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tonyjmartin

01:14PM | 05/14/05
Member Since: 05/13/05
6 lifetime posts
Bvroofing
Hi All!

I posted this to the Insulation BBS, but I saw an unanswered question on this subject here, so I thought I'd ask.

I'm adding ventilation to our 55-year-old ranch style home. The entire roof is a hip-roof (no gables), with about 300 feet of gutter attached to sealed soffits that drop down about a foot below the top of the 9" brick exterior wall.

There are two small "gable" type vents at each end of the main roof peak, and no soffit venting. Moisture wasn't really a problem until I started going into the attic to work on the house wiring, but the heat up there in the summer has now come to my attention. My guess is that it gets up to at least 150 degrees in the attic during peak August sun. There's currently about 16" of 1970's vintage blown-in insulation up there, but I've been moving it around a bit. I figure that as long as I'm dealing with the heat situation, I'll be stopping any future moisture issues. Right now, I'm working at the top of the exterior walls, but I'll be adding soffit/ridge vents at a later time when I do some more math.

I've got a few pictures of what I'm doing at

http://pg.photos.yahoo.com/ph/tonyjackmartin/my_photos

Each rafter is plugged at the outside of the exterior wall with a 2x6, nailed from the soffit side (remember that this house has 300' of SEALED soffit). What I'm doing from the attic side is using a Speedbore bit with an extension and a Sawzall to cut a 1" high slit in the 2x6 where it meets the roof decking. I'm then notching the ProVent rafter baffles to get a better seal against the 2x6.

My question is this:

How concerned should I be about getting a perfect seal here?

Spray foam does not stick to overhead surfaces very well, and I'm concerned about it expanding into the slit in the 2x6. I've also thought about craming some fiberglass batt insulation into the area where the baffle meets the 2x6, and then inserting more uncompressed fiberglass insulation until I reach the inside top of the exterior wall (resulting in about R-15). I've also thought of making rigid foam insulation cutouts that would fill basically cover the inside of the 2x6 (ADOVent makes cardboard cutouts, but not to fit the 16" on-center of my rafters).

Or should I not really be concerned about air leaks at all, and just spread the cellulose insulation all the way to the 2x6 and top off the attic to 16" when I'm done?

As a side note: baffles are useless at the inside corners of this hip roof (almost 3 feet each way from the corners). Should I fill in those areas to the roof decking, or should I just cover the attic floor and leave an air space between the cellulose insulation and the roof?

Thanks in advance for your help.

Tony

dodgeroof

04:01PM | 05/14/05
Member Since: 03/27/05
95 lifetime posts
Not an insulation expert...I just felt moved to compliment you on your whole "presentation", from the photos to the diagram. Are you an engineer? Have done work for some who draw out diagrams, etc. when they want to explain something to me about their ideas on their roof.

Not being an true expert on the venting, I don't think it's critical that you have an "air-tight" seal between the baffles and the 2by6 area. But blocking would be good just to keep out wasps and bees, who like any small openings into the house.

Over the last half dozen years, there's been a rash of Honey Bee colonys actually moving into structures around here, complete with hives full of honey, causing much damage to drywall, etc.

A roof CAN be your friend

tonyjmartin

04:56PM | 05/14/05
Member Since: 05/13/05
6 lifetime posts
Thanks for your reply, dodgeroof!

No, not an engineer, but I spent about 15 years in professional theatre before I became a Stay-at-Home Dad, so I've done my share of drafting. I actually started on a plan view of the house a couple years ago on a whim, and it's grown to a couple dozen layers, including plumbing, landscaping, etc. I added the roofing details in three layers in about half an hour. The baffle cross section was done in Word because I didn't want to set up an entire CADD drawing for it. The pictures just sort of happen as I work when I take the digital camera out of a zip-loc bag when I feel like something's worth emailing to family.

Anyway, I should clarify that the soffits are HORIZONTALLY sealed at about 1-foot below the top of the exterior walls. Screened soffit vents should deter most bugs, I hope. Mostly wasps around here in Wyoming.

Thanks!

Tony


tonyjmartin

05:22PM | 05/14/05
Member Since: 05/13/05
6 lifetime posts
Hi Again!

I just updated the cross-section drawing of the baffle/soffit situation in our home (BaffleCrossSection2.jpg). Should make things a bit clearer. Pictures can be found at:

http://pg.photos.yahoo.com/ph/tonyjackmartin/my_photos

Thanks Again!

Tony

dodgeroof

06:11AM | 05/15/05
Member Since: 03/27/05
95 lifetime posts
I still don't think you need to be concerned with the baffle/2by6 slotted-area abutment being

100% air tight...but what about just trimming the baffle at the same angle as the 2by6?

And maybe trying to apply a bead of that expanding foam, then QUICKLY sliding the baffle into place, embedding it into the foam?

But I'm more curious about how it is working in such a confined space. Sounds like hard belly work, not to mention, once you're in position and need something that isn't within reach.

A roof CAN be your friend

tonyjmartin

07:08AM | 05/15/05
Member Since: 05/13/05
6 lifetime posts
dodgeroof wrote:

"...but what about just trimming the baffle at the same angle as the 2by6?"

I've cut a couple notches in the ProVents at that end, and it helps. Maybe I'm just being too anal about getting a good seal since our winters can drop to below zero degrees for weeks at a time here in Wyoming.

"And maybe trying to apply a bead of that expanding foam, then QUICKLY sliding the baffle into place, embedding it into the foam?"

Now THAT'S an idea. I've been concerned about the foam expanding into the 1" slit, but with this method, I could be more precise. Just have to stretch my arms pretty far to apply the foam.

"But I'm more curious about how it is working in such a confined space. Sounds like hard belly work, not to mention, once you're in position and need something that isn't within reach."

The straight sections are easier than the corners. Just shovel, drill, cut, and staple. And use lot's of 3/4" ply to lay on. And a tool tote nearby helps. I guess that spending many years installing audio, video, and intercom in the most outrageous locations in theatres has tempered my patience. Nothing like scrambling 40-feet over ductwork and forgetting your coil of solder. Grrrrrrrr.

Thanks!

Tony


robnmary

04:04PM | 11/13/05
Member Since: 11/12/05
1 lifetime posts
Hi, Tony. So, how did this attic insulation project conclude?


tonyjmartin

06:28PM | 11/13/05
Member Since: 05/13/05
6 lifetime posts
Hi robnmary!

The project has been on hold since last June when it got so hot in the attic that my wife feared for my health.

Your question is timely, as I am just about to crawl up there and start installing the baffles again. It has been unseasonably warm here in S.E. Wyoming as of late (80 degrees just a few days ago), but that now appears to be past us.

With winter appproaching, the project is going to continue in phases, with the two north sections of two wings of the house getting complete soffit venting to combat the moisture problems, as well as finishing the electrical in those areas. Then I'll be finishing a bathroom remodel for holiday guests. Then I'll return to the attic in January when I can dedicate the time to finishing the electrical/baffles and adding blown-in insulation all at once.

Pictures of the rafter baffle installation from last spring, as well as the addition of continuous soffit vents along the north roof sections last week can be seen at:

http://pg.photos.yahoo.com/ph/tonyjackmartin/my_photos

Ridge vents are slated to be installed when it starts getting hot again in May/June.

Take Care,

Tony
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