeople();