Condensation in walls during winter creating mold farm

[protivakid]

I have an issue that I've noticed on one corner of my house but probably have elsewhere. My wife noticed some mold along the baseboard in one room's closet. I peeled back the board and saw some more mold. I started cutting the drywall and discovered that in the Massachusetts winter, condensation seems to form inside the wall on the outer wood. This then melts when the temps warm up and has nowhere to go creating the mold.

Originally I wondered if it was a leak however we've had a good amount of rain the past couple days in the summer and the wall is dry as can be. Is there anything I can do to correct this? Or is this expected in New England?

I imagine the mold was on the baseboard because the vapor barrier doesn't go all the way down to the floor, still extending it so the floorboard didn't mold would just hide the problem better with the issue still being present inside the wall.

Pics below from winter after I cut into the wall:

Hard to see but the wood is shiny on the back from ice / moisture

 

[WorthFlorida]

I would guess that one of the walls is on the north side of the home. The rusted nail or screw heads bleeding through the paint also indicates condensation. From the picture it is hard to tell if there is a plastic sheeting vapor barrier. I can't say if this can be an area opened, fixed and drywalled or remove all the of the drywall wall from the exterior walls. Replace any fiberglass insulation that has mold or upgrade to spray foam and then cover it with plastic sheeting with all overlaps taped over. Do not rely totally on insulation that reads "paper vapor retarder". Since there is a textured finish that creates an issue if you want to redo the texture.

Sometime wood will bleed out its sap and look shiny. Rub it and if it is like a powder, it dried mold.

It also can indicate there is too much moisture in the home. A humidifier set too high, no bathroom exhaust fans or not used enough can all contribute. On line it is very easy to find humidity meters that sit on a table top, For this next winter get a few of them and place them around the home.

From a google search
50%
Every homeowner should own a hygrometer that measures temperature and relative humidity (RH). The ideal relative humidity for health and comfort is about 40–50%. In the winter months, it may have to be lower than 40% RH to avoid condensation on the windows.

 

[Sponsor]

 

[protivakid]

I would guess that one of the walls is on the north side of the home. The rusted nail or screw heads bleeding through the paint also indicates condensation. From the picture it is hard to tell if there is a plastic sheeting vapor barrier. I can't say if this can be an area opened, fixed and drywalled or remove all the of the drywall wall from the exterior walls. Replace any fiberglass insulation that has mold or upgrade to spray foam and then cover it with plastic sheeting with all overlaps taped over. Do not rely totally on insulation that reads "paper vapor retarder". Since there is a textured finish that creates an issue if you want to redo the texture.

Sometime wood will bleed out its sap and look shiny. Rub it and if it is like a powder, it dried mold.

It also can indicate there is too much moisture in the home. A humidifier set too high, no bathroom exhaust fans or not used enough can all contribute. On line it is very easy to find humidity meters that sit on a table top, For this next winter get a few of them and place them around the home.

From a google search
50%
Every homeowner should own a hygrometer that measures temperature and relative humidity (RH). The ideal relative humidity for health and comfort is about 40–50%. In the winter months, it may have to be lower than 40% RH to avoid condensation on the windows.

The corner is actually on the south/west side of the house. Maybe we get more wind there that hits it? There is a plastic barrier between the drywall and the studs but it's not very thick. It's a closet so I can easily open up this one section and re-do the drywall if needed, I just hope it's not happening elsewhere that I can't see. I don't care about the texture, but it sounds like you think re-drywalling that wall with good insulation and a good barrier is the solution?

I will absolutely get a hygrometer for the winter. We do have fans in both of our bathrooms that we turn on for showers and leave on a good 20 minutes after. We don't have a humidifier anywhere.

 

[WorthFlorida]

Look around the home for more rust stains from the drywall screws or nails. If any it does indicate too much moisture. Since these are into the wood studs I would guess the moisture is from the inside of the home. Also this being a closet there is no air circulation. Boxes, shoes, etc is piled up against the wall and the closet door kept closed. Who doesn’t do this? It’s no different than my closets.

Being a closet I would take down the bottom three feet on the exterior walls to check for mold. If any and just a localized spot or two, clean it with a mold cleaner you can get at Lowe’s or HD and you can determine if the entire wall would need to be done. Just to get the vapor barrier right you may need to do the whole wall.

A closet is a good place to learn how to drywall if you have never done it before and any mistakes no one would know. If you saw my first drywall job in my first home on the living room wall, anyone would know it. I now can do it and no one would know it was patched.

Check the outside for air circulation on that corner of the home. No leaves, dirt or bushes should be touching the home and a few inches of clearance from the top of the concrete foundation to the dirt level. I’m in my fifth house in forty years and I kept one rule, plants planted no closer than 3 ft to the wall and keep the bushes trimmed to at least 1 ft from the house.

 

[Reach4]

I wonder if a door blower test would be worthwhile. Maybe for a house as loose as yours it would not be so helpful. I am thinking an odor free smoke generator would show you the leakage spots.

 

[Dana]

The air tightness to the interior has a much bigger affect on moisture accumulation in the sheathing than the plastic vapor barrier. (Technically the moisture accumulates in the form of adsorb, not liquid condensation, and will only condense liquid pn the surface when the moisture content of sheathing is nearly saturated.) A square inch of air leak from the interior brings more moisture in than a whole wall's worth of vapor diffusion through standard interior latex paint on wallboard, and a dozen houses worth of vapor diffusion through 4 mil polyethylene. If it's humid enough ice is forming on the surface you either have a big air leak, or bulk water is getting in there via some path. There is NO WAY it can get that wet via vapor diffusion alone.

If the roof above that section is prone to ice dams/icicles there are leakage paths that could occur in winter that never happen in summer. I have a section of wall in the kitchen/pantry that was prone leakage inside the walls once the ice dams reach a certain level,with the water entry point ~18' above the top plate of the wall. Fixing the heat leaks that caused the ice dams fixed the problem.)

Discolored/dirty fiberglass insulation would be a clear sign of air leakage, but it's not all that clear in the picture.

What type of siding/cladding is there on that sheathing? Back-ventilated goods such as vinyl siding offer a substantial amount of drying capacity toward the exterior in winter, which lowers the risk. Brick veneers store significant amounts of dew & rain moisture, and on sun-exposed sections of walls suffer ultra-high humidity drives toward the sheathing from the exterior when the sun is heating up that brick (year-round.)

If the cavity wasn't fully insulated, (even a half-inch gap between the batt and bottom plate at the bottom) could make the baseboard itself cold enough to take on adsorb and get moldy in the winter. This is more likely to happen in a closet, which runs cooler than the main room- even empty partition walls with wallboard on both sides runs about R4, insulating the closet from the fully heated conditioned space. But that wouldn't explain skim ice on the framing or sheathing in the cavity.