Is it safe to make a hole here?

Hi, here is a photo of our furnace room which is outside the house next to the front door:



Behind this, on the opposite side of the back wall, is a coat cupboard.

In that cupboard we've installed an Aprilaire 800 humidifier, so the room gets a little hot (not too bad).

Is it safe to make a hole and add a vent at the top of the coat cupboard wall? Said hole would essentially be directly behind the top of the silver area pictured (the coil enclosure). I'm certain there are 2 sheets of drywall there sandwiched by studs, so I'd only be cutting through the inner drywall to expose the wall cavity. Obviously I wouldn't cut through to the coil/furnace room.

Additionally you can see an air vent just like the one I want to install, near the bottom of the back wall pictured. That air vent runs into the same cavity I want to cut into (though I'll be cutting the opposite sheet of drywall.)

My concerns are:

- CO2
- Impairing the HVAC efficiency

Advice greatly appreciated. Thanks!

 

I'm a little confused. Did you cut the sheetrock in the closet out to install the humidifier ?

 

No not at all. The humidifier is mounted with screws onto the sheetrock.

Then the hose runs from the closet, up to the top of the closet door (90 degrees to the right), and we use the fan pack installed above the closet door to blow steam into the house. We aren't connecting directly into the HVAC system (concerns about mold etc.)

 

Ahhhh...ok. Understood. So the furnace is insulated from the living space.
So why do you need to open the wall cavity ?

 

As per my first message, the closet gets a little hot. Heat rises so I want to ventilate the closet and let the warm air out into the sheetrock cavity.

Is it safe to make a hole and add a grille vent at the top of the coat closet wall?

 

Letting the warm into the cavity isn't going to help. It can't go anywhere. The top of that wall will be blocked off. You could cut from the closet all the way thru to the room and add a grill on both sides.

 

Gotcha. If the top of that wall isn't blocked off, is it safe to do? CO2?

 

Basically what you are asking to do is put an opening to the outside. Like putting an open window in the closet. Don't know but building codes might be an issue. Can you instead replace the closet door with a louvered one?

 

You want to go from the coat cupboard (inside the house) to inside the house. That is fine.
The wall you want to cut thru should be a regular inside partition. If it is..... it will be blocked off at the top.

Technically you'd want to use a short sleeve thru the wall so that the heat doesn't get trapped inside the wall.

 

Astuff, it's not to the outside, there would still be 2 layers before the outside.
1. Inner drywall of the closet
(Cavity)
2. Outer drywall of the cavity
(Furnace room)
3. Furnace room door
I'm only cutting through "1" to expand the air space and lose some heat

Pete, long story but inside to inside isn't an option.

Are either of you able to confirm there's no CO2 safety issue cutting through "1" above?

 

I'm lost..... lose some heat to where ? Just into the wall ?
The wall between the furnace and the coat closet.

I would not penetrate the wall between the furnace room and the coat closet.
It's not the CO..... it's part of the fire stop.

 

Yes, if I punch into the cavity, the cooler sheetrock on the furnace side (house outside cupboard) will help temper the warm air.

Thanks for your advice. I'll consider the options.

 

The top of the furnace room you said is not blocked off. I see a grill above the door. Is that where you want the heat to go?

 

There is no vent in the top of drywall "2" though so I don't think it will quite do what you asked, though the front yard vent might help a little. Either way there is some airflow right through

 

Ahh. I see now. You want to dump heat into the wall cavity. In colder climates it would be filled with insulation but probably not in your case. As mentioned it might be a fire rated wall. If you do this I doubt you will get much heat transfer.

 

I would want the fire integrity of the furnace enclosure to remain intact in case there ever was an issue with the furnace.