Allowable EIFS foam thickness to triple

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Author Message Bob Woodburn, RA CSI CCS CCCA LEED AP Senior Member Username: bwoodburn Post Number: 275 Registered: 01-2005 Posted on Monday, March 02, 2009 - 02:50 pm:    Sto Corp.'s Winter 2009 issue of Protect (just received) says "Codes on exterior insulation and finish system (EIFS) claddings no longer limit projects and manufacturers to the 4-inch thickness that has long been the standard. Changes in the wording of Chapter 26, Section 2603 of the International Building Code now allow for any thickness, based on mandated individual manufacturer testing. This is big news, and will ultimately bring building enclosures and the industry one step closer to carbon neutrality." But at the top of the same page it says "EIFS up to 12" is allowed, boosting R-values." How that statement goes with "Changes...now allow for any thickness" in the quote above is anybody's guess. Mine would be that some company, perhaps Sto, has successfully tested a system using 12-inch foam, but no thicker. Conceiveably, a 3-1/2 inch stud wall with high-density fiberglass batts (R-15) and 12" of high-density EPS foam (R-57.6, at 4.8 per inch) could have a total insulation R-value of 72.6 (or 59.4, with low-density EPS, 3.7 per inch) -- a dramatic improvement in total R-value over what is currently feasible. Any comments? Curt Norton, CSI, CCS Senior Member Username: curtn Post Number: 132 Registered: 06-2002 Posted on Monday, March 02, 2009 - 03:09 pm:    Bob - I believe you have it right. The code becomes unlimited, but each system has to be tested before using that thickness. Hoever, the goal of being able to add insulation to the exterior of the wall is to keep your stud cavity warmer and free of insulation. If you keep your dew point in the EIF system, you eliminate one of the many potential problems with the exterior wall assembly. Adding a weather/air barrier coating to exterior side of the stud sheathing protects the wall from bulk moisture and creates a near perfect wall regardless of climate. The key is ALWAYS perform a dew point analysis on your wall assemblies. Wayne Yancey Senior Member Username: wayne_yancey Post Number: 166 Registered: 01-2008 Posted on Monday, March 02, 2009 - 03:13 pm:    Well said Curt. It is good to find and hear from another member of the choir. Curt Norton, CSI, CCS Senior Member Username: curtn Post Number: 134 Registered: 06-2002 Posted on Monday, March 02, 2009 - 03:17 pm:    Thanks. It'ss good to know we are not completely alone! Bob Woodburn, RA CSI CCS CCCA LEED AP Senior Member Username: bwoodburn Post Number: 276 Registered: 01-2005 Posted on Monday, March 02, 2009 - 03:43 pm:    This office typically performs dew point analyses. Reminds me of something that mystified me for the first decade or two of my career. All the relevant publications recommended a vapor barrier on the "warm side" of the wall. But I couldn't find an answer to "Which side is the warm side? (or "Which warm side?) That is, until USG published recommendations that it be located on the outside in warm, humid climates, and on the inside up north -- and that it didn't matter much whether there even was one in the area in between (defined by lines on a map). Of course, that was before "air barriers," let alone dew point analyses. I wonder how many vapor barriers are on the wrong side due to confusion... Randall A Chapple, AIA, SE, CCS, LEED AP Senior Member Username: rachapple Post Number: 26 Registered: 12-2005 Posted on Monday, March 02, 2009 - 05:57 pm:    Bob, The warm side is correct. Unfortunately in many climates the warm side can vary throughout the year! Bob Woodburn, RA CSI CCS CCCA LEED AP Senior Member Username: bwoodburn Post Number: 277 Registered: 01-2005 Posted on Monday, March 02, 2009 - 06:10 pm:    My point exactly. Still looking for a vapor barrier that automatically relocates itself from one warm side to the other on those occasions... Ronald L. Geren, AIA, CSI, CCS, CCCA, SCIP Senior Member Username: specman Post Number: 743 Registered: 03-2003 Posted on Monday, March 02, 2009 - 06:42 pm:    Just put it on both sides! ;-) Just kidding, obviously. But you want to place the vapor retarder on the warm side with the higher humidity. For example, if during winter the humidity inside is higher than the humidity would be outside during summer, then inside would be the worse case situation, and vice versa. Ronald L. Geren, AIA, CSI, CCS, CCCA, SCIP RLGA Technical Services www.specsandcodes.com Ron Beard CCS Senior Member Username: rm_beard_ccs Post Number: 295 Registered: 10-2002 Posted on Monday, March 02, 2009 - 07:08 pm:    How much is the R-value reduced by a drainage panel or mesh in an EIFS system? Bob Woodburn, RA CSI CCS CCCA LEED AP Senior Member Username: bwoodburn Post Number: 278 Registered: 01-2005 Posted on Tuesday, March 03, 2009 - 09:56 am:    Curt, you wrote, "the goal of being able to add insulation to the exterior of the wall is to keep your stud cavity warmer and free of insulation." Yes, it keeps the stud cavity warmer. But if analysis confirms that the dew point is located well within the EIFS insulation (with insulation also in the stud cavity) doesn't the additional insulation help save more energy? And isn't that good? Or is there some inherent benefit in leaving the stud cavity "free of insulation"? Randall A Chapple, AIA, SE, CCS, LEED AP Senior Member Username: rachapple Post Number: 27 Registered: 12-2005 Posted on Tuesday, March 