Cathedral/attic hybrid...ventillation?

Hello, all! I’ve recently begun planning for a re-roof on my house. I’ve discovered lots of…interesting choices by the previous homeowners that I’ll not delve into currently. The one issue I would like to discuss is, venting my semi-cathedral ceiling in my added-on family room. I’m sure there’s a better term than “semi-cathedral ceiling” for it than that, but for now, it’s all I’ve got. What happens is, at the walls, it begins as a cathedral ceiling, with the drywall ceiling following the pitch of the roof, until about halfway up each side, at which point, it levels off, and there’s a tiny attic space I cannot get into (the ductwork for the room runs through the only opening big enough for a human to fit in). There’s currently an ancient aluminum ridge vent running the length of the attic, and a tiny gable vent.

So, in attempting to be proactive on a rainy day, I thought I’d install a soffit vent or two, as there was none previously. So, I cut into the plywood soffit, and see what appears to be R-90 between the rafters; much too in the way for any kind of airflow, let alone the proper variety. At this point, does anyone have any thoughts on what I should try? I’d prefer not to pull up the decking (OSB) and apply spray-foam-type insulation, but I do want to do it right (dammit).

And, hi. 8)

You probably have enough insulation to stop any heat gain from the roof into your house. If you want to have air flow for this roof you need to install a system called vented nailbase. This is a layer of polyisocyanurate insulation, 1" airspace, 1/2" OSB laminated together. You install shingles on top of the OSB. This system utilizes a ridge vent and eave or soffit ventillation. Data sheet: rmax.com/files/9013/9964/912 … 7-2013.pdf

Thanks! So, would I run this up until the attic opens, or all the way up? My concern would be for the stagnant attic space. I’m no pro or anything, so I might be over-thinking it, but just want to be sure so the next homeowner isn’t cussing ME! :stuck_out_tongue:

All the way up.

Hunter panels like suggested by DonL are a great way to achieve the desired results, but IMO you can get a better result for roughly the same cost by installing a cold roof.

Thanks for chiming in! I’m having a bit of difficulty finding where to actually buy this type of material. Axiom - how would you suggest implementing a cold roof in this situation? Would you run the vented polyiso up the cathedral portion, then leave it open when the attic opens up, with insulation at the attic floor? Please let me know if any more information would be helpful!

If you’re looking for Hunter Panel then call their toll free number and they will give you the nearest dealer.

hpanels.com/index.php/engine … -208188024

I agree with Axiom. If you positively don’t want more insulation, a cold roof will do the trick. Basically, this is the vented system without insulation. Lay 1x2’s perpendicular to the eaves all the way to the ridge then put OSB over them. Vent the ridge and eave/soffit.

You could build your own insulated nail base panel, and it would probably be cheaper. Nail down insulation, then screw down vertical strapping, and then new OSB over the strapping.

Thanks for the insight, guys! I’m assuming, if I go that route, I’ll want to block off the little gable vent?

[quote=“johnnyreece”]Hello, all! I’ve recently begun planning for a re-roof on my house. I’ve discovered lots of…interesting choices by the previous homeowners that I’ll not delve into currently. The one issue I would like to discuss is, venting my semi-cathedral ceiling in my added-on family room. I’m sure there’s a better term than “semi-cathedral ceiling” for it than that, but for now, it’s all I’ve got. What happens is, at the walls, it begins as a cathedral ceiling, with the drywall ceiling following the pitch of the roof, until about halfway up each side, at which point, it levels off, and there’s a tiny attic space I cannot get into (the ductwork for the room runs through the only opening big enough for a human to fit in). There’s currently an ancient aluminum ridge vent running the length of the attic, and a tiny gable vent.

So, in attempting to be proactive on a rainy day, I thought I’d install a soffit vent or two, as there was none previously. So, I cut into the plywood soffit, and see what appears to be R-90 between the rafters; much too in the way for any kind of airflow, let alone the proper variety. At this point, does anyone have any thoughts on what I should try? I’d prefer not to pull up the decking (OSB) and apply spray-foam-type insulation, but I do want to do it right (dammit).

