# Question about venting a shop attic, humidity, etc.



## Bertha (Jan 10, 2011)

Fellow LJ's, I'd appreciate any input you might provide. When I purchased my home, it came with a small detached shop. The home inspector remarked that the attic space above the shop is sealed and that an access was recommended. I already had a list of repairs to submit to the seller, so I let this one go.

I went on to insulate the lower shop, new floor, new electric, etc. One day, when I was particularly brave, I recip'd a hole into the attic and peered in, expecting who knows what. It was empty, thankfully, just an uninsulated OSB ceiling. The soffets are perforated metal and I can see light peering up at me. Fearing that I needed to ventilate the space, I installed a centrally located turbine (a job I would not like to do again). I have a 50Qt. humidifier within the shop below.

My questions are, if it were your shop:
1) would you install a permanent drop down access and quit
2) would you insulate the attic and if so, with what kind
3) should I just tear out all the OSB and raise my ceiling a few feet (small stickering loft?)
4) have I already screwed up in some manner?

Any thoughts appreciated!


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## racerglen (Oct 15, 2010)

Al, how much space is in that attic ? if there's enough for some storage then a drop down's a good idea otherwise I'd just put a hatch in.
Insulation's a good idea anywhere, vapor barier with fiberglas bats over works for me, I'm thinking you probably get some hot summer weather, keeps you cooler as well as warm in winter.
on item 3 I go back to how much space is above the OSB..? I don't think much of that for a ceiling, drywall's safer..
#4..think you've made the right moves so far

Glen


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## Bertha (Jan 10, 2011)

Thanks Glen, there's not much up there, 3 feet at the peak at most. I could slide a few boards up there but I don't think it's worth fighting with OSB to gain a small bit of storage. It looks pretty standard, so your pre-cut bats might be just what I need. Thanks again!


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## grittyroots (Jan 13, 2011)

i would just put in a hatch to access. you could put a gable fan in that worksoff the rising heat. very easy to install


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## Bertha (Jan 10, 2011)

Thanks Roots, that's what I'm inclined to do. I might even just build a hatch because the ladder my be a moot point, given that it's barely large enough to crawl around in. I installed a wind operated turbine and it seems to move a good bit of air. I might consider adding a powered fan. Thanks again!


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## dbray45 (Oct 19, 2010)

You don't want to put a vapor barrier in the ceiling, only the walls. You do want moisture to go up from the space below. I would put 19" of insulation in the ceiling but do not cover the vents in the soffits A roof vent or fan might be a good idea to keep the heat down in the summer.


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## mrtoasty (Jan 13, 2011)

Check around your area for a company that blows in insulation for the local builders. They will put in cardboard folded in a v shape to prevent insulation from getting in the soffit area and still let air circulate. I had them blow in my shop attic to a R 42 and it was just a little more than the cost to buy the batts.


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## Bertha (Jan 10, 2011)

Thanks Les! I even considered renting a blower from Lowes & doing it myself. I might die, of course, but I'd be saving a ton! To Not Very Good, I installed a turbine at the ridge, so there's light coming through there. Prior to that, it looked solid as a rock. The house was built in 2007 and the roof looked great according to the inspector. I really wanted a tin roof but I'm not ready to trash a perfectly good roof for my sense of style. I haven't yet had a humidity problem but I'd like to thwart it before it starts. Thanks to all above!


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## saddletramp (Mar 6, 2011)

Al, it sounds as if you already have soffit vents and you have installed a turbine vent at the peak. All you sould have to do is install rafter vents to keep the insulation out of the soffits and then you can either blow in insulation or put down batts.

edit: Oops, seems as if I'm a post or two late.


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## Bertha (Jan 10, 2011)

Thanks Saddle, do I require rafter vents if I'm using batts & stop them a tad short of the soffit? I imagine I probably do if I'm going to add any thickness of insulation. I'm glad to hear that I won't have to paper the roof. I wasn't looking forward to that  Rafter vents look like they should be cheap. Are they? And does anyone know of the ideal spacing?


