Wall Condensation

[PorscheGAL]

Need some suggestions:

I have an interior wall that is building up condensation behind pictures. The other side of the wall is a non-temperature controlled storage area. This picture is the backside of the wall that has moisture.

It is not a small amount of water. I found water pooled in the frame of one picture and mold is growing under the picture that has only hung there about 2 months.

Of course, we live in a very humid area. How do I fix this?

[cabmandone]

The dark stuff down at the floor by the insulation down towards the fishing poles looks like water. Are you sure it's condensation? If you have an IR thermometer you can shoot your wall temps and it might give you some idea of what's causing the problem if it is condensation.

[PorscheGAL]

Not water. Just junk on the floor, I need to clean.

IR Thermometer is a good idea

[cabmandone]

Seems odd to me that you have a condensation problem when you're running your A/C. Part of what A/C does is remove humidity. What room is the condensation an issue and are your supply registers fully open? Is there a return air in the room? Or is it a bathroom where the issue is occurring?

[pete3799]

Do you know if the insulation is faced on the other side? If it isn't that could be your problem. There needs to be a vapor barrier on living space side.

[PorscheGAL]

Originally Posted by cabmando

Seems odd to me that you have a condensation problem when you're running your A/C. Part of what A/C does is remove humidity. What room is the condensation an issue and are your supply registers fully open? Is there a return air in the room? Or is it a bathroom where the issue is occurring?

This is a former bedroom, we have converted to a home theatre. All the registers are open. There is not a return air in the room but in the hallway.

[PorscheGAL]

Originally Posted by pete3799

Do you know if the insulation is faced on the other side? If it isn't that could be your problem. There needs to be a vapor barrier on living space side.

The insulation is faced.

[cabmandone]

Shoot the wall temp where the picture is hanging and report back. Seems you have to have heat transfer from the unconditioned space that is causing condensation in the conditioned space. Does the room feel warmer to you? You might try leaving the door open if there's a door still in place. I have a room that is kind of off on its own that when I enter from the hallway, I can tell is warmer than the hallway I was just in.

[cabmandone]

Here's an article about moisture on the ceiling in the summer. Same principle would apply because you're dealing with an unheated space.
https://homereference.net/ceiling-condensation/

[908/930]

Is there a well sealed vapour barrier? .5mm poly?

Should be on the warmer side of the wall, up here it is the inside of the house, I believe that at some point heading down south it switches to the outside of the insulation, not sure about SC.

[PorscheGAL]

No poly.

We were thinking of having someone come in to replace some of the insulation with foam insulation next spring. Any chance that would have an effect if we went that route?

[cabmandone]

Originally Posted by PorscheGAL

No poly.

We were thinking of having someone come in to replace some of the insulation with foam insulation next spring. Any chance that would have an effect if we went that route?

Yes. That's what I was going to suggest is spray foam on the inside wall then the fiberglass over that. A less expensive option might be insulating the roof of the unheated space and putting sheetrock on the common wall with the conditioned space with a vapor barrier.

[dad911]

Is there cross ventilation in that attic/storage space?

[john70t]

Moisture will build up wherever there is a cold surface next to warm humid air.
(think of a cold pop can outside...oh sorry..soda or coke for yuh sutherners.. )

Closed cell spray foam will provide a vapor barrier to the outside as long as it wraps around the surface continuously.
Even an inch is better than gaps.

That slanted walkway with the water heater is now considered "outside" air.
It wants to transfer and steal heat to both the side wall and the floor underneath.

I would spray the underside of the roof and rafters and outer wall to include that space inside the "heat envelope" or "conditioned space".

The one drawback might be that there is probably no active air flowing through it.
A few vents at top and bottom would allow some natural passive circulation through it and help prevent moisture buildup.
Some air movement is needed everywhere but in the right direction.

In the meantime, spray down everything with a 10% solution of bleach in a spray bottle.

Be warned that closed-cell foam has isocyanides and will make you seriously ill for the first couple days to a week while it is off-gassing.
Do not mess around with that stuff.
I got sick when my home was done, and also later when spraying it outside with a 2-part tank kit from HD.
Even the 3M chemical masks are not enough..
Rent a fresh-air suit kit with hoses and everything if you DIY. Seriously.

[908/930]

If you can just do a properly sealed poly layer that should take care of it, or turn the temp up.

Up here there are a couple of foam types, with different moisture permeability, You need to make sure you do not trap moisture or you will get rot. I do like fiberglass insulation because it does not burn, but I did get some tricky to seal areas spray foamed. Before you spray foam check with your building department if you need to cover it with drywall to be code compliant.

[cabmandone]

Originally Posted by dad911

Is there cross ventilation in that attic/storage space?

That's a good point! Some ventilation to allow the heat to escape might be a good option. Even a few vents on the end walls with a power vent in the roof that works off of humidity or temp.

[Zeke]

If the return air is in the hall, how does the air from the home theater exit? I see a lot of homes where the door to a room is too low to the floor to allow air to move under. That's usually the only path back to the return register. Door open, no problem, but if the door remains closed most of the time, no circulation.

If noise or privacy are concerns for any given room and the door is cut to just skim the carpet, you must install a transfer duct or through wall pair of registers to allow free circulation. I can't tell you how many doors I have cut to allow an inch above the carpet or hard flooring.

Look at it this way, if the register is a 6 x 12 on a 6" duct. that's nearly 30 sq in for the duct and 72 for the register. A 30" door with a one inch gap at the bottom ='s 30 sq in.

If it's an 8" duct (not likely unless it's a large room), that's 50 sq in trying to leave under a 30 sq in the under-door condition. Won't flow correctly w/o an additional return area.

I can say in general that all doors in a home need to have about an inch of clearance. First thing I look at when folks complain of temperature imbalance.

[PorscheGAL]

Thanks for all the input guys.

The storage area had some Tupperware boxes stacked that could be blocking some of the air flow so we unstacked those to reduce the chance. I have placed little felt pieces behind the pictures to allow them to not sit directly on the wall.

The door stays open unless we are in there watching a movie or playing games.

Like I said, we have been discussing having spray foam done in some areas so that may be our next step. Now to find a reputable installer.