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Originally Posted by 21boat

No need to vapor up over the joist just between The 'baffle" thing As long as you have a min of 2" open space in the bay of the roof rafter and the 2 form side to side rafter your perfect for airflow The baffle is to insure that no insul or blown insul is plugging that air passage from soffit up under the roof sheeting bay. you mentioned way back you were going to get the loose insul blown in I would use the baffle to ensure the venting gap doesn't get clogged and hopefully the wont force loose into inside soffit bay. The baffels are a bit deeper for air flow but its not full with from rafter and the depth accounts fo that.

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Regarding vapour barrier: good to know... that I just have to staple it to the floor or just the bottom edge of joist. (should I staple or tape - tuck tape it?)

As for the baffles: do I need a baffle per rafter? The rafters are about 24" apart..some are 2x6" some (on a smaller section of roof)... are 2"4's...
See photo... at the moment, there seems to be adequate air flow...
As you say, how could I ensure that no insulation gets blown into the soffits (that I have cleared)... they had BATTS laying in them. Should I remove them all to give complete air flow?

Yes staple vapor to bottom inside of joist and tape it if you can. Yes baffle per truss bay. In the summer it gets hot and humid this is when you really need the air flow and move the air and vent through roof vents. Also so attic balances static pressure and air keeps flowing.
Evenly.
If a little blown insul touches the baffle no bigger. A speck or two in soffit trough no bigger
Old days just gable vents.
Then plywood soffits with drilled holes and screens.
Now modern soffit with venting. The more air flow you can get the better it is. All bays baffel

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Originally Posted by 21boat

YES great install the way you drew it.
Brush away, barrier,, the re blown

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There are also some gaps (about 1 - 1 1/2 " wide)...in the floor of the attic...where the vent stack comes up, where I added the bathroom fan, the fixtures, etc...

HOw (must they be sealed?) can I seal these gaps? Can I use a material called "GREAT STUFF" to seal these gaps? Will this prevent hot air from coming up into the attic?

Does this stuff work to seal these gaps? Or can I seal the gaps using something else? Thanks

Yes "stuff works fine to seal around gaps. It expands quick so start slow. Its like welding point the tip slightly against the inside hole edge and work it around

21 Boat

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Originally Posted by 21boat

yes "stuff works fine to seal around gaps. It expands quick so start slow. Its like welding point the tip slightly against the inside hole edge and work it around

21 Boat

If I Helped to Answer Your Question Please Rate My Answer

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... how do mean "like welding"... could you give a little more explanation 21boat? Do I stick the nozzle into the crack / gap and squeeze the trigger?.

I have read all this information and have been left with several questions.
Bat insulation with VB is better in density than blown in insulation?
What is the recommended routing of bathroom ceiling exhaust fans? Into soffet, closest vertical wall or roof mounting? I am in Northern Illinois and have been having truss uplift problems and cracking drywall. After inspecting my attic I have noticed icing under the roof deck and excessive moisture in the range of 70-72%. I rerouted the exhaust fans from the soffet as I figured the moisture was coming back into the attic space. 2 years ago I added several inches of blown insulation on top of existing 5-6 inches. I have 3 roof vents over the main roof, and 2 more over the master bedroom (cathedral ceiling). I don't know where to begin now to reduce this moisture in the attic space.

1. Remove blown insulation, add VB(plastic), return blown insulation.
2. Remove blown insulation, add bats w/ VB, add unfaced above this, dispose of blown insulation?
3. Reroute exhaust fans to roof.
4. Add Ridge vents across both roofs?

Thank you

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Originally Posted by PCEKDAS4

I have read all this information and have been left with several questions.
Bat insulation with VB is better in density than blown in insulation?
What is the recommended routing of bathroom ceiling exhaust fans? Into soffet, closest vertical wall or roof mounting? I am in Northern Illinois and have been having truss uplift problems and cracking drywall. After inspecting my attic I have noticed icing under the roof deck and excessive moisture in the range of 70-72%. I rerouted the exhaust fans from the soffet as i figured the moisture was coming back into the attic space. 2 years ago I added several inches of blown insulation on top of existing 5-6 inches. I have 3 roof vents over the main roof, and 2 more over the master bedroom (cathedral ceiling). I dont know where to begin now to reduce this moisture in the attic space.

1. Remove blown insulation, add VB(plastic), return blown insulation.
2. Remove blown insulation, add bats w/ VB, add unfaced above this, dispose of blown insulation?
3. Reroute exhaust fans to roof.
4. Add Ridge vents across both roofs?

Thank you

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Dear PCEK...
A couple of questions...
...
1. do you currently have a VB now on your ceiling? If you do not... how many months (years) have you NOT had one?. this may be the cause of your moisture in your attic...

1a) do you have peforated soffits? Baffles to allow air to come in? Are your soffits clocked with insulation (blown or batts)?

2. I wouldn't add BATS w/ VB as it may be difficult to cover all the empty floor spaces of your ceiling / drywall...

3. the soffit vent that I have sends the moisture to the outside... I cut a hole in the soffit and mounted the vent to the soffit with screws... there is a spring loaded trap which prevents air from coming back into the vent... I do not think that warm air is being brought back into the attic from the outside.

4. From what I have read: 1 sq foot of venting for every 300 sq feet of floor space (with a VB)... and 1 sq ft of vent for every 150 sq feet of attic floor (without a VB)..

Trying to retro fit a vapor barrier into joists is a waste of time in my humble opinion.