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## saddletramp (Mar 6, 2011)

They are fairly cheap Al and they span the area between every pair of rafter from the soffit up for 48 inches. At least between every pair that has a soffit vent if you don't have a continuous vent in mthe soffits.


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## Bertha (Jan 10, 2011)

Thanks Saddle, I've got a continuous vent in the soffit, so I'm thinking a few between each rafters might keep the insulation from blocking the flow. I'm glad you mentioned this because I probably would have just piled insulation over them. After all, I managed to staple through some Romex when installing the wall insulation


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## saddletramp (Mar 6, 2011)

Here is a link that will help explain how they are used and installed. It does mention both 24" and 48" vents but I would highly recommend the 48". DAMHIKT


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## Bertha (Jan 10, 2011)

48" it is. No link, but I'm sure I can find one quickly. Thanks again for the help. While I have you, do you prefer "Saddle", "Tramp", or Bob?


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## saddletramp (Mar 6, 2011)

sorry about that here it is:
http://www.buildingforhealth.com/proddetail.php?prod=ADO-DV


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## saddletramp (Mar 6, 2011)

You can call me anything but late to dinner.


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## reedwood (Jan 27, 2011)

Hey Al,
I will assume it's a typical 2.5 car, Gable 7/12 pitched roof garage with a 16 ft. door. Right?

It's really weird that there is OSB on the ceiling joists and you had to cut thru to get to the floor above. How did they get out? Is that how it is? Very odd they didn't put in an access panel.

May I suggest you consider something more drastic? Vault half the ceiling. Use the other half for open storage.
It doesn't sound like you're starved for storage. What the heck could you put up there anyway?

Take a look at my shop I have posted. The ceiling height is awesome. It allows room for surface mounted light fixtures without worrying about smashing the bulbs with a long board and allows room for the Jet air cleaner, and easy storage of long stock. You can't store 12 ft. material thru an attic stairway very easily.

As far as vapor barriers go, they belong on the outside walls, behind the siding anyway. Not really that necessary for a garage that's already built. I did install it when I resided my garage last year.
My guess, you won't be keeping it heated full time and your garage door is your weakest link. You only want it sealed good enough while heating it, otherwise, let it breath.

If we had money like the government, you could:
Remove half the hideous OSB, Add a ridge beam, staple the right size rafter vent baffles continuously past the top plate and to the ridge beam, install R 25 kraft faced insulation for 2×6 rafters, (doesn't fall on your head every time you slam the door or blow off the walls and ceiling with an air hose.) and install drywall, no glue.

Screw everything so you can change it later. I didn't even tape the joints. I've replaced 2 sheets already from a leak. You will have to add a ridge vent too, which is not that hard.

Get advice from a good carpenter that can tell you what beams may be needed. You can't just go removing ceiling joists to vault the ceiling. not sure of your back ground.

Did I spend all your money yet?

have fun.


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## Bertha (Jan 10, 2011)

It's actually a detached log shop (to match the home) but it's pretty similar to a typical garage sans the garage door. When I moved in, it was stained uneven concrete floors and bare walls. And yes, the ceiling is hideously white-painted OSB with no access (until I broke out the Sawzall). I actually like the idea of a half ceiling quite a bit. It could give me a touch of storage & wouldn't have to disturb the turbine I already installed. It's a very small space, though, suitable for infrequently used items. I could even store finishing products in the unenclosed portion. It would also save me the few hundred bucks for the drop down attic access stairs. I'll take some pictures tonight so y'all can better understand what I'm talking about. I'm getting a new vintage 20" Delta bandsaw tonight, so I'll be out there anyway!


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## reedwood (Jan 27, 2011)

Nice band saw. include picture of it as well. good luck!


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## reedwood (Jan 27, 2011)

Bob, sorry I came in late, 
good picture of the vent. did I step on your toe?


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## Bertha (Jan 10, 2011)

Took a few pictures. You'll see how small the space is, my crude turbine installation, and the perforated soffits. You'll also see my new toy delivered about an hour ago.





































