Has anyone here succeded in having Los Angeles Department of Building and Safety approve an unvented attic? I spoke with them today and they said, there is absolutely no provision for an unvented attic in the City of LA.

The City of LA is as tough as it gets when dealing with the building department. There are provisions in the Calif. Title 24 which allows an engineering performance approach to supersede building energy codes if they prove to be more effective than the code stated.The city is probably more concerned with moisture and condensation problems which could causie damage to the structure and roof components.You will need a engineer and architect to do battle for you.

Maybe you should call it "storage space that is part of the conditioned interior".

Greetings,

Yes, there are problems with moisture migrating(?) to the attic from the earth in your area. The most critical time seems to be up to about 12 pm.

The best insulation for this problem is RB, however, I don't know if the cal energy comm is still being influenced by the FG industry.

Several years ago the RB industry presented data to the comm that the RB performed better than the FG, but due to pressure (?) by the FG industry they voted against the RB.

You might get LA city to approve the RB if you use the installation method I recommend and show heat gain data that I supply in my article. You can't beat 2 btu/hr/sf on a 100 deg day.

I can't think of the town, but you have Superior Insulation Mfg Co out there in your area.

Posted By rbisys1 on 06 Sep 2011 08:12 PM
Greetings,

Yes, there are problems with moisture migrating(?) to the attic from the earth in your area. The most critical time seems to be up to about 12 pm.

The best insulation for this problem is RB, however, I don't know if the cal energy comm is still being influenced by the FG industry.

Several years ago the RB industry presented data to the comm that the RB performed better than the FG, but due to pressure (?) by the FG industry they voted against the RB.

You might get LA city to approve the RB if you use the installation method I recommend and show heat gain data that I supply in my article. You can't beat 2 btu/hr/sf on a 100 deg day.

I can't think of the town, but you have Superior Insulation Mfg Co out there in your area.

When you say RB, what are you referring to exactly?

Condensation in roof assemblies from interior moisture drives is not a problem in an Los Angeles climate. Thermally it can be made to work.

IN 2010 CA adopted R806.4 from the IRC into the CRC. See Section 67 e on page 5 of this document:

http://ladpw.org/BSD/lib/fp/Building/Residential/2011%20Code%20Version/2011%20Residential%20Plan%20Review%20List.pdf


Los Angeles is in Climate Zone 3. The text of R806.4:


----------------------------------------------------------------------------------------------------------

R806.4 Unvented attic assemblies. Unvented attic assemblies (spaces between the ceiling joists of the top story and the roof rafters) shall be permitted if all the following conditions are met:

1. The unvented attic space is completely contained within the building thermal envelope.

2. No interior vapor retarders are installed on the ceiling side (attic floor) of the unvented attic assembly.

3. Where wood shingles or shakes are used, a minimum 1/4 inch (6 mm) vented air space separates the shingles or shakes and the roofing underlayment above the structural sheathing.

4. In climate zones 5, 6, 7 and 8, any air-impermeable insulation shall be a vapor retarder, or shall have a vapor retarder coating or covering in direct contact with the underside of the insulation.

5. Either Items 5.1, 5.2 or 5.3 shall be met, depending on the air permeability of the insulation directly under the structural roof sheathing.

5.1. Air-impermeable insulation only. Insulation shall be applied in direct contact with the underside of the structural roof sheathing.

5.2. Air-permeable insulation only. In addition to the air-permeable installed directly below the structural sheathing, rigid board or sheet insulation shall be installed directly above the structural roof sheathing as specified in Table R806.4 for condensation control.

5.3. Air-impermeable and air-permeable insulation. The air-impermeable insulation shall be applied in direct contact with the underside of the structural roof sheathing as specified in Table R806.4 for condensation control. The air-permeable insulation shall be installed directly under the air-impermeable insulation.

TABLE R806.4 INSULATION FOR CONDENSATION CONTROL



CLIMATE ZONE MINIMUM RIGID BOARD ON AIR-IMPERMEABLE INSULATION R-VALUEa

2B and 3B tile roof only ----------------- 0 (none required)

1, 2A, 2B, 3A, 3B, 3C -------------------R-5

4C-------------------------------------------R-10

4A, 4B-------------------------------------- R-15

5-------------------------------------------- R-20

6-------------------------------------------- R-25

7--------------------------------------------R-30

8--------------------------------------------R-35

------------------------------------------------------------------------------------------------

http://publicecodes.citation.com/icod/irc/2009/icod_irc_2009_8_sec006_par003.htm


Basically, don't build yourself a moisture trap by putting up an interior-side vapor barrier, use a minimum of R5 between the interior an the less permeable exterior, and you'll be good to go. An inch of XPS above the roof deck, or an inch of closed cell spray foam on the interior would allow you to fill in the rest of the code-minimum R with cheaper fiber. (An all open-cell solution works there too.)

