NOTE: For another article by Steve Andrews explaining the IECC 2000 and addressing issues of complexity and compliance tools to deal with it click here.

Meeting the IECC 2000

(Steve Andrews, E-Star Colorado, April 11, 2003 draft)

There are three ways to comply with the International Energy Conservation Code 2000: Chapter 6, the prescriptive approach; Chapter 5, the tradeoff approach; and Chapter 4, the systems analysis approach. Those methods are laid out in a vastly simplified fashion below. Note the key list of 31 required items.

Chapter 6: Simplified Prescriptive Approach

for Denver climate: 6,000-6,499 HDD zone

(6020 heating degree-days; 679 cooling degree-days)

If you elect to meet the residential energy code requirement by using the Simplified Prescriptive Approach, then the total window area, including sash and frame, must not exceed 15% of the gross area of the exterior wall for type A-1 dwellings (single-family). For type A-2 dwellings (attached housing), the maximum is 25% of the exterior wall area. If your Proposed Design does not meet this determining requirement, then use either the Systems Approach (Chap 4) or the Component Approach (Chap. 5) to energy code compliance.

If you can meet this initial minimum requirement, then the following items are also required. They vary by climate-zone around the state.

Component	Required Insulation value	Comment / details
Ceilings, and cantilevered floors	R-38	If attic equipped with energy heel trusses, then R-30 is acceptable. One marker per 300 ft2 required
Exterior walls*	R-18	Includes only cavity insulation and insulating sheathing, not drywall, siding, framing, etc. (If sheathing not min. 50% coverage, do not include it.)
Floor R-value	R-21	Floors above garages; cold crawl spaces
Crawl space walls (in warm crawls)	R-20	Extends fully from the sill plate to dirt floor, which should be covered with a continuous vapor retarder (joints sealed; edges sealed to the foundation wall)
Slab-on-grade	R-9 (if slab is heated, R-11 is required)	From top of foundation wall and extending down 4’ below grade; all exterior insulation must be protected where it extends above grade
Basement walls	R-10	Insulate mud sill to top of basement floor
Windows	U-0.35 (R-2.86)	NFRC label rating for entire window unit (incl. frame and sash); up to 1% of the total glazing area is exempted from this requirement. If not NFRC rated, use default table 102.5.2(1) on p.3 of IECC.
Doors	U-0.35 min.	One door can be excluded
Air leakage	Prescriptive air sealing	Caulk, seal or gasket all penetrations, rough openings and other pathways in order to limit uncontrolled air movement
Water heating sys.	EF= 0.53 (53% eff.)	Refer to notes under Components (Chap 5)
Heating system	AFUE = 78% efficiency	Refer to notes under Components (Chap 5)

· * For homes built with steel framing, one of the following combinations is required: R-13 cavity and R-10 foam sheathing (including over attic kneewalls, garage walls, beneath cantilevers and beneath rooms over garage); R-19 cavity plus R-9 foam sheathing; R-25 cavity plus R-8 foam sheathing.

· * For homes built with mass walls (e.g., concrete block), refer to p. 95 of the IECC.

For more details about items on the above table, see attached sketches and drawings. [ not yet drawn]

Chapter 5 (simplified): Component Performance Approach

Using Chapter 5, you start by meeting any one of the three approaches below:

A. First, you can select one of the optional building envelope packages from Table 1 listed below. (Column 1, the window area, determines the other variables that are factored in here.)

B. Second, you can select your own package of energy features, as long as use of "RESCheck" demonstrates that your proposed energy package will have no greater heat loss than a home built to the "relevant % window area formula" per the chart listed below. (RESCheck is a free code-compliance tool available at no cost on the internet at www.energycodes.gov)

C. Third, submit your own "formula of energy features" using any other acceptable compliance technique (e.g., manual calculations), as long as that method demonstrates you will be complying with the criteria in Table 2.

HINT: The most reasonable way to comply using Chapter 5 is to use the RESCheck tool.

Reminder: You must then also meet the list of requirements below (see #1 – 31).