And for Reedwood:


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## saddletramp (Mar 6, 2011)

Not at all Mark.

Al, that's a sweet saw. Oh, and for the record, YOU SUCK! LOL


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## Sawkerf (Dec 31, 2009)

Those look like engineered trusses, so you don't want to whack on them. Your turbine probably helps vent the space, but a couple of gable end vents would do a better job.

You could frame an opening in the ceiling, but you won't get much storage space.


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## Bertha (Jan 10, 2011)

Thanks Saddle and Kerf! I think you're right about the trusses. My home is timerframed but the shop screams kit made to look like true log construction. It's appears pretty thrown together to be quite honest, worlds apart from the home. The ceilings are also taller than they appear and it's awkward to get up there. I think I'll probably just add gable end and rafter vents; insulate it to some degree, and install a hinged trap door. The thought of pulling down that OSB is discouraging, although I like the idea of removing 1/2 of it.


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## reedwood (Jan 27, 2011)

TRUSSES!..... I should have know when you said 2007. 
Well, That changes everything. You might be able to create a huge 8×8 skylight shaft in the middle and have access doors inside the shaft. Done that with trusses and it worked great.

I thought the OSB was IN the attic. A picture is worth… you know the rest. They probably nailed the crap out of it with hot glue gun nails and glued it to boot. Nothing wrong with it so might as well leave it. It's whatcha got.

Blown in insulation would indeed be a better choice around all that framing. 4' baffles at the bottom only needed.
That drawing from Bob was pretty good info. 
And, unfortunately storage other than cardboard boxes and light stuff is all you can put up there. with the insulation and spiders.

I'm an old school framer. I hate trusses. Now you know why.

That band saw is killer. already refurbished!


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## reedwood (Jan 27, 2011)

agreed. ridge vent…thumbs up
I like the ones that you cover with shingles. they hide better.


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## Bertha (Jan 10, 2011)

So, this ridge vent would be in addition to my turbine?



















You've all seen the miniscule space. I'd prefer not to tear up the ridge if possible. And you're right above, they porcupined it with nails, both liquid and metal. I think I'm stuck with the OSB but the skylight is very intriguing. Is this one of those cardboard tube jobbies? Are they pricey?


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## Grandpa (Jan 28, 2011)

In my part of the country those devices that get the air past the insulation are called "air chutes". Around here they are usually made of styrofoam and stapled to the bottom side of the decking with short staples shot through a spring powered stapler such as an Arrow T50. More is better. The soffit vent is great. I always say it is difficult to over ventilate an attic. All the soffit vents in the world won't help if the air can't circulate from them and into the attic. What makes this work? Vents on the top. The closer to the ridge the better. There are several types of vents used and many work equally well. Remember you need about the same area (in sq inches) as the soffits have in area. I will get hammered over the equal statement but facts are facts and people have preferences. What do I have on my house. I used the vinyl ridge vent that comes in 4 ft. sections that you put ridge cap shingles over so it looks better. I have used turbines and I think they worked. I have been on roofs that had shingles that looked like they had been boiled. In SW Oklahoma the attics can get up into the 170 deg. range if not well ventilated. I measured that temp. with an infrared temp. device. Ventilation will make the structure last longer without repairs. If you insulate the attic the insulation will go into the soffits rendering the soffit vents useless you use air chutes. These are a must. The 2 ft vs. 4 ft. depends on the depth of the insulation and the pitch of the roof. We don't use more than 16" of blown insualtion. There is a time when more insualtion is not cost effective. It think there is a formula that depends on your climate and the expected temperatures for your area. We get by with a lot of things that people in Washington state would never get by with. We are dryer and warmer. I think we are warmer. As they stated above never cut a truss. An engineered truss loses its integrity when any part of it is cut. Leave them alone. A skuttle hole through the ceiling will give access with little expense. There just isn't much storage area in your attic. Like I said before and I think the others have also said….when it comes to ventilation more is usually better. 
I just looked back at the photo of your wind turbine intallation. Those are usually installed with the bottom edge of the flashing on top of the shingles. This is split with about 50% on top of the shingles with the upper 50% of the flashing under the shingles. This makes the rain shed (wish we could get about 6 inches of rain) and keeps it on top of the roof. Also would have made the installation easier. With the lower edge of the flashing under the shingles water can work its way in and get under the shingles. Then you have moisture under your shingles and ready for a leak. I hope a little of this might help with your decision.


