Soundproofing a large closet with HVAC inside.

[frule]

I have an LP furnace and heat pump. The furnace is indoors inside a large closet
with bi-fold doors 4 total doors that fold 2 to each side when opened. The fan (blower)
is very loud and I'd like to quieten it if feasible. The closet is typical 2x4 construction
with drywall.

Anyone have an opinion on whether I can attain a good amount of noise reduction at 
a reasonable expense? What sound deadening to use? Also, there is not a lot of room around
the unit (about 6" on 3 sides, plenty on the service side).

Thanks, Fred

[woodhead]

Are your doors louvered for air to return to the unit?



Al

[Splinter Puller]

Assuming the closet has other sources or make up air and return air, your best bet would be to seal the door.  Replace the bi-folds with a pair of solid core doors with sound gasketing or sound seals.   This will take care of the bulk of  your problem.  Sound goes right through most bi-fold doors.   For further mitigation I would increase the mass of the walls by adding rock wool inside the stud cavities and then of further mitigation is needed, adding layers of drywall to the inside.  If the ceiling of the room is not finished this will be needed to be done also (or the walls extended up to the underside of the sheathing above)

[Roly]

Being LP it needs combustion air and air make up for flue gases going outside.    If it doesn't get that the exhaust gases will come in the house.  Carbon monoxide.        Roly

[daddo]

For safeties sake, it wouldn't hurt to pay a hvac guy to look at it and advise you what you should and shouldn't do. Combustion air and venting being the most important issue here.

[bottd]

Been said already but will say it again. With any furnace burning fuel you need to make sure you have sufficient combustion air and I would bet the louvered doors are there to provide that air. Good idea to find a HVAC contractor that knows what they are doing to take a look at it and advise you. If replacing the doors is not an option there might be some ways to quiet the blower down with some ductwork modifications or adjustments to airflow.

[Roly]

Another issue is that the 6" clearance on 3 sides may be required by the furnace manufacturer as a distance from combustible material.    As said a hvac  guy may be the best way to go for advice.   Roly

[fixtureman]

what about blowing in insulation between the studs.

[MikeBob]

what about blowing in insulation between the studs.

That could help a bit, but it is the studs that transfer most of the sound.

[fixtureman]

When I was doing commercial work we would insulate ans double the drywall for sound proofing