Why is it Raining in my attic!?

A few years ago I was called out to inspect a rural New Glarus home. This was a nice sized ranch home with a new roof. The homeowner said the roof had been replaced within a few years. Now, this was a bitterly cold December day. As I always do, I start on the outside checking the lots and grounds, then the exterior, then the roof. There was no snow on the roof so I was able to walk the roof, and as they stated, the roof looked fine (from the exterior at least). This is where this one got interesting…

When I enter the home I like to start from the top and work my way down. So I grabbed my step ladder and opened the attic access. Once I got into the attic, I started to get wet, I looked up and the plywood sheathing was completely soaked with heavy water droplets everywhere. My first thought was a ventilation issue, but the roofer on this job did a good job with the ventilation.

When I looked at the plywood sheathing I noticed there was an antimicrobial treatment done, which would indicate that there was a mold problem in the past, upon further investigation I found advanced deterioration of the plywood. I kind of swallowed hard after that as I already walked the roof… The last part of my investigation was the insulation at the attic floor. Ahhh, there’s the culprit I thought. As I made my way through the attic I found that there was only an average of about 3 inches of insulation.

In southern Wisconsin’s climate one of the most important parts of a healthy home is the condition and construction of the attic. To prevent heat buildup, condensation problems, and extremely high energy costs the attic must incorporate a few things.

  • Proper ventilation
  • Adequate insulation
  • Adequate Air barrier/Air sealing

In many cases cellulose insulation is an effective air barrier, But this must be done in a manner that seals off any place that indoor air may escape. So a minimum depth is necessary. More insulation and/or sealant may be required at penetrations to prevent warm air from entering the attic during winter months. In the diagram below you can see some common areas that air leakage happens. This air leakage always causes condensation damage during cold weather.

As you can see, there are many areas that produce air leakage. The most common issues I come across is at the attic access point and bathroom ventilation fans. Any ventilation or heating duct in the attic also must be either insulated or buried beneath blown in insulation. Below are two diagrams that show proper attic access insulation and air sealing.

To continue the story, that 2+ year old roof had to be mostly replaced since the roof sheathing was so deteriorated. I heard that when the original re-roof was completed, the roofing company quoted a new roof, re-designed ventilation, AND updating of the insulation levels. In this case, the homeowner said: “Nope, I only want a new roof!”

Sometimes, an independent third party can be called in when a rehab is being quoted to verify a quote is legitimate and it is not an unscrupulous contractor trying to take advantage of an unsuspecting homeowner. Attic air sealing, ventilation, and insulation have a direct impact on the comfort of the home, so trying to save a buck in this department is generally a mistake.

If you have questions or concerns about your attic condition, ventilation, or insulation condition, I can perform an attic-only inspection with thermal imaging to show you any deficiencies and a correct course of action to make your home more comfortable (click here). This is one of my most reported on defects when I am called upon to perform home inspections as it is so important to a healthy home. But I digress…

As always, I hope you took some value from this post and if you have any home related questions, please let me know at the email address below.



Aaron M. Zuehlke is the owner and inspector at Zuehlke Inspection Service, LLC, a full-service home inspection company serving Southern Wisconsin. Specializing in Home inspection, Radon Testing, Mold Testing/inspection, Well Inspections/Well Water Testing, Residential Thermal Imaging, and Manufactured Home Foundation Certifications. He also manages several rental properties through Zuehlke Properties, LLC. He can be reached by email at Aaron@Zuehlkeinspections.com or by calling the office at 608-931-7485.

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