insulation in unheated garage soffits?

[gzuckier]

Hi, newbie here. Can't find an answer to this particular weird question. ..
I've got a pretty big garage, it was built for two contractor's trucks so it's 20 feet high at the peak. It's unfinished (studs, no wallboard, no ceiling, and unheated). So it's uninsulated, except that the soffits are stuffed with fiberglass insulation. Under the insulation they are wide open, those plastic soffits fill of holes with no wood or anything blocking the ventilation. The roof has a ridge vent also.
Given that the whole thing is just one big empty space, "attic ventilation" isn't an issue. But could the insulation in the soffits be doing anything at all? I can't see that it's keeping the place warmer at all. I have an urge to take it out, because it's pretty dirty and scraggly looking. I have occasional mice in the garage, but I'm pretty sure they're a lower level problem. No squirrels, I'm pretty sure.
Thanks in advance.

 

[megalo]

Insulation doesn't belong in soffits. In fact, you should install baffles (something like Accuvent) in your rafter bays to keep insulation from sliding down into the soffit and blocking airflow when you insulate the ceiling.

 

[GYPSY400]

^^ agreed.. the idea of vented soffit is to permit air flow from the soffit area, up to the top (ridge vent).. this should be sealed off from the inside as the underside of the roof sheeting should be ambiant outside temperature to prevent condensation ( which rots the sheeting) and ice buildup under the shingles ( which rots the shingles )

this pic shows the louvers used to prevent the insulation from touching the roof sheeting, yet providing airflow.

This is the start of proper attic insulating.. double of whatever you choose for the walls.

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[megalo]

Are those raised heel trusses? I should have done that...

 

[GYPSY400]

Are those raised heel trusses? I should have done that...

Yes they are called scissor trusses.. I gained 2ft in the center.

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[megalo]

Yes they are called scissor trusses.. I gained 2ft in the center.

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Err, I'm looking at the heel of the truss over the top plate - it's not a standard truss. It looks like an energy heel/raised heel. They might just be the standard design up North.

 

[Highbeam]

Megalo is right, a regular scissor truss only means that the bottom chord and top chord are sloped. That raised heel was done for insulation and in the case of a steep roof, to provide clearance for the rafter tails.

 

[TractorJeff]

Probably someone stuffed insulation into the soffits because the wind was blowing in through the vent holes(like it is supposed to).
Which explains why it is dirty and scraggly looking.
My house they did that too.
Previous owner didn't know better is my guess?
I took it out and added more proper insulation and sealed up the leaks from the attic into the living areas.

 

[Tyberius]

This is the start of proper attic insulating.. double of whatever you choose for the walls.

One thing that I like to do is start my vapor barrier at the highest point and work down. In the event of a leak, the water will flow to the wall and down and not damage finished space. I also like to tape all my seams, staple holes and box cutouts.

 

[Chris705]

Gzuckier - as Tractor Jeff above notes I am sure the insulation was put there to stop drafts and perhaps snow from blowing into the garage thru the soffit vents.....with your garage wide open as you describe, I imagine it offers some added comfort not having the wind blow in on cold winter days. That said yes it could be removed and something put back in its place if you don't like the drafts. Possibly you could replace the vented soffit w/ unvented soffit material but I would caution about summer heat buildup. If you have asphalt shingles you may opt to keep the soffit vents w/ the ridge vent. Most unheated garages leak enough air that heating up of the shingles isn't likely to be a problem w/ premature failure.

 

[GYPSY400]

Probably someone stuffed insulation into the soffits because the wind was blowing in through the vent holes(like it is supposed to).
Which explains why it is dirty and scraggly looking.
My house they did that too.
Previous owner didn't know better is my guess?
I took it out and added more proper insulation and sealed up the leaks from the attic into the living areas.

This is true.. mine was windy as heck before the insulation went in.

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[GYPSY400]

Err, I'm looking at the heel of the truss over the top plate - it's not a standard truss. It looks like an energy heel/raised heel. They might just be the standard design up North.

Ahh ok.. they are "engineered" trusses so I guess climate and snow load are factored in.



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[GYPSY400]

One thing that I like to do is start my vapor barrier at the highest point and work down. In the event of a leak, the water will flow to the wall and down and not damage finished space. I also like to tape all my seams, staple holes and box cutouts.

Tomate-o Tomat-o I guess.. my builder finds it easier to start on the eve side as clearance is minimal. Roof leaks are not an issue here unless a tree falls on the building. You may also notice that the batts are staggered so air cant creep up the between the batts. And yes, all seams are taped.. the building is like a Ziploc bag now.



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