diff --git a/cara/apps/calculator/model_generator.py b/cara/apps/calculator/model_generator.py
index e50cc67f..64b28fa0 100644
--- a/cara/apps/calculator/model_generator.py
+++ b/cara/apps/calculator/model_generator.py
@@ -44,13 +44,15 @@ class FormData:
     ventilation_type: str
     volume_type: str
     window_height: float
+    window_type: str
+    window_width: float
     windows_number: int
     windows_open: str
 
     @classmethod
     def from_dict(cls, form_data: typing.Dict) -> "FormData":
 
-        valid_na_values = ['windows_open', 'mechanical_ventilation_type']
+        valid_na_values = ['windows_open', 'window_type', 'mechanical_ventilation_type']
         for name in valid_na_values:
             if not form_data.get(name, ''):
                 form_data[name] = 'not-applicable'
@@ -66,7 +68,8 @@ class FormData:
                              ('mask_wearing', MASK_WEARING),
                              ('ventilation_type', VENTILATION_TYPES),
                              ('volume_type', VOLUME_TYPES),
-                             ('windows_open', WINDOWS_OPEN)]
+                             ('windows_open', WINDOWS_OPEN),
+                             ('window_type', WINDOWS_TYPES)]
         for key, valid_set in validation_tuples:
             if key not in form_data:
                 raise ValueError(f"Missing key {key}")
@@ -114,6 +117,8 @@ class FormData:
             ventilation_type=form_data['ventilation_type'],
             volume_type=form_data['volume_type'],
             window_height=float(form_data['window_height']),
+            window_type=form_data['window_type'],
+            window_width=float(form_data['window_width']),
             windows_number=int(form_data['windows_number']),
             windows_open=form_data['windows_open'],
             infected_start=time_string_to_minutes(form_data['infected_start']),
@@ -414,6 +419,8 @@ def baseline_raw_form_data():
         'ventilation_type': 'natural',
         'volume_type': 'room_volume',
         'window_height': '2',
+        'window_type': 'hinged',
+        'window_width': '2',
         'windows_number': '1',
         'windows_open': 'interval'
     }
@@ -427,6 +434,7 @@ MASK_WEARING = {'continuous', 'removed'}
 VENTILATION_TYPES = {'natural', 'mechanical', 'no-ventilation'}
 VOLUME_TYPES = {'room_volume', 'room_dimensions'}
 WINDOWS_OPEN = {'always', 'interval', 'breaks', 'not-applicable'}
+WINDOWS_TYPES = {'sliding', 'hinged', 'not-applicable'}
 
 
 def time_string_to_minutes(time: str) -> int:
diff --git a/cara/apps/calculator/static/js/form.js b/cara/apps/calculator/static/js/form.js
index db3874a7..9764d71b 100644
--- a/cara/apps/calculator/static/js/form.js
+++ b/cara/apps/calculator/static/js/form.js
@@ -30,6 +30,12 @@ function require_fields(obj) {
       require_mechanical_ventilation(false);
       require_natural_ventilation(true);
       break;
+    case "window_sliding":
+      require_window_width(false);
+      break;
+    case "window_hinged":
+      require_window_width(true);
+      break;
     case "air_type_changes":
       require_air_changes(true);
       require_air_supply(false);
@@ -107,10 +113,17 @@ function require_natural_ventilation(option) {
   require_input_field("#windows_number", option);
   require_input_field("#window_height", option);
   require_input_field("#opening_distance", option);
+  $("#window_sliding").prop('required', option);
+  $("#window_hinged").prop('required', option);
   $("#always").prop('required', option);
   $("#interval").prop('required', option);
 }
 
+function require_window_width(option) {
+  require_input_field("#window_width", option);
+  disable_input_field("#window_width", option);
+}
+
 function require_air_changes(option) {
   require_input_field("#air_changes", option);
   disable_input_field("#air_changes", option);
@@ -324,7 +337,7 @@ function validateValue(obj) {
   $(obj).removeClass("red_border");
   $(obj).next('span').remove();
 
-  if (!isNonZeroOrEmpty($(obj).val())) {
+  if (!isLessThanZeroOrEmpty($(obj).val())) {
     $(obj).addClass("red_border");
     insertSpanAfter(obj, "Value must be > 0");
     return false;
@@ -332,9 +345,9 @@ function validateValue(obj) {
   return true;
 }
 
-function isNonZeroOrEmpty(value) {
+function isLessThanZeroOrEmpty(value) {
   if (value === "") return true;
-  if (value == 0) 
+  if (value <= 0) 
     return false;
   return true;
 }
@@ -402,6 +415,7 @@ $(document).ready(function () {
   require_fields($("input[name='lunch_option']:checked"));
   require_fields($("input[name='volume_type']:checked"));
   require_fields($("input[name='mechanical_ventilation_type']:checked"));
+  require_fields($("input[name='window_type']:checked"));
   require_fields($("input[name='hepa_option']:checked"));
 
   // Setup the maximum number of people at page load (to handle back/forward),
diff --git a/cara/apps/calculator/templates/calculator.form.html.j2 b/cara/apps/calculator/templates/calculator.form.html.j2
index 87e301fa..932fa712 100644
--- a/cara/apps/calculator/templates/calculator.form.html.j2
+++ b/cara/apps/calculator/templates/calculator.form.html.j2
@@ -79,6 +79,12 @@
     <div id="DIVnatural_ventilation" style="display:none">
         Number of windows: <input type="number" id="windows_number" class="non_zero" name="windows_number" min="1"><br>
         Height of window: <input type="number" step="any" id="window_height" class="non_zero" name="window_height" placeholder="meters" min="0"><br>
+        Window type: 
+        <input type="radio" id="window_sliding" name="window_type" value="sliding" onclick="require_fields(this)">
+          <label for="window_sliding">Sliding</label>&nbsp;&nbsp;
+        <input type="radio" id="window_hinged" name="window_type" value="hinged" onclick="require_fields(this)">
+          <label for="window_hinged">Hinged</label>&nbsp;&nbsp;<br>
+        Width of window: <input type="number" step="any" id="window_width" class="non_zero" name="window_width" placeholder="meters" min="0"><br>
         Opening distance: <input type="number" step="any" id="opening_distance" class="non_zero" name="opening_distance" placeholder="meters" min="0"><br>
         Windows open: <input type="radio" id="always" name="windows_open" value="always">
                         <label for="always">Always</label> &nbsp;&nbsp;
diff --git a/cara/apps/calculator/templates/report.html.j2 b/cara/apps/calculator/templates/report.html.j2
index 90c84604..2ab6bcf1 100644
--- a/cara/apps/calculator/templates/report.html.j2
+++ b/cara/apps/calculator/templates/report.html.j2
@@ -53,6 +53,10 @@
 		<ul>
 			<li><p class="data_subtext">Number of windows: {{ form.windows_number }}</p></li>
 			<li><p class="data_subtext">Height of window: {{ form.window_height }}</p></li>
+			<li><p class="data_subtext">Window type: {{ form.window_type }}</p></li>
+			{% if form.window_type == "hinged" %}
+			<li><p class="data_subtext">Width of window: {{ form.window_width }}</p></li>
+			{% endif %}
 			<li><p class="data_subtext">Opening distance: {{ form.opening_distance }}</p></li>
 			<li><p class="data_subtext">Windows open: {{ form.windows_open }}</p></li>
 		</ul>