TABLE 1: Options packages for Type A-1 residential buildings

Window area as % of gross ext. wall area	Glazing U-factor	Ceiling R-value (also cantilever R-value)	Ext. wall R-value (if steel-framed, must use Tables)	Floor R-value	Basmnt wall R-value	Slab perimeter R-value (and ft. below grade)	Crawl space wall R-value (unvented)
8%	0.45	R-38	R-16	R-19	R-10	R-7, 4ft	R-16
12%	0.40	R-38	R-18	R-19	R-10	R-6, 4ft	R-16
15%	0.35	R-38	R-18	R-21	R-10	R-9, 4ft	R-16
18%	0.34	R-49	R-22	R-19	R-10	R-8, 4ft	R-17
20%	0.31	R-49	R-24	R-19	R-10	R-7, 4ft	R-17
25%	0.25	R-49	R-19	R-21	R-10	R-9, 4ft	R-20
Addition to existing home	0.35	R-49	R-21	R-21	R-11	R-13, 4 ft	R-20
Replace-ment windows	0.35	na	na	na	na	na	Na

Table 2: Heating and Cooling Criteria (Table 502.2, p. 70)

Element	Mode	Type A1 res. bldgs.: Uo	Type A2 res. bldgs.: Uo
Walls (includes windows, doors)	Heating or cooling	Uo =0.125	Uo =0.215
Roof/ceiling	Heating or cooling	Uo =0.26	Uo =0.26
Floors over unheated spaces	Heating or cooling	Uo =0.05	Uo =0.05
Heated slab on grade	Heating	R-7	R-7
Unheated slab on grade	Heating	R-5	R-5
Basement wall	Heating or cooling	U = 0.096	U = 0.096
Crawl space wall	Heating	U = 0.06	U = 0.06

Required items

1. A vapor barrier (aka vapor retarder) of 1 perm or lower is required on warm side of frame walls, floors and ceilings (whenever those individual building assemblies are not ventilated for moisture control). [NOTE: this is not in alignment with “best building science practices,” as identified by the US-DOE-funded “Building America” teams.]

2. Recessed lights within insulated ceilings shall be air-tight and IC-rated.*

3. Window tightness. Allowable infiltration rates for windows and doors, in cfm per square foot of area, are 0.3 (windows and sliders) and 0.5 (swinging doors).

4. Air sealing. Caulk or otherwise seal joints, seams and penetrations that could allow air leakage, either into or out of the conditioned spaces. This includes around tubs and showers, attic hatches, crawl-space hatches, holes and joints between houses and attached garages, plus all electrical and plumbing penetrations. [For “best practice,” use details show in Builder’s Guide: Cold Climates, p. 97 – 101 (available through www.eeba.org).]

Notes about wall assembly requirements for special walls

5. If you build with steel studs, then you must either A) select an insulated wall assembly with an R-value equivalent to the wood-framed wall used as the standard (see IECC p. 85), or B) you must use Equation 5-3 to perform calculations showing your compliance path.

6. If you build with mass walls that include either exterior insulation, interior insulation or integral insulation (e.g., log walls), you have two choices; A) design in accordance with the equation and table on p. 77; or B) install R-10 on the outside of a high-mass wall or R-15 on the inside of a high-mass wall (p. 86).

7. The R-value of skylights must be averaged into the ceiling U-value calculation. (E.g., 994 ft2 of R-38 and 6 ft2 of R-2 skylight = R-34 overall for the entire attic area; conversion requires U-values, not R-values.)

8. The side walls of skylight shafts shall be insulated to minimum R-19.

9. The R-values of walls and closed ceiling cavities listed in Table 1 reflect only the R-values of cavity insulation and insulated sheathing; they exclude R-values of other materials in the wall assembly (drywall, exterior finish, air films, etc.).

Foundation issues

10. All slabs must be insulated on either the exterior or the interior of the stem wall. Slab insulation shall either cover down 48" from the top of the slab or run down and then horizontally a total of 48" (with the horizontal portion covered by minimum 10" of soil).

11. Basement walls must be insulated from the top to the bottom of the wall, or to 10 feet below grade (whichever is less).

12. When a slab is heated, increase the slab's perimeter by R-2. (E.g., if R-6 is required for unheated slab, then increase it to R-8 for a heated slab.)

13. Crawlspace wall insulation only applies to unvented crawlspaces.

14. Any floor over outdoor air (e.g., cantilever) shall meet the ceiling R-value requirement.

Window issues

15. The total window area in a home is determined by adding up all window and skylight rough-opening areas in that home. Basement window rough openings are to be included in this calculation.

16. % window area: The window area as a percent of gross wall area is simply the number of total window square footage divided by the total exterior wall area.

17. One percent of the gross window area shall be exempted from the window U-value requirement.

18. Attic insulation variance: Whenever any type of roof truss is employed that allows for full-height insulation right to the outer edge of each wall's top plate (e.g., a raised heel or other "energy truss" design), a ceiling with R-30 can be substituted for and be judged equivalent to the R-value requirement of R-38.

