Do it by using the B&W layer as a track matte; specifically, a luma matte.
Click on (toggle swiches / modes ) button in the timeline to reveal trackmatte or press F4
a new column withh appear called Trkmat:
Put the black and white layer on top and
for the second layer ( the layer below ) select: Luma matte
Thanks but now when i applied luma matte and denoiser filter, everything around the building is still black. So my guess is i have to put another layer with same sequence of images at the bottom. Is that correct?
Remove The denoiser effect,
Set the luma matte for the layer
them select both layers and precompose them, right click -> pre-compose
with move all attribute on
then apply the denoiser on the pre-comp
But when i precompose two layers - layer with bw mask and colored layer its still black around the building - no change. So my guess was to place another squence below so it will be replaced. Or which layers you meant to precomp...?
And what do you mean set the luma matte for the layer... Its already seted for the second layer