WHY Double Strapping & Ridge Ventilation Eliminates Condensation Buildup Problems Associated with Traditional Metal Roofing
The image above shows a correctly constructed double strapped roof deck that provides both proper drainage and ventilation
DISPELLING METAL ROOF CONDENSATION MYTHS
Don't be fooled by claims that interlocking metal shingles installed directly on to a roofs sheathing deck will prevent condensation build up beneath metal shingles . Its impossible to prevent condensation from forming beneath metal roofing even if there is only a 1/8 inch airspace. This is the reason that all metal roofing requires a vapor barrier. Whenever temperatures drop, the temperature of metal roofing drops simultaneously . If warm, moist air contacts this cool metal roof surface, its “dewpoint” is reached and condensation develops. Metal shingles do no ventilate this condensation and moisture away from beneath the shingles because they are installed directly on the roof sheathing deck. Trapped moisture can potentially damage your roofs sheathing deck over an extended period of time because metal shingles use concealed fasteners that create hundreds of perforations in the vapor barrier as well as your roof deck. In Winter, this condensation freezes beneath metal shingles and remains there till Spring.... imagine 50 winters!
A KITCHEN COUNTER EXPERIMENT TO DEMONSTRATE HOW CONDENSATION FORMS BENEATH METAL SHINGLES
Fill a glass with water and ice cubes. Place the glass of water on your kitchen table. Position 3 coins in a triangular formation and use the coins to elevate your glass 1/16" off the table table. Within minutes you will notice condensation forming on the sides of the glass as well as under the glass. After 5 minutes this condensation will build up and precipitate on to your kitchen counter. What is happening on your kitchen counter is exactly what happens on a roof deck beneath metal shingles. The only difference is that a roof deck has a surface area of thousands of square feet while a glass has a circumference of only 3" inches
Don't be fooled by claims that interlocking metal shingles installed directly on to a roofs sheathing deck will prevent condensation build up beneath metal shingles . Its impossible to prevent condensation from forming beneath metal roofing even if there is only a 1/8 inch airspace. This is the reason that all metal roofing requires a vapor barrier. Whenever temperatures drop, the temperature of metal roofing drops simultaneously . If warm, moist air contacts this cool metal roof surface, its “dewpoint” is reached and condensation develops. Metal shingles do no ventilate this condensation and moisture away from beneath the shingles because they are installed directly on the roof sheathing deck. Trapped moisture can potentially damage your roofs sheathing deck over an extended period of time because metal shingles use concealed fasteners that create hundreds of perforations in the vapor barrier as well as your roof deck. In Winter, this condensation freezes beneath metal shingles and remains there till Spring.... imagine 50 winters!
A KITCHEN COUNTER EXPERIMENT TO DEMONSTRATE HOW CONDENSATION FORMS BENEATH METAL SHINGLES
Fill a glass with water and ice cubes. Place the glass of water on your kitchen table. Position 3 coins in a triangular formation and use the coins to elevate your glass 1/16" off the table table. Within minutes you will notice condensation forming on the sides of the glass as well as under the glass. After 5 minutes this condensation will build up and precipitate on to your kitchen counter. What is happening on your kitchen counter is exactly what happens on a roof deck beneath metal shingles. The only difference is that a roof deck has a surface area of thousands of square feet while a glass has a circumference of only 3" inches
the eco roof difference
1. ECO METAL ROOFS ARE ‘DOUBLE STRAPPED’ to TRUSSES OR RAFTERS not ‘SCREWED DIRECT TO THE ROOF DECK’?
An Eco roof is double strapped and dual ridge ventilated to cycle fresh air throughout your roof and attic all year round.
ADVANTAGES; A double strapped metal roof reduces heat transfer in to your attic by 45% . This significantly improves indoor comfort levels and saves up to a 15% on your summer and winter energy costs. A self ventilating roof design eliminates condensation build up beneath panels and improves roof & attic ventilation. It eliminates the need for 1000's of perforations in your roof sheathing deck and vapor system barrier (common feature of metal shingles)
Your homes structural integrity is also significantly improved with a double strapped roof as evidenced by the recent tornado's in Ottawa. No ECO ROOF in the direct impact zone of the Greenbank touchdown was torn off , while adjacent properties with shingle roofs were severely damaged.
BENEFITS; Above-sheathing ventilation improves the summer performance of the attic assembly and also reduces heat losses by night-sky radiation during winter.
