site built vent baffles...

[jpcjguy]

Hi all,

Thought this was a cool pic this morning. It was 29 degrees out. I have been building site-built baffles in my detached garage(yes I know I am a glutton for punishment). You can see where on the far right lift bay with scissor truss, I have only gone up 4 feet from the eave and the other part of the garage is attic trusses that I have gone up 16 ft, which will get me above the insulation height of the flat part of the attic truss.
I still have to seal/caulk all the baffles - more fun!

 

[Bretny]

That should work fine..and add some Insulation in like any baffle. Caned foam work good for sealing around the edges of that. It also adds some support to the foam.

 

[jpcjguy]

That should work fine..and add some Insulation in like any baffle. Caned foam work good for sealing around the edges of that. It also adds some support to the foam.

The plan is to have a local company come in and do the actual batt insulation. Ideally I can get R-38 from top to bottom on the slope. I had the attic trusses scabbed with an additional 2x6 in the room section so even with my baffles (which are 1/2" XPS spaced 1.3" from the roof deck), I still have 9" for batts!
That should get me R38.
As for the canned foam, I did use that some already and what a mess and hard to control - since I am not "filling a gap" that stuff just goes everywhere!
Plan is to use construction sealant in a caulk for 90% and the foam the gaps where my baffle cut was not great.

 

[spudley]

Nice sunrise and good job on the baffles.

 

[nmk_61802]

The plan is to have a local company come in and do the actual batt insulation. Ideally I can get R-38 from top to bottom on the slope. I had the attic trusses scabbed with an additional 2x6 in the room section so even with my baffles (which are 1/2" XPS spaced 1.3" from the roof deck), I still have 9" for batts!
That should get me R38.
As for the canned foam, I did use that some already and what a mess and hard to control - since I am not "filling a gap" that stuff just goes everywhere!
Plan is to use construction sealant in a caulk for 90% and the foam the gaps where my baffle cut was not great.

Buy the $25 pro gun and the large cans. Much easier control and more economical. With the pro gun you can dial down to a 1/4" bead and treat it like a caulk gun.

 

[kroc0005]

The plan is to have a local company come in and do the actual batt insulation. Ideally I can get R-38 from top to bottom on the slope. I had the attic trusses scabbed with an additional 2x6 in the room section so even with my baffles (which are 1/2" XPS spaced 1.3" from the roof deck), I still have 9" for batts!

That should get me R38.

As for the canned foam, I did use that some already and what a mess and hard to control - since I am not "filling a gap" that stuff just goes everywhere!

Plan is to use construction sealant in a caulk for 90% and the foam the gaps where my baffle cut was not great.

This is interesting to me as I'm contemplating insulating my garage too.

Did you add 1x2s along the roof sheathing to create the vent from the soffit?

Do you do that to the roof?

Are you insulating just the sheathing/overhead area?

Will you need insulation on the floor boards too?

Just curious. I've seen plastic baffles extend from the soffit but never insulated. I thought you wanted fresh air to get in and not sure how this is allowing it to...

Can you keep sending progress pics of your next stage,?

Thank you!

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[jpcjguy]

This is interesting to me as I'm contemplating insulating my garage too.

Did you add 1x2s along the roof sheathing to create the vent from the soffit?

Do you do that to the roof?

Are you insulating just the sheathing/overhead area?

Will you need insulation on the floor boards too?

Just curious. I've seen plastic baffles extend from the soffit but never insulated. I thought you wanted fresh air to get in and not sure how this is allowing it to...

Can you keep sending progress pics of your next stage,?

Thank you!

Sent from my SM-T720 using Tapatalk

kroc0005 - I ripped some boards that I had to 1.25" spacers that are about 3" long and used my air stapler and mounted them every 2 feet (8 per side) on each side of the rafter. That way when I cut the 1/2" XPS and push it into the bay, it stops at the right spot. I then staple the XPS to the block. This gives me a nice air duct from soffitt to ridge vent. Each bay gets 1 sheet of XPS cut to 17.5" (I am on 19.25" truss spacing). I get 2 pieces out of the sheet so that is 16 feet.
The plan is to then use R38 batts from bottom to top. I thought these would be better than the flimsy plastic/foam ones you staple to the sheathing. One of the biggest killers of "R-value" for fiberglass insulation is air wash through it. This way I will seal the channel and let the batt do its job. (In theory of course!)

Attached are pics of the spacers and the air gap.

 

[danfromsyr]

just an question, why not use strips of foam stapled in as your spacer boards? then glue the runs to secure/seal the baffle to the foam strips?

 

[kroc0005]

Thanks for the response and additional pics! Looking forward to see the Batts going in!

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[The Cobbler]

I did the same in my shop, I used 1/4 luan ply with 1x2(actually 2" , ripped myself) stapled them to the trusses , the luan stapled to them . not sure why you would seal them tho

 

[jpcjguy]

just an question, why not use strips of foam stapled in as your spacer boards? then glue the runs to secure/seal the baffle to the foam strips?

I guess I could have, but I had the wood to use and I felt that the blocks are more secure.

 

[jpcjguy]

I did the same in my shop, I used 1/4 luan ply with 1x2(actually 2" , ripped myself) stapled them to the trusses , the luan stapled to them . not sure why you would seal them tho

Sealing them is to prevent airflow in the insulation that reduces the effectiveness (especially batts)

 

[Vahispd]

Hi all,

Thought this was a cool pic this morning. ... You can see where on the far right lift bay with scissor truss, I have only gone up 4 feet from the eave and the other part of the garage is attic trusses that I have gone up 16 ft, ...

