If this only on windows? I can't see any difference in size on mac. Havn't looked the the code for a while but it should copy from the cache folder a fresh copy into the release folder:
https://github.com/mllrsohn/node-webkit-builder/blob/master/lib/index.js#L317-L329

Not sure. It was on Windows 8.1 that I noticed.

I ran into an issue, what it ended up being is that the way I was calling nwbuild, it was targeting not only my source, but my old build and all of my node modules, turning what was a 50mb app into a 170mb app.

Each time I built the size of the app was doubling because it would recopy the old build into the new one.

I changed my nwbuild target to a src folder that included only my source files and a package.json specific to nw. That resolved my issues.

The build folder and cache folder should be automatically excluded when building, as well as any devDependencies
That way you wouldn't have to maintain duplicate package.json files.

We should skip devDependencies. +1

I ran into this issue too and adding exclusions to the files property of NwBuilder seemed to help.

var nw = new NwBuilder({
  files: ['./**/**', '!./build/**/**'], // use the glob format
  version: "0.12.0",
  platforms: ['osx32', 'osx64', 'win32', 'win64']
});

notice the !./build//. I didn't think about excluding cache but I should add that too.