And, hi. 8)[/quote]

I’d say if your add-on isn’t hotter than the rest of the house in the summer or colder in the winter, don’t fix it. I don’t think the pay off would be worth the hassle.

It actually is. I’d blamed it on shoddy ductwork (which is very likely still part of the issue), but this can’t help. Oh, and, I don’t know what I was typing when I hit R-90…I believe the rafters are 2x6, which definitely excludes R-90…I’m still mulling over ideas. I’ll keep everyone posted with the final plan!

Gentlemen, it appears that I’m going to have to compromise here…I don’t see anything that’s going to be cost-effective, nor feasible without making a lot of other changes…It’s about the lowest I’ve felt so far in trying to get things “right”. I think I’m going to have to just give up on this, and try to fix this at a later time by ripping out drywall and extending towards the inside rather than out. As crazy as it’s making me to do it, I think that’s the route I’ll have to go.

I’ve verified that, in the 5.5" my rafters have, I’ve got R19 right now, which should have 6+inches. From what I’ve gathered, this is probably performing somewhere around R17, as it is. Living in Indiana, this is nowhere close to the R38-R60 I’m recommended to have. I want to do violent things to the previous “contractors” right now…Them, and the home inspector who told me everything was hunky-dory when I moved in. Iso board, while offering a higher R value, is not a possibility for me with minimum orders required…

The best solution I’ve been able to come up with (that is in my budget) provides ventilation, but only a modest improvement in R value. I can remove the R19, install R15 at 3.5", then install 1" R5 board over top of that, leaving 1" of ventilation, and a total of R20. I could also install R21 fiberglass, but I’d prefer to have a layer of solid insulation to avoid condensation issues in the ceiling.

I’m sorry to be one of those people who ask for advice only to ignore it, but this is getting much bigger than my pocketbook and ambition can handle. I do offer sincere thanks for all the thought put into this!

[quote=“johnnyreece”]Gentlemen, it appears that I’m going to have to compromise here…I don’t see anything that’s going to be cost-effective, nor feasible without making a lot of other changes…It’s about the lowest I’ve felt so far in trying to get things “right”. I think I’m going to have to just give up on this, and try to fix this at a later time by ripping out drywall and extending towards the inside rather than out. As crazy as it’s making me to do it, I think that’s the route I’ll have to go.

I’ve verified that, in the 5.5" my rafters have, I’ve got R19 right now, which should have 6+inches. From what I’ve gathered, this is probably performing somewhere around R17, as it is. Living in Indiana, this is nowhere close to the R38-R60 I’m recommended to have. I want to do violent things to the previous “contractors” right now…Them, and the home inspector who told me everything was hunky-dory when I moved in. Iso board, while offering a higher R value, is not a possibility for me with minimum orders required…

The best solution I’ve been able to come up with (that is in my budget) provides ventilation, but only a modest improvement in R value. [highlight=#ff4080]I can remove the R19, install R15 at 3.5", then install 1" R5 board over top of that, leaving 1" of ventilation, and a total of R20. I could also install R21 fiberglass, but I’d prefer to have a layer of solid insulation to avoid condensation issues in the ceiling.[/highlight]I’m sorry to be one of those people who ask for advice only to ignore it, but this is getting much bigger than my pocketbook and ambition can handle. I do offer sincere thanks for all the thought put into this![/quote]

That sounds a little bit like running around in circles to me. taking out insulation and putting two kinds in. If you are re-roofing this is the time to fix the problem. It seems to me that "shazapple"s idea of nailing insulation on top of your sheathing then adding some verticle boards to create an air space and then osb on top of that should be doable. :lol: that’s easy for me to say, It took me a year to do my roof without adding insulation.

