This prerequisite is a big one, not only because it’s required for all projects, but also because it feeds directly into EAc1: Optimize Energy Performance, where about 15% of the total available points in LEED are at stake. Master the minimum requirements under EAp2, and you will be well on your way to earning points under EAc1. Keep in mind that any LEED-NC v2.2 project registered after June 26, 2007 must achieve at least two energy use reduction points via EAc1 methodology. Plan for this in your approach to EAp2.
You won’t earn the prerequisite by accident, though. Although “energy efficiency” is on everyone’s lips, the mandatory and performance-based requirements for EAp2 go beyond code compliance in most places. That said, there is nothing to stop you from meeting the requirements with a reasonable amount of effort, and the environmental benefits as well as the operational cost savings are significant.
Meeting ASHRAE 90.1-2004
All projects must meet all the mandatory provisions (Sections 5.4, 6.4, 7.4, 8.4, 9.4, and 10.4) of ASHRAE/IESNA Standard 90.1-2004 (without amendments).
There are prescriptive compliance paths available for the prerequisite. However, all projects registered after June 2007 have to obtain two points under EAc1, which offers three compliance paths. You probably should choose a compliance paths that allows you to achieve both EAc1 and EAp2.
If energy modeling is not planned for the project, must meet either the prescriptive requirements (Sections 5.5, 6.5, 7.5, and 9.5) of ASHRAE 90.1-2004 (without amendments) or as selected for EAc1.
Choosing your path (consider energy modeling)
Energy modeling alone gives you access to all of the points available through EAc1, and offers the most flexibility in giving you credit for innovative designs.
First, you need to meet the mandatory requirements of ASHRAE 90.1-2004 for all major components, including the envelope, HVAC, lighting, and domestic hot water. The best way to do is look up the list of mandatory requirements and fill the ASHRAE 90.1 compliance forms.
Second, you need to demonstrate energy cost savings as determined for EAc1 point goals for your designed building compared with a baseline case meeting the minimum requirements of ASHRAE 90.1. You can do this by creating a computer model following rules described in Appendix G of ASHRAE 90.1, or pursuing one of the other EAc1 compliance paths.
Computer modeling offers the following key advantages:
- It can be used to provide feedback on your design both early on, and as the design progresses, so it’s best to use in this way rather than simply demonstrating compliance.
- It can help your team focus on the most cost-effective efficiency strategies, by plugging in different options and seeing the results.
- If your building is unconventional or complex in design, an energy model is the best way to account for that.
However, if your building type and size allow, and you don’t want to embark on the complex process of computer modeling, which also requires expert assistance from a modeler or from a member of the mechanical engineer’s team, the ASHRAE prescriptive compliance paths are a good way to earn the prerequisite simply by following a checklist.
Note, however, that when you get to EAc1, there are a lot fewer points on the table for the prescriptive paths, and that you have to follow each prescriptive requirement. These paths also require more collaboration and focus early on in design than you might think. The design team must work together to integrate all of the prescriptive requirements.
Reduce energy loads first
As a general rule that applies to all energy credits, energy efficiency offers a clear combination of environmental benefit and benefit to the owner through reduced operational expenses, and potentially reduced first costs, if you’re able to reduce the size and complexity of your HVAC system with a more efficient envelope.
High-tech HVAC systems, and onsite renewable energy generation are often signature components of green buildings, but consider these strategies more “icing” on the cake, rather than a place to start. Start with building orientation and passive design features first. Also look at envelope design, such as energy-efficient windows, walls and roof, before looking at HVAC and plug loads. A poorly designed envelope with a high-tech HVAC system is not, on the whole, efficient or cost-effective.
Energy modeling and district heating
If your building includes the use of purchased steam supplied to your HVAC system, the proposed (design) building should be modeled as if the steam system is “located” in the building—with the same efficiency with which it typically operates. The designed building is allocated only the fuel cost (for natural gas or oil) required to generate and deliver the steam needed for the building. The steam purchased is actually considered “free,” as steam rates are not included. And here is where your building really benefits—if the steam system also co-generates electricity along with steam, that electricity is assumed to be “free” to the proposed building, as well. (Refer to the latest guidelines from USGBC.)