How to make the frontside of a material transparent?

Hi all,
Is there a way to make the fronsides of the wall transparent when using ExtrudePolygon in this example?

I only want to be able to look at the back of the wall, as if I could look inside the house.
I tried to solve it with a material but it doesn’t work.

This is one way

Thanks for your answer, but I’d like to make it dynamic. I already managed to create this effect by the following material settings.

var transparentMaterial = new BABYLON.StandardMaterial("transparentMaterial", scene);
        transparentMaterial.diffuseColor = new BABYLON.Color3(.5, .5, .5);
        transparentMaterial.emissiveColor = new BABYLON.Color3(0.5, 0.5, 0.5);
        transparentMaterial.alpha = 0.01;
        transparentMaterial.specularPower = 16;

        transparentMaterial.reflectionFresnelParameters = new BABYLON.FresnelParameters();
        transparentMaterial.reflectionFresnelParameters.bias = 0.05;

        transparentMaterial.opacityFresnelParameters = new BABYLON.FresnelParameters();
        transparentMaterial.opacityFresnelParameters.leftColor = BABYLON.Color3.White();
        transparentMaterial.opacityFresnelParameters.rightColor = BABYLON.Color3.Black();

But that’s still not the effect I need. Are there any other possibilities?