19. Opaque doors to the exterior shall have a maximum U-factor of 0.35 (R-2.86). One door shall be exempt from this requirement. (Sliding patio doors and French doors are to be counted as windows.) [varies from code]

20. For additions to existing homes, the total window area (including sliding glass and French doors) shall not exceed 40% of the gross wall and roof area of the addition.

21. Replacement skylights shall have a maximum U-factor of 0.50. (Sunrooms that are thermally isolated from the home aren't subject to this standard.)

HVAC issues

22. Heating and cooling systems shall be sized according to load calculation procedures described in either the ASHRAE Handbook of Fundamentals; Manual J 8^th edition (published by ACCA—the Air Conditioning Contractors’ Association); or equivalent computation method. [Note: over-sizing of air-conditioning equipment by a factor of two is commonplace in Colorado.]

23. Thermostats: must be capable of being set as low as 55 deg.F. (heating mode), as high as 85 degrees F (cooling mode), and must have a deadband range of 5 degrees F wherein the thermostat can be set to call for neither heating nor cooling energy. (Exception: thermostats that require manual changeover between heating and cooling modes.)

24. Humidistats used to control winter-time humidification must be capable of being set to shut off at 30% RH.

25. Insulating ductwork: Heating ducts outside the conditioned space must be insulated to R-8. [The 2000 IECC specifies both R-5 and R-8; the 2001 IECC Ammendments cleared up this confusion by specifying R-8.) This applies to ducts within garage ceilings, ducts running up garage common walls, ducts within vented crawlspaces, ducts in attics, ducts within cantilevers and ducts running up exterior walls.

26. Duct sealants must be used on all ductwork, in order that ductwork is substantially air tight. All joints in ductwork require sealing except those longitudinal joints manufactured in the factory. Note that gray-colored duct tapes do not qualify as sealants and should not be used on ductwork. [Mastic, butyl/mastic tape and aerosolized sealants are encouraged.]

27. Pipe insulation for hydronic heating systems should be 1" foam or greater (R-4 per inch or higher). This applies for piping within both conditioned and semi-conditioned spaces. (Exception: if the piping carries fluids heated or cooled between 105 and 55 degrees F, no insulation is required; example, for in-floor hydronic heating.) If piping is exposed to outdoor air, increase to 1.5" insulation.

28. Dampers for exhaust fans: Mechanical ventilation systems must be equipped with gravity- or automated dampering systems to shut them down when not specifically in use.

Water heaters

29. Water heaters shall meet the following Energy Factors (as listed in the GAMA Directory):

Water heater capacity (gallons)	Storage and instantaneous gas-fired (Energy Factor: EF)	Electrically heated (Energy factor: EF)
30 gallons	EF = 56%*	EF-0.91
40 gallons	EF = 54%*	EF-0.90
50 gallons	EF = 53%*	EF-0.88
75 gallons	EF = 48%*

*The Denver Building Dept. actually specifies EF=0.60 in their existing code.

30. Pipe insulation. When recirculating systems are used for delivering hot water, half-inch insulation is required on all lines. (Exception: if a passive thermosyphon recirculating system is used, the insulation should not be applied for the "return lines" which carry water from the high point in the system back to the water heater.)

31. Heat traps are required on both the inlets and outlets lines of all water heaters. (Exceptions: if the water heater was equipped with heat traps at the factory; or if the water heater is hooked up to a house with a recirculating system.)

For issues relating to A-2 residences, please refer to the full code document.

Chapter 4: Systems Approach

If you elect to meet the residential energy code requirement by using a total energy use calculation procedure, you must use a comprehensive computerized tool that meets certain requirements specified in the IECC code and approved by the local Building Department.

[the City of Denver’s proposed language, as of July 2001; since put on hold]

This computer-calculated approach offers the most amount of flexibility by allowing all alternatives not specified above. If the proposed average annual energy use does not exceed that of the same house built to prescriptive path standards (Chapter 4), the proposed house complies.

The City and County of Denver is currently accepting the results from using the E-Star home energy-rating program, which is a recognized computer evaluation tool that produces an energy-efficiency rating. A $75 fee reduction in the building permit fee is available to builders who utilize this program. The City and builders both benefit with the reduced plan review and inspection time since the initial energy rating is all that is required to obtain a permit. The builder must commit to using the program by signing the City agreement form at the time of building permit application.

The E-Star minimum required rating score at time of completion must be “82” or higher, on their 0-to-100 rating scale. A certified E-Star rater is required to verify compliance from plans and again when the construction of the building is complete.