Cool Roofing with ABOVE SHeATHING VENTILATION. WHY 'ASV- Makes Good Economic Sense
LETS DO THE MATH!
Ontario's average homeowner electricity costs for running a 1200 BTU central air conditioner for 6 hours a day for 6 months of the year ranges between $150 -$200 per month. That is the average cost to cool a 1500 sq foot home.
$150 / month x 6 months = $900/Year with a regular shingle roof
OR
$100 / month x 6 months = $600 / Year with an above sheathing ventilated metal roof
INVEST IN ECO ROOF AND ENJOY UP TO 33% SAVING ON YOUR SUMMER COOLING COSTS FOR LIFE
Over 15 Years (or 1 shingle replacement) x $300/Yr Saving = $4500 Saved
PLUS ENJOY WINTER SAVINGS ON HEATING BILLS OF UP TO 5% (Click to find out more)
Ontario's average homeowner electricity costs for running a 1200 BTU central air conditioner for 6 hours a day for 6 months of the year ranges between $150 -$200 per month. That is the average cost to cool a 1500 sq foot home.
$150 / month x 6 months = $900/Year with a regular shingle roof
OR
$100 / month x 6 months = $600 / Year with an above sheathing ventilated metal roof
INVEST IN ECO ROOF AND ENJOY UP TO 33% SAVING ON YOUR SUMMER COOLING COSTS FOR LIFE
Over 15 Years (or 1 shingle replacement) x $300/Yr Saving = $4500 Saved
PLUS ENJOY WINTER SAVINGS ON HEATING BILLS OF UP TO 5% (Click to find out more)
An ENERGY SAVER Roof Deck Provides Above Sheathing Ventilation & up to 10% in Annual Energy Savings IF YOU USE A CENTRAL HVAC SYSTEM TO HEAT AND COOL YOUR HOME
A double strapped roof deck (shown below) VS a single strapped roof deck
While both provide ventilation, only a double strapped roof provides both the drainage and ventilation needed to deal with the condensation that forms beneath ALL metal roofing
Condensation specifically gets trapped behind horizontal single strapped systems because there is no drainage, and this can eventually rot out both the wood strapping and the sheathing deck that holds the metal roof panels in place.
The inherent flaws of this design have given self ventilated metal roofs a reputation of trapping moisture which is totally unwarranted
NEVER LET YOUR ROOFING CONTRACTOR INSTALL ONLY SINGLE STRAPPING BENEATH YOUR NEW METAL ROOF. EITHER INSTALL YOUR METAL ROOF 'DIRECT TO SHEATHING DECK' & FORFEIT ENERGY SAVINGS, OR DOUBLE STRAP YOUR ROOF.
While both provide ventilation, only a double strapped roof provides both the drainage and ventilation needed to deal with the condensation that forms beneath ALL metal roofing
Condensation specifically gets trapped behind horizontal single strapped systems because there is no drainage, and this can eventually rot out both the wood strapping and the sheathing deck that holds the metal roof panels in place.
The inherent flaws of this design have given self ventilated metal roofs a reputation of trapping moisture which is totally unwarranted
NEVER LET YOUR ROOFING CONTRACTOR INSTALL ONLY SINGLE STRAPPING BENEATH YOUR NEW METAL ROOF. EITHER INSTALL YOUR METAL ROOF 'DIRECT TO SHEATHING DECK' & FORFEIT ENERGY SAVINGS, OR DOUBLE STRAP YOUR ROOF.
WHY AN ECO ROOF DOES NOT USE SINGLE STRAPPING
SINGLE STRAPPING A ROOF CAN LEAD TO MOISTURE BUILDUP BEHIND THE STRAPS AND EVENTUALLY ROT THEM OUT. THE IMAGE BELOW SHOWS A SINGLE STRAPPED ROOF DESIGN
What is 'Above Sheathing Ventilation' or 'ASV'
Studies on the Effects of ASV on Coated Metal Roofs - Oakridge Lab at Stanford University
Stanford's study concluded that a battened air cavity ventilates the roof, which Oak Ridge National Laboratory labeled as Above Sheathing Ventilation or 'ASV'.
ORNL said “we serendipitously discovered the second major advance in roofs for our century: We found that elevating the roof cover from the roof deck to induce above-sheathing ventilation is as important as increasing solar reflectance and may be the stronger player in reducing heat gain into the attic. The two combined can reduce heat gain through the roof by 50% compared to nailed asphalt shingle roofs.”
Miller, Wilson, and Karagiozis (2006) concluded that ventilating the roof deck is just as important as increasing solar reflectance and is the stronger player in reducing heat gain into the attic.
What is 'Above Sheathing Ventilation' or 'ASV'
- ASV- is an acronym for Above Sheathing Ventilation. Numerous industry studies have proven that ASV vented roofing can dramatically reduce attic temperatures even when dark colored roofing materials are used.
- Above Sheathing Ventilation is typically created by a ‘battened’ sub-tile airspace formed between roof sheathing and metal roofing panels.
- This airspace is an approved alternative to California’s Title-24 Energy Code that requires a 20% reflective roof covering.
- Installing an air-space across a roof deck meets California’s ‘2008 BUILDING ENERGY Efficiency Standards for Residential and Non-Residential Buildings’, Effective Jan-1, 2010.
- The code allows exceptions to installing the required 20% reflective roof covering by installing a roof that provides either insulation with a thermal resistance of at least 0.85hrft 2-F/Btu (R-0.85), or a least a ¾” inch air-space is added to the roof deck over an attic.
An ASV cool roof complies with Title 24 California Building Standards, Section 152, and NAHB Green Building Standard, Chapter 7, which both state that roofs installed with an appropriate air gap are considered equivalent to the prescriptive definition of a cool roof (i.e cool pigment roofs)- regardless of the roof color and it's associated solar reflectance.
See: California energy commision cec title 24-policy letter
Studies on the Effects of ASV on Coated Metal Roofs - Oakridge Lab at Stanford University
Stanford's study concluded that a battened air cavity ventilates the roof, which Oak Ridge National Laboratory labeled as Above Sheathing Ventilation or 'ASV'.
ORNL said “we serendipitously discovered the second major advance in roofs for our century: We found that elevating the roof cover from the roof deck to induce above-sheathing ventilation is as important as increasing solar reflectance and may be the stronger player in reducing heat gain into the attic. The two combined can reduce heat gain through the roof by 50% compared to nailed asphalt shingle roofs.”
Miller, Wilson, and Karagiozis (2006) concluded that ventilating the roof deck is just as important as increasing solar reflectance and is the stronger player in reducing heat gain into the attic.