Characterization of 5 to 9 Unit Residential Buildings in Minneapolis

A study done by the Minneapolis Energy Office (MEO) characterizing 5 to 9 unit residential buildings in Minneapolis was conducted as one segment of an overall multifamily baseline study. Although MEO has served some buildings in this size range over the last three years, relatively little was known about them, since they fall into a grey area between single family homes and apartment buildings, and the office's multifamily programs had focused on 10 to 50 unit buildings. Yet 42% of the 5 or more unit multifamily buildings in the city are in this size class (representing 13% of the 5+ dwelling units).

The goals of the present study were: 1) to characterize these buildings using easily available data from the City Assessor and MEO's audit records, 2) to check the accuracy of the Assessor's data since they are used routinely in multifamily audits, 3) to sort the buildings into readily recognizable categories in order to effectively market MEO's conservations programs, which serve house-like buildings differently than apartment-like buildings, and 4) to create a data base that could be expanded in later research and program efforts. Two groups were analyzed: a random sample of 94 5 to 9 unit buildings and all the buildings in this size range (n=93) that had been audited by MEO or by the Self-Reliance Center (SRC) under contract to MEO. Data consisted of Assessor's records, audit records and notes about physical characteristics collected during brief site visits.

The study found that while these buildings represent a diverse sector of the multifamily building stock, they cluster into only four groups: as-built apartments, apartments with commercial space, rowhouses and converted single family homes or duplexes. As-built apartments comprise the largest and most heterogeneous group (52%), and are generally characterized by hot water heat, with average gross building area (GBA) of 6384 sq. ft. and average year built (YB) of 1938 (with two peaks--in the 1920s and the 1960s). Apartments with commercial space have larger areas Cave GBA=17,189) and steam heat. Rowhouses (11%) were younger (ave YB=1960), larger (ave GBA=8152) and high in forced air heat. Conversions (34%) were old (ave YB=1897), small (ave GBA=3169) and high in hot water heat. Other physical characteristics that may be relevant in developing program approaches were also investigated (e.g. location, number of units, sheathing, roof and construction types).

A discriminant analysis using Minneapolis City Assessor's data correctly classified 95% of the test cases into the appropriate group. Using these results, further classification of buildings can be automated to produce lists of buildings by type that can be used to market MEO's conservation programs.

Assessor's data were compared to site visit data and many discrepancies were found. This may be due to the unimportance of physical characteristics in determining taxable value of multifamily buildings (in contrast to single family homes) and the subsequent lack of completeness and reliability in recording these variables. Data from the audited buildings were also compared with assessor's data and similar levels of discrepancy were found.

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Characterization of 5 to 9 Unit Residential Buildings in Minneapolis