For the first time, multifamily real estate developers have a tool to lower the cost of their buildings even while adopting more stringent energy codes. A 350,000 sf apartment building in Decatur, GA used cove.tool to reduce the cost of construction by $2 million.
While the current energy code in Georgia is based on the ASHRAE 90.1 2007 version, this developer opted to use the energy code based on the 2013 version since Georgia is switching code versions at the end of 2019. Based on the minimum code requirements, this apartment building should have a minimum energy use intensity (EUI) of 35 kBTU/sf. This is almost a 40% energy reduction compared to the current code. The energy code allows for the design to be done either prescriptively (i.e. preselected options in a table) or by running a full building energy model. Using the prescriptive model, the building was set to cost an additional $2 million through the use of higher roof insulation, wall insulation, window u-values, Solar Heat Gain Coefficient (SHGC), upgraded HVAC, and more efficient water heaters and appliances.
However, when using the simulation approach, there is no need to max everything out. For example, increasing window u-values and SHGC can reduce the heating load enough to use a smaller HVAC system and save money. The only problem is that there are so many options to choose from that the design space became unmanageable. Typically, projects can only look at 3 to 4 “bundles” of options when there are millions of combinations of materials, equipment, and system selections that cost much less and perform at higher efficiencies. We examined 2 different HVAC Types, 4 different roof insulation, 4 different lighting type, 3 different wall types, 5 different glass types, and 4 different PV Panel options. After simulating all these combinations with cove.tool we found a bundle that performed the same and cost $2 million less than the prescriptive requirements. This is a big deal that we were able to drop 40% of the energy consumption and keep the cost exactly the same.
“Optimization with cove.tool helped us meet the new energy code without increasing the cost”