Commercial Building Envelope Air Leakage

Transcription

1 Commercial Building Envelope Air Leakage Presented by: Matt Heron, P.E., Pie Consulting & Engineering Stu Reeve, Energy Manager, Poudre School District Kim DeVoe, Energy Services Engineer, Fort Collins Utilities,

2 Why Test & Repair Air Barriers? Energy conservation Reduce heating and cooling loads EPACT 2005 / EISA % reduction over ASHRAE by 2012 Net zero by 2030 (Executive Order 13514) Mechanical System Sizing/Operation Air Exchange 20% to 50% of thermal load Designing / Modeling Infiltration Loads Moisture and mold control Water vapor transport via air movement Very costly to remediate Politically volatile Pollutant transport (IAQ) Example: TEMF facilities Fumes Microclimate Conditioning

3 Historic Performance of Commercial Buildings ASHRAE Fundamentals (CFM / ft2)

4 Whole Building Air Tightness Testing ASTM E779: Standard Test Method for Determining Air Leakage Rate by Fan Pressurization ASTM E1827: Standard Test Methods for Determining Air tightness of Buildings Using an Orifice Blower Door US Army Corps of Engineers Air Leakage Test Protocol for Measuring Air Leakage in Buildings (Engineering & Construction Bulletin dated October 30, 2009)

5 Existing Building Retro Commissioning Poudre School District 2011 Testing

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7 Air Tightness Testing Diagnostics ASTM E1186: Standard Practices for Air Leakage Site Detection in Building Envelopes and Air Barrier Systems

8 Low Slope Roof to Wall Interfaces

9 Steep Slope Roof to Wall Interfaces

10 Expansion Joints & Dissimilar Interfaces EXTERIOR AIR LEAKAGE PATHWAY EXTERIOR INTERIOR AIR LEAKAGE OBSERVED INTERIOR OBSERVE FOR SEALANT

11 Beam Pockets

12 Doors & Operable/Fixed Windows

13 Soffits & Mansard Roofs

14 Clerestory Assemblies & Skylights

15 Thermal Discontinuities

16 PSD 2011 Air Leakage Testing Results

17 City of Fort Collins Civic Center

18 High Electrical usage but low gas usage? LEED Gold building 3 story, 72,000 sf, built in RTU s split N S VAV s have electric reheat Metasys BAS identified high electrical use on the 1 st floor Comfort complaints by clerks on the 1 st fl; electric space heaters under desks $1.60 $1.40 $1.20 $1.00 $0.80 $0.60 $0.40 $0.20 $- $0.35 $0.30 $0.25 $0.20 $0.15 $0.10 $0.05 $- Electricity Cost for Selected City Buildings ($/sf/yr) 215 N. Mason 281 N. College Downtown Library Harmony Library City Hall Selected City Buildings Gas Cost 215 N. M ason 281 N. College Downt own Library Harmony Library City Hall

19 IR investigation & Building Shell Study IR images taken by Gary Schroeder, Fort Collins Utilities Senior Engineer Shell leakage investigation performed by Kevin Knight, Architectural Testing Inc. Findings: Cold air on 1 st fl caused by Stack effect Exterior building materials penetrating inside the thermal boundary Misaligned/discontinuous & missing air barrier causing air leakage into above ceiling return air plenums

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21 Stack Effect: where it leaks matters

22 Misaligned or Missing Air Barrier, Exterior Finish penetrating the Thermal Boundary

23 Roof Air Barrier Continuity

24 Air Leakage at floor and roof decks

25 The Air Barrier Is Now Continuous (But only in accessible areas above ceiling grid)

26 Results Building Air leakage Test out by Stuart Mitchell, PIE Consulting and Engineering Air leakage reduced from 0.43 cfm/sf to 0.26 cfm/sf. A 41% reduction! Reduced comfort complaints & space heaters Discovered / repaired return air imbalances in building which were adding to the stack effect winter electric usage decreased due to reduced electric reheat in winter; increased natural gas usage for overall heating cost savings Summer electrical usage did not increase, even during the hottest summer on record!

27 Civic Center GHG Reduction Exceeds Goal (based on electrical use)

28 Percent Annual Energy Savings due to improved building air tightness (Modeling results from Annex 46) 50% 45% Energy Savings 40% 35% 30% 25% 20% 15% 0.4 cfm/ft cfm/ft cfm/ft2 10% 5% 0% 1A 2A 2B 3A 3B 3C 4A 4B 4C 5A 5B 6A 6B 7A 8A Climate Zone Source Leakage Rate at 0.3 in w.g. (75 Pa) cfm/ft 2 Baseline 1.0 ASHRAE Std requirement for air sealing 0.40 Current Army requirement for air sealing 0.25 Proposed requirement for air sealing 0.15

29 BECx in Rating Systems/Codes/Specs ASTM E2813 Standard Practice for Building Enclosure Commissioning

30 Raising the Bar for Commercial Buildings in Fort Collins New Commercial Building Tightness Standards: ASHRAE: 0.40 cfm/sf U.S. Army Corps of Engineers (ACE): 0.25 cfm/sf City of Fort Collins: 0.25 cfm/sf Developed New Building Code Amendments Fort Collins Utilities consulting w/ PIE Lessons learned from testing and repairs done to the Fort Collins Civic Center

31 Building Tightness Testing as a Design Tool to Meet Goals for Poudre School District Impact of Providing the Right Tools to Challenge Conventional Design Building Envelope Studies and Impact on Energy Modeling Design Team Confidence to Right Size Mechanical Systems Reinforcing Goals Throughout the Design Process Final Design Energy Modeling Rebates and Incentives for High Performance Design We ll Keep You Posted

32 Thank You! Matt Heron Stu Reeve Kim DeVoe