diff --git a/build/Modules/Umbraco.Build/Build-UmbracoDocs.ps1 b/build/Modules/Umbraco.Build/Build-UmbracoDocs.ps1
index 23041cd3ec..dc9ad843c7 100644
--- a/build/Modules/Umbraco.Build/Build-UmbracoDocs.ps1
+++ b/build/Modules/Umbraco.Build/Build-UmbracoDocs.ps1
@@ -24,12 +24,8 @@ function Build-UmbracoDocs
 
   Write-Host "Build UI documentation"
 
-    # get a temp clean path (will be restored)
-  $p = $env:path
-  $nodePath = $uenv.NodePath
-  $gitExe = (get-command git).Source  
-  $gitPath = [System.IO.Path]::GetDirectoryName($gitExe)
-  $env:path = "$nodePath;$gitPath"
+  # get a temp clean node env (will restore)
+  Sandbox-Node $uenv
  
   push-location "$src\Umbraco.Web.UI.Client"
   write "" > $tmp\belle-docs.log
@@ -50,7 +46,8 @@ function Build-UmbracoDocs
   (Get-Content $indexPath).Replace("location.href.replace(rUrl, indexFile)", "'$baseUrl'") `
     | Set-Content $indexPath
     
-  $env:path = $p
+  # restore
+  Restore-Node
   
   # zip
   &$uenv.Zip a -tzip -r "$out\ui-docs.zip" "$src\Umbraco.Web.UI.Client\docs\api\*.*" `
diff --git a/build/Modules/Umbraco.Build/Umbraco.Build.psm1 b/build/Modules/Umbraco.Build/Umbraco.Build.psm1
index 807b8dccd6..b7ca0439f7 100644
--- a/build/Modules/Umbraco.Build/Umbraco.Build.psm1
+++ b/build/Modules/Umbraco.Build/Umbraco.Build.psm1
@@ -65,6 +65,51 @@ function Prepare-Build
   Copy-File "$webUi\web.Template.config" "$webUi\web.config"
 }
 
+function Clear-EnvVar($var)
+{
+  $value = [Environment]::GetEnvironmentVariable($var)
+  if (test-path "env:$var") { rm "env:$var" }
+  return $value
+}
+
+function Set-EnvVar($var, $value)
+{
+  if ($value)
+  {
+    [Environment]::SetEnvironmentVariable($var, $value)
+  }
+  else
+  {
+    if (test-path "env:$var") { rm "env:$var" }
+  }
+}
+
+function Sandbox-Node
+{
+  param (
+    $uenv # an Umbraco build environment (see Get-UmbracoBuildEnv)
+  )
+  
+  $global:node_path = $env:path
+  $nodePath = $uenv.NodePath
+  $gitExe = (get-command git).Source  
+  $gitPath = [System.IO.Path]::GetDirectoryName($gitExe)
+  $env:path = "$nodePath;$gitPath"
+  
+  $global:node_nodepath = Clear-EnvVar "NODEPATH"
+  $global:node_npmcache = Clear-EnvVar "NPM_CONFIG_CACHE"
+  $global:node_npmprefix = Clear-EnvVar "NPM_CONFIG_PREFIX"
+}
+
+function Restore-Node
+{
+  $env:path = $node_path
+  
+  Set-EnvVar "NODEPATH" $node_nodepath
+  Set-EnvVar "NPM_CONFIG_CACHE" $node_npmcache
+  Set-EnvVar "NPM_CONFIG_PREFIX" $node_npmprefix
+}
+
 #
 # Builds the Belle UI project
 #
@@ -81,12 +126,8 @@ function Compile-Belle
   Write-Host ">> Compile Belle"
   Write-Host "Logging to $tmp\belle.log"
   
-  # get a temp clean path (will be restored)
-  $p = $env:path
-  $nodePath = $uenv.NodePath
-  $gitExe = (get-command git).Source  
-  $gitPath = [System.IO.Path]::GetDirectoryName($gitExe)
-  $env:path = "$nodePath;$gitPath"
+  # get a temp clean node env (will restore)
+  Sandbox-Node $uenv
   
   push-location "$($uenv.SolutionRoot)\src\Umbraco.Web.UI.Client"
   write "" > $tmp\belle.log
@@ -100,8 +141,8 @@ function Compile-Belle
   # fixme - should we filter the log to find errors?
   #get-content .\build.tmp\belle.log | %{ if ($_ -match "build") { write $_}}
 
-  # restore path
-  $env:path = $p
+  # restore
+  Restore-Node
   
   # setting node_modules folder to hidden
   # used to prevent VS13 from crashing on it while loading the websites project