CNC Report 08.26.24 8.5x11 - Flipbook - Page 134
05 DECARBONIZATION PATHWAY
Deep Energy Retrofits for reducing carbon typically include both envelope and HVAC improvements
including switching to electricity from natural gas-based heating/ hot water/ cooking. Conventional
prioritization begins with the envelope improvements to therefore reduce the size of the heating and
cooling system needed. However, it may be less expensive overall and also beneficial for carbon to
prioritize fuel switching, because of both the reduced embodied carbon and annual operational carbon
impact.
With PV, a pathway with only PV + Heat Pump performs better for cumulative carbon than PV + Heat
Pump + Envelope Retrofit.
For this best case scenario of PV + Heat Pump, 20% more PV is required to provide the electricity to
cover the whole carbon footprint, which adds significant cost and also requires 20% more PV area
which may not be available on site.
Geothermal Heat pumps provide higher efficiency than what is shown but come with higher capital
cost. Deep energy retrofit EUI can be further reduced, but needs to include other measures like
efficient appliances and lighting.
15 YEARS
Decarbonization Pathways
Buildings in Memphis
120.0
EUI
Natural Gas
Heating and Hot
Water
kBtu/sf-yr
40
Total Carbon Operational + Embodied [lbsCO2/sf]
100.0
Envelope
Retrofit Only
32.2
80.0
ASHP only
30.9
ASHP +
envelope retrofit
60.0
25.7
ASHP +
envelope retrofit
+ PV
40.0
ASHP + PV
30.9
20.0
0.0
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
9.0
Year
Operational Carbon Impacts
Embodied Carbon
Added Here
ASHP = Air Source Heat Pump
PV = Photovoltaics
134
25.7
archimania
Transsolar
KlimaEngineering
10.0
11.0
12.0
13.0
14.0
15.0
