Humidity Gone Rogue

Frozen attic condensation can cause a frost like appearance on the inside of your attic

Rogue : a deceitful and unreliable scoundrel.

Seems funny to apply the word “rogue” to humidity. But during midwest winters it fits. Here’s why:

Every winter is bound to have a couple days to a couple weeks of below zero weather. When temperatures start to rise, homeowners start to notice brown spots on their ceiling that resemble roof leaks. This could be a sign of a roof leak; it could also be a sign that the home’s humidity was too high during the cold temperatures- causing attic condensation to freeze.

Furnace humidifiers are often forgotten to be adjusted during winters and create too much humidity. This moisture freezes when it hits your attic
Furnace humidifiers are often forgotten to be adjusted during winters and create too much humidity. This moisture freezes when it hits your attic

Many homes have humidifiers on their furnaces. Almost all new homes have this or homes with real wood floors. It’s a great thing to have, but homeowners need to be mindful of appropriate humidity levels. If the humidity is set higher than it should be during negative temperatures, the moisture rises up to the attic and before it can escape, it hits the bottom of the snow covered roof and freezes. Sometimes icicles even form off the nails! Once the weather warms up and one of the first things to thaw is attic condensation. Depending on high the humidity has been set on your house, this can be a decent amount of moisture coming down – thus causing brown spots on ceilings. It looks identical to spots from roof leaks.

What is the appropriate level of humidity for your home?

If the outside weather is…

  • 20 to 40 degrees, humidity should be less than 40%
  • 10 to 20 degrees, humidity should be less than 35%
  • 0 to 10 degrees, humidity should be less than 30%
  • -10 to 0 degrees, humidity should be less than 25%
  • -20 to -10 degrees, humidity should be less than 20%
  • below -20 degrees, humidity should be less than 15%

This will prevent attic condensation, mold, or any other issues caused by overly humid and warm air.

What about you?

These guidelines are the optimal levels to make your home comfortable, but what about the people living in it? Dryer air is not always the best for us to live in but there are ways to keep both you happy and your home comfortable. Instead of using whole house humidifiers use individual ones when you are using the room. Use programmable timers to turn on and off humidifiers. Buy indoor humidity sensors – these range from $5-$50. Click here to see the “indoor hygrometers” on


It’s so easy to forget to monitor or change your humidity. Many people don’t even realize this is what’s going on until it’s too late – brown spots appear! If this happens to you, don’t  panic but it’s still good practice to have a trusted roofer inspect to confirm no roof leaks.


It’s that time of year…

As we all anxiously anticipate Spring, ideas for home improvement and thoughts on home repairs come rolling through our head. A good place to start knowing what and who is available to you is at your local home show.

Our booth at the Bloomington Normal Area Home Show
Our booth at the Bloomington Normal Area Home Show

If your roof showed it’s age this winter with all the ice and snow, a new roof is probably first on your list of home repairs. A new roof is a considerable investment to any home and if installed correctly will improve its value. Many contractors try to cut corners on roofs and will tell you things that what’s skipped is not a necessity. Caleb Gee, Roofing Project Manager of Carlson Exteriors Inc., built a great demo to inform homeowners what is essential to your roof.

Roof Anatomy
Roof Anatomy- Click to Enlarge

When you begin roofing, it’s important to lay down Ice and Water at all valleys and at the rake of the roof (like pictured here). Ice and Water is a thermoplastic, which means as it gets warm it will seal around any nail holes or protrusions; preventing melting ice dams from leaking down to the roof deck. It’s good practice to lay this under the metal Drip Edge on the slant edges of the roof but on top of the Drip Edge at the eaves- in case a strong wind would push rain under the shingles exposing the Drip Edge, the roof deck will still be protected by the Ice and Water.  Once the Ice and water has been laid down, roll out the Synthetic Felt over the rest of the exposed roof deck with a 6 inch overlap with the Ice and Water. After the Drip Edge has been nailed in, lay Starter Strip not only on the base of the roof but along the whole perimeter of the roof.  Starter Strip has a line of tar to seal with the shingles that are laid on top of it. Using Starter Strip on the sides will seal the shingles down on the edge,the most prevalent spot for wind to pull up the shingle tabs. Now it’s time for the shingles! Work your way up all the way across the bottom and then upwards. When starting the next row of shingles, make sure the shingle edges from the first row are a full tab separate from the next row. This is important to control water flow by preventing it from getting under shingles to the deck.

Air shoots in attic
Air shoots in attic

It’s important not to skip on air shoots in the attic to ensure proper air flow from the intake vents at the soffit up to the exhaust at the ridge vent. Ridge vents are a popular choice when it comes to roof ventilation but make sure enough of it is installed for you net free area within your attic space, or, explore other venting options (read our previous post about proper roof ventilation to learn more)