Low-Rise Multifamily Energy Code Study

Russ Landry, P.E., Lauren Sweeney, Dave Bohac, P.E.

Project Update

The study's findings revealed that most buildings in Minnesota met code requirements for all the measures explored in the study. The biggest opportunities for improvement in Minnesota low-rise multifamily buildings that did not meet code requirements included additional wall insulation; increased window U-factor values; and efficient lighting measures for exterior spaces. The final report is nearly complete and will likely be published in later summer 2020. Read the full update. 

Why This Research Is Needed 

The Low-Rise Multifamily Energy Study will improve understanding of energy code practices in low-rise multifamily dwellings. Previous research has shown that energy code for multifamily dwellings straddles that of single-family homes and commercial spaces, and is interpreted differently across jurisdictions. Because of the different interpretations, energy code compliance is more complicated than it needs to be. 

Project Process and Expected Outcomes 

This project will collect information on building energy design and construction characteristics in new multifamily constructions. Working with Ecotope and Slipstream, CEE will collect construction data from 25 low-rise multifamily buildings in Minnesota, and complete air tightness testing on 14 of them. Slipstream will collect this data in Illinois, and Ecotope will collect it in Washington and Oregon.  

Researchers will use the construction data for low-rise multifamily buildings in each state to evaluate current energy efficiency levels for numerous design elements. Analysis will also look at the potential energy savings that could be realized by reaching certain industry standard efficiency levels. The findings will provide valuable information to guide industry professionals and energy program planners.

The air tightness testing results will help resolve the current industry divergence between two air tightness testing approaches: the compartmentalization type test and the whole building envelope type test. To do this, researchers will:

  • Determine whether a relationship between these two tests exists for the Common Entry and Garden Style multifamily building types

  • Provide an appropriate and practical envelope air tightness test protocol(s) to determine energy code compliance for multifamily buildings

  • Provide guidance for the development of language addressing envelope tightness in model energy codes aimed at the low-rise multifamily sector

  • Assess the energy impact of air tightness testing using the protocols in this study

The research team’s intention is for the outcomes of this study to be useful to other state and regional organizations to quantify energy efficiency opportunities across the country.

This research is funded in part by a grant from the U.S. Department of Energy.

Project Info


Oct. 2016 – Sept. 2019


Collect data on low-rise multifamily buildings that will be used as a baseline to assist in energy code compliance

Non-Energy Benefits

This research is the first step in standardizing multifamily energy code around energy efficiency, which would benefit building owners, designers, contractors, and occupants.  


Newly constructed low-rise multifamily buildings in Minnesota, Illinois, Oregon, and Washington