Thermal Comfort Rating Metric: A Proposed Asset Rating System Tim Beggs, Manager, Innovation What Is a Comfort Metric? Comfort Index Comfort Index 46 HERS® Index image courtesy of RESNET (http://www.resnet.us/) WHY NOW? SAVING ENERGY ≠ DELIVERING COMFORT Lower Loads = New Risk Potential • Better enclosures • Lower loads • Lesser airflow • Potential for poor air mixing, lesser run time • Temperature swings and stratification Trends: Comfort Issues 36 EFL Homes Measured in the Southeast Psychrometric chart, House 24 – Most Compliant Trends: Comfort Issues 36 EFL Homes Measured in the Southeast Psychrometric Chart, House 25 – Least Compliant Trends: Comfort Issues Comfort issues are on the rise even in low load homes shortcomings of other metrics Comfort Rating Use Cases • Comparing homes (purchase & sales) • Designing homes (new homes) • Valuing homes (sales, appraisal, mortgages) • Developing a residential application of ASHRAE Standard 55 for thermal comfort (performance standard) • Assessing homes (retrofit) • Scoping a retrofit project (setting better targets) WHAT IS IT? Aspects of Comfort ENVIRONMENTAL FACTORS • Temperature • Temperature difference • Air speed • Humidity • Radiant PERSONAL FACTORS • Clothing insulation • Metabolic rate • Health Factors Affecting Comfort Architectural Design • Orientation • Spatial layout / floor plan/ elevation design • Volume of space Building Enclosure Characteristics • R-value / U-value • Air leakage • Solar management • Window-to-wall ratio • Shading coefficient • Shading (int + ext) • Mass-lag effects HVAC System Characteristics • Type + capacity of space conditioning • Duct layout • Temperature gain • Leakage • Air balancing • Diffuser placement • Diffuser air throw / selection Room Air Balance • We need to return air from each room • Air return strategy • Door undercut, typically no! • Doors open vs. closed • Transfer grilles ducts, yes! Photo Source: GreenBuilder Media Programmable Thermostat Use of Setback • Ability for comfort to recover • Its there when you need it • Room-by-room temperature set points (availability?) Room-by-Room Zoning • Damper on each branch duct • Manual vs. automatic dampers • Individual room units multi-zone climate control TODAY 30 YEARS AGO Ventilation Balanced vs. unbalanced Direct delivery (raw) Mixed delivery (preconditioned) Occupant Behavior • Range of behavior will maintain comfort • Level of sensitivity for the house • # of people, what they’re doing • Ability of system to respond for a control set point Improved sense of comfort + peace of mind HOW WOULD IT BE MEASURED? Foundation Metrics Thermal Comfort Performance Index (TCPI) Foundation Metrics Histo-Contour Comfort Map Foundation Metrics Ramp and Drift “Hair-plot” Foundation Metrics Heat Map Foundation Metrics Binary Heat Map What May Yield a Better / Poorer Score? Better Poorer Comfort Index • Multi-zone • Single thermostat temperature sensing • Over / under sized for control equipment • Right-sized or variable • No exterior shading speed equipment • Hot ceiling • Exterior shading • Dumping untreated Comfort • Neutral radiant ventilation air Index surfaces • Stratified air 46 • Dehumidification temperatures control • Continuous fan? • Improved air mixing • Fireplace? • Continuous fan? • Fireplace? Present IBACOS Activities with TCRM . Establishing the new home/retrofit industry needs . Continue introducing the concept . Webinar, blog, utilities, ASHRAE, RESNET, HPC, White Paper . Generating interest from stakeholders . Prompting feedback and documenting . Seeking collaboration and development partners . Establishing justification to move forward . Refining the vision for path forward Some Questions Moving Forward 1. What boundary conditions should exist on application a) Low load homes, all homes, igloos? 2. How should the scale be developed? 3. Should a reference home be involved as a baseline? 4. How can we accurately and appropriately model the comfort experience? 5. How can system dynamics be appropriately modeled? 6. What modeling would a user of the TCRM conduct, and what applications would be used? 7. What overlap with HERS-related field assessments exist, what other survey is required? 8. Etc..