Offset-mounted metal roofing with a batten and counter-batten system reduces the heat transfer penetrating your roof deck by 45% compared with the heat penetrating the deck of an attic covered with asphalt and metal shingles.
2. ECO METAL ROOFS ARE DUAL RIDGE VENTILATED not STACK VENTILATED ?
A London Eco roof is double strapped roof and dual ridge ventilated with a concealed ridge vent system. This proven Scandinavian roof and attic ventilation design keeps your roof and attic in balance with Mother Nature all year round.
ADVANTAGES; Your get more than just a new metal roof. Every London Eco roof comes with a solar attic ventilation system that’s also 100% maintenance free . A cool roof harnesses the heat energy of the sun and converts it to convective energy which rapidly cycles fresh air beneath your roof panels and throughout your attic.
BENEFITS: Enjoy reduced attic air temperatures and lower energy costs , plus improved attic air circulation and freshness - The concealed dual ridge ventilation means no unsightly external vent stacks spoiling your homes aesthetics or curb appeal.
An Eco roof is double strapped and dual ridge ventilated to cycle fresh air throughout your roof and attic all year round.
ADVANTAGES; A double strapped metal roof reduces heat transfer in to your attic by 45% . This significantly improves indoor comfort levels and saves up to a 15% on your summer and winter energy costs. A self ventilating roof design eliminates condensation build up beneath panels and improves roof & attic ventilation. It eliminates the need for 1000's of perforations in your roof sheathing deck and vapor system barrier (common feature of metal shingles)
Your homes structural integrity is also significantly improved with a double strapped roof as evidenced by the recent tornado's in Ottawa. No ECO ROOF in the direct impact zone of the Greenbank touchdown was torn off , while adjacent properties with shingle roofs were severely damaged.
BENEFITS; Above-sheathing ventilation improves the summer performance of the attic assembly and also reduces heat losses by night-sky radiation during winter.
Offset-mounted metal roofing with a batten and counter-batten system reduces the heat transfer penetrating your roof deck by 45% compared with the heat penetrating the deck of an attic covered with asphalt and metal shingles.
2. ECO METAL ROOFS ARE DUAL RIDGE VENTILATED not STACK VENTILATED ?
A London Eco roof is double strapped roof and dual ridge ventilated with a concealed ridge vent system. This proven Scandinavian roof and attic ventilation design keeps your roof and attic in balance with Mother Nature all year round.
ADVANTAGES; Your get more than just a new metal roof. Every London Eco roof comes with a solar attic ventilation system that’s also 100% maintenance free . A cool roof harnesses the heat energy of the sun and converts it to convective energy which rapidly cycles fresh air beneath your roof panels and throughout your attic.
BENEFITS: Enjoy reduced attic air temperatures and lower energy costs , plus improved attic air circulation and freshness - The concealed dual ridge ventilation means no unsightly external vent stacks spoiling your homes aesthetics or curb appeal.
The Importance of Using A Breathable Membrane Vapor Barrier Beneath Metal Roofs
|
|
Most metal roofing systems installed in Canada are typically installed over 1 layer of existing asphalt shingles. Many companies cut costs by applying impermeable vapor barriers over the existing asphalt shingles. When this happens, residual moisture in the shingles becomes trapped between the shingles and the impermeable vapor membrane and can cause mold to develop. For this reason it is important to ensure that a permeable vapor membrane with a diffusive air layer is installed which prevents condensation build up between the vapor barrier, the shingles and the roofs sheathing deck, thereby enabling the existing roof to both "breath" and remain 100% watertight.
THE Stanford university STUDY ON ROOF VENTILATION
THE QUESTION COMMONLY ASKED BY METAL ROOF BUYERS
Will a double strapped metal roof lead to condensation forming beneath my metal panels? Great question.
The inherent flaws of single strapped metal roofing are well documented and have given self ventilating metal roofs built on double strapping an unwarranted reputation of trapping moisture beneath the steel roof panels. Condensation occurs because warm, moist air collects in an air space which has contact with a cooler metal roof surface. Whenever temperatures drop, the temperature of metal roofing drops simultaneously . If warm, moist air contacts this cool metal roof surface, its “dewpoint” is reached and condensation develops.
There are no exceptions to this rule, condensation forms beneath both metal shingles and continuous sheet steel panels.
Metal shingles have no way of dealing with this condensation other than the protection of the vapor barrier system applied beneath the shingles.
While single strapped and double strapped roofs both provide ventilation, only a double strapped roof provides both the drainage and ventilation needed to deal with condensation build up behind metal roofing.
