Insulation, Radiant and Vapor Barriers - Very Cold Bathroom

I have a Master bathroom in the North/East corner on the second floor. The ceiling has 3 highhats, an exhaust fan and a duct for the A/C. This bathroom is always colder than the rest of the rooms on the 2nd floor (feels like a 10 degree drop).

I climbed up in the attic a few weeks ago and found that one of the highhats had the insulation pushed aside, so some of the sheetrock is exposed to the attic. That particular highat is roughly 3 feet away from the soffit vent from the front of the house (North/East side). Also, there are some slight gaps between the highhats/ducts and the sheetrock cutout area. While in the bathroom, I lit a match, blew it out and saw the smoke drift up through the rim of the highhat.

Would these gaps alone be the cause of the coldness in the bathroom ? What should I use to seal the gaps ?
What else should I look for ?

Thanks,
Scott

http://www.neo.state.ne.us/home_const/details/rcld.htm

What is occurring in your bathroom is referred to as the "Attic Bypass Phemomena". The above site shows a diagram to resolve your problem. Please note; the canister is "IC" rated.

resercon,

Thank you for your response.
From what I gather, these leaks in the ceiling need to be sealed with proper attention to the canisters. I'm also guessing that the plumbing vents that run through the attic aren't sealed either. Didn't realize that this would create such a significant drop in temperature.

Thanks again,
Scott

You are correct about sealing around your vent stack too. The thing to remember here is that the volume of air remains constant within a confined space, like your house or a bathroom in this situation. The natural bouyancy of warm air will cause the heated air in the bathroom to go through these canisters. Since the volume of air remains constant in the bathroom, the same volume of heated air that goes through the canister into your attic is equal to the volume of cold air in the attic that will go into the bathroom. that is because cold air is heavier than warm air and it has the characteristic of falling. Unlike a convective loop, in this situation the cold air in the attic is merely replacing the amount of air leaving the bathroom. This would explain the huge temperature differences between the bathroom and the rest of the house.

Well, I was up there a few days ago to check on the canisters and it appears that the canister that is toughest to reach is non-IC rated and the canister I have easier access to is IC rated (go figure).

I didn't see any IC marking on the can itself. Is it safe to say that the canister that has holes in it is not IC rated ? and the canister without holes is IC rated ? I believe I read that somewhere.

Thanks again,
Scott

The slots that you see in non-rated "IC" canisters are there to allow heat to dissipate from the canister when the light is on. However, not all non-rated "IC" canisters have slots in them. If you cannot determine if the canister is rated "IC", I would strongly recommend you treat them as a non-rated "IC" canister.

I'm going to treat all of them as non-ic rated canisters. Better to be safe.

Thanks again,
Scott