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108Stitches 02-02-2009 04:17 PM

Basement Return Questions
First, I've searched through the forums and have read lots of great responses to return air questions for basements, but none of them really seem to hit home for what I'm looking at.

I'm finishing off an office / bathroom in my basement. Both of these rooms will be located on the below grade side of the house (it's a walk-out basement). The remainder of the basement will remain unfinished (due to budget constraints). My furnace / water heater are located in the center of my basement, and as part of this finishing, I will be "boxing" these in (rather large box 12x12 or so). I understand that I have to allow for adequate venting of this room, and will be cutting holes and installing grilles on all four walls of this box.

One of those grilles will be located in the office area, where I'm also running a new service line. The question I have, will this grille serve the same purpose as a return vent, even though it will not be tapping into the return, or will I have to also install a return vent and tap directly into the existing return lines?

The bathroom will have an exhaust fan vented outside the house, so it will not require a return vent (right?).

Thanks in advance...and realize this will probably not be my last post, as I start tackling my electrical and plumbing!

beenthere 02-02-2009 05:44 PM

Bathrooms are not allowed to have a return by code.

Combustion air vents are not allowed to be used as return air vents.

You will nee to run a dedicated rn for the office.
I also would put a combustion air vent into the office.

108Stitches 02-03-2009 02:16 AM

Thanks for the insight...

Contrary to most of my friends, I went ahead and pulled a permit for all of my work, so expect to have it all inspected and want to tackle as much of it as possible on my own (since as far as I can tell, we're not talking rocket science here), but want to make sure the inspector doesn't give me a 100 item check list.

So, can I put the compustion return 12" from the floor, then put the return 12" from the ceiling? The biggest problem I have is the closest wall to the furnace area does not have a normal header, but rather has the header butted against the steel I beam that support the upstairs...which naturally leads to a non existent normal route for the return vent....I would either have to put it straight into the ceiling, or get creative with the adjoining bathroom wall (one side bathroom, other side office interior).

beenthere 02-03-2009 05:47 AM

Depending on your area.

They may make you install a high and low combustion air intake.
Might want to call and find ut what your code enforcement requires.

For heat in a basement, I prefer to use high supplies, and low returns.

If you use a high return, with a high supply, you need a higher velocity from your supply to get good air mixture.

This can lead to a cool draft feeling at the end of the heat cycle when the supply air is cooling down.

Michael Thomas 02-03-2009 08:49 AM


Originally Posted by 108Stitches (Post 224130)
So, can I put the compustion return 12" from the floor, then put the return 12" from the ceiling?

Just to keep the terminology straight, there is no such thing as a "combustion return", only ""combustion air intakes".

A "return" as generally used in HVAC work refers to a point of entry into the return air ductwork - heated air flowing away from the furnace moves via "supply" ductwork and is returned to the furnace through "returns" via return ductwork.

One of the major objectives of the code requirements relating to forced air heating systems is to supply enough combustion air to the burners so that no exhaust fumes are pulled back into the return air ductwork and circulated inside the structure.

108Stitches 02-03-2009 10:56 AM

I will be doing high / low intakes for that inclosed furnace area (putting them on all four walls to insure adequate flow of air through that area).

I'll have to see if I can figure out a way to put in low returns with that steel I-Beam in the way (already have the high supplies in).

Thanks again for the help (and for correcting my terminology).

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