Could frost on soffit vent cause mold inside room?

[weatherby460]

I'm getting some mold on the shingles and I'm seeing water spots on the inside edge of the north side of this 4 season room. On the south side of this room no water spots or mold, but I found frost on the soffits, and I think it's from the furnace vent. Could that be my issue? If so, any ways to fix it? Unfortunately no access point to this room. I may have to make one this spring. I had a insulation guy over to look at it. He said he can see batts of insulation from the main portion of the house in that room, but he cant get close enough to see what the issue is because of a vaulted ceiling on the main part of the house not allowing access. The wall inside is made of cedar sheets. Thanks for any help.

 

[JRC3]

Without pics??? But if the furnace vents below a vented soffit the moisture certainly could stack up into the soffit, and from there anywhere in the attic space and other soffits. Just curious how the roof is vented?


https://inspectapedia.com/chimneys/Gas-Heater-Direct-Vent-Clearances.php

 

[weatherby460]

Here are pics.

 

[weatherby460]

The room is only 14'x14'.

 

[yeldogt]

The vents in the soffits can allow moisture to enter the roof cavity.

It's more common than you think ... it way I don't like them. In many areas of the country it occurs each morning as the sun warms a building ---- the dew off the grass enters the building s the heated air goes up.

My guess is you are seeing it because the colder temps are having the heater run more and any quiet wind day allows the moisture to enter the building.

it will dry out

 

[JRC3]

I certainly would suspect it being vented in the corner like that. I think you need at least 36".

Also the moisture could be coming from another source, the roof. What do you know about it? Was the room a recent addition? How about the roof, is there ice guard up there? If moisture is up there the heat from the furnace vent might be pulling it out of the soffit vent as it rises past. For that matter as that happens it could be pulling air out of the attic space...If that's happening the negative pressure could pull air from elsewhere...Causing condensation as the new cold air enters and warms up.

I would bet $20 that furnace vent in the corner is the culprit, no matter what. I would bet it needs vented along the wall and up past the eaves.

 

[JRC3]

Not to mention your vent is right below a window, a big no go.

 

[weatherby460]

Any idea what the best way to fix it would be?

 

[wrenchguy]

4 seasons room heated? 4 season's room no insulation in attic? If not i'd say the attic is all frosted up. The vents are telltale showing frost wicking out. You got issues with the south and north exposures warming and not warming the attic area. Take the ceiling down.

 

[JRC3]

^Nah, not that extreme, did you look at the pics of the venting?

Any idea what the best way to fix it would be?

You might get away with a little extending on that exhaust side of the concentric...Then rotate the top 90 degree PVC fitting 45 degrees away from the corner. Kinda like the pic.

Best bet is probably to periscope it up past the eave like a typical radon exhaust.


Some real HVAC guy should be along at some point to offer better advice.


Or go over to the terrylove forum, those guys are always eager to help too. https://terrylove.com/forums/index.php?forums/hvac-heating-cooling.13/

 

[wrenchguy]

Yep, its showing moisture coming out result of north wind. My guess is thats a captured 14x14 attic. 2me brickwork shows its a addition, its got its own climate in there.

 

[JRC3]

Yep, its showing moisture coming out result of north wind. My guess is thats a captured 14x14 attic. 2me brickwork shows its a addition, its got its own climate in there.

The exhaust rising and flowing past the soffit could pull air out, and/or rise into the soffit. I'd suspect there is more then one problem here. No matter what that exhaust is not correct for several reasons and would be the first thing I'd correct.

 

[mobetta]

I concur that it appears to be an issue resulting from the location of the furnace vent termination.

Where is the mech room? is it feasible to relocate the venting? maybe even to the other side of the Compressor?

I'd think that if you added more pipe you run a risk of the condensation icing up the vent pipe??

 

[Denwood]

Yep, that sure looks like furnace vent moisture ending up as frost on the upper wall area via the soffit vent, then melting there and causing the issue inside.

It looks like you have a ridge vent, so you may be able to just close off the soffit vents on the frosty side and let the other side of the eaves manage venting by doubling the vent openings there. You likely can't extend the furnace vent another eight feet, but I'd look into your options to see if you can exit the sun room wall via routing it via crawl space/basement.

Having the vent firing towards those stairs likely doesn't help much with icing!

 

[Showkey]

It’s going to be near 40* this week........the “problem” will go away.

 

[weatherby460]

UPDATE...HVAC guys said the furnace exhaust is the problem. They want to cap the existing, but leave the cold are return. Then run a new exhaust only 3" pipe to the other side of the house. Any issues having cold air in and exhaust on opposite sides of the house?

 

[iced98lx]

UPDATE...HVAC guys said the furnace exhaust is the problem. They want to cap the existing, but leave the cold are return. Then run a new exhaust only 3" pipe to the other side of the house. Any issues having cold air in and exhaust on opposite sides of the house?

No but make sure the run is within spec to the manual on the unit length wise, there is of course a maximum that it can be run and specs to keep the sealed combustion chamber "In balance".

do you have any attic access to the porch? if so, take a look and see if there is a bunch of frost up there regularly, make sure that once that is moved it dries out via existing venting and stays that way or you're only prolonging the time until the ceiling comes down and venting gets fixed imo.

 

[ant.foste]

UPDATE...HVAC guys said the furnace exhaust is the problem.

100% agree! That current exhaust is in a completely dead air space when the condenser unit isn't running (fan moving air).

They want to cap the existing, but leave the cold are return. Then run a new exhaust only 3" pipe to the other side of the house. Any issues having cold air in and exhaust on opposite sides of the house?

No problem at all as long as they stick to manufacturers guidance, industry best practice, and code regarding the new exhaust run.