Air Barrier Requirements for Low-Slope Roof Assemblies Myths vs. Facts

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1 Air Barrier Requirements for Low-Slope Roof Assemblies Myths vs. Facts Peter Kalinger Canadian Roofing Contractors Association Dr. B. Baskaran National Research Council of Canada 1

2 Air Leakage Controlling air leakage critical to achieving thermal efficiency 2

3 Roof as Air Barrier

4 Air Leakage It is generally accepted that the air leakage rate of an air barrier material should not exceed 0.02 L s/m²@ 75 Pa (0.004 cfm/ft²@ 1.57 psf) It is generally accepted that the air leakage rate of an air barrier assembly should not exceed 0.2 L s/m²@ 75 Pa (0.04 cfm/ft²@ 1.57 psf) 4

5 National Building Code of Canada

6 Canadian Standards for Air barriers CAN/ULC-S741, Standard For Air Barrier Materials Specification Air permeance 0.02 L/(s m²) at 75 Pa CAN/ULC-S742, Standard for Air Barrier Assemblies Specification A L/(s m2), A2 0.10, A3 0.15, A4 0.2, A

7 IECC Air Barrier Requirement for Roofing Systems It is the U.S. model code adopted by many state and municipal governments for the establishment of minimum design and construction requirements for energy efficiency for new commercial and residential construction. 7

8 IECC 2012 A continuous air barrier shall be provided throughout the building thermal envelope permitted to be located on the inside or outside of the building envelope, located within the assemblies composing the envelope, or any combination thereof 8

9 IECC : Air Barrier Assembly Testing 9

10 U.S. Standards for Air barriers ASTM E 2178 Standard Test Method for Air Permeance of Building Materials cfm/ft 3 (0.02 L/s m 2 ) at 0.3 inches water gauge (75 Pa) ASTM E 2357 Standard Test Method for Determining Air Leakage of Air Barrier Assemblies 0.04 cfm/ft 3 (0.2 L/s m 2 ) at 0.3 inches water gauge (75 Pa) 10

11 Materials: IECC cfm/ft 3 (0.02 L/s m 2 ) at 0.3 inches water gauge (75 Pa) using ASTM E2178 Assemblies: 0.04 cfm/ft 3 (0.2 L/s m 2 ) at 0.3 inches water gauge (75 Pa) using ASTM E2357, ASTM E1677 or ASTM E283 11

12 IECC 2012 Deemed to comply options SPF (closed cell), min. 1.5 pcf, min. 1½-inches thick Built up roof membrane Modified bituminous roof membrane Fully adhered single-ply roof membrane (also includes cast in place concrete, sheet steel or aluminum, grouted block masonry) 12

13 Roof Systems Requiring Testing Mechanically-attached single-ply membranes Ballasted single-ply membranes Metal panels Steep-slope (asphalt shingles, tile, slate, wood) Confusion regarding system requirements versus material requirements 13

14 Canadian Standards for Air Barriers Proposed CAN/ULC Standard for Air Barrier Materials and Assemblies. Canadian Construction Materials Centre Technical Guide for Air Barrier Systems for Exterior Walls of Low-Rise Buildings. Would require extensive and costly testing to determine air barrier properties of membrane roofing systems, similar to current IECC. Industry maintained low slope membrane roof systems are effective air barriers. 14

15 Air Leakage and Low slope Roof Membrane Assemblies 15

16 Air Leakage Testing

17 Air Leakage Testing

18 Canadian Standards for Air barriers CAN/ULC-S741, Standard For Air Barrier Materials Specification Air permeance 0.02 L/(s m²) at 75 Pa CAN/ULC-S742, Standard for Air Barrier Assemblies - Specification Five classifications of air leakage rates A L/(s m2), A2 0.10, A3 0.15, A4 0.2, A5 0.5 All at a pressure difference of 75 Pa. 18

19 Canadian Standards for Air barriers CAN ULC S COMPLIANCE A5 the reference air leakage rate shall not exceed 0.50 L/(s-m 2 ) at a pressure difference of 75 Pa 19

deemed to have an air leakage rate not exceeding 0.

