Twists in the IECC 2000

Builders in the Built Green program must meet the International 2000 Energy Conservation Code using one of three methods. Often-overlooked requirements of that code are discussed below.

"Every pint bottle should contain a quart."
- Sir Boyle Roche, 18th century Brit

"Sometimes a cigar is just a cigar."
- Sigmund Freud

There are three ways for Built Green participating builders to meet the IECC 2000. Those three compliance paths are laid out in Chapters 4. 5 and 6 of the labyrinthine code. Those same three methods are listed as the first three items on the Built Green Checklist.

Due to some misunderstandings about what all code compliance paths involve, that process is summarized below.

Chapter 6: Prescriptive Compliance

The prescriptive method of code compliance is described in both Chapter I I of the IRC and Chapter 6 of the IECC. It's also line-item 3 on our BG Checklist. The heart of prescriptive compliance for any builder is a list of required R-values for insulating walls, ceilings and foundations, plus window U-values. There are also some important non-R-value or U-value requirements spelled out and/or referenced.

The prescriptive shell mandates are determined by climate - more specifically, by local heating degree-days (HDD). Denver falls in the 6,000 to 6,499 HDD climate zone. Boulder builders in the 5,500-5,999 HDD hand, and Castle Rock builders in the 6,500-6.999 HDD zone. That means a Denver-area builder following the prescriptive method has to install the items listed in Table 1. (There are some other fine points for unusual wall assemblies: mass wall or steel-framed systems.)

If windows in a home equal more than 15 percent of the total wall surface area, that builder must meet the code by one of the other two methods. Additionally, any builder who doesn't want to use this method can elect to use another compliance path method.

In addition to Table 1 features, Chapter 6 spells out other requirements:

• cantilevered floors = R-38 (or same as attic);
• a continuous vapor retarder (1 perm or less) is required over exposed earth in crawl spaces;
• basement insulation must start at the top of the concrete wall;
• exterior basement insulation above grade must be protected with a weather-resistant covering:
• all joints, seals, penetrations, rough openings, and other sources of air leakage through the building envelope must be caulked, gasketed, weather-stripped. wrapped or otherwise sealed to limit uncontrolled air movement;
• heating. cooling and water heating equipment and installations must comply with requirements in Chapter 5 (below); and
• doors to unconditioned space or to the exterior must have a maximum U-value of 0.35 (wood doors won't qualify), except that one opaque door can be exempted from this requirement.

Again, the seven items above are required to meet the code via the prescriptive method. Additionally, note one "allowable practice": up to 1 percent of the total glazing area is exempted from the U-value requirement on Table 1. That means stained glass in a front door and sidelight wouldn't need to he low-e coated.

Chapter 5: Component tradeoff approach

Chapter 5 is the route most builders take to meeting the Built Green requirement. Good news and bad news here. First, Chapter 5 includes the most complex wording this side of the tax code; it contains tour excruciating formulaic methods of compliance. The good news is that the RESCheck computer program, developed by the U.S. Department of Energy (free download at www.energycodes.gov), provides a very easy means of complying through one of the formulas. And the RESCheck tool provides substantial flexibility in your choice of insulated shell and HVAC equipment choices for meeting the code.

But as in Chapter 6, there are a number of "general requirements" in Chapter 5 that go beyond the R-value. U-value and AFUE tradeoffs allowed in RESCheck. Those required items include items 1-7 listed above, as well as the following:

Recessed lights in insulated ceilings must he either a) air-tight. IC-rated cans, b) the cans must be located inside a scaled. airtight box in the attic, or c) the cans must not leak more than 2 cfm under test pressure (75 pascals).

Maximum allowable air leakage for

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Chapter 5 includes the most complex wording this side of the tax code; it contains four excruciating, formulaic methods of compliance.

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windows and/or slider doors is 0.3 cfm per ft' of window area (0.5 cfm/1V for swinging doors). Note: this factor is optional on the NFRC energy performance label that you find on nearly all windows today, so you may have to hit up your manufacturer for this data.

