Continuous Insulation for Exterior Cavity Walls

There is some debate regarding the best type of insulation to use as the continuous insulation in exterior cavity walls. The most prevalent product used in America is foam plastic insulation (FPI), but we are becoming increasingly aware of its shortcomings. This article will look at some of the issues and then some solutions.

The primary shortcoming of FPI is that it is combustible, and combustible materials are not permitted in concealed spaces in Types I and II construction except under specific conditions. Chapter 7 lists a few exceptions, of which FPI is not one, but cross references to Chapter 6 [717.5 ex. 1] where in regards to FPI, there is a cross reference to Chapter 26 [603.1 no. 3].

In interior or Type V construction, the FPI must have flame spread <= 75 and smoke developed <= 450 [2603.3], and there must be a thermal barrier between FPI and the interior of the building (except in certain specific circumstances not related to typical cavity wall situations) [2603.4]. In exterior walls of all other types of construction, there are more requirements:

1. If the wall is required to be fire rated, you need to document that ASTM E 119 results remain valid. [2603.5.1]
   
2. There must be a thermal barrier between FPI and the interior of the building (except in certain specific circumstances not related to typical cavity wall situations). [2603.4 as reaffirmed by 2603.5.2]
   
3. The potential heat of the FPI (NFPA 259) cannot exceed that permitted by NFPA 285. [2603.5.3]
4. FPI must have flame spread <= 25 and smoke developed <= 450. (ASTM E 84) [2603.3 as modified by 2603.5.4]
5. The whole wall assembly needs to be tested to NFPA 285 [2603.5.5] (except for certain one story buildings. [2603.4.1.4]).
6. The FPI needs to be labeled. [2603.5.6]
7. The FPI needs to be tested to NFPA 268 for ignition. [2603.5.7]

One exception is if the FPI is applied to the interior face of the exterior wall. In such a situation, it may be construed that it is not longer a component of an exterior wall assembly, and therefore only needs to be protected by a 15 minute thermal barrier  complying with 2603.4.

Now that we know the issues, we can look for solutions.

FPI
Looking through the ICC Evaluation Service Reports, there are lots of EPS, XPS, and polyiso products that meet the requirements for Type V construction. However, only a few qualify for other Types of construction. For Types III and V construction, there are products by Baysystems North America, Icynene, Inc., SWD Urethane Co., and Thermal Foams. For all construction types, I have only found only the following:

• Dow Chemical Company: STYROFOAM (XPS), ASTM C 578 Types IV and X (http://www.icc-es.org/reports/pdf_files/ICC-ES/ESR-2142.pdf) when used up to 2.5" thick in steel stud or masonry backed cavities with 4" brick veneer. R-value = 5.0/in.
  
• Dow also has a Thermax system for which the facing can be 4" clay brick, 3/4" 3-coat stucco, 2" limestone, metal composite material (MCM), 1-1.25" terra cotta, cement board, or metal panel. This system has achieved a 1-hour fire rating.
• Falcon Foam, A Division of Atlas Roofing Corporation: EPS Insulation Boards, ASTM C 578 Types I, II, VIII, and IX (http://www.icc-es.org/reports/pdf_files/ICC-ES/ESR-1962.pdf). The product is used in approved EIFS assemblies, but I have no information that it has been tested in any cavity wall assemblies.
  
• Centria: invelope has passed NFPA 285. Although Centria has not listed with ICC-ES, the other aspects of 2603.5 are easily addressed.

Fiber Board
The scarcity of legal FPI products for non-type V construction is good enticement to check out other products. Fiberglass is not a good choice because it doesn't hold up well to the water exposure that is always present on the exterior side of the weather barrier membrane. Mineral wool, on the other hand, is naturally water resistant and has the added advantage of being fire proof! The following manufacturers manufacture mineral wool products with waterproof binders that are appropriate for cavity installations, R-value = 4.2/in.:

• Fibrex
• Roxul
• Thermafiber

The drawback to fiber insulation is you need 2-1/2" thickness to achieve the same R-10 insulating value as 2" FPI. Fortunately, this additional thickness is still within the range of common masonry anchoring systems.

