Taken from FSEC-CR-1807-09
June 30, 2009
Specific
differences between the provisions of 90.1-2004 and 90.1-2007 are as follows:
·
Demand Control Ventilation (DCV) required
for high-occupancy spaces (addendum v)
· Minimum efficiency for HVAC equipment increased (Addendum b, f, g)
· Minimum efficiency for boilers increased (Addendum t )
· Baseline fan power allowance reduced (addenda ac, ar)
· More Stringent opaque elements – Roof s, walls, Floor, (Addendum as)
· More stringent Fenestration elements (Addendum at)
o Dependence of U and SHGC on %WWR eliminated.
o Dependence of U and SHCG now on Fenestration framing type & application
o U and SHGC are now tighter in 90.1-2007 than 90.1-2004
· Prescriptive compliance limits WWR to 40% (instead of 50%) (Addendum at)
· Baseline WWR for Energy budget method limits WWR to 40% (was 50%) or proposed building value whichever is less (Addendum at)
· Estimated average stringency of 90.1-2007 compared to 90.1-2004 is approx 10%
A simulation analysis comparing the performance differences between 90.1-2004 and 90.1‑2007 has also been conducted.[1] Typical models for three building types: a strip mall, a small office and a medium office, were simulated using the EnergyPlus and EnergyGauge software. The building models are constructed in accordance with two different baseline standards: 90.1-2004 and 90.1-2007.
The models for strip mall and the medium office building were obtained from the DOE commercial building benchmark database developed jointly by NREL, PNNL and LBNL.[2] The strip mall is a 22,500 ft2 building with 8 small and 2 large zones served by packaged single-zone equipment. The strip mall has a 26% window-to-wall area ratio (WWR) with all of the glazing facing south. The medium office is a 53,626 ft2, three-story building with 50% (WWR) of evenly distributed glass for the 90.1-2004 model and 40% (WWR) of evenly distributed glass for the 90.1-2007 model. The small office is a 10,000 ft2 single-story building with 50% (WWR) glass for the 90.1-2004 model and 40% (WWR) for the 90.1-2007 model. Tables 1-3 present results from the analysis.
Table 1 Comparison results for
|
|
ASHRAE
90.1 2004 |
ASHRAE
90.1 2007 |
|
|||||
|
|
Electricity
(GJ) |
Natural
Gas (GJ) |
Total (GJ) |
Electricity
(GJ) |
Natural
Gas (GJ) |
Total (GJ) |
%
Difference |
Absolute
Difference |
|
|
2824.01 |
402.86 |
3226.87 |
2704.6 |
271.3 |
2975.9 |
7.8 |
251.0 |
|
|
2959.99 |
259.82 |
3219.81 |
2818.16 |
169.91 |
2988.07 |
7.2 |
231.7 |
|
|
3109.77 |
94.38 |
3204.15 |
2861.09 |
78.37 |
2939.46 |
8.3 |
264.7 |
Table 2 Comparison results for Strip Mall
|
|
ASHRAE
90.1 2004 |
ASHRAE
90.1 2007 |
|
|||||
|
|
Electricity
(GJ) |
Natural
Gas (GJ) |
Total (GJ) |
Electricity
(GJ) |
Natural
Gas (GJ) |
Total (GJ) |
%
Difference |
Absolute
Difference |
|
|
1299.04 |
159.49 |
1458.53 |
1254.96 |
137.06 |
1392.02 |
4.6 |
66.5 |
|
|
1363.53 |
65.02 |
1428.55 |
1311.42 |
54.09 |
1365.51 |
4.4 |
63.0 |
|
|
1619.07 |
9.33 |
1628.4 |
1536.29 |
9.63 |
1545.92 |
5.1 |
82.5 |
Table 3 Comparison results for Small Office
|
|
ASHRAE
90.1 2004 |
ASHRAE
90.1 2007 |
|
|
|
|
Total
(MBtu) |
Total
(MBtu) |
%
Difference |
Absolute
Difference |
|
|
668 |
606 |
9.3% |
62 |
|
|
649 |
602 |
7.2% |
47 |
|
|
721 |
678 |
6.0% |
43 |
Results of this analysis show that the performance
requirements of 90.1-2007 are 4% to 9% more efficient than 90.1-2004. As a result, the current 2009 FEC (with its
requirement that buildings exceed 2007 FEC requirements 15%), exceeds the
minimum performance requirements of 90.1‑2007 by 6% to 11%, depending on
building type and size.