Background after an exterior rendered model

Sir question lng po, is there anyway para marender ang isang exterior model without having a background and also without affecting the render quality nung mismong model in preparation kse sana for post processing sa photoshop mas madali kse magpalit ng sky na background diba kapag wlng existing background yung mismong rendered image no need to make detailed selections para s mga locations na papalitan direktang patong nalang nung sky image thanks!

save as .PNG

Hehe! I know medyo basic lng po ung question ko but im really having a hard time finding the solution talaga wala kse ako mkita tutorials regarding this but Thank you very much sir laking tulong po!

heto pa hindi man lamang nag-basa ng mga rules sa forum