Three.js - Stencil only on certain objects - three.js

Question

I'm looking into making kind of a portal effect using Three.js.
The main idea is to be able to see through multiple windows another Scene.
Exactly like in this example :
https://www.ronja-tutorials.com/post/022-stencil-buffers/ (See gif in article, too big to upload here)
I found an exact example of what i'm trying to do using three.js.
Here is the link :
https://sites.google.com/site/cgwith3js/home/masking-with-stencil
The fiddle was not working but I changed it to make it work :
http://jsfiddle.net/yzhreu6p/23/
scene = new THREE.Scene();
sceneStencil = new THREE.Scene();
...
scene.add(box); // red one
...
function animate() {
requestAnimationFrame(animate);
renderer.clear();
// animate the box
box.position.x = Math.cos(clock.getElapsedTime()) * 10;
var gl = renderer.getContext();
// enable stencil test
gl.enable(gl.STENCIL_TEST);
//renderer.state.setStencilTest( true );
// config the stencil buffer to collect data for testing
gl.stencilFunc(gl.ALWAYS, 1, 0xff);
gl.stencilOp(gl.REPLACE, gl.REPLACE, gl.REPLACE);
// render shape for stencil test
renderer.render(sceneStencil, camera);
// set stencil buffer for testing
gl.stencilFunc(gl.EQUAL, 1, 0xff);
gl.stencilOp(gl.KEEP, gl.KEEP, gl.KEEP);
// render actual scene
renderer.render(scene, camera);
// disable stencil test
gl.disable(gl.STENCIL_TEST);
}
Then I reuse the code in my project where I have kind of a town with buildings, and the hidden scene has a nyan cat textured box.
The problem I'm having is that the planes are disappearing when a building is behind and more serious problem, when there are buildings back the nyan cat texture, we see the texture in the building.
To better explain here is an image
I'm looking for a solution where the images are not visible inside the building, I found people that are talking about stencilMask but it's new for me.
Do I need to create another scene to make it work independently ?
If someone can help me, thank you for reading.