flightcrazed Posted April 8 Share Posted April 8 Hi all, wondering if anyone has created Ventilation drawing/s in a Cali WUI area? I'm particularly interested in a ridge vent, shed roof, and eave design with stucco exterior. I know Vulcan is an approved Ember resistant vendor and have attached one of their diagrams. Per the code, it appears to be missing the required mesh in front of the "Cor-A-Vent", if i'm interpreting it correctly. Hoping someone has created or found a drawing to put in layout for permit submission. Thanks all! Link to comment Share on other sites More sharing options...
Renerabbitt Posted April 8 Share Posted April 8 7 minutes ago, flightcrazed said: Hoping someone has created or found a drawing to put in layout for permit submission. Thanks all! You simply need a non-combustable non-corrosive mesh which you can just draw in with a cad line and add a note Link to comment Share on other sites More sharing options...
flightcrazed Posted April 8 Author Share Posted April 8 Thanks @Renerabbitt! Seems redundant to add the mesh in front of Cor-A-Vent and also have Vulcan so I'm not sure if that's a best practice. Perhaps just putting the mesh in front of the Cor-A-Vent is good enough? Link to comment Share on other sites More sharing options...
Renerabbitt Posted April 8 Share Posted April 8 17 minutes ago, flightcrazed said: Thanks @Renerabbitt! Seems redundant to add the mesh in front of Cor-A-Vent and also have Vulcan so I'm not sure if that's a best practice. Perhaps just putting the mesh in front of the Cor-A-Vent is good enough? well since you are making the argument, arguably if your substrate or insulation is not a combustible issue then the vulcan vent is your fire stop and should suffice as that is the "vent" to the building envelope Link to comment Share on other sites More sharing options...
JKEdmo Posted April 8 Share Posted April 8 25 minutes ago, flightcrazed said: Seems redundant Yes, I would argue the Vulcan vent functions as the attic vent and the Cor-a-vent is "cosmetic." The Cor-a-vent may however need to satisfy the Class A requirement of the roofing system. I'd suggest looking into that. Jim Link to comment Share on other sites More sharing options...
flightcrazed Posted April 9 Author Share Posted April 9 8 hours ago, JKEdmo said: Yes, I would argue the Vulcan vent functions as the attic vent and the Cor-a-vent is "cosmetic." The Cor-a-vent may however need to satisfy the Class A requirement of the roofing system. I'd suggest looking into that. Jim Yep, that's my dilemma. If the Cor A Vent just catches fire anyway, doesn't seem like a good design (from Vulcan). But if I put Mesh in front of Cor A Vent, probably don't need Vulcan. I haven't found an ember resistant vent in the application shown for Cor A Vent....that would be nice Appreciate the collab @JKEdmoand @Renerabbitt! Link to comment Share on other sites More sharing options...
JKEdmo Posted April 9 Share Posted April 9 I google "Class A ridge vent" and it appears there are a number of products out there: Brandguard, Air Vent, etc. Once again, I don't think you need the mesh at the ridge vent. It's already built into the Vulcan vent and it keeps embers from entering the attic space. My guess is the the ridge vent product would just need to be compatible with your Class A rated roof -- I'm assuming asphalt shingle. So, I think you could make your detail work. Link to comment Share on other sites More sharing options...
Gawdzira Posted April 9 Share Posted April 9 From that diagram, is the Vulcan vent only at that location. Do you have eave venting? In what I have built I put the Vulcan vent at the point of intake (eave in my situation). This does not make sense to me to have the Vulcan vent at this location. In theory, the top of the roof would be an exhaust as the heat would rise and exit there. But, in the event of a fire, would this still be the case? Therefore, I would supplement the Cor-A-Vent with 1/8" HDG screen mesh. Link to comment Share on other sites More sharing options...
flightcrazed Posted April 9 Author Share Posted April 9 16 minutes ago, JKEdmo said: I google "Class A ridge vent" and it appears there are a number of products out there: Brandguard, Air Vent, etc. Once again, I don't think you need the mesh at the ridge vent. It's already built into the Vulcan vent and it keeps embers from entering the attic space. My guess is the the ridge vent product would just need to be compatible with your Class A rated roof -- I'm assuming asphalt shingle. So, I think you could make your detail work. You're awesome Jim! Appreciate the help Link to comment Share on other sites More sharing options...
flightcrazed Posted April 9 Author Share Posted April 9 11 minutes ago, Gawdzira said: From that diagram, is the Vulcan vent only at that location. Do you have eave venting? In what I have built I put the Vulcan vent at the point of intake (eave in my situation). This does not make sense to me to have the Vulcan vent at this location. In theory, the top of the roof would be an exhaust as the heat would rise and exit there. But, in the event of a fire, would this still be the case? Therefore, I would supplement the Cor-A-Vent with 1/8" HDG screen mesh. Hi Alan, the plan was to use Vulcan at both ridge and eave locations (the ridge is just their continuous vent). I'll check out the HDG screen mesh as well...thanks for the recommendation! Link to comment Share on other sites More sharing options...
