builtright3 Posted October 12, 2020 Share Posted October 12, 2020 I probably need a Californian for this one! This wonderful energy code is now asking for not only R-30 in the ceiling joist but also R-19 in between the roof deck rafters. I'm not sure how to show a detail with the proper air flow gap from the roof eaves to the attic. I was wondering if anyone has a detail for this or can help me out in some way? I'm under the gun and this is the final correction on this plan. These are open rafter tails with blocking. I will gladly pay for a detail if you already have one. I can draw it but I'm not even sure what it would look like. Thank You Link to comment Share on other sites More sharing options...
jmsisco Posted October 12, 2020 Share Posted October 12, 2020 Joe Check out these links they should be a good resource. The perfect wall bsi-001_perfect_wall_2010rev2_0.pdf Dept of Energy web site https://energy.gov The building America Web Site https://basc.pnnl.gov/ EEBA https://www.eeba.org/resources CAD Details https://basc.pnnl.gov/cad-files Link to comment Share on other sites More sharing options...
DzinEye Posted October 12, 2020 Share Posted October 12, 2020 Here's a couple in an article about it, but your engineer (assuming you're using one?) will usually want to know what's happening with regards to this, as sheer transfer is often involved between the roof and the walls. Usually engineer will want the holes in the center of the block not toward the top as shown in the top detail here though... in which case you need to show a baffle to hold the insulation out of the way of the vent holes. Also you'll need to calculate the venting area provided by the vent holes in relation to the 1/150th or 1/300th required venting ... fun stuff. https://www.sbcmag.info/news/2015/may/ventilation-v-eaves-blocking-seismic-zones Link to comment Share on other sites More sharing options...
builtright3 Posted October 13, 2020 Author Share Posted October 13, 2020 This is what I was trying to do. But how to I manipulate the insulation to have a 1" gap, path of travel is what im having a problem with. The title 24 is stating I have to have the insulation in-between the roof rafters and the ceiling joist which is a new requirement. I guess I'm missing something but this correction ("B") is confusing to me. Link to comment Share on other sites More sharing options...
DzinEye Posted October 13, 2020 Share Posted October 13, 2020 2 minutes ago, builtright3 said: . But how to I manipulate the insulation to have a 1" gap, path of travel is what im having a problem with Joe, post the T-24 requirements document... something seems off. You shouldn't have to insulate both up at the rafters and down at the ceiling...that makes no sense. Be that as it may... there's a product called insulation baffles or attic baffles that you can specifyhttps://www.google.com/search?q=insulation+baffles&rlz=1C1ZCEB_enUS804US804&oq=insulation+baffles&aqs=chrome..69i57j0l7.5230j0j1&sourceid=chrome&ie=UTF-8 Link to comment Share on other sites More sharing options...
jmsisco Posted October 13, 2020 Share Posted October 13, 2020 Is this what you want? or is it a cathedral ceiling? Link to comment Share on other sites More sharing options...
rlackore Posted October 13, 2020 Share Posted October 13, 2020 You may already know everything I'm about to cover, but here we go. California's rules for low-rise residential provides for two basic scenarios: If the air handlers and ducts are located in conditioned space (e.g. on a floor below the attic), then you can insulate the attic in a conventional manner, with the insulation placed above the ceiling to separate the unconditioned attic from the floor below. If you're placing the air handlers and ducts within the attic, then you have to create a conditioned space for the equipment by insulating both the ceiling (attic floor) and the roof deck; in this scenario, you don't have to condition the entire attic - you could create a separate conditioned space in the attic for the HVAC equipment. Regardless, I suggest https://www.energy.ca.gov/sites/default/files/2020-06/03-BuildingEnvelope_ada.pdf as a good starting point; start reading on page 3-52. Link to comment Share on other sites More sharing options...
builtright3 Posted October 13, 2020 Author Share Posted October 13, 2020 One thing that I noticed in the title 24 is that I don't need the radiant barrier so I'm removing it. Apparently the extra R-19 insulation has more value. Also, I spoke to the plan checker and according to code I don't need the eave vents at all. If I'm following the 1 to 150 ratio I can do it with gable vents and dormers for cross ventilation. In all the years I have been doing this I have never heard that. He said most new houses don't use eave vents because of the fire code. I don't do new construction so I would have not known that. So, I'm reading through R806 to get more familiar Thank You! Link to comment Share on other sites More sharing options...
