Party Walls

Here’s a question that we’re often asked by our clients: “I’m building a new residential building, should I use LEED for New Construction (NC) or LEED for Multifamily Midrise (MFMR)?” The answer isn’t exactly simple, especially with the introduction of new credit requirements in LEED v4 and the fact that USGBC allows project teams to choose between the two rating systems. Ultimately, it will come down to a difficult decision based on the goals and final design of the project. So, in an effort to help clear up the confusion and possibly make the decision a little easier for you, we decided to break down a few scenarios that highlight key differences between the rating systems that may not be apparent upon first glance.

In our first installment, we took a look at a four story multifamily building and highlighted many of the key differences between the rating systems; you can find that post here. In this edition, we will explore the options for a different building type.

Certifying a Mixed-Use Building

Our sample project is a 10-story building with ground-floor retail. We’ve been seeing a lot of these being constructed in the Mid-Atlantic region over the past few years, and we’ve worked with project teams who have chosen both rating systems. We’ll use this building type to highlight a few of the key differences in residential and commercial building systems to hopefully clear up the decision making process a bit.

Retail

We are often asked about whether a project with retail can even use the LEED for Multifamily Midrise rating system. The simple answer is yes. In fact, the MFMR rating system provides the same flexibility as the New Construction rating system when it comes to retail spaces of a building. Since retail portions of the project are frequently fit out separately from the rest of the building, we often see projects exempt the space from the project. The MFMR rating system allows for up to 10% of a building to be exempted from certain calculations, just as LEED NC does. Midrise can be used even when projects choose to include the retail portion of the project, so don’t let the fact that your building has retail spaces sway you into one rating system or the other.

Systems

As we noted in our first post, one of the key decision-making factors in determining which rating system to use should be the types of mechanical systems installed in the building. A 10-story project will often use a combination of residential and commercial building systems to provide heating, cooling, and ventilation to occupants, such as a central boiler/chiller system connected to individually controlled heat pumps in each unit. This hybrid approach allows for multifamily buildings to utilize more efficient central systems while still providing the benefit of individual unit controls for occupant comfort. However, these complex systems can complicate the rating system decision, as both MFMR and NC have advantages and disadvantages when it comes to this set-up.

In-Unit Testing

We already discussed the advantages of individual unit testing under the MFMR program in our first post, and those advantages still apply in today’s example, as ductwork will still be utilized in each unit. The complications begin to arise when larger central systems such as boilers, chillers, and cooling towers are utilized in a building, as the LEED for New Construction Fundamental and Enhanced Commissioning requirements more effectively address the installation and start-up of these of these systems than LEED for Multifamily Midrise. Additionally, depending on the number of units in the building, the costs of in-unit testing may begin to catch up to the costs of the additional LEED documentation and commissioning required in LEED NC, complicating the decision even further.

Conclusion

At the end of the day, each building is unique and the decision on which rating system to select will depend on the priorities of the project and the building systems utilized within it. We would love to see USGBC simplify matters by developing a single rating system for multifamily buildings by taking the best attributes from both the LEED Homes and LEED for New Construction rating systems. The market for this building type is only growing stronger.

If you have a project that falls in the gray area between these rating systems, get in touch! Our expertise continues to lead the industry as we continue to help builders and developers make the best choices for sustainable, energy-efficient buildings.

By Sean Fish, Senior Sustainability Consultant