Foam Glass
Pittsburgh Corning manufactures and markets cellular glass insulation in Europe for exterior wall applications. If you're interested in imports, it is a consideration. See http://www.foamglasinsulation.com/building/.

EIFS is Legitimate

The 2009 IBC has canonized EIFS as an acceptable exterior wall finish, much like metal composite materials such as Alucobond. Up to this version, EIFS has only been acceptable as an alternative design, and was covered by evaluation reports.

This is due to the apparently tireless efforts of EIMA (the EIFS Industry Members Association, comprising BASF, Dryvit, ParexLahabra, and Sto) to develop test methods and installation procedures, and to assert better controls over their contractors, that will result in successful and durable EIFS systems as a matter of course.

The most recent development is ASTM E 2568 and ASTM E 2570, which are the conversions of the ICC acceptance criteria AC 219 and AC 212. ASTM E 2568 is the specification for the EIFS system as a whole and ASTM E 2570 is the specification for the water resistive barrier between the insulation and the substrate. These in turn reference other EIMA standards and ICC procedures that were converted into ASTM's within the past few years: ASTM E 2098, ASTM E 2134, ASTM E 2273, ASTM E 2486, ASTM E 2430, and ASTM E 2485.

The result is that, in order to be an exterior wall material, EIFS has to comply with ASTM E 2568 and needs to undergo special inspections. Take note that ASTM E 2568 includes a grueling application of ASTM E 331 - 6.24 pounds of pressure for 2 hours, the requirement for barrier wall designs. Your standard exterior enclosure spec could likely require something far less and may need to be updated. The only relief is if the EIFS is drainable according to ASTM E 2273, a far better system that is required by the code if EIFS is installed on a residential building of Type V construction.

Even better yet might be the pressure equalized reainscreen (PER) EIFS, but it's a little harder to come by. Only Dryvit markets PER EIFS in the United States. In Canada, where PER designs are often mandated, Senergy and Sto also market PER EIFS.

Speaking of the Canadian market, Dryvit and Sto use a mineral wool board as the insuation for their PER systems. This has the added advantage of being a fire proofing material, unlike the foam insulations we use in the United States which, let's be honest, are no more than solidified fuel that's been treated to be relatively self-extinguishing in fire.

And speaking of fire brings up yet another point: FM Global stopped approving EIFS in 2006. I don't know if this is due to moisture problems or the fire hazard or both, but apparently the improvements the industry has made have not been enough to reduce their claims exposure to acceptable levels.

Never-the-less, in spite of the improvements that could still be made, EIFS is now officially a legitimate exterior wall system, confirmation of a product that has been in active development since its invention in Germany 5 decades ago.

What Does the IBC Require on Your Construction Documents?

The International Building Code not only regulates buildings, it also regulates the documents used to construct the buildings.

Here is a complete list of all the information required to be on the construction documents to comply with IBC 2006 and IECC 2006. A QA checklist must include these items at a minimum.

