Frost on plywood board in attic

need help…!
i went up to my attic, and found there were lots of ice sheets (frost) formed and attached on the plywood board. And there was some water formed and dripping down into my bedrooms.

And I have a fairly new roof (2008), and there was no sign for the damage of shingles… I just cannot figure out solutions for this driving-me-crazy problem.

is there anyone here who can give me some suggestions?

Thank you very much.

Toronto, Canada

It can be one, or a combination of several things.

Inadequate ventilation.
Not enough insulation.
washroom/kitchen fans not properly vented etc.

Please provide more details, we have been getting several calls lately with leaks and most are a result of one or more of what is listed above.

What tump line said. Ditto.

I wrote this for my customers to explain ice damns and so forth, but it applies to frost and condensation just as much. … daming.htm

Some general advice which may be of help…
Make sure to run your kitchen fan when cooking, especially boiling water. make sure to run your attic fans when ever taking a bath or shower, and allow the fans to run for at least 20 minutes upon completion of the shower. Make sure these fans are vented to the outside and not just into the attic.

Check your humidifiers and consider turning them down to a lower, yet still comfortable level. One customer of mine was running 3 humidifiers in her 2nd floor and couldn’t figure out why she was having condensation issues. It was like a rain forest in her house.

Heating furnaces in the attic may also cause condensation due to their heat output. Hot air carrier moisture, and attics with heaters always require additional ventilation.

Make sure your insulation does not block your overhangs, assuming you have overhangs with an intake ventilation. Also make sure if you have aluminum of vinyl soffit panels that thewood soffit beneath the panels has been cut to allow air to flow into the attic space.

make sure you have adequate insulation. Older homes in my area were often built with an R value of 6-8, where current new construction code is often an R 48.

Make sure if you have an attic fan that the attic fan has a humidistat. The humidistat will turn the fan on when humidity gets high, even if it is winter. You may also consider a solar powered attic fan that works all day every day, but not at night.

Make sure you don’t have common ventilation problems like ridge vent mixed with a fan which causes more harm than good.

We are seeing a lot of this this year. It has usually been caused by an exhaust fan venting into the attic. Once we vent them through the roof, it fixes the problem. The thing that is baffling me is why am I seeing more this year? Most of the homes I am seeing it in are over 20 years old and the roofs are 5+ years old. Why is it a problem this year and not in years past?

South side we have been more than the usual amount of calls this year as well and I think it may be the weather pattern we have been going through.
Very little snow here in the toronto area,cold nights and a lack of insulation/ventilation etc result in a build up frost to form on the plywood.
Temps rise during the day and nice sunny conditions warm the shingles which melts the frost that has accumulated.

man the money spent to live in that snow.
i think we should all live around the equater
and just chill like tarzan and jane. mite cost 10 bucks a day.
and leave those real cold places for like distant american outposts.