Moisture Condensation Problem

[boze]

Condensation is draining down the walls in an automobile 4 car garage.
Construction is recent. High quality concrete construction wall and flat roof. Ceiling is insulated and covered with panels. Very tight construction, including doors, restricts natural air changes.

First consideration is to drill two openings in the garage walls, with a fan to promote forced air changes. Air changes per hour will be a wild initial estimate of 2-4 ACH. The cost to operate a fan, possibly continuous, is attacking the symptoms, not the problem. Louvered doors is not accepted at this point.

The second consideration is to remove the insulation, because it could be the primary sink for moisture to accumulate only when a warm car enters the enclosed space.
The moisture (with insulation in place) could then migrate to the horizontal walls, and then move down the bare interior walls. Source and causes would then be easier to evaluate.

Perhaps the most serious problem is to reduce the threat of mold accumulation over time.

I have reviewed the 2009 ASHRAE Fundamentals, and related sources. I understand that typical calculations, without a heat source (other than a car entering), or stack effect are difficult, and may require extensive analysis. I am assisting the Structural Engineer for determining a HVAC solution.

Typical winter conditions - Western Oregon

Comments, opinions, and suggestions will be appreciated.

 

[ChrisConley]

Is the condensation occurring during winter only?

What are the moisture sources?

What is the actual wall construction? Where is the vapor barrier?

I don't recommend removing the insulation from the walls unless you also plan to stop heating the building as well. A more expensive option would be to increase insulation levels.

Using a ventilation fan isn't attacking the symptoms only. The problem is that warm moist air condenses on cold surfaces and you are in cold climate. Ventilation (in winter) reduces the moisture level in the space and prevents condensation. Ventilating to prevent condensation is a legitimate solution,

 

[IRstuff]

Is the insulation even installed correctly? There's supposed to be a vapor barrier inboard of the outer layer of insulation that's supposed to keep moisture from reaching any cold surface with any degree of heat capacity.


TTFN

FAQ731-376

 

[boze]

The garage was constructed during the summer,and condensation was first noticed within the past month.

Observed condensation is at the ceiling to wall interface and working down the wall.
Only the ceiling is insulated, and I have contacted the supplier for specific data and installation instructions, including the permeability of the ceiling panels.

The only heat and moisture source, (very minor of course) would be when a warm and wet car is driven into the garage.
Because the garage is literally a closed dead air capsule, these minor inputs from the car could be the sole contributor, and have significance due to the airtight enclosure.

The 12" concrete floor has a vapor barrier, and I have requested information on the exterior waterproof sealing.

Granted that the moisture and heat source are relatively minor, but I looked very closely at the door sealing, and determined there was no crack to allow infiltration with this new construction.

Thank you for your input.

 

[IRstuff]

But, is the moisture coming through the interface from the roof above the ceiling? What's above the ceiling, and how is the air getting up there? Has anyone actuall gone up into the rafters?

TTFN

FAQ731-376

 

[willard3]

First thing to do is insulate the walls and install a good vapor barrier. The insulation can be on the outside of the masonry walls.

If the walls/ceiling are approx the same temp, you can treat the condensation problem with ventilation.

 

[msquared48]

If the garage is sealed with little air flow and it would be hard to vent, what about installing one or two de-humidifiers?

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[boze]

Thanks to all for their input.
Contractor will provide cross ventilation, and a fan with a timer for night operation.

At this time, having no data on the amount of condensate, I have suggested a 2-4 ACH, as a best guess.

I have also suggested as an alternative, to install a dehumidifier and drain line (which would provide data to determine the moisture collection rate).

 

[317069]

"The garage was constructed during the summer,and condensation was first noticed within the past month.

Observed condensation is at the ceiling to wall interface and working down the wall."

I wounder if the problem is not HVAC problem, it may be construction problem (water penetration, especially the area you are talking about is an ideal area for penetration), last month I guess it was some rain, it may be the souce of the problem.

Also I guess that the garage has been built after getting a building permit from the City, and there is a code regulats the ventilation level requirment for this type of building, this level is enough to prevent any problem related to the ventilation subject.
condensation happen when the wall surface temperature is less that the dew point of the space, so any air touch this surface will condensate regardless the air amout,
the solution is to play with the dew point temp.
when you incease the ACH that could lead to decrease the space temperature.
I think the construction need to be reviwed especially in the ceilling wall interface area

 

[willard3]

Dehumidifiers are ideal for producing legionella if they collect and store condensate.

 

[msquared48]

That's why the drain line...

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[msquared48]

... But I see what you're getting at if you want to measure the condensate. That would pose a problem, unless a pre-determined amount of bleach or some other chemical was placed in the storage container each time the level was checked.

Getting complicated here...

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask