im about to build a garage roof. The gable roof will be 2×6’s on 24″s. Is it possible to use ridgid foam and not havto vent?
What whould you suggest given the factors:
1.) budget is as limited as possible.
2.) sheetrock will cover inside of rafters.
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Greetings skyecore and Welcome to Breaktime, ROAR!
Various information regarding roof venting and foamboard insulation have been addressed here on Breaktime a number of different times in the past.
If you scroll down in the lower left corner of your screen there is a search function that will take you to previous threads dealing with whatever you type in the search bar.
If you type in 'roof venting' or similar keywords of the subject matter you'll get a good supply of data from those old threads.
Cheers
be a heh heh
thanks for the tip rez, i did try that but maybe i just need to get more creative with my search criteria.. I'll give it another shot-->
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I figured you knew all that.
It was just more of a bump up for your thread.
cheers
Edited 12/11/2004 10:44 am ET by rez
appriciated.-->
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Don't listen to rez.Go to the upper left corner and use ADVANCED SEARCH. It gives you lot more options and features.
you don't have to vent the rafters if you fill the space solid. 5 1/2 " of rigid insulation will probably cost more than ventilating the roof. Is this garage a vaulted ceiling?
it will be heated and it will be vaulted cielings.-->
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A vaulted ceiling in a GARAGE??
vaulted ceiling in a GARAGE
Usual true, but not entirely wacky.
If it's shop space the additional volume is actuall better. An eight foot ceiling on a 24' deep space can be right "low" feeiling.
But, alose consider how usefull a storage loft would be in that vaulted ceiling. They make cool storage lifts for bikes & the like--they'll go right up into that vault.
Now, around here, they build what are called "Texas Basements." That's a dyrwalled, walk-up staircase, finished room over the garage. Some are built like living spaces--some aren't. Vaulted ceiling work pretty nicely in them, though.Occupational hazard of my occupation not being around (sorry Bubba)
i will just vent it, that is a good point about the expense of foam diamond, I acxtually just priced it out yesterday and came to the same conclusion. Today we started with the rafters, taking into account the ridge venting. This is what I did.. it sounds correct right?I'm putting the rafters 1/2" above the ridge beam so that it will allow air from all of the rafter bays to pass through the top in between the roof sheathing and out of the ridge vent.question about that: how big of a gap do i leave between the two pieces of sheathing?Thanks everyone for taking the time, i really do appriciate it.-->
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So the question will be the distance from the edge of the sheathing and the top of the ridge beam to match the depth of your vent channels between the foam sheet and the backside of the sheathing.
Commonly said to be 1 1/2 inch. Not enough depth and it won't move enough air, too much depth and you'll invite cross currents which will impede the upward flow to the ridgevent.
sure.............WHAT THE HECK?!i did dot understand that.. I appriciate your input but will you clarify, I know all of the words that you used but it sounded like fridge magnet poetry.Try again if you'd be so kind, but this time pretend like you're talking to the 17 y/o helper...*on the edge of my seat*-->
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You going to use the premade pop-in vent pieces or make your own?
I meant to say just keep an unimpeded 1 1/2inch flow of air to the ridge vent which would include having a 1 1/2 inch space between each side of the ridgebeam and the sheathing on each side.
You're opening a can of worms you know. Strong views on to-vent or not to-vent forces gather here on occasion to duke it out. Sometimes not a pretty site.
Data of technical merit supports both claims and I don't know. I come to the conclusion that each situation warrants it's own study.
You being in Oregon I don't think it gets cold enough to need a dollar$ excessive amount of insulation foamboard depth to do ok, so perhaps you could bypass the venting issue and go solid foam.
But for me to speak I run the risk of someone playing chopchop on my head.
You could probably stick the popin vent chutes in there and your R-19 fiberglass bats and it'll be ok as many others have done over the years and lived to tell about it.
1 1/2 inch venting space has often been the common number thrown about for years but some will question that as not enough or others saying not needed and you can go less. I'd say if venting do the 1 1/2.
But ask Piffin.
disclaimer: the above poster does not have the experience and expertise to stand behind this presentation of questionable theory and per this disclaimer cannot be held accountable in any fashion for any and all possible results that may occur by the application of such either public, private, or otherwise, be it in damage to personal property or that found in the marketplace, wherewithal any claims made must be addressed solely to FineHomebuilding care of Taunton Press.
Edited 12/12/2004 12:15 pm ET by rez
If it is not heated or producing a source of moisture, a garage roof needs neither insulation nor venting
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oops, that post to diamond was supposed to be to you piffin.-->
measure once
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Since you are DIY and seem to not be concerned with time or labour cost as much as cost of materials ( do I have that right? ) and the 2x6s are already on the way in or already there, and since this will be a cathedral cieling with insulation and heat, here is my prescription for the best compromise in your case.
Cut the sheathing down an inch to an inch and a half on each side of center line of ridge.
The drawing is with rafters at 24" OC but could be done similarly with them at 16" oc.Lower foam could be 1-1/2" instead of 1" to add r-value.
EPS foam would figure to add R5 per inch
or
Thermax polyiso would add Closer to R-7/inchso this system design would grant you somewhere between R-23 and R-30 depending on the variables you chose
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Minor hijack. It is relevant because it shows what can happen if you do things wrong. Piff, I have a less than fine homebuilding repair issue similar to this. I am a trying to help a sweet little lady with a leak that I think is possibly both a ventilation and leak issue.
It is a small bump out on a really poorly executed kluge of add-ons. It is very low pitch (did not measure but probably less than 2 1/2 in 12. Originally had roll roofing but metal was installed over it (directly with no purlins). It has 2x6 rafters with ply decking and drywall on the ceiling. They put full batts with no airspace. Without looking at how it was added I doubt that there would have been any flow through to the old attic anyway.
At first visit found many places that water could get in and think I addressed them. She said had a hard blowing rain and did not see any leaks. Pulled the rotted fascia (partly from gutter issue) and everything was soaked. As much as I hate to do it it appears that need to pull out ceiling, insul, open up to old attic area, put channel all the way up and reinsulate. This room is heated by a Monitor type kerosene sealed heater. Did not see any vapor barrier other than the Kraft on the insulation.
Any suggestion other than cry uncle. I told the son that a total restructure of the roof including the rest of the house would be the best answer but probably not worth it. The rest of the house roof looks like a good set of moguls at one of the ski slopes around here.
Bob
Hi, Jack!Look at the attachment in the above psot I made. That should help, but your job has more problems than a sow has teats...First and possibly worst, I think I understand you to say that the oil fired heater has no outside vent for exhaust fumes. If so, I don't know how it could be legal, but it sure is bad for the occupant, healthwise and it is also bad for the health of the house. all the by-product of combustion, including CO, CO2, and water vapour is still kept inside the home, making it a greenhouse atmosphere.I have no doubt that there are lots of ugly things growing between rafters so you need to be safety equipped when you tear it down, and protect everything in the house from the spores that will be floating around.The existing insulation is sopping wet so it is not insulating, due to lack of venting, leaks, etc. The lack of R-value in the wet insulation will increase the condensations and the ice damming, so it al has to be fixed, and fixed right. At one time, it might have been accomplished by three things - venting the heater, applying a VB paint and caulk to the inside, and installing the metal rof over sleepers to create a vented cold roof.Now, it sounds like things could have to go so far as to replacing rafters to get it right.I don't like 2x6 for rafters, especially in cathedral cielings but if that is what we are dealing with, so be it.
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Thanks, the Monitor heater ( there are several other brands that are similar -Toyo, Laser ) is a vented item quite popular down here in hillbilly country. They use a concentric exhaust/intake air pipe smaller than most car exhausts. The outer shell intake provides the cooling for the center exhaust. They are very efficient and should not create moisture other than just heating the area. They are sealed and not a threat.
The rest of your thoughts are sort of what I expected. I may shoot a couple of pictures tomorrow. There is no easy way to do much with the roof. I told the son when he first called that roofs were not my thing, that I could look for small leaks and repair flashing, etc but that was about it. His request was to replace the fascia.
The best thing would be to take the whole thing down and put in a modular. The owner is surely in her upper 70's or lower 80's.
I am going to meet over there with a wisened sidekick to advise tomorrow.
Bob
I'm familiar with Monitors, but the way you worded that left it a little unclear.
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I had never heard of them until several years ago. I have an old one that was given to me that had a bad circuit board. Got it repaired but have never installed it though. I worked on a project where they had one and was really impressed how quickly it warmed the area.
http://www.monitorproducts.com/products/m2400.html
The 2200 model has a decimal missing in the fuel flow specs. At 22000 btu setting it burns .164gph.
Had a friend whose mother had one, house was vacant and dirty rotten ba*****s cut fuel line and stole it. Insurance had one heck of kerosene cleanup after it drained the tank.
Sorry I was not clear in first post.
Bob
I have three heaters like yours, two by Panasonic and one by Hitachi. Very effective. I like the Panasonic ones because they have metal screen filters and childlocks.Unvented kerosene heaters are also very effective. Here in Japan they are the common winter heat source for the hoi polloi, incredibly. Along with unvented gas heaters. Sheer stupidity, but this is what the market has chosen.I hear that in the US unvented kerosene heaters are illegal in a number of states, and that there are no manufacturers. If you wanted an unvented kerosene heater in the US you would have to get a gray market import of a Toyo or Cornona or other brand. But who would want to import an illegal and unhealthful device?Well, it turns out that these are favored by survivalists in Montana, etc. In the aftermath of Armageddon, when roving packs of hungry survivors are scouring the countryside for stocks or provisions, the reasoning goes, you don't want to be calling attention to yourself by burning wood and sending up a smoke plume. Better to get a kerosene stove and just lay in a huge stock of kerosene. Nutty.
wow piffin, i cant tell you how much I appriciate you taking the time to educate me.am i a DIY? no, but i do have alot to learn. I've been working in the feild of carpentry for about 2 1/2 years, but just reecently i decided to break off from my old job due to a back injury (not too serious but im only 24 and it kept getting worse) I decided to go to school (just about to finish my first term!!) and to pay bills, I'm just doing small jobs for friends and by word of mouth.All of the indevidual aspects of this garage are things that I have done before but I've never been the one making the decisions, and my goodness it is a learning expirience for me. I mentioned the story behind this particular garage in a previous post (i think it was called 'design questions' or 'design help for boring garage' or somthing).Anyway, again, thankyou! -->
measure once
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Piffin. I love your idea, i just have one question:Pardon my ignorance but what do you mean by "3/4inch strapping perpandicular to rafters"?do you mean that i can just use somthing like pine 1x2's perpandicular to the rafters as sheetrock nailers? Just wanted to make sure i understood correctly..-->
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do you mean that i can just use somthing like pine 1x2's perpandicular to the rafters as sheetrock nailers?
Yes, 1x2 on 16" centers will work out nicely. A 1x3 or 1x4 every 48" OC is a nice touch, too.
To revisit the garage wall thread, you could just use 7/16" OSB for the ceiling and skip the strapping. Drywall will likely be cheaper.
There's a couple of things to think through here, too. Your cathedral ceiling will "catch" a pretty good volume of warm air. Moving that air to where it is wanted will become an issue. If you are using a ceiling monted fan, framing a "flat" for it to sit on (or its base) is much easier ahead of time. (So is running the cable to power it.)
Getting that warm air out in the summer will be a good thing, too. But remembering the previous thread, you were becoming sold on the idea of a cupola. That's an excellent way to vent warm air in the summer. You'll want a way to close it off in winter, though.
One last item, have you thought about lighting? Bringing light to the equipment helps a person use it (it it's a shop space). If the lighting plan is to plan later--surface-mounted conduit (EMT or NMT) may be the way to go (it's "only" a garage). That would make OSB a slightly easier surface to work with. Just a thought.Occupational hazard of my occupation not being around (sorry Bubba)
" Your cathedral ceiling will "catch" a pretty good volume of warm air. Moving that air to where it is wanted will become an issue."Man you got that RIGHT, I am kicking myself now for that moment of genius...all the heat is right up there. Freezing cold downstairs...
I don't have to ask for somebody to shoot me, they'll find my frozen body when I wander too far from the woodstove.
Spheramid Enterprises Architectural Woodworks
Repairs, Remodeling, Restorations.
all the heat is right up there
All you need is a fan on thermostat.
And some ductwork.
How big a fan--that's a different thread altogether . . . <g>
Wow, just broght bac a memory of getting out the ladder and climbing up into a sensible thermocline (not a fun day masking nor painting).Occupational hazard of my occupation not being around (sorry Bubba)
Good thought but...not gonna cut it.Still need a lot more accoutrements b4 anything like that is gonna be happenin..If I make it thru this winter I'll all set by next yr. This is gonna be very interesting.
Spheramid Enterprises Architectural Woodworks
Repairs, Remodeling, Restorations.
Good thought but...not gonna cut it.
LoL!
Hey, you've got good bearing points in the ol' kentucky home, just sets some hooks in, and put a hammock, and a hanging papasan char up where it's warm . . . <g>
Or, a local waif, to operate a long handled fan (or a flapping carpet) . . .
Actually, a box fan in the corner will circulate some of that warm air back to where it's sensible. You can get a "goes on at 65º" fan thermocouple switch for under $15, IIRC.Occupational hazard of my occupation not being around (sorry Bubba)
Box fan is runnin..it's just that the roof/cieling/walls...are still a little TOO vented..a switch set at 65 would never go off..I got about 55 average upstairs and 45 down..see?
Spheramid Enterprises Architectural Woodworks
Repairs, Remodeling, Restorations.
are still a little TOO vented
Gotta hate that "wait'll next year chinking."
Go medieval, then. Hang tapestries (blankets); elevate the furniture; extra clothing; hope for an early spring . . .Occupational hazard of my occupation not being around (sorry Bubba)
that's the ticket..then wrap the whole house in christmas tyvek till spring.I knew it would be "drafty" but this is nuts..LOL
Spheramid Enterprises Architectural Woodworks
Repairs, Remodeling, Restorations.
Thanks CapnMac, I love the capula idea but i would havto cheat to do it(building cant be taller than 14' total. So if i do it, it will be quite a but later down the road and lately my thinking is that it will be too much trouble. Also Although I understand the concept, I've only framed simple gable roofs and although i'd love to learn, I dont want to get dad in trouble with the city.Yeah, i think we'll go drywall, and we will just put conduit on the surface so that it will be sort of modular in that he could more easily change around his elec.What do you think about 3/8" drywall? to weak to support its own weight? It sure does sound appealing now that i can attatch it every 16" (thanks to piffins cool insulation idea). Both dad and I have pretty wimpy backs-->
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The only timnes to use 3/8" are for under paneling or when you want to bend it on a radiused wall, IMO. The sagging will drive you crazy and make you spend the rest of yopur life saying "I wish I had used 1/2" rock on that cieling"
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ha, okay you convinced me. I'll use 1/2"
-->
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common practice in New England. For a cieling you need 5/8" rock but 1/2" ok at 16" oc and strapping helps flateen out things.In your case, the biggest advantage is t6hat if you add the full sheets of foam to make a thermal break over the rafters, you will have a hard time hitting rafter wood with SR screws ( AKA Piffinscrews) and they would need to be longer. The strapping gives you a broader surface to hit. When using strapping on bottom of floor joists for a room above, they add strengrth to the system and help reduce sound transmitsions
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yeah, i had a friend that lived in rhode island for a few years and he said "yeah, all those nutty east-coasters do it" -'talking about strapping that is' ha, It does make sence though. It seems like it would help minimaze the effects of the cieling joists moving(drying out etc..) as well.. is that true?-->
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I can start a new thread if suggested.
I checked the roof in question and would you believe 7/8" per foot per my digital level. Not sure what minimum pitch for tin roof is but would bet that it is considerably more than this. My buddy has not looked at it yet but I am thinking that epdm roof is about all that can be done.
There are numerous issues as I said before but my thoughts are to pull down drywall ceiling till I find clean dry insulation, replace, use a vapor barrier primer I have used before and put rubber roof on. If vapor barrieried top and bottom should be no worry from moisture infiltration and with rubber roof no ice dam worry. In this climate do not think it would be a problem for this with no ventilation. As you can see in the pictures there is not a lot of hope here.
Bob
alas poor RASCONC
I knew him well
Thanks for the encouragement!
;-)
EPDM or Polyglass for the roof, with some ticklish flashing details
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Thanks, so do you agree on the venting (or lack thereof) approach? It is feasible to pull down whole ceiling/insul, foam channel and cut openings to main roof ( which does not appear to have adequate if any ventilation) but does not seem worth it.
Those swales in the roof are not an optical illusion. I know this is kind of a lost cause but this is what the poor lady has.
Edited 12/14/2004 7:20 pm ET by RASCONC
Possibly. Theory is that denspack cells need no venting. I don't see much choice here.
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Thanks, confirms my thinking. Have you seen or used the primer I was talking about that doubles or claims to be a vapor barier for DW?
PermaPrep Latex Vapor Barrier Primer/Sealer by General Paint and Manufacturing Company. It claims a perm rating of less than 1.0. I used it once when redoing a very old church plaster wall.