Add a Small Space + New AC Drop

[nolimits76]

I have a small space that I am thinking about closing in. I haven't put a tape on it, but am guessing it's around 8'x6'. The way it is positioned makes it easy to close up. I don't have super elaborate plans. It's essentially framed out. I just need to tweak for a door. I have 1 wall I would throw some bat insulation in as the other 3 are already well insulated. And then I'd probably throw some fire rock on top of the studs and do a single pass over on mud & tape to seal up. Doubtful if I even paint.

But I do want some conditioned air! LOL

Coincidentally, one of the walls I have to button up has 2 vents that run vertically up and over to feed an adjacent bedroom. So access is VERY convenient. I haven't verified yet, but believe those are flex ducts. If so, it seems easy enough to install a wye and create a new drop for this space. Probably not ideal. I'm not well versed in HVAC but imagine splitting will change the dynamics of the bedroom it is currently feeding. And while in theory that may be true, the new space is very small and adjacent so how much of an adverse effect would it have?

The main unit sits about 10' away, but has framing & sheetrock in the way. More worrisome is I'm not sure how I would tie on exactly. It looks packed in very tight.

Just looking for a sanity check to see if this is a reasonable idea? What you may suggest different? What techniques, parts & pieces you recommend? And what it may cost? Finally, if I could DIY or need to hire someone?

 

[Jim greengo]

Pictures?

 

[karoc]

This 8x6 room will it have a door or just an opening that is on living space side or is access to room from uncondition space? Guessing maybe home office, that someone will be in there only couple hrs a day, or is this going to be workout room. Sounds like you have a plan in place tapping into an existing duct, but that may also reduce the air some to that room that the existing duct is going to. Can that room afford to lose any cfm's? I think your wye idea will work, but I would test it first before you close the duct work in with sheetrock just to make sure. Your really not adding that much more sq ft if your home ac system is not at its limit or undersize. I say go for it, 48 sq ft not that much.

 

[nolimits76]

I will get some pics and measurements.

Entrance will be from an unconditioned space. I plan to install a door, although that will be tricky because there is a short pony wall on one side and it angles upwards. I’ve seen it done but not done it myself before.

I’d probably use every few days for a few hours each time. Mainly for electronics and computer hobbies/projects and also housing our network equipment. Maintaining temp and humidity control will be fairly important. The adjacent room is a spare guest room and is not critical, although I don’t want to create an uncomfortable environment for guests (or kids if that happens again, lol).

 

[dhally]

The problem will be return air. What goes in must go out, or in this case what leaves the central air handler needs to come back. Otherwise it will leave through the cracks in the new door, and the central unit will pull in outside air to replace it. If the new space is adjacent to a conditioned room, possibly install two through-wall louvers in the common wall - one high and one low. If that doesn't work, make one of the louvers a powered louver (transfer fan).

 

[fitter30]

Just depends on how much electronics putting into the room. Havind a outside wall a 4k window unit mounted iǹ the wall and a small electric wall heater for heat. Vapor barrier would keep the rh from infiltrating and keeping it low.

 

[nolimits76]

I finally had time to pull a tape. I was pretty close on the eye balling, 8.375' x 5.90' is the main area. As you will see in the pictures, the entire roof line is sloped. Shortest wall is 4.08' tall. The middle wall is 6.25' tall and the tallest wall is 8.375'. Width of the "hall" leading to the room is 2.92' wide.

I actually have 3 flexible ducts in the space. All appear to be 6" diameter, R-42 and are on a shared wall between one of the bedrooms and this closet space area. I am not 100% sure which duct feeds which room(s). There is a bedroom & its closet directly behind this space but it only has 1 vent. We have a flex room/office across the hall and it has 2 vents in the ceiling. My best guess is these 3 ducts feed those 3 vents. There is another bedroom in the vicinity but I noticed another flex duct further away from this closet and more inline with that room.

 

[nolimits76]

@Jim greengo @karoc @dhally @fitter30 any additional thoughts after the additional info?