diff --git a/README.md b/README.md
index 6996b5a..16c0687 100644
--- a/README.md
+++ b/README.md
@@ -7,7 +7,9 @@ Modifications:
 - Additional export **Zip pack - keep hierarchy**   
 Standard Bat pack is doing an "assembly", modifying file internal links. This zip pack leave the file untouched. Behavior description:  
   - The root folder for zipping use the environment variable `ZIP_ROOT` (accessed with `os.getenv('ZIP_ROOT')` if defined).
-  - If there is no such env variable, it fallback to path specified in addon preferences.
+  - if `ZIP_ROOT` is not defined, use `PROJECT_ROOT` variable.
+  - If there is no such env variables, it fallback to path specified in addon preferences.
+  - A checkbox allow to avoid the replacement of root properties with env variables.
   - In the export browser window settings (sidebar), user can choose the packing root folder, prefilled by env or addon preference path
   - If nothing specified, root will be automatically defined with the most upper folder covering the whole dependancies hierarchy.
 
@@ -16,6 +18,11 @@ Standard Bat pack is doing an "assembly", modifying file internal links. This zi
 
 ### Changelog
 
+1.3.4
+
+- added: `PROJECT_ROOT` key is used if `ZIP_ROOT` is not specified. Fallback to initial property if neither exists
+- added: checkbox to disable env variable check
+
 1.3.3
 
 - code: sys.module name corrected when addon folder isn't named `blender_asset_tracer` as expected
diff --git a/__init__.py b/__init__.py
index d7f460f..7d89f0d 100644
--- a/__init__.py
+++ b/__init__.py
@@ -21,11 +21,12 @@
 # <pep8 compliant>
 
 __version__ = '1.3'
+# branched from source BAT since 1.3.0
 
 bl_info = {
     "name": "Blender Asset Tracer",
     "author": "Campbell Barton, Sybren A. Stüvel, Loïc Charrière and Clément Ducarteron",
-    "version": (1, 3, 3),
+    "version": (1, 3, 4),
     "blender": (2, 80, 0),
     "location": "File > External Data > BAT",
     "description": "Utility for packing blend files",
@@ -264,10 +265,19 @@ def menu_func(self, context):
     layout.separator()
     layout.operator(ExportBatPack.bl_idname)
     filepath = layout.operator(BAT_OT_export_zip.bl_idname)
-    root_dir_env = os.getenv('ZIP_ROOT')
-    if not root_dir_env: # if no env use prefs instead
-        root_dir_env = preferences.get_addon_prefs().root_default
-    filepath.root_dir = '' if root_dir_env == None else root_dir_env #os.getenv('PROJECT_STORE')
+
+    prefs = preferences.get_addon_prefs()
+    
+    root_dir_env = None
+    if prefs.use_env_root:
+        root_dir_env = os.getenv('ZIP_ROOT')
+        if not root_dir_env: # first fallback to PROJECT_ROOT
+            root_dir_env = os.getenv('PROJECT_ROOT')
+        
+        if not root_dir_env: # if no env, use prefs instead
+            root_dir_env = prefs.root_default
+    
+    filepath.root_dir = '' if root_dir_env == None else root_dir_env
 
 
 classes = (
diff --git a/preferences.py b/preferences.py
index 1b17f4c..1d3fa12 100644
--- a/preferences.py
+++ b/preferences.py
@@ -19,6 +19,12 @@ class myaddonPrefs(bpy.types.AddonPreferences):
         subtype='DIR_PATH',
         default='')
 
+    use_env_root : BoolProperty(
+        name="Use Environement Root",
+        description="Use root path specified by environnement keys at startup\nUsing key 'ZIP_ROOT' or 'PROJECT_ROOT' if exists (priority to key ZIP_ROOT if both are set)\nElse always use prefs.",
+        default=True,
+        )
+
     def draw(self, context):
             layout = self.layout
             col = layout.column()
@@ -28,6 +34,7 @@ class myaddonPrefs(bpy.types.AddonPreferences):
             col = layout.column()
             col.label(text='If specified, will be the default root folder path when using export to Zip')
             col.label(text='Typically the root folder of the current project')
+            col.prop(self, 'use_env_root')