When a building has no cooling system, the software simulates a hypothetical system with the characteristics required by Table 150.1-A or B if a cooling system was installed. The result is neither a penalty nor a credit.
When natural gas is not available, and all other eligibility criteria are met (see Chapter 4), a wood heating system is simulated as a hypothetical system with the characteristics required by Table 150.1-A or B for a typical heating system. When all eligibility criteria are met, the backup system is not modeled, otherwise see Section 8.8.3.
Buildings with multiple HVAC systems are treated as follows:
1. For buildings with more than one system type, equipment type, or fuel type, where the types do not serve the same floor area, model the building zone or floor area served by each unique type separately.
2. Supplemental heating may be ignored if two criteria are met: (1) If the capacity of the supplemental unit does not exceed 2 kilowatts (kW), or 7,000 British thermal units per hour (Btu/h), and (2) if the supplemental unit is controlled by a time-limiting device not exceeding 30 minutes. (§150.1(c)6.)
In a building with an appliance rated gas fireplace and a central gas furnace, the furnace is the primary system and the fireplace is the supplemental system. The controls for the fireplace would not need to meet the setback thermostat requirements (exception to §110.2(c))).
3. For redundant equipment, where the floor area is served by more than one heating or cooling system, equipment type, or fuel type, model the least efficient system. For any areas served by electric resistance heat and another heating system (except for wood heating meeting all eligibility criteria), the electric resistance system is the least efficient system.
When there is more than one system meeting the heating or cooling load for the same space, all systems must still meet all the mandatory requirements of the Energy Standards.
When higher than minimum efficiency is modeled, a HERS Rater must verify the efficiency. This includes seasonal energy efficiency ratio (SEER), energy efficiency ratio EER, and heating seasonal performance factor (HSPF).
The performance approach may be used to show compliance for alterations in existing buildings, new additions, and existing + addition + alteration discussed in Chapter 9. The following table can be used when existing conditions are unknown. The table is based on the year of the building construction.
Table 8-1: Default Assumptions for Year Built (Vintage) |
| |||||||||||
|
Conservation Measure |
Before 1978 |
1978 to 1983 |
1984 to 1991 |
1992 to 1998 |
1999 to 2000 |
2001 to 2003 |
2004 to 2005 |
2006 to 2013 |
2014 to | |||
|
Cool Roof |
0.10 |
0.10 |
0.10 |
0.10 |
0.10 |
0.10 |
0.10 |
Table 150.1-A or 150.1-B | ||||
|
Radiant Barrier |
None |
None |
None |
None |
None |
None |
Table 150.1-A or B |
Table 150.1-A or B | ||||
|
Roof/Ceiling |
0.079 |
0.049 |
0.049 |
0.049 |
0.049 |
0.049 |
0.049 |
0.049 |
0.031 | |||
|
Wall |
0.356 |
0.110 |
0.110 |
0.102 |
0.102 |
0.102 |
0.102 |
0.102 |
0.102 | |||
|
0.099 |
0.099 |
0.099 |
0.049 |
0.049 |
0.049 |
0.049 |
0.049 |
0.037 | ||||
|
Raised Floor-No Crawl Space |
0.238 |
0.238 |
0.238 |
0.064 |
0.064 |
0.064 |
0.064 |
0.064 |
0.049 | |||
|
Slab Edge F-factor |
0.73 |
0.73 |
0.73 |
0.73 |
0.73 |
0.73 |
0.73 |
0.73 |
0.73 | |||
|
Ducts |
|
R-2.1 |
R-2.1 |
R-2.1 |
R-4.2 |
R-4.2 |
R-4.2 |
R-4.2 |
Table 150.1-A or B | |||
|
LEAKAGE | ||||||||||||
|
Building (ACH50) |
7.7 |
7.7 |
7.7 |
7.7 |
7.7 |
7.7 |
7.7 |
6.8 |
5.0 | |||
|
Duct Leakage (%) |
15% |
15% |
15% |
15% |
15% |
15% |
15% |
15% |
6% | |||
|
FENESTRATION | ||||||||||||
|
U-factor |
Use Energy Standards Table 110.6-A , §110.6 for all vintages. | |||||||||||
|
SHGC |
Use Energy Standards Table 110.6-B , §110.6 for all vintages. | |||||||||||
|
Shading Devices |
Exterior: Assumed to have 50% bug screens, model actual overhangs. | |||||||||||
|
SPACE HEATING EFFICIENCY | ||||||||||||
|
Gas Furnace (Central) AFUE |
0.75 |
0.78 |
0.78 |
0.78 |
0.78 |
0.78 |
0.78 |
0.78 |
0.78 | |||
|
Gas Heater (Room)
|
0.65 |
0.65 |
0.65 |
0.65 |
0.65 |
0.65 |
0.65 |
0.65 |
0.65 | |||
|
Hydronic/Comb Hydronic |
0.78 |
0.78 |
0.78 |
0.78 |
0.78 |
0.78 |
0.78 |
0.78 |
0.78 | |||
|
Heat Pump |
HSPF |
5.6 |
5.6 |
6.6 |
6.6 |
6.8 |
6.8 |
6.8 |
7.4 |
7.7 | ||
|
Electric Resistance HSPF |
3.413 |
3.413 |
3.413 |
3.413 |
3.413 |
3.413 |
3.413 |
3.413 |
3.413 | |||
|
Electric Resistance Radiant HSPF |
3.55 |
3.55 |
3.55 |
3.55 |
3.55 |
3.55 |
3.55 |
3.55 |
3.413 | |||
|
SPACE COOLING EFFICIENCY | ||||||||||||
|
All Types, |
SEER |
8.0 |
8.0 |
8.9 |
9.7 |
9.7 |
9.7 |
9.7 |
13.0 |
13.0 | ||
|
WATER HEATING | ||||||||||||
|
Energy Factor |
0.525 |
0.525 |
0.525 |
0.525 |
0.575 |
0.575 |
0.575 |
0.575 |
0.575 | |||