Frost inside attic

How would you guys write this with frost in the attic? Frost

We’re you able to identify the source of the warm moist air?

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Is there adequate attic vents? Ever see attic vents closed for the winter, when they are needed most?

Then look for the source of indoor air below entering the attic. Bath vents, ceiling electrical, walls open at the top plate, leaking attic access…

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I’m in Minnesota and it was -26 F. this morning in my area. Many, if not most attics will have some frost in these conditions. Your area may be different.

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Insufficient insulation with heat escaping from house to attic and cold cold air produce frost.


And likely excessive air gaps between house and attic as well.

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Yes, that goes with it, as well as bath fan, etc…any warm air, Shane. Good thought!


Thanks for all the information. It was -3 today here. I will add this information into the report.
Hope everyone has an awesome day!


When you get up in the attic and preferably away from the light from the access area, shut your flashlight off. Look for light at the lower edge of the roof and at the ridge. Gable end vents are acceptable but not always adequate.
That will tell a lot.

Frost & ice can form in attics when warm, humid air accumulates and condenses on the underside of the roof sheathing.
The sheathing looks stable. When a little bit of frost forms, as in your image, this can occur after really low nighttime temperatures. By the looks of the plywood sheathing, it does not appear to be a big concern. The frost, a phase change from water vapor, a gas, to ice will likely melt, then evaporate so that the wood can dry.
The lumber looks clean.

Observation: Thin lay of Frost covering various areas of the roof plywood roof deck sheathing and fasteners.
Unable to observe daylight at the eaves.
Suspect: Insufficient attic ventilation.
Insufficient insulation. Uneven blanket.

Recommend: A licensed insulation contractor install additional insulation to meet the climate zone you are in to improve overall occupant comfort and decrease energy consumption.
Recommend: A licensed ventilation contractor adequately ventilate the attic.

Any icicles at the eave?

I would not even discuss it considering the conditions are indicative for your geographic region.

It is not a defect when it is expected to occur.

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Morning, David. I hope this posts find you well.

I concur. I have come across this situation on a few occasions. The sheathing exposes how many times the wood saturated.

Keep well.

That is very true! Water intrusion evidence never goes away and can always be evaluated by an inspector (unless the attic it painted over). If someone paints an attic you know I’m going to find out why!


Thank you for the information. I didn’t see any ice. This is the first time in our area we’ve have seen temps this low in 33 years. The roof had about 6 inches of snow on.
I haven’t seen this before during the winter. I just inspected a home(today) that was 10 years old with the same thing. It looks like we’re not adding enough insulation for this kind of cold.(wind chill was -25 with a temp of -4) I will make a note to my client.
Thanks for everyone’s comments, I appreciate it.

How Much Insulation Do I Need in my Home is not determined by you.

3.9. Attic, Insulation & Ventilation
IV. The inspector is not required to:

  1. enter the attic or any unfinished spaces that are not readily accessible, or where entry could cause damage or, in the inspector’s opinion, pose a safety hazard.
  2. move, touch or disturb insulation.
  3. move, touch or disturb vapor retarders.
  4. break or otherwise damage the surface finish or weather seal on or around access panels or covers.
  5. identify the composition or R-value of insulation material.
  6. activate thermostatically operated fans.
  7. determine the types of materials used in insulation or wrapping of pipes, ducts, jackets, boilers or wiring.
  8. determine the adequacy of ventilation.

Saying less is more in many cases. Do not wade into waters that you are unfamiliar with. The undercurrents can pull you out to sea leaving you at the whims of predators.
That is not to say do not study on everything involved but, know when to say less. KISS. Keep It Simple Student.
PS: We all are students and at the same level.

I would note the occurrence of frost during you inspection and recommend monitoring the attic during above average cold days. I bring sensitive measurement equipment with me like hygrometers or HVAC temperature relative humidity meters and measure exterior and interior spaces continuously. Once there is an anomaly in any level, readings are photographed and placed in reports.

Good luck.
Robert Young