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## Bertha (Jan 10, 2011)

Crap, I read the directions, although I had no idea what I was doing. I put two tubes of sealant up there. I hope it doesn't leak. Thank you Granpa for the very informative response. I wouldn't dare cut a truss. I don't even like leaning against them. I think I'll connect vents to the soffit vents, insulate, and see what it does. The little turbine whirls its heart away but if it becomes deficient, I might add a powered fan. All these suggestions are terribly helpful and I really appreciate it!


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## Grandpa (Jan 28, 2011)

I had a friend that built a home around 1980 and he tried to do all the "right" things to make it energy effecient. He had an energy audit done on it and the only thing the auditor said was the power vent would never save enough energy to pay for it so when it wore out to replace it with a wind turbine. I don't know. I am just passing along info. I do know that there are some basic things to remember when roofing. Gravel side up and water runs downhill so keep those flashing coming to the surface. LOL You will be okay and trusses are good things I think. I ready a study about why some homes were blowing away on the east coast of the U.S. (hurricane damage) The old home seemed to be staying and the new homes were blowing away. Their answer was nail guns. We can't afford to hire a person to hand nail the framing so we have to go with the gun nails. The trusses should be stronger unless the pwrson is very careful and very good with the gun and many are. I am okay with trusses personally. I live in tornado alley and they work okay here. I also live in a stick built house. just happened that way.


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## Bertha (Jan 10, 2011)

If I storm can take down my log home, I'll be quite impressed. If it blows my shop down the street, such is life. I'm insured so just imagine all those vintage goodies I could buy. I would sure miss my handplanes though. Thanks for the vote of confidence, Grandpa!


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## dbhost (Jul 20, 2009)

Okay let's go with a couple of assumptions…

#1. You want to control heat in / out of your shop.
#2. You want to control humidity in your shop.
#3. You didn't already cut a gaping hole for a turbine vent. (Others will disagree, I personally would love to do away with my turbines).

I would do the following…

#1. Install a ridge vent as illustrated above. 
#2. Install a radiant barrier. I have looked high and low on these, and have been most impressed with AtticFoil, this is the stuff I am in the process of installing in my home. VERY tough stuff, reasonable installation, and extremely effective! I am installing mine in the open ridge manner.
#3. Install as much insulation up there as you can get in there. I am assuming that those are 2×6's, but I am not sure… That would give you about R19 if you go even with the tops of the trusses, you could roll in R30, or better yet, blow in. 
#4. Since the ceiling / attic was uninsulated, assume the walls are too. At least check, if they aren't insulated, put that on your to do list.

Now mind you, this assumes that you didn't do what you did by cutting for that turbine. The open ridge style for the attic foil still works with turbines, just not as well… This is what I am doing in my house. A coworker of mine is doing his flat topped, I felt that open ridge allowed for better breathing OUT of the attic. Maybe I am wrong… What I do know is that AtticFoil REALLY helps my heating bills. I don't have much installed yet (45 linear feet on a south facing roof face) and it is already dramatically impacting my heating / cooling bill for the good…


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## Bertha (Jan 10, 2011)

Thanks for the info, DB. This is a tiny shop but I already insulated the walls well. It's also sheathed on the exterior with 1/2 cut 10" diameter logs to mimic the look of the home. I went with the expensive Pella's in the main house & I don't know about the R-factor but an ice cube will keep that thing cool for days. The weak point in the shop is clearly the uninsulated attic. I don't even have a true heating source in there yet but I'm picking LJ brains so I don't regret something I did next winter. I really like the idea of your attic foil. I guess I should have asked this question before I hacked a tunnel into my roof but I was feeling extra competent that day. Thanks for the suggestions!


