Above sheathing ventilation presentation (mca scott kriner-20080229)

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Natural convective air flow develops in an air space created between a roof product and the roof sheathing Buoyancy forces from heated air create a flow from eave to ridge Air flow dissipates heat build-up and reduces heat gain through the roof sheathing when compared to direct nailed roof products with no air space 4

! " Offset mounting Batten and counter batten sub- framing is common practice for some roof products Continuous air space is created from eave to ridge Profiled roofing products create space above the deck Special sandwiched sheathing products are available with space designed into them Batten/Counter-Batten Frame 5

# $ Natural airspace along with air permeability of installed tiles promotes air flow beneath and around tiles. 7

%& & ' ( Roof Coatings Manufacturers Association Tile Roofing Institute Cool Metal Roofing Coalition CEC PIER IRR Pigment Project DOE, MCA and Stone Coated Metal Mfrs. Renegade Roof Systems, Poly Foam Corp., Tile Roofing Institute, Louisiana Pacific 8

%& & ) Various types of tile roofing (2001) and metal roofing (2003) Control: direct nailed asphalt shingle Measurements of temperature, heat flux, weather conditions, solar reflectance and thermal emittance 9

* & + ( , , , $ Formulate and Validate AtticSim for Cool Color and Above-Sheathing Ventilation 10

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# ( (- (a) As air temperature under the roof surface increases, heated air rises toward the ridge and draws cooler air into the system through vented eave. (b) Heated air exhausts through the vented ridge assembly. High profile roofing products allow more heated air to exhaust through ridge vent. 12

. # Tile, slate, metal shingles Plan view of the roof showing air flows between tiles and underlayment Eave are air permeable Wind direction Permeability 0.5-1.0% of the laid area Ridge Complicated flow networks Eave Flow influences: Outward acting pressures Energy performance over leeward slope Streamlined Wind loading flow Driving rain performance Separated wake (very unstable) Batten space flows Dispersion of moisture Area of separated Flow near eaves Lafarge Roofing Technical Center 13

Control - Asphalt Shingle (SR093E89) Shake Dark Gray (SR08E90) Batten and Counterbatten Shake Light Gray (SR26E90) Batten-Counterbatten 40 Heat Flux through Roof Deck 30 [Btu/(hr · ft2)] 30%Drop 20 45%Drop 10 0 -10 0 72 12 84 24 96 12 108 24 120 12 132 24 144 Time into Week (hrs) ASV results in a 30% drop in heat gain compared to asphalt shingle. A cool (IR reflective) surface adds an additional 15% to reduction in heat gain. 14

/ ( 01 ) & R 38 Attic Insulation with AC ducts insulated to R-6 15

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/ & The lower the solar reflectance of the roof, the more ventilated heat exits the ridge vent 17

/ & . Reduced moisture content in OSB is well below content without a vented cavity 18

/ Empirical algorithm captures energy benefits of Above Sheathing Ventilation 19

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) & Reflectance of 0.25; Emittance of 0.90 21

Light Gray Shake, (SR246E90) Underside Unpainted Batten & Counter batten 22 22

& - - * Field Testing at FSEC (1994) Tile roofing, variety of venting designs Temperature and heat flux measurements 45-50% reduction in heat gain vs. dark shingle direct nailed Research at Lafarge Technical Center (UK) Predicted ORNL field data on clay tile 24

' ( 2008 CA Building Energy Efficiency Standards (Title 24) 45-day language as equivalence option to cool roofing Passive cooling section in Energy Efficiency Category of NAHB Green Building Standard (under development) 25

US Department of Energy Energy Efficiency and Renewable Energy Roof Material Foil backed OSB Upper air channel Radiant barriers PCMs Upper air channel Lower air channel Insulation w/ foil Gypsum board 26

' ( & ! Full System Integration 90% reduction in peak demand PCM Shaves Peak Demand and Reduces Night Sky Losses July 28, 2006 27

Above Sheathing Ventilation alone causes a 30-50% reduction in heat gain, compared to dark asphalt shingle direct-to-deck Range from metal vs. tile roofing Reduction in heat gain is equivalent to 15 points of solar reflectance Combining ASV with cool surfaces reduces the heat gain even more 28

Above sheathing ventilation presentation (mca scott kriner-20080229)

by Cool Roof Innovations on Oct 16, 2010

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Above sheathing ventilation presentation (mca scott kriner-20080229) — Presentation Transcript