CFR > Title 10 - Energy > CHAPTER II—DEPARTMENT OF ENERGY > SUBCHAPTER D—ENERGY CONSERVATION (parts 400 to 491) > PART 435—ENERGY EFFICIENCY STANDARDS FOR NEW FEDERAL LOW-RISE RESIDENTIAL BUILDINGS > SUBPART C—Mandatory Energy Efficiency Standards for Federal Residential Buildings (§435.300 to §435.306) > 435.305—Alternative compliance procedure.

435.305—Alternative compliance procedure.

(a) If a proposed building design includes unusual or innovative energy conservation measures which are not covered by the COSTSAFR program, the Federal agency shall determine whether that design meets or exceeds the applicable energy consumption goal in compliance with the procedures set forth in this section.
(b) The Federal agency shall determine the estimated discounted energy cost for the COSTSAFR prototype building design, which is the most similar of the COSTSAFR prototypes to the proposed building design, by—
(1) Printing out the COSTSAFR compliance forms for the prototype showing the points attributable to levels of various energy conservation measures;
(2) Calculating the estimated unit energy cost on the compliance forms, on the basis of selecting the optimum levels on the compliance forms or otherwise in the User's Manual for each energy conservation measure; and
(3) Multiplying the estimated unit energy cost by 100.
(c) The Federal agency shall determine the estimated discounted energy cost for the proposed building design by—
(1) Estimating the heating and cooling total annual coil loads of the proposed building design with the DOE 2.1C computer program on the basis of input assumptions including—
(i) Shading coefficients of 0.6 for summer and 0.8 for winter;
(ii) Thermostat setpoints of 78 degrees Fahrenheit for cooling, 70 degrees Fahrenheit for heating (6 am to 12 midnight), and 60 degrees Fahrenheit for Night Setback (12 midnight to 6 am, except for houses with heat pumps);
(iii) The infiltration rate measured in air changes per hour as calculated using appendix B of the COSTSAFR User's Manual;
(iv) Natural venting with a constant air change rate of 10 air changes per hour—
(A) When the outdoor temperature is lower than the indoor temperature, but not above 78 degrees Fahrenheit; and
(B) When the enthalpy of the outdoor air is lower than the indoor air.
(v) Internal gains in accordance with the following table for a house with 1540 square feet of floor area, adjusted by 0.35 Btu/ft 2 /hr to account for changes in lighting as the floor area varies from 1540 square feet—
Table 1—Internal Gain Schedule (Btu)
Hour of day Sensible Latent
1 1139 247
2 1139 247
3 1139 247
4 1139 247
5 1139 247
6 1903 412
7 2391 518
8 4782 1036
9 2790 604
10 1707 370
11 1707 370
12 2277 493
13 1707 370
14 1424 308
15 1480 321
16 1480 321
17 2164 469
18 2334 506
19 2505 543
20 3928 851
21 3928 851
22 4101 888
23 4101 888
24 3701 802
(vi) Thermal transmittances for building envelope materials measured in accordance with applicable ASTM procedures or from the ASHRAE Handbook;
(vii) Proposed heating and cooling equipment types included in COSTSAFR or having a certified seasonal efficiency rating;
(viii) Weather Year for Energy Calculations (WYEC) weather year data (WYEC data are on tapes available from ASHRAE, 1791 Tullie Circle, N.E., Atlanta, Georgia 30329), or if unavailable, Test Reference Year (TRY) weather data (obtainable from National Climatic Data Center, 1983 Test Reference Year, Tape Reference Manual, TD-9706, Asheville, North Carolina) relevant to project location.
(2) Estimating the discounted energy cost for the heating and cooling energy loads, respectively, according to the following equation—
Where:
Total Annual Coil Load=the total heating or cooling annual coil load calculated under paragraph (c)(1);
Fuel Cost=the heating or cooling fuel cost calculated in accordance with sections 3.3.D and 3.3.E of the User's Manual;
UPW*=the uniform present worth discount factor; selected from the last page of the compliance forms.
Equipment Efficiency=the test seasonal efficiency rating of the heating and cooling equipment only (i.e., not including duct or distribution system losses).
(3) Estimating the discounted energy cost for water heating and refrigerator/freezer energy consumption—
(i) For equipment types covered by the COSTSAFR compliance forms, by multiplying the estimated unit energy cost by 100; or
(ii) For equipment types not covered by COSTSAFR—
Where:
Fuel Cost and UPW* are as defined in paragraph (c)(2) of this section; Annual Energy Consumption is as calculated in 10 CFR 430.22; and Energy Factor is the measure of energy efficiency as calculated under 10 CFR 430.22
(iii) [Reserved]
(4) Adding together the discounted energy costs calculated under paragraphs (c)(2) and (c)(3) of this section;
(d) If the discounted energy cost of the proposed building design calculated under paragraph (c)(4) of this section is equal to or less than the discounted energy cost of the COSTSAFR prototype building design calculated under paragraph (b) of this section, then the proposed building design is in compliance with the applicable energy consumption goal under this part.

Code of Federal Regulations

[56 FR 3772, Jan. 31, 1991]