diff --git a/caimira/apps/calculator/static/js/form.js b/caimira/apps/calculator/static/js/form.js
index 25ca0af4..5361a043 100644
--- a/caimira/apps/calculator/static/js/form.js
+++ b/caimira/apps/calculator/static/js/form.js
@@ -147,8 +147,6 @@ function require_air_supply(option) {
 function require_venting(option) {
   require_input_field("#windows_duration", option);
   require_input_field("#windows_frequency", option);
-  set_disabled_status("#windows_duration", !option);
-  set_disabled_status("#windows_frequency", !option);
 }
 
 function require_lunch(id, option) {
@@ -233,6 +231,20 @@ function on_ventilation_type_change() {
   });
 }
 
+function on_window_opening_change() {
+  opening_regime = $('input[type=radio][name=window_opening_regime]')
+  opening_regime.each(function (index) {
+    if (this.checked) {
+      getChildElement($(this)).show();
+      require_fields(this);
+    }
+    else {
+      getChildElement($(this)).hide();
+      require_fields(this);
+    }
+  })
+}
+
 function on_hepa_option_change() {
   hepa_option = $('input[type=radio][name=hepa_option]')
   hepa_option.each(function (index) {
@@ -493,7 +505,7 @@ function validate_form(form) {
   });
 
   //Validate window venting duration < venting frequency
-  if (!$("#windows_duration").hasClass("disabled")) {
+  if ($("#windows_open_periodically").prop('checked')) {
     var windowsDurationObj = document.getElementById("windows_duration");
     var windowsFrequencyObj = document.getElementById("windows_frequency");
     removeErrorFor(windowsFrequencyObj);
@@ -824,6 +836,12 @@ $(document).ready(function () {
   // Call the function now to handle forward/back button presses in the browser.
   on_ventilation_type_change();
 
+  // When the window_opening_regime changes we want to make its respective
+  // children show/hide.
+  $("input[type=radio][name=window_opening_regime]").change(on_window_opening_change);
+  // Call the function now to handle forward/back button presses in the browser.
+  on_window_opening_change();
+
   // When the hepa filtration option changes we want to make its respective
   // children show/hide.
   $("input[type=radio][name=hepa_option]").change(on_hepa_option_change);
@@ -839,7 +857,6 @@ $(document).ready(function () {
   // When the short_range_option changes we want to make its respective
   // children show/hide.
   $("input[type=radio][name=short_range_option]").change(on_short_range_option_change);
-
   // Call the function now to handle forward/back button presses in the browser.
   on_short_range_option_change();
 
diff --git a/caimira/apps/templates/base/calculator.form.html.j2 b/caimira/apps/templates/base/calculator.form.html.j2
index 07561755..770df231 100644
--- a/caimira/apps/templates/base/calculator.form.html.j2
+++ b/caimira/apps/templates/base/calculator.form.html.j2
@@ -235,18 +235,20 @@
         </div>
         <input class="ml-2" type="radio" id="windows_open_permanently" name="window_opening_regime" value="windows_open_permanently" onclick="require_fields(this)" checked="checked"></span>
           <label for="windows_open_permanently" class="col-form-label ml-2">Permanently</label>
-        <input class="ml-2" type="radio" id="windows_open_periodically" name="window_opening_regime" value="windows_open_periodically" onclick="require_fields(this)"></span>
-          <label for="windows_open_periodically" class="col-form-label ml-2 mr-2">Periodically:</label><br>
+        <input class="ml-2" type="radio" id="windows_open_periodically" name="window_opening_regime" value="windows_open_periodically" onclick="require_fields(this)" data-enables="#DIVperiodic_opening"></span>
+          <label for="windows_open_periodically" class="col-form-label ml-2 mr-2">Periodically</label>
+        
+        <div id="DIVperiodic_opening">
+          <div class="form-group row tabbed">     
+            <div class="col-md-5"><label for="window_duration" class="col-form-label ml-2">Duration (min):</label></div>
+            <div class="col-md-5"><input type="number" step="any" id="windows_duration" class="non_zero form-control" name="windows_duration" value="10" min="1" data-has-radio="#windows_open_periodically"></div>
+          </div>
+          <div class="form-group row tabbed">
+            <div class="col-md-5"><label for="window_frequency" class="col-form-label ml-2">Frequency (min):</label></div>
+            <div class="col-md-5"><input type="number" step="any" id="windows_frequency" class="non_zero form-control" name="windows_frequency" value="60" min="1" data-has-radio="#windows_open_periodically"></div>
+          </div>
+        </div>
 
-        <div class="form-group row tabbed">     
-          <div class="col-md-5"><label for="window_duration" class="col-form-label ml-2">Duration (min):</label></div>
-          <div class="col-md-5"><input type="number" step="any" id="windows_duration" class="non_zero disabled form-control" name="windows_duration" value="10" min="1" data-has-radio="#windows_open_periodically"></div>
-        </div>
-        <div class="form-group row tabbed">
-          <div class="col-md-5"><label for="window_frequency" class="col-form-label ml-2">Frequency (min):</label></div>
-          <div class="col-md-5"><input type="number" step="any" id="windows_frequency" class="non_zero disabled form-control" name="windows_frequency" value="60" min="1" data-has-radio="#windows_open_periodically"></div>
-        </div>
-        <br>
     </div>
     <br/>
     <div class='sub_title'>HEPA filtration:</div>