You'll never get it sealed tightly enough to accomplish what you seem to want to accomplish here. Moisture will continue to accumulate on the bottom of the joists and your going to get mold.

ALSO I have read w figure stating a vapor barrier is not needed if your in a region with less than 9000 degree days.

http://lwf.ncdc.noaa.gov/img/documen...ngDD_hires.jpg

All I know is there is apparently insufficient air movement, too much moisture, and damp inefficient insulation in my attic space, which requires some attention.

Now I am confused,.
Can a bathroom exhaust fan be vented through the soffit? (in other words... a hole is cut in the soffit and the warm air is pushed outside through this hole)... will the warm air (that has just been pushed out) be sucked back into the attic by the perforated soffit holes? Thanks

You really get around ;-)

Vent it through the roof.

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Originally Posted by Rivethead

You really get around ;-)

Vent it thru the roof.

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It has already been done... I am now concerned that it was done incorrectly. Will warm air come back into attic? Thanks

It has been vented through the roof? Not much you could do to do it wrong (famous last words). Your concern is...

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Originally Posted by Rivethead

It has been vented thru the roof? Not much you could do to do it wrong (famous last words). Your concern is....

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... no, it is vented through the soffit... but I have heard that since the exhaust fan is an "active" vent and the soffit is a "passive" vent, the warm air should be pushed away and not re-enter the soffit...
What are thoughts on this? Anyone?

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Originally Posted by wilsonfrench

Dear PCEK...
a couple of questions...
...
1. do you currently have a VB now on your ceiling? if you do not...how many months (years) have you NOT had one?...this may be the cause of your moisture in your attic...

There is no vapor barrier currently in place. The home was built in 96 and there has never been one in place.

1a) do you have peforated soffits? baffles to allow air to come in? are your soffits clocked with insulation (blown or batts)?

The soffetts are vented, the original builder blocked the truss spaces at the wall headers with small rolls of bat insulation, only had 3 std roof vents on back side of house. I removed blocking, added styrofoam liners between each truss both sides, when I had the house re roofed in 04. I also left the original roof vents in as an alternative to a ridge vent hoping I would have sufficient airflow. Also have heard ridge vents can let in fine snow in windy area. We are near farmland in far northwestern suberb of chicago, with constant breeze and winds.

2. I wouldn't add BATS w/ VB as it may be difficult to cover all the empty floor spaces of your ceiling / drywall...

Even if i remove all the blown insulation?

3. the soffit vent that I have sends the moisture to the outside...I cut a hole in the soffit and mounted the vent to the soffit with screws....there is a spring loaded trap which prevents air from coming back into the vent...I do not think that warm air is being brought back into the attic from the outside.

Unfortunately in my situation the builder :mad: who couldnt build a tree house correctly dumped the 2nd floor bathroom exhaust directly INTO the soffet.

4. From what I have read: 1 sq foot of venting for every 300 sq feet of floor space (with a VB)...and 1 sq ft of vent for every 150 sq feet of attic floor (without a VB)..

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Attic space is approximately 1300 sq ft. 1/3 of which is a cathedral ceiling over a master bedroom. Both attic spaces are connected. 2 Vents over cathedral area, 3 vents over remaining, which according to above calculations would provide adequate venting for 1500 sq ft.

I just also placed a temperature humidity sensor in the attic for monitoring. The current outside air temperature is 29dg F Indoor humidity is 41%, thanks to an April Air Humidifier with auto controls from outddo air sensor. The attic space is reading 78% Humidity @ 39F :eek::mad::eek:

What do you think?

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Originally Posted by PCEKDAS4

ALSO I have read w figure stating a vapor barrier is not needed if your in a region with less than 9000 degree days.

http://lwf.ncdc.noaa.gov/img/documen...ngDD_hires.jpg

All i know is there is apparently insufficient air movement, too much moisture, and damp inefficient insulation in my attic space, which requires some attention.

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That map is hard to read. I am on Lake Ontario (canadian side)... altough we have cold winters and hot summers, I do not know how to calculate 9000 degree days... what is that, exactly?

As for your situation:

1. try venting the bathroom exhaust outside through roof... if that is not possible, vent it to the soffit, but make sure it comes through the soffit (cut a hole in it) and buy a soffit vent that attaches / affixes to the underside of your soffit.

2. we cannot get faced BATTS in CAnada. We use plastic / poly. I have been informed to use plastic as a vapour barrier on my ceiling (read through entire thread)

3. more vents wouldn't hurt

4. make sure yyour soffits are not plugged with insulation (blown or batts)

Hope this helps/

Quote:

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Originally Posted by PCEKDAS4

Attic space is approximately 1300 sq ft. 1/3 of which is a cathedral ceiling over a master bedroom. Both attic spaces are connected. 2 Vents over cathedral area, 3 vents over remaining, which according to above calculations would provide adequate venting for 1500 sq ft.

I just also placed a temperature humidity sensor in the attic for monitoring. The current outside air temperature is 29dg F Indoor humidity is 41%, thanks to an April Air Humidifier with auto controls from outddo air sensor. The attic space is reading 78% Humidity @ 39F :eek::mad::eek:

What do you think?

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PCEK, from your location (hard to accurately read your map) it looks like you're in the 6500 degree range... so, according to your calculation, you do not need a VB.. but there are very helpful pieces of info in this thread.

I posted what I think you should do to increase ventilation, reduce moisture, etc.

I cannot help you with your humidity questions. Sorry.