20 CAN/ULC-S742, Standard for Air Barrier Assemblies - Specification Where the air barrier is a low sloped roof membrane assembly, it is deemed to have an air leakage rate not exceeding 0.20 L/(s m²) A4 - when constructed in accordance with typical details contained in Annex 20

21 CAN/ULC-S742, Standard for Air Barrier Assemblies - Specification 21

22 Location of Air Barrier In Roofs NBCC position minimizes the accumulation of condensation. Unlike vapour barriers, location of air barrier is not critical and not governed by climatic conditions. Important considerations : attachment, ability to resist peak pressures, subsequent tearing and dislocation. 22

23 Roof as Air Barrier In mechanically fastened (MF) assemblies wind, mechanical pressure or stack effect may cause flutter and pumping of air into the assembly Occurs when there is no, or an ineffective vapour retarder Can lead to accumulated condensation at underside of membrane Function of membrane properties (extensibility), fastener spacing and pressure differential 23

24 Air Intrusion Testing Problem of air intrusion not leakage through the envelope 24

25 Roof as Air Barrier Flow of air into assembly can be reduced by inclusion of air/vapour retarder SIGDERS research shows wind resistance of MF systems by 50% with VB Part of increased resistance due to decrease in membrane deflection In Canada, millions of square feet of roof air barriers are installed on cold side without moisture related problems 25

26 Air Intrusion Testing SIGDERS - Phase V Reporting air intrusion volume in accordance with ASTM D

27 Air Intrusion Testing 27

28 Air Intrusion Testing Small scale study with thermoset system With and without air retarder With and without differential pressure gradient (suction pressure) 28

29 Air Intrusion Testing

30 Air Intrusion Testing Without air/vapour retarder air intrusion is a significant driving force in transporting moisture into the system Air/vapour retarder at the deck level minimized the moisture loads in the roof system both due to vapour transmission and air intrusion Proper installation of air/vapour retarder is vital in the installation of mechanically attached roofing systems 30

31 Air Intrusion Testing 31

32 Address IECC Roof Air Barrier Assembly Testing AIR Air Movements Impact On Roofing Systems 32

33 Air Movements Impact on Roofing Systems (AIR) A Research Proposal for the Air Movement Impact on Roofing Systems (AIR) Objective 1: Development of Air Leakage Test Method for Low Sloped Roofing Systems - The air leakage method will be developed to meet the three criteria of IECC air barrier assembly Continuity, Strength and Air Leakage 33

34 Air Movements Impact on Roofing Systems (AIR) Insulation Installation Curb Detailing Installation of Pressure Taps Around the penetrations Completed System 34

35 Air Movements Impact on Roofing Systems (AIR) Qualitative Approach of Air Leakage Compliance Through Flood Test (Verification) 35

Air Movements Impact on Roofing Systems (AIR) Objective 2: Air Moment and Moisture Tolerance in Roofing Systems Quantifying the impact of air/moisture movement on moisture accumulation

36 Air Movements Impact on Roofing Systems (AIR) Objective 2: Air Moment and Moisture Tolerance in Roofing Systems Quantifying the impact of air/moisture movement on moisture accumulation and thermal performance Evaluate the control strategies such as air retarder, vapour permeability, reflectivity and air vents in minimizing the impact of moisture in roofing systems. 36

37 DRF Air Intrusion and Hygrothermal Testing Facility 37

38 Wetting Vs. Drying Potential 38

39 Condensation & Cool Roofs 39

40 Condensation & Cool Roofs 40

41 Roof as Air Barrier Most roofing membranes, although located on the cold side of the insulation, will perform as effective air barriers provided that: All penetration and openings are sealed and made airtight. Continuity is provided by tying in the roof membrane to the other (wall) air barrier elements. Vapour retarders, installed in mechanically fastened flexible membrane systems can limit vapour diffusion, air intrusion and membrane deflection. 41

Understanding Energy Codes

NRCA University Webinar October 17, 2013 Understanding Energy Codes presented by Mark S. Graham Associate Executive Director, Technical Services National Roofing Contractors Association Some background