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## Bertha (Jan 10, 2011)

NVG, I learned the tar lesson the hard way. It completely destroyed anything it touched. Any hints about getting it off stuff? It was my first experience with that evil mess.


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## dbray45 (Oct 19, 2010)

Paint thinner, kerosene


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## racerglen (Oct 15, 2010)

And time….

;-)


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## bubinga (Feb 5, 2011)

I go out side , over the fire pit and use gas to get the (tar) crap off
Then burn off the gas so it doesn't soak in the ground
Immediately wash skin with soap and water
Then have a smoke


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## Grandpa (Jan 28, 2011)

I try to use throw away tools to apply or smooth the tar type products. It costs more to clean that to replace. You are correct that stuff sticks to everything and is close to permanent. The attic foil products are reported to offer a substantial decrease in the heat in an attic. 40 degree decrease or something like that. The sky is the limit when you start into this stuff. About the same as buying shop tools. LOL Where do we stop? WE DON'T!!


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## Bertha (Jan 10, 2011)

Thanks to all. I put in rafter vents, laid down standard insulation, and built a little trap (no stairs, they wanted $300). I put my spare dust collection tubing/fittings up there for now.


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## Grandpa (Jan 28, 2011)

Good looking job too!!


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## Bertha (Jan 10, 2011)

Thanks, Gramps. I just made a little pine frame with a Kreg & routered out the hinge mortise with a laminate trimmer. 1/2 inch ply door and some galvanized hardware. It won't win any awards but it's better than a sawzall hole in my ceiling I found some drop-down stairs for around $300 but there's not enough room to do much in there anyway. I'll get a little chain ladder at some point if I ever start using it. Thanks for all the help!


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## Grandpa (Jan 28, 2011)

It is difficult to make the transition from the pull down steps into a low attic like you have. I have a Werner ladder that is the folding type and unfolds like a step ladder. I can be used straight too but it makes an 11 ft step ladder. It shortens on each rung so I sit it under the opening and climb up it. They are stable but too expensive for an attic stair. I own it for my business. A good step ladder will work. You probably won't get up there often anyway.


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## teejk (Jan 19, 2011)

as long as we're on the topic, does anybody know how to block blown-in insulation from the soffits on a typical "pole-barn" ceiling? trusses are 8' on center and employ purlins (2×4's on edge) every 2' up to the vented ridge.

I've been scratching my head on this one…the purlins effectively block all air movement to the vented soffits other than the ribs on the roof steel that is attached to the tops of the purlins.

I already see that I am NOT going to get R38 in the ceiling at the sidewalls…I might get max 6" there (praying that my in-floor radiant doesn't send a lot of heat up to the ceiling).

thanks in advance


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## mrtoasty (Jan 13, 2011)

How many rib openings are on the roof sheets? That may be enough to vent ok, but you are right the insulation will be a little thin at that location.

I have radiant floor heat as well and I installed 3 ceiling fans. In the heating season I reverse them and set them on low and let them run 24/7. That might help your problem.

Les


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## teejk (Jan 19, 2011)

les

steel is the standard building stuff so ribs are probably every 8" or so. If you can picture it, effectively I have a 1" hole (depth of the rib) on top of the purlins every 8" the entire length of the shop. I don't know if that is enough to allow adequate air/moisture movement from the soffits to the ridge vent above the ceiling. Maybe the best solution will be gable vents.


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## Grandpa (Jan 28, 2011)

You could use gable vents both in the upper part of the gable and down low near the insulation line. this allows the cool air a place to come in and the warm air exits the upper vents. I am always trying to cool the attic since we air condition more days than we heat where I live. There are vents available to put on the roof near the insualtion line also. This would be more difficult with the metal roof. It is just more difficult to penetrate the metal and flash it than on a composite roof. Just a thought.