1. Means of Egress: number of occupants on each floor, room and space [106.1.2]
2. Exterior wall envelope: Flashings, Dissimilar material intersections, Corners, End details, Control joints, Intersections at roof, eaves, or parapets, Means of drainage, Water-resistive membrane, and Opening details [106.1.3]
3. Site plan: Lot lines, Street grades, Finish grades, Flood hazard areas, Demolitions, etc. [106.2]
4. Hazardous Materials [414.1.3]
5. Fire alarm and detection systems: 1. A floor plan which indicates the use of all rooms. 2. Locations of alarm-initiating and notification appliances. 3. Alarm control and trouble signaling equipment. 4. Annunciation. 5. Power connection. 6. Battery calculations. 7. Conductor type and sizes. 8. Voltage drop calculations. 9. Manufacturers, model numbers and listing information for equipment, devices and materials. 10. Details of ceiling height and construction. 11. The interface of fire safety control functions. [907.1.1]
6. Smoke control systems [909.2 – 909.4]
7. Floor live load [1603.1.1]
8. Roof live load [1603.1.2]
9. Roof snow load: Flat-roof snow load, Pf; Snow exposure factor, Ce; Snow load importance factor, I; Thermal factor, Cf. [1603.1.3]
10. Wind: Basic wind speed (3-second gust); Wind importance factor, I, and occupancy category; Wind exposure; Internal pressure coefficient; Design wind pressures to exterior component and cladding materials [1603.1.4]
11. Earthquake: Seismic importance factor, I, and occupancy category; Mapped spectral response accelerations, SS and S1; Site class; Spectral response coefficients, SDS and SD1; Seismic design category; Basic seismic-force-resisting system(s); Design base shear; Seismic response coefficients(s), CS; Response modification factor(s), R; Analysis procedure used [1603.1.5]
12. Flood: Special loads; Systems and components requiring special inspections for seismic resistance; (Penetrations, fire-resistant joints, roof assemblies); [1603.1.6] special documentation [1612.5]
13. Systems requiring special inspections for seismic resistance [1603.1.8]
14. Concrete: compressive strength, reinforcement strength, size and location, control joints, prestressing forces, lap splices, splices, isolation joints, posttensioning, diaphragm designations [1901.4]
15. Masonry: reinforcement size, grade, type and location, welding procedures, structural sizes and locations, control joints [2101.3]
16. Steel Joists: special loads, special considerations, deflection criteria for non-SJI standard joists [2206.2]
17. Wood Truss (16 requirements) [2303.4.1]
18. Glass with less than four-sided support [2403.2]
19. Temporary structures [3103.2]
20. Demolition [3303.1]
21. Energy: insulation materials and their R-values; fenestration U-factors and SHGCs; system and equipment efficiencies, types, sizes and controls; duct sealing, insulation and location; and air sealing details.
22. Alternative Energy Compliance: Annual energy use and associated costs, Energy-related features, Input and output report(s), Written explanation(s).

Code Analysis Summary

A quality code summary on the code cover sheet will exhibit four characteristics:

1. Clarity: It will present the information in a logical and legible way so that information can be easily located.
2. Conciseness: It will not contain irrelevant information or information that does not vary from one project to another.
3. Correctness: It will reflect an accurate analysis of the building and will display requirements next to actual design attributes for easy confirmation.
   
4. Completeness: It will encompass a summary of all categories necessary to demonstrate code compliance.

The National CAD Standard provides several categories for code information: Governing Regulations Summary, General Building Summary, Room-by-Room Egress, Foor-by-Floor Egress, Fire Resistance Ratings, Accessiblity, and Plumbing Fixture Tabulation.

This is a good start, but not quite complete. Many jurisdictions will want, for example, a listing of the responsible design professionals, a summary of the Life Safety features, key Structural Design assumptions, and an Energy Summary. All these are important and varying considerations in the International Building Code.

Here is a more complete outline for a clear and concise code summary:

• Project Information
• Jurisdiction Information
  
• Applicable Governing Regulations
  
• List of Design Professionals
• Site-Related Design Criteria
• General Building Summary
  
• List of Special Uses and Occupancies
• List of Fire Areas (showing mixed occupancies)
• Occupancy Separation
• Fire Resistance Ratings
• Fire Protection Features
  
• Means of Egress Summary
  
• Accessibility Counts
• Energy Efficiency Summary
  
• Structural Design Criteria
• Plumbing Fixture Counts

The IBC 2006 Code Analysis is a tool for analyzing and calculating key building code requirements as they relate to a particular project. This Excel spreadsheet is designed to help you achieve the four principles enumerated above. After the analysis is complete, you can copy the compiled information it into a word processor or drafting program for further formatting and editing.