Attic located HVAC condensation issues, Oh my !!

[Onboard 2.0 9083]

Despite being in the building industry, I know just enough about HVAC issues to get myself in trouble.  I was up in the attic last night because we have a leak at one of the vent stack roof penetrations.  I noticed that all of the insulated attic HVAC trunk lines are sweating (can't be more than R-2 or R-3 on any of the ducts).  The attic located air handler isn't insulated (and isn't sweating that much at all, but is sweating a bit into its pan)  We have 20" x 24" insulation board main trunks, with insulated 6" and 8" flex duct lines running to the room diffusers.  The house was built in '89 or '90, so I know it's way out of date with regard to how we're installing systems today.

My first guess is not enough insulation, but not sure if that's the actual culprit. Or if it's a combination of issues. I laid down an extra layer of 10" batts over the original blown in insulation several years ago, and the flex duct lines running under that extra blanket are also sweating.  The main trunks are above that extra layer so I'm guessing that's why the flex duct lines are still sweating ??

Doing a little reading on the topic, and it looks like it could also be a poorly ventilated attic with too much humidity.  We're in the mid Atlantic so humidity is always an issue in the summer.  I know it's not ventilated like I'd design a home: with ridge/hip vents, gable vents, and maybe roof mounted vent hoods. We have 3 gable vents, and that's it.  Can't be enough ventilation, but even with better ventilation, the temperature/humidity differential between duct work, and air temp. would still be more than 20 degrees I'm betting.

Before I begin doing things that could be a pain, any thoughts on where I should start ?  More insulation on the ducts ?  Tackle the venting issue in the attic?  both ?  We're getting the house ready to sell in the next 6-8 months, and I don't wanna pass a problem on to the next buyer, but I don't wanna do things that aren't going to actually accomplish anything.

[Parliament 14594]

The cheap fix is more ventilation. The good fix is to insulate the attic and make it part of the house's "conditioned space."

[South Austin 53222]

It’s probably the bypass line.

[Onboard 2.0 9083]

28 minutes ago, Parliament said:

The cheap fix is more ventilation. The good fix is to insulate the attic and make it part of the house's "conditioned space."

Yeah, I've been thinking about that for years now.  I always recommend that to homeowners when designing new homes. 

That's a much bigger project. I've never retrofitted an attic to be conditioned, so not sure what all the steps are.  Closing the soffit and gable vents, an extra HVAC trunk to add some air in the attic ?

That could start to get more expensive than I'm probably wanting to spend. More ventilation, and a dehumidifier (in a drained pan)  were one my thoughts right now.  Thought I could route a drain line from the dehumidifier thru the soffit so I wouldn't have to empty the collector reservoir.

[Upgrayedd 5889]

Sounds like a Division 7 problem.  You should sue.

[Onboard 2.0 9083]

33 minutes ago, South Austin said:

It’s probably the bypass line.

Is that next to the Fetzer valve ??

[C-Man 27779]

Doing everything 220 or 221?

[Parliament 14594]

3 hours ago, Onboard 2.0 said:

Yeah, I've been thinking about that for years now.  I always recommend that to homeowners when designing new homes. 

That's a much bigger project. I've never retrofitted an attic to be conditioned, so not sure what all the steps are.  Closing the soffit and gable vents, an extra HVAC trunk to add some air in the attic ?

That could start to get more expensive than I'm probably wanting to spend. More ventilation, and a dehumidifier (in a drained pan)  were one my thoughts right now.  Thought I could route a drain line from the dehumidifier thru the soffit so I wouldn't have to empty the collector reservoir.

To be clear, I'm not recommending that.  It's good advice for the new owner though.  Probably not REAL expensive?  Close off the vents, remove the ceiling insulation then spray foam under the room.  Matt Reisinger is a builder on Austin, and his Youtube channel is great for this kinda thing.

[Onboard 2.0 9083]

41 minutes ago, Parliament said:

To be clear, I'm not recommending that.  It's good advice for the new owner though.  Probably not REAL expensive?  Close off the vents, remove the ceiling insulation then spray foam under the room.  Matt Reisinger is a builder on Austin, and his Youtube channel is great for this kinda thing.

Yep been looking at the options for conditioning a roof deck . I'll check out the Austin builders site for ideas.  Also talking to a couple guys here in town.  

We've got a building scientist here in town. He has lots of info on insulation systems, and building envelope compatibility. 

The conditioned space move would be a next step idea if I can't control the humidity in a more low tech DIY way.

Current preferred options:

humidity removal

better venting

extra duct insulation

 

[BigDHornfan 6630]

On 7/12/2019 at 10:34 AM, C-Man said:

Doing everything 220 or 221?

whatever it takes.