Energy Use in Multifamily Housing

Modeled Beauty vs. Ugly Reality

Unit-level Rem/Rate simulation projections for 15 multi-family developments


Measured unit-level energy use from 15 multi-family developments


The Virginia Center for Housing Research (VCHR) at Virginia Tech evaluated the simulated versus measured energy use of 300 apartments in 15 EarthCraft Multifamily (ECMF) certified developments.  REM/Rate was used for the energy simulation and was found to over-predict energy use by 17% on average.  Measured unit-level energy use was highly variable, suggesting an opportunity to better understand the relationship between the occupant and the broader system in high performance housing.   A follow-up study in currently underway, evaluating longitudinal energy use over 3  years, construction costs of high performance buildings and the role occupant education in reducing variability in performance outcomes. 

Warwick SRO 

Balancing Historic Preservation and (Measured) Building Performance 


The Warwick is a historic, seven-story brick façade structure originally constructed in 1883. Fire destroyed most of the original structure in 1960. The first renovation, an adaptive re-use, was performed in 1995. CHP transformed the remaining structure into permanent supportive housing units for formerly homeless individuals. The Warwick single-room occupancy (SRO) facility contains 88 units. Shared spaces include the lobby, offices for staff, group therapy space, two community resident lounges, computer lab, and laundry facilities.


The renovation of the Warwick included measures required to obtain EarthCraft multifamily certification of the building. Not only did CHP prioritize measures that reduce energy consumption, indoor air quality was also given significant attention to improve the health and safety of residents. The full retrofit took more than a year and included the following upgrades and additions:

  • Unit-level compartmentalization through airsealing & diagnostic testing

  • Variable Refrigerant Flow (VRF) heating and cooling system

  • Energy Recovery Ventilator(ERV) fresh air for each unit and all common areas

  • High efficiency water heaters

  • Energy Star light fixtures, dishwashers, refrigerators

  • New Energy Star windows

Pre and Post-retrofit Energy and Utility Savings

Warwick SRO Newport News, Virginia

Photo credit: Community Housing Partners

Source: DOE/Better Buildings Challenge

Project Partners

Matt Waring and I had the opportunity to spend the day with our friend and colleague, Anthony Cox, Building Science Manager for Energy Solutions.  For those of you who don't know Anthony, he is the known as the Godfather of Weatherization Diagnostics. He's extremely knowledgeable and all about experiential learning.  He's probably best known for developing the House of Pressure building science training demo.  He's also a BBQ connoisseur and a bit of a technology geek.


He's been working with a small team of enclosure consultants and building physicists to develop an ASTM standard for testing large commercial buildings. Part of the standards development process evaluates validity of the testing process.  We offered to run through their draft procedure to help test repeatability.  

Standard Method for Building Enclosure Airtightness Compliance Testing

Repeatability Testing | ASTM Standard Development

Anthony Cox (L) and Matt Waring (R) begin manometer field calibration and discuss the test plan prior to setting up the 12k sq. ft.  commercial up for a series of enclosure tests.

Commercial enclosure test setup: 1 of 6 fan stations and 1 of 4 weather stations.  Don't underestimate the time necessary to setup a commercial enclosure test properly.  Develop a test plan, with all needed equipment before test day.

With 6 fans, 4 weather stations, and 2 interzonal manometers, preparing a commercial building for testing is where most of the work happens. We used the Energy Conservatory's WIFI Link System to wirelessly report back to TECLOG for a cleaner data collection and reporting process.  Hard wired (Dat) systems are available to connect the fan stations to TECLOG if you don't have access to WIFI, but the WIFI Link System cuts down on cable mess and looks a lot cleaner.

Like most wireless setups, give yourself time for network, device configuration and testing to ensure smooth sailing for the real test(s). Anthony used of a GoPro synced to facetime so we could trouble shoot connectivity issues between the fan station(s) and the Under Pressure testing headquarters we established. Since most commercial enclosure tests require a team of folks to set up, manage and break down the test, it's nice to project the testing data on a screen if possible, so everyone can geek out together instead of hovering over one person's computer.  Having tested several commercial buildings with Anthony, a sound system capable of playing Queen's Under Pressure  is also a must when planning your next enclosure test.

Department of Energy | Race to Zero

National Renewable Energy Laboratory (NREL) | Golden, CO

Over the last two years, I've had the opportunity to participate in the Department of Energy's (DOE) Race to Zero. The Race to Zero was developed to offer architecture, engineering and construction students an opportunity to propose market ready solutions for zero energy housing.  This is unique competition since it has a particular focus on building science education and enclosure analysis/detailing.  The competition culminates with a mid-April visit to DOE's National Renewable Energy Laboratory in Golden, Co.  It is a well organized event that provides an opportunity to meet NREL staff, industry leaders and colleagues from other universities.

Virginia Tech's team partnered with Community Housing Partners to evaluate redeveloping an existing senior housing property as a zero energy development.  The first step was to make a trip to the project site to conduct an energy assessment and establish a baseline. Beyond the typical insulation, lighting and appliance assessment;  we measured duct leakage, enclosure tightness, room to room pressure differences and day lighting (or lack thereof) using a lux meter.

April weather in Golden, CO.

HOBO WIFI data logger install.  We were particularly interested in the water heating load and indoor temperature and relative humidity data in the existing building condition.

One advantage to redeveloping an existing property toward zero energy performance is the opportunity to collect baseline energy performance and indoor environmental quality data.  We installed a series HOBO wireless data loggers that measured circuit-level energy consumption as well as temperature and relative humidity data.

Design Solution

As an existing wood framed, brick veneer structure, we had limited opportunities to improve the enclosure without significant demo and cost.  We identified a significant thermal bridge at the slab to above grade wall intersection.  Our proposed design solution called for adding two inches of mineral wool sheathing to the exterior with integrated flashing and parge coating.  The optimized detailed resulted in a drastic reduction in thermal bridging at the slab-above grade wall intersection.  Note, the bulk water detailing is not included in the THERM analysis image below.  

Promoting Quality Enclosures Beyond Design

Following the baseline assessment and comprehensive design research and analysis, our team focused on developing tools for ensuring the quality installation of the enclosure upgrades.  A full color, step by step enclosure installation guide was developed for each detail to provide the contractor with the sequence and specified material(s) necessary to meet the designer's intent. This detail also serves as a quality assurance tool for the HERS Rater and Site Superintendent.

Once the contractor has successfully installed the enclosure improvements we implement our enclosure testing plan to measure the success of our efforts.  Each of the four buildings within the development consist of 6 identical apartments. The enclosure testing plans calls for six fan locations to create a uniform pressure difference between inside and out of the building.  We also call for three interzonal manometer locations to better understand the pressure relationship between the unit(s) and the new shared laundry room additions.

Multifamily enclosure testing schematic.   Having a formal testing plan is a must when planning a multi-fan enclosure test.

Final Design 

Working with an existing wood framed, brick veneer structure, presented limited opportunities to improve the enclosure without significant demo and cost.  We identified enclosure and mechanical improvements as well as optimized glazing solutions that resulted in enhanced day lighting quality and occupant experience.  The result was revitalized affordable housing development that is designed to achieve zero energy performance and improve the quality of life of the existing senior resident community at Old Orchard Place Apartments.

Old Orchard Place Apartments (BEFORE)                                                                      Old Orchard Place Zero Energy Apartments (AFTER)

© 2020 by Philip Agee | Research & Engineering