You probably are already using a microphone spider for isolating floor rumble.
A condenser mic is not per se more sensitive to outside noise. It only seduces you to use setups sensitive to outside noise.
The Røde NT1A is a very, very quiet large-diaphragm condenser microphone with good sensitivity. That means that if you are creating an audio setup in relation to its electronic noise floor, the relevant noise floor in the recording will be more likely than not an acoustical noise floor of actual noise unless you are working in a professionally isolated studio.
So position your microphone in a manner (and use rumble filters and close your doors and switch off heating timely before recording sessions to avoid cracking pipes and take off wall clocks you can hear on the recording) that the ambient noise is not a problem.
Oh, and feed your cat.
Basically a large-diaphragm condenser like the Røde NT1A is a nice microphone for snooping (where you are actually interested in outside noise) but its low electric noise floor becomes mostly relevant in studio settings. As a primary recording mic outside of studio conditions, you'll rather use it for the typical large-diaphragm artifacts (a somewhat silky sound coloring for vocals and overhead drums) or as a secondary microphone to capture the ambient sound of large rooms, in addition to closely positioned main microphones.
Yes, you can place it across the room without getting annoyed by an electronic noise floor, but in reflectionless studio surroundings this is sort of pointless since it will sound sort of the same, not having a large proximity effect and the studio not having much of ambient reflections. And in not-so studio environments, you'll get enough noise from elsewhere to not make it advisable as the primary recording mic.