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## mrtoasty (Jan 13, 2011)

I like Grandpa's idea but I might try just the upper gable end vents first and see how it goes. If I figure right, each 8' section of roof would have the equivalent of almost a 5" diameter hole for intake of outside air. I don't know how long your shop is but that gives you a starting place.

Les


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## Bertha (Jan 10, 2011)

I'm loving this thread, learning a lot!


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## teejk (Jan 19, 2011)

grandpa/les/Al

guess I need to figure out how to post a picture here! [email protected]!


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## DMIHOMECENTER (Mar 5, 2011)

If you already have soffit venting, then ALL you need is ridge venting. As a matter of fact, gable vents and turbines *can* disrupt the thermal engine that drives a soffit / ridge vent system. For every volume of air that heats and rises constantly to and through the ridge vent, the same volume of cooler outside air is sucked in through the soffit vents. It is a constant thermal engine (as long as the air is hotter in the attic than outside) thanks to physical laws of warm air rising and displacement. No power required.

The addition of gable vents or turbines can disrupt this natural upward flow with cross currents that can actually slow it down and hence make it less effective.

I have built many houses. Each and every one has used the soffit/ridge vent system with good results.

Also, go with blown cellulose insulation instead of batted. Don't listen to the urban legends about it being a fire hazard. I can't make it catch fire with a plumbers torch. As soon as the heat is removed it goes out. Also, it has boric acid as part of its makeup. This is the same material that Roach Proof powder is. Added benefit is that you will not have insects colonizing your insulated spaces that have this.

Echoing others here, but DO NOT cut an engineered truss system for any reason unless you really know what you are doing. The sum is greater than the parts on trusses, so a simple cut may have surprising and unwelcome results. Those are 24" on center and are 2×4 truss members, so they are already working hard enough without getting cut.


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## teejk (Jan 19, 2011)

David

Thanks very much for the post…but realize this is a pole barn and the trusses are 8 feet OC (typical). The issue is how to get air from the soffits to the ridge vent without blowing insulation into the soffit space. Some type of blocking is required but now the purlins seem to be the problem. Poly would work but then the only egress to the soffits would be the ribs on the roof steel.

I'll take a pix and post it to give you a better idea.

and cutting a truss??? beauty of trusses is that you get by cheap over rafter framing solely by "engineering"...I would not even run a drill bit through one of those, much less taking a Sawzall to one! The way I figure it I am already on the "edge" with them intact.


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## Bertha (Jan 10, 2011)

I'm dumb, but not dumb enough to mess with a truss. Mine appear as if they're going to topple down at any moment. I get nervous even crawling around up there, worried i'm going to bump the fasteners off


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## teejk (Jan 19, 2011)

al…like I said, trusses are "engineered"...unless rated as such (doubtful unless you paid extra for it), they are meant to handle roof load on the top and a ceiling on the bottom, nothing more. No storage, minimal weight in the "web" unless you distribute it properly. Most of them are 2×4 cut-offs attached with gang-plates. They work great if you don't violate the intended use.


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## Bertha (Jan 10, 2011)

Understood, TJK. My gang plates seem haphazardly applied, some crooked and incompletely seated. But like you said, I'm leaving them alone. Eventually, I'll build a barn/shop on my property and relegate my current small shop to lawn storage/planting shed. Until then, I'll tread carefully upstairs


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## S4S (Jan 22, 2011)

in answer to question number 4 , i would say …No Way dude !


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## Grandpa (Jan 28, 2011)

Moment is correct. Haven't screw up yet if we overlook the shingles and flashing on the turbine. Trusses are good so don't sweat them. so, how are things going after nearly a year in the shop. Loving that big bandsaw I think.


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## Bertha (Jan 10, 2011)

Grandpa, I can't say that this turbine has done anything. I rarely even see the little guy spinning. At least it encouraged me to put a hatch in the roof. I've captured a bit of storage space up there and installed some track lighting but haven't insulated properly yet. All in good time, my good man


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