Yes, a very cool pic. Really shows the temperature difference between the length of baffles.
I had planned to do about 4 foot long baffles on my house, but I might have to rethink that after seeing that pic.

 

[kroc0005]

So I was thinking about this...this all sounds great for the winter to ward off some of the winter chill.

Will this attic space be heated? Or are you anticipating some residual heat from garage on lower floor (if heated) will permeate up to the attic area?

What about the summertime? If you store stuff up there in summer, wont there be minimal to no air flow and therefore become more of an oven? Or does the baffle spacing and insulation (foam attached to sheathing baffle and batts) act as a barrier from heat generated by the sun/shingles?

Reason I ask as that without insulation, my garage attic is an oven as is in the summer. I'd like to add a heater to my garage so all this is really interesting to me. Thanks all!



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[jpcjguy]

So I was thinking about this...this all sounds great for the winter to ward off some of the winter chill.

Will this attic space be heated? Or are you anticipating some residual heat from garage on lower floor (if heated) will permeate up to the attic area?

I am hoping that some heat will just migrate from the downstairs since there will be no insulation between the floors. Right now the upstairs is just going be drywalled and used for storage and if it becomes an actively used room then I would probably install a small mini-split for that area.

What about the summertime? If you store stuff up there in summer, wont there be minimal to no air flow and therefore become more of an oven? Or does the baffle spacing and insulation (foam attached to sheathing baffle and batts) act as a barrier from heat generated by the sun/shingles?

In theory the baffles and insulation should keep it reasonable, but obviously it will be hotter than downstairs. I am taking a wait and see viewpoint.

Reason I ask as that without insulation, my garage attic is an oven as is in the summer. I'd like to add a heater to my garage so all this is really interesting to me. Thanks all!



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See above for comments

 

[kroc0005]

Thanks for feedback, keep it up!

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[jpcjguy]

You can really see where I built the baffles with a little snow this morning!
Today I am supposed to have the crew come in and put in R-38 batts throughout the garage. Glad since our temps are steadily falling and I don't want my 1/2 bath pipes to freeze. But I think it would take consistently lower temperatures for that to happen.....

 

[yeldogt]

The baffles are insulation? You have no insulation in the one area .... residual heat is leaking into that area of the roof. It's warmer

I'm in PA ... I never do baffles or vented roofs. What are you venting ?

 

[jpcjguy]

The baffles are insulation? You have no insulation in the one area .... residual heat is leaking into that area of the roof. It's warmer

I'm in PA ... I never do baffles or vented roofs. What are you venting ?

No - the baffles are not insulation. They are to prevent air wash from the soffit through the insulation. R-38 is going everywhere (except walls). The baffles are made from XPS that is R-3. Just cool pic on how even a little R-3 holds the heat and prevents the snow from melting. The worst thing for batts is air flow through them, so I did the sealed site built baffles to prevent that. On the lift bay side, I only went up 8 feet because the insulation is not against the roof deck, it will be between the lower cord of the scissor truss - like in the attached pic

 

[thammel]

So the R3 is insulation...just not R38...

 

[firebirdparts]

That looks like something I'd do! Nice job. My shop is not usually heated, so I get lots of feedback from looking at the roof, too. Snow stays on it for a week and the frost until noon.

 

[jpcjguy]

The 1/2” Foam board that I used to build the baffles happens to be R3 then R38 batts will go between the baffle in the drywall

 

[bradpac]

Why not just have an unventilated setup? I have heard arguments for both and even seen a few installations where they have a metal roof, then vented strips or diagonal strips open for venting, then the roof deck with a sealed attic. Not sure there's enough gain from the venting to warrant the extra cost, but what are your thoughts?

 

[jpcjguy]

Why not just have an unventilated setup? I have heard arguments for both and even seen a few installations where they have a metal roof, then vented strips or diagonal strips open for venting, then the roof deck with a sealed attic. Not sure there's enough gain from the venting to warrant the extra cost, but what are your thoughts?

To be unventilated, you should really spray foam to get the proper depth. Spray foam around here is really $$$. I got a good price on the foam board and had enough wood left over to make the spacers, so it was just my time.
I am not 100% on the gain, but I know it will not hurt

 

[bradpac]

To be unventilated, you should really spray foam to get the proper depth. Spray foam around here is really $$$. I got a good price on the foam board and had enough wood left over to make the spacers, so it was just my time.
I am not 100% on the gain, but I know it will not hurt

You are right about that, if it wasn't a major cost, no other reason not to. Just in your photos you already have a proven gain.

 

[yeldogt]

No - the baffles are not insulation. They are to prevent air wash from the soffit through the insulation. R-38 is going everywhere (except walls). The baffles are made from XPS that is R-3. Just cool pic on how even a little R-3 holds the heat and prevents the snow from melting. The worst thing for batts is air flow through them, so I did the sealed site built baffles to prevent that. On the lift bay side, I only went up 8 feet because the insulation is not against the roof deck, it will be between the lower cord of the scissor truss - like in the attached pic

Sure they are ..... they insulate one space from another.

You are correct -- fiberglass is a poor restrictor of air movement. That's why you always see it with a VB. Or .. now ZIP (or like) sheathing.

If you take plastic sheeting -- you can heat a space outside .. no "R" value.