Air sealing is also required around the following items where they are adjacent to or part of the insulated building shell:

• around tubs and showers;
• attic and crawl space panels;
• at recessed lights (e.g.. trim gaskets): and
• around all electrical and plumbing penetrations. plus any of these openings between conditioned and unconditioned spaces (e.g., garages and crawl spaces).

Heated slabs require an extra R-2 level of insulation.

HVAC equipment must he sized according to calculations (ACCA's Manual J, 8th edition, is allowed).

Thermostats must be capable of set-back to 55 degrees F and up to 85 degrees F, with a 5 degree dead-hand where the stat controls both heating and cooling appliances.

Required duct insulation: R-5 when located in exterior walls, cantilevers, garage ceilings and common walls, vented crawl spaces, etc. (This increases to R-8 with the 2001 amendments and in the IECC 2003, but is not required by the IECC: 2000.)

Duct sealing is required on all longitudinal and transverse joints, seams and connections of supply and return ducts. Ducts need to he "securely fastened": screw metal together and strap-and-mastic flex-ducts to takeoffs. All ducts must he sealed with "welds, gaskets, mastics (adhesives), mastic-plus-embedded-fabric systems or tapes installed in accordance with the manufacturer's instructions." Since -following manufacturer's instructions" rarely happens in the real world, the strong recommendation from equipment manufactures and E-Star is use of either mastic or foil-hacked butyl tape.

Approved duct sealants: "Tapes and mastics used with rigid fibrous glass ducts shall be listed and labeled in accordance with UL 181 A. Tapes and mastics used with flexible air ducts shall be listed and labeled in accordance with UL 18113. [Gray or other colored] 'duct tape' is not permitted as a sealant on any ducts." For metal ducts, the non-code-required recommendation is use of either mastic or foil-backed butyl tape.
Pipe insulation is required on hydronic heating systems - typically 1-inch material rated at R-4/inch.

Water heaters require some type of heat trap -either external or integral - on both the hot and cold water lines.

Constant re-circulation hot-water systems require one half-inch pipe insulation on the circulation supply loop.

While not a "requirement," it is worth noting that un-vented (conditioned) crawl spaces are allowed (502.2.1.5) in the IECC. And if you are building a custom home with a swimming pool, see the code requirements for covers, switches and tine clocks.

Chapter 4: Systems analysis approach

Think of Chapter 4 as the "home energy rating system" (HERS) approach. The bottom line is a computer-projected total mercy use calculation for the home, including the impacts of solar energy on the building. That energy use translates into a score on the 0-to-100 uniform home energy rating scale. Along the Front Range, a score of 82 is deemed to the meets the IECC requirement via Chapter 4.

Don't read Chapter 4 unless you have insomnia. Essentially it spells out a very detailed computer analysis approach that requires some field performance testing, such as a blower-door test to establish tightness. In addition to house tightness. other factors that the computer program must analyze include orientation and solar access of all windows: water heater efficiency: an assessment of duct leakage to the outdoors: the impacts of internally generated heat: and use of any renewable energy systems (e.g., solar hot water heater; passive solar design: etc.).

Raters using the Chapter 4/HERS approach must supply much more detailed information about a home than a builder using Chapter 5 and 6 methods. Furthermore, Chapter 4 specifies tightness factors with respect to both ductwork and air leakage through the building shell. However, the "required items" listed above (items 1-19) are not required separately as part of the Chapter 4 approach, though a number of them are "built in" to performance tests.

Bottom line

The most commonly used compliance method is the RESCheck sheet, with an E-Star rating next and the prescriptive method last. Remember that when complying via the prescriptive Chapter 6 method, you must meet the thermal requirements for your shell plus required items 1-7. And when selecting the Chapter 5 approach, you will likely use the RESCheck tool to identify qualifying features; and you are required to install items 1-19.

Steve Andrews consults with builders for E-Star Colorado and writes on energy issues (sbandrews@att.net). E-Star (www.e-star.com), is a nonprofit home energy rating system that works with both new and existing homes statewide.

2008 Built Green Colorado

Home Builders Association of Metro Denver, 9033 E. Easter Place, Suite 200, Centennial, CO 80112
(303) 778-1400 fax: (303) 733-9440  info@builtgreen.org

Last Updated: 10/05/2007