[quote=“xrayguy”]
That sounds a little bit like running around in circles to me. taking out insulation and putting two kinds in. If you are re-roofing this is the time to fix the problem. It seems to me that "shazapple"s idea of nailing insulation on top of your sheathing then adding some verticle boards to create an air space and then osb on top of that should be doable. :lol: that’s easy for me to say, It took me a year to do my roof without adding insulation.[/quote]

Yeah, I’m looking at it again with fresh eyes this morning. I may have found a local supplier who can get me what I need at a cost within reason. Coupled with a new and improved idea on what I might do (insert laughter here), I think it might be do-able. I’m thinking of building the roof up over the vaulted portion of the house. I’ve done a crappy MS Paint picture to describe what it will look like. Please excuse the lack of detail/talent. I’m thinking of adding 4" Polyiso, with 1" furring strips topped off with 7/16" OSB. That should add another 20+ to the R value of my roof, which should get me close to where I need to be. Does this look feasible?

[quote=“johnnyreece”]

[quote=“xrayguy”]
That sounds a little bit like running around in circles to me. taking out insulation and putting two kinds in. If you are re-roofing this is the time to fix the problem. It seems to me that "shazapple"s idea of nailing insulation on top of your sheathing then adding some verticle boards to create an air space and then osb on top of that should be doable. :lol: that’s easy for me to say, It took me a year to do my roof without adding insulation.[/quote]

Yeah, I’m looking at it again with fresh eyes this morning. I may have found a local supplier who can get me what I need at a cost within reason. Coupled with a new and improved idea on what I might do (insert laughter here), I think it might be do-able. I’m thinking of building the roof up over the vaulted portion of the house. I’ve done a crappy MS Paint picture to describe what it will look like. Please excuse the lack of detail/talent. I’m thinking of adding 4" Polyiso, with 1" furring strips topped off with 7/16" OSB. That should add another 20+ to the R value of my roof, which should get me close to where I need to be. Does this look feasible?[/quote]

My gut reaction to that idea is, it would be like building a roof on top of a mattress. I could see running 2x4s up the roof and then laying the insulation in between them, then OSB nailed to the 2x4s… 2x6s would give more room for insulation. Im not sure how stable that would be.

[quote=“xrayguy”]

[quote=“johnnyreece”]

Yeah, I’m looking at it again with fresh eyes this morning. I may have found a local supplier who can get me what I need at a cost within reason. Coupled with a new and improved idea on what I might do (insert laughter here), I think it might be do-able. I’m thinking of building the roof up over the vaulted portion of the house. I’ve done a crappy MS Paint picture to describe what it will look like. Please excuse the lack of detail/talent. I’m thinking of adding 4" Polyiso, with 1" furring strips topped off with 7/16" OSB. That should add another 20+ to the R value of my roof, which should get me close to where I need to be. Does this look feasible?
My gut reaction to that idea is, it would be like building a roof on top of a mattress. I could see running 2x4s up the roof and then laying the insulation in between them, then OSB nailed to the 2x4s… 2x6s would give more room for insulation. Im not sure how stable that would be.[/quote]

I don’t like the idea of nailing 2x4’s over foam either but I have worked with a couple builders that have done it.

My concern is that the 2x4’s aren’t tight against wood and the only thing really holding them (and the sheathing attached to them) is the nails that are going through 2" of foam before hitting any wood.
That is an awful lot of shear that fastener has to endure.

It seems to me that under the right conditions the whole roof assembly can shift or eventually slide downward.

Personally I would use screws, not nails. The Hunter panels are OSB glued to little strips of styrofoam, which are glued to board insulation. The whole thing is screwed down anyway so it’s not much different.

I installed board insulation on the inside of my cathedral ceiling at home. It’s a great way to get extra R-value and lower thermal bridging, but it’s a pain in the ass to install. Transitions and light fixtures take some work, cutting is messy, and putting the screws in is hit or miss. It’s far easier than cutting and fitting board insulation between

Yes, I was planning on this method, borrowing the installation instructions from the premade panels (Rmax, Hunter, etc.). I suppose I could use lag bolts to fasten through the furring strips :lol: I do plan on marking where my rafters are so that I’m not just using the original decking to fasten to, if possible.

Just checking, it seems that the following might be appropriate fasteners:

bestmaterials.com/detail.aspx?ID=16665

Any thoughts?