03, 2009 - 11:35 am:    We typically design rainscreen systems with an air/vapor barrier on the sheathing covered by insulation and the cladding material. Works for all climates. Bob Woodburn, RA CSI CCS CCCA LEED AP Senior Member Username: bwoodburn Post Number: 279 Registered: 01-2005 Posted on Tuesday, March 03, 2009 - 12:18 pm:    Insulation outside the air/vapor barrier? What is the air/vapor barrier--a liquid-applied system? J. Peter Jordan Senior Member Username: jpjordan Post Number: 312 Registered: 05-2004 Posted on Tuesday, March 03, 2009 - 01:10 pm:    In Houston (where Bob and I work), it is almost always more humid outside than it is inside, even in the winter. I would argue that this does not change much until you get up to the Dallas area. I have seen, however, a chart that address this issue based on the number of heating/cooling days in a year. I have worked on buildings in climates where it was always "warm" (or at least damp) outside. Diego Garcia comes to mind as does Fiji. Hawaii depends too much on where you are. If you are working on one of the telescope facilities atop Mauna Kea (at 14,000 ft. above sea level; where it snows), then you don't want to do the same thing you do for a destination resort on Kohola coast (at about 30 ft. above sea level; about 50 or 60 miles away from the telescopes). Just goes to show you that it isn't only general location that determines design parameters. There are many areas where "micro climates" may differ dramatically from the general climate conditions in a particular area. Curt Norton, CSI, CCS Senior Member Username: curtn Post Number: 135 Registered: 06-2002 Posted on Tuesday, March 03, 2009 - 01:23 pm:    Yes, saving energy is better. However there are a couple of other factors to consider. 1. There is nothing wrong with insulation in the stud cavity per se. If you have a mass wall with enough insulation that the dew point stays in the rigid plastic foam, you would be fine. Because most walls end up being 6 inch nom thickness, that creates a lot of R-value in the wall. The rule of thumb I recall is that 2/3 needs to be outside the sheathing. Therefore you would need at least R-38 outboard. That would be about 11 inches of extruded foam. I can’t imagine the cost of all that insulation could be justified when energy payback time is considered. (plus, after spending that money, how much heat loss do you end up with in your windows and doors?) 2. R-Values for stud wall systems are calculated based on theory and not measured. Most of the loss in a system is from air leakage. Next is thermal transfer. The old ‘averaging” method for calculating R-value of a stud wall without continuous insulation has too many flaws. If you get frost on the interior of the wall in winter, you can through the R-value of the system out the window. 3. If my memory serves me correctly, you can stop about 80% of your heat loss with 1 inch of continuous XPS. Each additional inch only cuts down 50% of the remaining heat loss. (I may not have this stated exactly right. I need to check my resources, but you get the idea) 4. I believe you are far better off with blocking air leakage, allowing the wall to breathe with vapor permeable materials, and putting the appropriate amount of insulation on the outside of the cavity too make it continuous. Having said that, there is no single solution for wall assemblies if you consider standard commercial office space, high humidity spaces such as pools and cold environments such as freezers. Also, check out the Perfect Wall http://www.buildingscience.com/documents/insights/bsi-001-the-perfect-wall/ Wayne Yancey Senior Member Username: wayne_yancey Post Number: 167 Registered: 01-2008 Posted on Tuesday, March 03, 2009 - 02:08 pm:    I second Curt's comments and this morning also re-read Dr. Joe's article titled the Perfect Wall. The rule of thumb is 1/3 interior of the air/vapor barrier and 2/3 exterior. However, this ratio will depend on the project location. WUFI Pro, Version 4.1 simulation modelling will help for specific locations for the lower 48 and Alaska. As an Alberta boy where winter temperatures dip to -40 deg F and in summer rise to the mid 90's, we always strived for the "PERFECT WALL/ROOF/FOUNDATION". Thickness of the exterior insulation is dependant on several factors. The source and cost of energy was one. Natural gas is plentiful in Alberta and when I left for the PNW in 1999, still cheap. Generally, 2-2.5" of XPS. As Curt highlighted, the continuous air/vapor barrier was the backbone of the system. When I left Alberta, vapor impermeable products were King with W.R. Grace and Henry/Bakor leading the pack. We did a recent simulation for a project in Vail Colorado to determine the ratio of exterior to interior insulation. The simulation of 4 wall assemblies demonstrated that a certain amount of batt insulation in cavity was unlikely to develope moisture accumulation or mold growth and mitigated risk for the owner and design professional. For your information, the National Building Code of Canada 2005 contains a table and formula to determine the ratio of outboard to inboard thermal resistance. The ratio is based in the heating degree days of building location. In celcius of course. Interested parties may e-mail me at wayne.yancey@callison.com for a PDF verison. Curt Norton, CSI, CCS Senior Member Username: curtn Post Number: 136 Registered: 06-2002 Posted on Tuesday, March 03, 2009 - 10:43 pm:    Wayne - Thanks. The air/vapor barrier is the correct reference point.