Hi,

I have a customer who recently had condensation on an interior wall of an unheated detached garage.  We replaced her roof last fall.  We installed 6t of ice shield along the eaves, exceeding code of 24 inches past the interior wall.  We covered the entire surface with a superior synthetic underlayment.  We cut the ridge and installed ridge vent.  The structure was up and over.  

We are a contractor in Michigan.  We have experienced extreme weather conditions this season.  It was below zero for several days in a row and then up to 40 degrees.  

The customer has a portable gas heater but says they did not heat it prior to the condensation build up.  They do wood working in this space.  There is no attic space.  It is open.  They have insulation stapled between the rafters.  I believe the garage is built on a slab.

can anyone tell what the cause of this is?  

Thanks,

Pam

Views: 435

Reply to This

Replies to This Discussion

I agree with previous comments that the primary sources of moisture are the un-vented space heater and the slab.  But there could be additional sources.  It is not clear if this space is primarily a wood shop or a garage.  A wood shop could have a lot of wood that is not dried down yet and a garage could have piles of snirt.  Snirt is a Minnesota term for the combination of snow, dirt and salt that collects around the tires.  Whenever you get a warm spell you get puddles of water on the floor.  Also, extended cold spells create lots of frost on roof decks and sudden warm spells melt all of the frost and ice buildup, wetting other surfaces.  I would suggest moving the thermal boundary to the flat ceiling, sheet rocking the ceiling, add soffit vents and install a vented heater.

For condensation you need one simple condition. A surface below the dew point. There are lots of reasons, this isn't the exterior surfaces. They mostly boil down to paper surfaces and sun heating the exterior.

Increasing the ventilation will reduce this situation. HVAC engineer fix that problem with sensible reheating, which means heat with no moisture.  The gas heater is unvented combustion, which means the gas and O2, becomes CO2 and water vapor. That water vapor could be condensing on a cold surface.This building lacks a reasonable moisture barrier due to sloppy, unfinished construction and installation of insulation.

If the heater isn't the source then the slab is the most likely source.  If it is the Slab, there are a few means to reduce it. Keep the water away by gravity. Gutters, slop grading away from structure, drains. Now that moisture is away from the slab, stop it coming through the slab with an epoxy coating.  You want some permeability, just less than the raw concrete.  

Ridge vent is 4 steps beyond the construction you have pictures. If there is no propervent / ventchutes allowing air to move under the roof decking, then you shouldn't have a ridge vent. They have a HotRoof. This means that the shingles are installed on an insulated surface.  This robs a few years off the life of the shingles. If I have to take care of this building, I install an exhaust fan, at least 0.5 cfm per square foot of garage floor. Then control it with a line voltage humidistat. 

Do not be fooled it is very common problem for cast iron wood working equipment to sweat and rust if keep in  a unheated garages when the weather changes quickly from cold to warm and damp.

Now wet drywall is very strange. To me drywall does not have enough thermal mass to stay below the dew point long enough to get very wet.

I would like to see photos of the wall damage.

I guess the lesson to be learned is if it works don’t change the can vents.

Walta

RSS

Latest Activity

Brett Little posted events
14 hours ago
Ben Thompson replied to Stuart Perkin's discussion TrueFlow in the group Energy Auditing Equipment for Sale, Trade or to Purchase
"Hi Stephen. Do you still have a Trueflow that you would sell? Ben Thompson,…"
yesterday
Ben Thompson replied to Landon's discussion WANTED: Blower door complete set Retrotec or Minneapolis in the group Energy Auditing Equipment for Sale, Trade or to Purchase
"Hi Landon. I have a Minneapolis blower door set-up that I would like to sell. It's in…"
yesterday
Ben Thompson added a discussion to the group Energy Auditing Equipment for Sale, Trade or to Purchase
Thumbnail

Wanted: TrueFlow plate

Seeking an Energy Conservatory TrueFlow plate (grid) in good condition. Ben Thompson.…See More
yesterday
Scott Partlo replied to Jerry Needham's discussion Closed cell on roof deck to prevent mold.
"You say that 2" of closed cell foam is applied OVER the roof deck.  Where exactly was the…"
yesterday
ayazfudugo1 replied to Tom Smith's discussion Are Energy Efficient Windows worth the investment?
"For both new and existing homes, Energy efficient windows are an important consideration Heat…"
yesterday
Profile IconTodd Williams and Haley Keegan joined Diane Chojnowski's group
Thumbnail

Hall of Shame

In this group, members share an array of images from the field, showing the kinds of issues…See More
Friday
Todd Williams liked Diane Chojnowski's group Hall of Shame
Friday
Home Energy Magazine posted a blog post
Thursday
Leona Zoey posted a blog post

Landlords Are Your Friends

While it may be easy to forget given their apparent position of power over you, landlords usually…See More
Thursday
Haley Keegan joined Building Performance Institute's group
Thumbnail

Building Performance Institute (BPI)

BPI is the nation's premier standards development, quality assurance and credentialing organization…See More
Thursday
Donald Hester replied to Jerry Needham's discussion Closed cell on roof deck to prevent mold.
"For the roof shingle issue that is an unfortunate issue with many home inspectors that have been…"
Thursday
Profile IconJason Green, Dennis Smith, Alex Ortega and 2 more joined Home Energy Pros Forum
Thursday
tedkidd replied to Quinn Korzeniecki's discussion BPI CEO Larry Zarker's Review of "The Home Comfort Book" in Healthy Indoors Magazine in the group Building Performance Institute (BPI)
"...free chapters of book available here - http://bit.ly/HPchapterlist"
Thursday
tedkidd liked Quinn Korzeniecki's discussion BPI CEO Larry Zarker's Review of "The Home Comfort Book" in Healthy Indoors Magazine
Thursday
William Collins's video was featured

Foam Kits vs. Spray Sealants Gun

How does the Foam Kit stack up to the Spray Sealants Gun when it comes to simplicity? When you integrate the Spray Sealants Gun to a 16lb Canister, you creat...
Thursday
Scott Becnel added a discussion to the group Energy Auditing Equipment for Sale, Trade or to Purchase
Thumbnail

Brand new DucTester at a discount

Brand new DucTester at a discountI have a brand new 300 DucTester system from Retrotec for sale at…See More
Wednesday
Scott Becnel joined allen p tanner's group
Thumbnail

Energy Auditing Equipment for Sale, Trade or to Purchase

Discuss the pros and cons of the equipment you are interested in prior to purchase. Post equipment…See More
Wednesday
Lucyna de Barbaro liked Home Energy Magazine's blog post AeroBarrier: The Silver Bullet to Zero Energy Affordability, by Paul Springer
Wednesday

Photos

  • Add Photos
  • View All

© 2018   Created by Home Performance Coalition (HPC)   Powered by

Badges  |  Report an Issue  |  Terms of Service