DzinEye Posted October 13, 2020 Share Posted October 13, 2020 1 hour ago, rlackore said: but here we go Thx for posting that Robert! I've never yet had either of my regular T-24 consultants recommend the solution with insulation in both rafters and ceiling so that was news to me. In houses with cathedral ceilings I almost always urge homeowners to spring for spray foam insulation so the attic is conditioned and there's no issues with venting or HVAC equipment in non-conditioned space. Ever since I stopped doing my own T-24 calcs years ago when it required special software I stopped trying to keep up with the rules and leave it up to the consultants. Link to comment Share on other sites More sharing options...
builtright3 Posted October 14, 2020 Author Share Posted October 14, 2020 Here is the Title 24 if in reviewing T24.pdf Link to comment Share on other sites More sharing options...
Gawdzira Posted October 14, 2020 Share Posted October 14, 2020 Holy guacamole. I am glad I looked at this thread. That code item is banana-pants. Link to comment Share on other sites More sharing options...
jmsisco Posted October 14, 2020 Share Posted October 14, 2020 Here is a detail that may work for you. See the attached pdf document for an Insulation resource. The project is in Climate zone 9 and requirements will depend on if you are doing a vented or non vented attic. 102219_BI_BID_285_CA_Title24_MultiFamily.pdf Link to comment Share on other sites More sharing options...
builtright3 Posted October 14, 2020 Author Share Posted October 14, 2020 Just now, jmsisco said: Here is a detail that may work for you. See the attached pdf document for an Insulation resource. The project is in Climate zone 9 and requirements will depend on if you are doing a vented or non vented attic. 102219_BI_BID_285_CA_Title24_MultiFamily.pdf Thank you, this is helpful Yes that helps because it gives me a visual for what I need to do. I will have to v=create it without the soffit because mine are open rafter. I wont need it right now though because the plan checker says I don't need to do eave vents and I can just use dormer vents. Link to comment Share on other sites More sharing options...
builtright3 Posted October 14, 2020 Author Share Posted October 14, 2020 23 hours ago, DzinEye said: Joe, post the T-24 requirements document... something seems off. You shouldn't have to insulate both up at the rafters and down at the ceiling...that makes no sense. Be that as it may... there's a product called insulation baffles or attic baffles that you can specifyhttps://www.google.com/search?q=insulation+baffles&rlz=1C1ZCEB_enUS804US804&oq=insulation+baffles&aqs=chrome..69i57j0l7.5230j0j1&sourceid=chrome&ie=UTF-8 Thank you, this is good information. I resolved my problem and I will keep this for future reference Link to comment Share on other sites More sharing options...
builtright3 Posted October 14, 2020 Author Share Posted October 14, 2020 22 hours ago, rlackore said: You may already know everything I'm about to cover, but here we go. California's rules for low-rise residential provides for two basic scenarios: If the air handlers and ducts are located in conditioned space (e.g. on a floor below the attic), then you can insulate the attic in a conventional manner, with the insulation placed above the ceiling to separate the unconditioned attic from the floor below. If you're placing the air handlers and ducts within the attic, then you have to create a conditioned space for the equipment by insulating both the ceiling (attic floor) and the roof deck; in this scenario, you don't have to condition the entire attic - you could create a separate conditioned space in the attic for the HVAC equipment. Regardless, I suggest https://www.energy.ca.gov/sites/default/files/2020-06/03-BuildingEnvelope_ada.pdf as a good starting point; start reading on page 3-52. Thank you for your help! Link to comment Share on other sites More sharing options...
Gawdzira Posted October 14, 2020 Share Posted October 14, 2020 I would consider a methodology to avoid attic / roof venting altogether. If you put a layer of rigid insulation on top of the roof sheathing you can avoid the need to ventilated the roof. The thickness of the insulation will vary according to your climate zone. I am very paranoid about any roof vents. Roof and eave vents are the most common ways for fire embers to enter a house. If you must use vents, look for fire safe venting options. Link to comment Share on other sites More sharing options...
builtright3 Posted October 14, 2020 Author Share Posted October 14, 2020 I found out that Eave vents are not required if I can use dormer and gable vents and I like that better. I'm not concerned with fire too much because 99% of my remodels are not in high fire zones and they are all additions so the existing house would not be altered for fire and it would only be the addition so what's the point anyway and I want to keep a consistent look. Also, we don't always replace the entire roof so we have to match up with existing. Thank you for your input, its is very much appreciated. Link to comment Share on other sites More sharing options...
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