DANA1 you are referencing the County of Los Angeles. I am asking about the City of Los Angeles. Even though the city is in the county, the city has their own guidelines and requirements (which are probably the strictest and most ridiculous in the country). I am pretty sure the city also adopted the CRC as you indicate, but they excise or "don't adopt" certain aspects of it. I believe the unvented attic being one of the sections. Unfortunately, when you call to talk with an inspector, they are jerks and don't really want to answer any questions!

I've never built in L.A., but I've definitely run into jerk-of-a-clerk inspectors more than once. See if you can't find the relevant section in the most current version of the city code either online, or in the library, and make a copy of it. I didn't find an exception or amendment to R806.4 in the L.A. code amendments here:

http://www.amlegal.com/nxt/gateway.dll?f=templates&fn=default.htm&vid=amlegal:lamc_ca

Scroll down to division 15 "Roofs and Roof Structures".

See also:

http://ladbs.org/LADBSWeb/codes.jsf#amlegal

Greetings,

07 Sep 2011 10:17 AM QuoteQuote ReplyReply AlertAlert
IN 2010 CA adopted R806.4 from the IRC into the CRC. See Section 67 e on page 5 of this document:

http://ladpw.org/BSD/lib/fp/Building/Residential/2011%20Code%20Version/2011%20Residential%20Plan%20Review%20List.pdf


Los Angeles is in Climate Zone 3. The text of R806.4:


----------------------------------------------------------------------------------------------------------

R806.4 Unvented attic assemblies. Unvented attic assemblies (spaces between the ceiling joists of the top story and the roof rafters) shall be permitted if all the following conditions are met:

1. The unvented attic space is completely contained within the building thermal envelope.

2. No interior vapor retarders are installed on the ceiling side (attic floor) of the unvented attic assembly.

3. Where wood shingles or shakes are used, a minimum 1/4 inch (6 mm) vented air space separates the shingles or shakes and the roofing underlayment above the structural sheathing.

4. In climate zones 5, 6, 7 and 8, any air-impermeable insulation shall be a vapor retarder, or shall have a vapor retarder coating or covering in direct contact with the underside of the insulation.

5. Either Items 5.1, 5.2 or 5.3 shall be met, depending on the air permeability of the insulation directly under the structural roof sheathing.

5.1. Air-impermeable insulation only. Insulation shall be applied in direct contact with the underside of the structural roof sheathing.

5.2. Air-permeable insulation only. In addition to the air-permeable installed directly below the structural sheathing, rigid board or sheet insulation shall be installed directly above the structural roof sheathing as specified in Table R806.4 for condensation control.

5.3. Air-impermeable and air-permeable insulation. The air-impermeable insulation shall be applied in direct contact with the underside of the structural roof sheathing as specified in Table R806.4 for condensation control. The air-permeable insulation shall be installed directly under the air-impermeable insulation.

TABLE R806.4 INSULATION FOR CONDENSATION CONTROL



CLIMATE ZONE MINIMUM RIGID BOARD ON AIR-IMPERMEABLE INSULATION R-VALUEa

2B and 3B tile roof only ----------------- 0 (none required)

1, 2A, 2B, 3A, 3B, 3C -------------------R-5

4C-------------------------------------------R-10

4A, 4B-------------------------------------- R-15

5-------------------------------------------- R-20

6-------------------------------------------- R-25

7--------------------------------------------R-30

8--------------------------------------------R-35

------------------------------------------------------------------------------------------------



QUOTE:Basically, don't build yourself a moisture trap by putting up an interior-side vapor barrier, use a minimum of R5 between the interior an the less permeable exterior, and you'll be good to go. An inch of XPS above the roof deck, or an inch of closed cell spray foam on the interior would allow you to fill in the rest of the code-minimum R with cheaper fiber. (An all open-cell solution works there too.)

Very good, you just built yourself a moisture trap.

RB is for Radiant Barrier.

One thing I did forget and is very important is to use a vapor barrier on the ground before you pour concrete.

Another thing that can help alleviate the problem is to use tile roofing as that provides alot of air circulation and allows moisture to escape.

Since you are a high AC use area go to : koolcoat.com and talk to Chuck about spraying ceramic beads over the roof tiles, if you use tiles. This will take a big thermal load off the roof sys. You can also spray ceramics over the stucco wall finish. Since the exterior surfaces are the first line of defense the ceramic beads would save alot of energy, especially if the bld;g inspector forces you to use inferior insulation.

One thing I forgot to mention in my previous comments about the Cal Energy Comm is that the probable primary reason that they endorsed FG was because you use 2-3 times as much energy to AC the home as with radiant barriers. That energy is taxed and brings in millions of dollars in revenue. For millions of dollars do you think they care how much it costs you or the old folk heat deaths?

