diff --git a/win/readme.md b/win/readme.md
index 89a6922be0..8af62504c2 100644
--- a/win/readme.md
+++ b/win/readme.md
@@ -32,13 +32,30 @@ easily more than 2 GBs of RAM while converting.
 
 After this, one can build the project using the `IfcOpenShell.sln` file in the build folder. Build the `INSTALL` project
 if wanted. Convenience batch files `build-ifcopenshell.cmd` and `install-ifcopenshell.cmd` can also be used. The batch files
-expect `%1` and `%2` in same fashion as above and possible extra parameters are passed for the `MSBuild`call. The project will
+expect `%1` and `%2` in same fashion as above and possible extra parameters are passed for the `MSBuild` call. The project will
 be installed to `installed-vs<VERSION>-<ARCHITECTURE>\` folder in the project's root folder and the required IfcOpenShell-Python
 parts are deployed to the `<PYTHONPATH>\Lib\site-packages\` folder.
 
 **Note:** All of the dependencies are build as static libraries against the static run-time allowing the developer
 to effortlessly deploy standalone IFCOS binaries.
 
+Using an already existing Python installation
+---------------------------------------------
+
+Let's say you have already installed 64-bit Python 3.5.1 to `C:\Python3`.
+Before building the dependencies, disable the script from installing Python:
+```
+> set IFCOS_INSTALL_PYTHON=FALSE
+> buid-deps.cmd
+```
+
+After bulding the dependencies, create BuildDepsCache file to `IfcOpenShell\win` which tells the used Python version and intallation directory:
+```
+> echo PY_VER_MAJOR_MINOR=35> BuildDepsCache-x64.txt
+> echo PYTHONPATH=C:\Python3>> BuildDepsCache-x64.txt
+```
+
+After this you should be able to run `run-cmake.bat` normally. If using 32-bit Python, the name of the file must be `BuildDepsCache-x86.txt`.
 
 Directory Structure
 ------------------
@@ -55,6 +72,7 @@ Directory Structure
 |   install-ifcopenshell.cmd        - Builds IFCOS's INSTALL project
 |   readme.md                       - This file
 |   run-cmake.bat                   - Sets environment variables for the dependencies and runs CMake for IFCOS
+|   set-python-to-path.bat          - Utility for setting PYTHONPATH (read from BuildDepsCache-<ARCH>.txt) to PATH
 |   vs-cfg.cmd                      - Utility file used by the build scripts
 +---sln                             - Contains the old Visual Studio solution and project files
 \---utils                           - Contains various utilities for the build scripts
diff --git a/win/set-python-to-path.bat b/win/set-python-to-path.bat
new file mode 100644
index 0000000000..613a69c149
--- /dev/null
+++ b/win/set-python-to-path.bat
@@ -0,0 +1,36 @@
+:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
+::                                                                             ::
+:: This file is part of IfcOpenShell.                                          ::
+::                                                                             ::
+:: IfcOpenShell is free software: you can redistribute it and/or modify        ::
+:: it under the terms of the Lesser GNU General Public License as published by ::
+:: the Free Software Foundation, either version 3.0 of the License, or         ::
+:: (at your option) any later version.                                         ::
+::                                                                             ::
+:: IfcOpenShell is distributed in the hope that it will be useful,             ::
+:: but WITHOUT ANY WARRANTY; without even the implied warranty of              ::
+:: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the                ::
+:: Lesser GNU General Public License for more details.                         ::
+::                                                                             ::
+:: You should have received a copy of the Lesser GNU General Public License    ::
+:: along with this program. If not, see <http://www.gnu.org/licenses/>.        ::
+::                                                                             ::
+:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
+
+:: Pass x86 or x64 as %1, if not specified x64 assumed.
+
+@echo off
+set TARGET_ARCH=%1
+if "%TARGET_ARCH%"=="" set TARGET_ARCH=x64
+if not exist BuildDepsCache-%TARGET_ARCH%.txt. (
+    echo BuildDepsCache-%TARGET_ARCH%.txt does not exist
+    goto :EOF
+)
+for /f "delims== tokens=1,2" %%G in (BuildDepsCache-%TARGET_ARCH%.txt) do set %%G=%%H
+if not defined PYTHONPATH (
+    echo PYTHONPATH PYTHONPATH not defined
+    goto :EOF
+)
+
+echo %PYTHONPATH% set to PATH
+set PATH=%PYTHONPATH%;%PATH%