How to Maintain Reflections on Glass While Underlaying Sky Behind?

[rhull]

I am trying to figure out how I can add a sky image as a background to a rendering after the fact in photoshop while keeping reflections on the glass. So far, I've only been able to do one or the other. I've applied the neutral glass texture from Vray to my windows. When I change the Affect Channels in both Reflection and Refraction to Color + Alpha, the glass against the sky is not rendered, allowing an image to be added behind it, but the reflections are not maintained. If I have those set to Color Only, then the sky is not transparent. Examples of both are attached. I'm saving all the images as png. I do not have GI turned on in the Environment Overrides. I am using the standard SunLight from Vray for the global illumination. This is really driving me crazy; any advice anyone has to offer would be greatly appreciated! Thanks!

[ValeroStudio]

I typically save out the reflections channel, sit it on top of my beauty pass, set it to Linear Dodge (Add), and mask it over the window glass. I always like to save out that channel so I can bump up or add some reflections to any objects. Also save out a Material ID and a Render ID if you want to make selecting easier.

[rhull]

Thanks for the response Matthew!! That makes sense and is probably a good idea in general for me to add a reflection channel to be able to save that image like you said to increase reflections, etc. I will give the Linear Dodge setting a try. Thanks again!