Stay away from FG or cellulose in your area.

Greetings,

I should address another subject about insulating any building.

To minimize problems you should insulate the space closest to the interior living. That is stud areas and the cord area above the ceiling. Any time you start moving the insulation envelope away from those areas you open your self to problems. Doing this and using a eff ridge vent/ soffit vent sys will give you about as good as you can get on a standard construction build'g.

Certainly using the attic as a large vented rainscreen is proven and works well. But so do other designs.

jonr, haven't you figured it out yet? In the world according to rbisys1 all fiber insulation in any stackup is by definition a non-performing moisture trap, QED. ('ceptin' maybe for the "D" ;-)   Don't waste your time.)

Dana. John and others, I use these forums to expand my knowledge and better inform my customers on making better decisions. I am taken back by some individuals that try to promote their businesses and believes no matter what the real truth may be. The sad truth is there are lots of people that will take anything that is posted on these forums and think that it is the gospel truth.I will continue to weed through the posts and learn what I can and discard the myths and other non informative statements.

Greetings,

QUOTE: jonr, haven't you figured it out yet? In the world according to rbisys1 all fiber insulation in any stackup is by definition a non-performing moisture trap, QED. ('ceptin' maybe for the "D" ;-) Don't waste your time.)

In any situation FG is a poor performer. According to in house test by O. C. in insitu testing. the best they could get was about "R"5.73 for their 3.5" batt. That's about 1.64 "R" per 1" So explain how FG got up to "R" 4/ in?

Also explain why a FG, no AC house with no roof shade on a 95 deg day will get up to 100+ Deg on the interior and a RB house only about 80 Deg? Isn't the FG suppose to retard heat flow? Why do think ACs run all day and half the nite with FG?

Also you have to take into consideration the absrb.emiss of the materials. A 5-10% eff (FG) will be subservient to a 20% eff foam as will both of those be subservient to a .97% eff material, RB. The lowest absorb / emiss material will always dominate. For instance if you put a RB on a sheet of foam the RB becomes the dominate insulator. RB 97% eff, foam about 20% eff. In other words the least efficient material will have little or no eff on the sys, in other words about useless.

This is particularly true since the first 3-4" of any bulk insulation is going to save up to 80% of the energy that it can save, not energy actually saved. If you go from a "R" 19 in the ceiling to a "R" 38 the increase in insul eff ( not energy saved) is about 6.5 %, hardly worth the time and effort. So just how many "R" factors do you want to waste money on? In fact your losing heat to the second "R" 19 almost as fast as you lose it to the air.

You don't have to have dripping moisture to dramatically reduce the insulation effectiveness. High humidity alone can do that.

Send me an E-m and I'll send you the NBS tests and other info that will help you understand.

QUOTE: Certainly using the attic as a large vented rainscreen is proven and works well. But so do other designs

Yes they can work, but you're opening yourself up to additional possible problems.
The roof sys has to breathe and the best way is to keep as much wood as possible exposed.
Keep it simple and use proven by time methods. Insul next to drywall, quality ridge vent sys. cor-a-vent.com

rbisys1 - how about if you get a couple of coolers, do some tests comparing cellulose, fiberglass, foam and rb and then we discuss the results?

And here he thinks all fiber insulation is low-density low-performance fiberglass too, go figure?

And company test data or third party test data is somehow only available backchannel, not online?

Seriously jonr- don't waste your time!

So I did a little research (DANA1 inspired me by citing the codes).  Anyhow, here is what I have come up with so far.  The section of the CRC that allows unvented attics is Chapter 8, specifically, R806.4 Unvented attic assemblies.  Then I found this document from the LA CIty Attorney  (see page 25) in which it appears that Chapter 8 of the CRC is adopted.  It notes some exceptions, but my preliminary reading didn't notice unvented attics.  So, if I am correct the inspector I spoke with has failed to read the CRC which was recently adopted in the city.


I am going to do some more reading.  But do you think I am correct?  Am I missing a particular link?

So my next question is  . . . assuming its allowed - I am tryin gto decipher R806.4.  There is alot of technical language in there about air permeable, etc.  Assuming a standing seam metal roof, is there anything special that needs to be done to meet the code?  Or if I use spray foam under the roof sheathing will that suffice?

I'm thinking you ARE correct- building inspectors aren't neccesarily avid readers (and they're certainly not as a class the best building-scientists.) Legally you should be able to pull this off, but with jerk-inspectors you often have to play patty-cake with 'em or they'll make your life miserable- don't go out of your way to prove how right you were, or how wrong they were, eh? ;-) It was only drafted into the CRC last year, after all, most inspectors are probably still in the dark on that aspect.