For all the valid reasons not to add insulation there are also reasons when you need insulation.
Insulation between first and second floor.
Second we re debating whether to insulate the ceiling of the main floor of the addition i e between the main floor and the second floor as well as the 2 4 walls between the addition and the original house both floors i m assuming we would just use fiberglass.
One would be surprised at the heat loss from the first floor to the second.
Reasons for heatproofing insulation between floors.
Acoustic insulation in the mid floor.
This will also increase thermal insulation for the room above and below making them more comfortable to be in and quieter too.
If the first floor soffits open into the joist bays these should be air sealed and insulated.
Insulated between floors have very little if not quite no insulating benefit.
You can also add rigid foam insulation under the rafters which adds r value and eliminates thermal bridging through wood rafters.
The main reason to insulate between floors is to reduce the noise transfer between floors.
I can tell a noticeable difference when my guys are walking on a second floor of a remodel where they did not insulate between the floors in comparison to when they walk on the second floor of a home we built and insulated between the floors.
You have properly diagnosed the existence of a problem but the treatment is something other than removing the insulation between the floors.
Here are some situations when you need floor insulation.
Other than that not required.
Presuming the insulation is adequate you have an imbalance in the air flow between the two floors.
In my opinion it is reduced by at least 75 just putting bats between the floors.
Children shouting loud music or even a noisy washing machine can create.
If the floor is above a cold space you need insulation.
Putting insulation between the ground and first floor should in theory stop sound vibration and heat from moving between levels in your property.
Acoustic insulation is very effective at reducing airborne noise.
Just push it as far as you like gradually bring it back toward you.
Consider using high density r 30 batts which are as thick as r 25 batts but fit into 2x10 framing.
A vent baffle should be installed between the insulation and the roof decking to maintain the ventilation channel.
Let s look at the yes answer for should there be insulation between floors.
However there are certain scenarios and reasons like sound proofing to insulate between floors.
Between the ceiling of the ground floor and the floor of the second storey.
Agreed and as jim pointed out for rental units sometimes it is also wise to insulate the second floor to retain the heat on the first floor unit when the two apartments have seperate heating units and responsible for their own heat.
Sometimes buildings are construction with first floor eaves and soffits.