Gawdzira Posted April 9 Share Posted April 9 The other question is, why are you doing a vented roof assembly? There are good options for unvented assemblies even if you want to avoid spray foam at the underside of the sheathing. Depending on the size of your roof, with Vulcan vents running continuously on each side that is a lot of money. The last time I purchased Vulcan vents (a little over 2 years ago) they were over $10/ lin.ft for the eave/strip vent type. For fire issue reasons, I have been avoiding vented roof systems as well as vented crawl spaces. Link to comment Share on other sites More sharing options...
flightcrazed Posted April 9 Author Share Posted April 9 2 hours ago, Gawdzira said: The other question is, why are you doing a vented roof assembly? There are good options for unvented assemblies even if you want to avoid spray foam at the underside of the sheathing. Depending on the size of your roof, with Vulcan vents running continuously on each side that is a lot of money. The last time I purchased Vulcan vents (a little over 2 years ago) they were over $10/ lin.ft for the eave/strip vent type. For fire issue reasons, I have been avoiding vented roof systems as well as vented crawl spaces. @Gawdzira honestly I'd prefer the unvented route if I can get away with it so I appreciate you challenging me on this . I thought it would be required given the Energy Code/Title 24. Sounds like you've been able to avoid the vented route while still complying with T24. Do you have any examples (section details or references) that you'd be willing to share? Much appreciated! Link to comment Share on other sites More sharing options...
flightcrazed Posted April 10 Author Share Posted April 10 For anyone following this topic, I did speak to my T24 "guy" and Unvented is definitely an option as they have lots of levers to pull to maintain Energy compliance. Interestingly, nobody in my "circle" has done an unvented attic so I'm on my own so to speak. Will re-post back here if anyone interested. (?) Thanks! Link to comment Share on other sites More sharing options...
flightcrazed Posted April 11 Author Share Posted April 11 Curious if anyone has a CAD block they'd be willing to share for the unvented attic? (i'm working on modifying these since they are close to my design) Link to comment Share on other sites More sharing options...
flightcrazed Posted April 11 Author Share Posted April 11 @Gawdzira, curious if you lean towards something like this: or this: Link to comment Share on other sites More sharing options...
Gawdzira Posted April 12 Share Posted April 12 All of the unvented assemblies I have done so far have been Flash and Batt. I am in climate zone 3 so about 2.5" of spray foam (approx. r-19) and then batt to make up the difference to get to r-30. The spray foam goes in before the sprinkler piping to avoid a hot spray foam to piping issue. For my next project I am looking towards something like you show #2. #4 looks expensive for construction and still gets you the fire issue for embers entering the assembly. With #2, either fill that soffit with spray foam or vent it. That is an area where you will have issues if it is left as shown. Link to comment Share on other sites More sharing options...
flightcrazed Posted April 13 Author Share Posted April 13 On 4/11/2024 at 10:31 PM, Gawdzira said: All of the unvented assemblies I have done so far have been Flash and Batt. I am in climate zone 3 so about 2.5" of spray foam (approx. r-19) and then batt to make up the difference to get to r-30. The spray foam goes in before the sprinkler piping to avoid a hot spray foam to piping issue. For my next project I am looking towards something like you show #2. #4 looks expensive for construction and still gets you the fire issue for embers entering the assembly. With #2, either fill that soffit with spray foam or vent it. That is an area where you will have issues if it is left as shown. Appreciate your help here @Gawdzira! How do these look? This would be in Climate Zone 3B Link to comment Share on other sites More sharing options...
Gawdzira Posted April 13 Share Posted April 13 I think the r-5 is short on the ratio you would want for the flash and batt or "perfect roof" system. I think you want closer to 25% of your insulation value on the top side or the spray foam layer to cut off the dew point issue. Are you looking at the info from Building Science Corporation? I assume you are since you mentioned "perfect roof". https://buildingscience.com/documents/reports/rr-9904-unvented-cathedralized-attics-where-we-ve-been-and-where-we-re-going/view Link to comment Share on other sites More sharing options...
flightcrazed Posted April 13 Author Share Posted April 13 I actually used this table in the CBC to come up with the R-5 (hoping to minimize costs ). According to this table, it seems "they'd" be ok even without spray foam if i went with a tile roof (Zone 3B) but I'm not a big fan of them. Also not sure that's a best practice. The foam I'm using here is R6.8 per inch which is more likely what the result would be (vs R5). But sounds like I should step it up to 1.5"-2" to get to the 25% recommendation? I think i did find the drawings I shared previously from Building Science...was just looking for a reference to compare against my drawings. Link to comment Share on other sites More sharing options...
Gawdzira Posted April 13 Share Posted April 13 Good to know. I wonder if you could do that with Zip R on the roof sheathing layer. I will quiz my engineer about that. That would be a lot cheaper than spray foam and less likely to poison the workers. I can smell that spray foam for days and I always suspect if you can smell it, it is not your friend. Link to comment Share on other sites More sharing options...
flightcrazed Posted April 13 Author Share Posted April 13 52 minutes ago, Gawdzira said: less likely to poison the workers. I can smell that spray foam for days and I always suspect if you can smell it, it is not your friend. So true! I do like the Zip sheathing. I did however find this on their website: Despite their position, not sure why it would be any different than rigid foam. I am curious though, let me know what you find out from your engineer! I'll do some more digging as well. Link to comment Share on other sites More sharing options...
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