Learn how using advanced underlayments with DECRA Metal Roofing products can increase energy-efficiency by up to 218%.
DECRA contracted with R&D Engineering* to compare DECRA roofs to the conventional 3-tab asphalt shingle roofing systems which are still the most common roofing material, used on nearly 70% of U.S. homes today.
DECRA stone-coated steel was once again the walk away champion for energy-efficient roofing, excelling in thermal performance as it does in every other roofing performance category against any other roofing material.
Discerning homeowners and construction professionals know that asphalt shingles are only a temporary roofing solution even in the most ideal climates. But aside from their tendency to delaminate, fish mouth, and blister, asphalt shingles are the worst performers when reducing cooling costs is the priority.
When it comes to improving energy-efficiency with a roof upgrade, there are three physical characteristics to increase, also known as thermal performance:
- Thermal Resistance: The insulation value of the entire roof
- Emissivity: The ability of the roof to radiate solar heat gains up and away from the house or building
- Reflectivity: The ability of the roof to reflect radiant heat back to the direction from which it came
Shingles, wood shakes, and clay tiles are all rated very low in these categories, obviously. The only way to improve the roof performance in all 3 thermal categories is to upgrade to a metal roof.
Reducing Solar Heat Gain With DECRA Metal Roofs
For the DECRA thermal analysis, R&D Engineering analyzed thermal resistance to solar heat gain across the entire roofing assembly including:
- Roofing Material
- Roof Deck Sheathing (7/16” oriented strand board (OSB) or 1/2” CDX plywood)
- Roofing Underlayment (15 lb. felt versus reflective radiant barrier)
- Air Film (on both the exterior and interior roof system surfaces)
- Direct-to-Deck and Batten Installations (battens are wood grids providing an air space under the roofing material)
R-Value Increases With DECRA Stone-Coated Steel Roofing
The most basic thermal performance comparison is the R-Value number which measures insulating thermal resistance. Using standard roof deck materials and economical 15 lb. felt DECRA products easily topped the total 2.28 R-Value achieved by 3-tab asphalt shingle roofs.
The table below shows performance increases for DECRA roofing profiles with no special underlayments for projects such as roofing over, remodeling, and speedy upgrades.
All DECRA stone-coated steel roofing products provide significant “stand-alone” thermal improvement and energy savings, even with the most basic roofing materials.
But we’re just getting started.
Supercharged Energy Efficiency with DECRA Metal Roofs
The 48.7% increase with DECRA Tile above is pretty good but the R&D analysis revealed that we can do better. How about a 218% increase in thermal performance? That number is only achievable with DECRA.
The roof’s underlying 15 lb. felt, commonly known as “tarpaper” can be replaced in the roofing system by space-age materials that have a dramatic effect on energy efficiency.
DECRA roofing systems with advanced underlayment materials such as Low-E Therma Sheet with closed-cell foam core or Sol-R-Skin with woven fiberglass mat and radiant barrier skin increase thermal performance exponentially.
Radiant Barrier Underlayments Increase Reflectivity
The R&D Engineering team tested DECRA roofing systems with two advanced underlayment materials substituting for common 15 lb. felt:
Low-E Therma Sheet roof underlayment – manufactured by Environmentally Safe Products, Inc. with 5/16” closed cell foam core & radiant barrier skin
Sol-R-Skin Thermal Underlayment – manufactured by International Insulation Products, LLC with fiberglass mat core & radiant barrier skin.
DECRA Tile and DECRA Shake on 2X2 wood battens topped the radiant barrier performance charts:
- DECRA Tile increased performance by 218% with Sol-R-Skin with an incredible R-Value of 7.25. With Low-E Therma Sheet there was a 210.5% increase with an R-Value of 7.08
- DECRA Shake followed closely in second place with increased performance at 216.7% and an R-Value of 7.22 with Sol-R-Skin. Testing with Low E-Therma Sheet registered a very respectable 209.2% increase with an R-Value of 7.05
Importance of the Roof Air Space For Thermal Performance
The study highlighted the importance of the air space created with batten installations for maximum thermal emittance, or the ability of the roof surface to radiate absorbed heat. 2X2 battens provide the maximum airspace and volume to allow heated air to escape up and away from the home through the ridge vents.
Even in cool conditions, the 1-½” air space from 2x2 battens provides an extra insulating layer to keep heating costs down.
The study also analyzed more common 1x4 batten systems and DECRA roofing products posted significant performance increases there as well.
- DECRA Villa Tile on 1x4 battens has an R-Value of 3.14 with a 37.7% performance increase even when standard 15 lb. felt is used.
- DECRA Villa Tile on the same 1x4 battens leaps to an R-Value of 4.85 and improvement escalates to 112.7% when a radiant barrier underlayment is added.
ALL DECRA roofing panels provide the minimum required ¾” airspace so direct-to-deck DECRA installations also benefit from radiant barrier underlayments as well. DECRA metal roofs are highly efficient at releasing absorbed heat, unlike asphalt shingle roofs which continue to radiate heat down into the home long after the sun goes down.
DECRA Villa Tile direct-to-deck installations with a radiant barrier underlayment have an R-Value of 4.64 with a 103.5% improvement versus an asphalt shingle roof and 77.8% versus DECRA Villa Tile with 15 lb. felt.
DECRA Stone-Coated Steel Strength For the Roof of a Lifetime
Easily fractured clay tiles, fragile weathered wood shakes, and saggy asphalt shingles simply don’t have the stand-alone structural integrity or impact resistance to bear loads over a super-efficient batten system without support.
DECRA stone-coated steel panels are unmatched for strength with the highest UL2218 Class 4 impact rating, so they are fully walkable with either direct-to-deck or batten installations.
While conventional roofing materials are intended to last just a few short decades at best, DECRA metal roofs are designed to endure for a century or more with the industry’s most comprehensive lifetime warranty, transferrable up to 20 years after the initial DECRA installation.
When you’re ready to improve the thermal performance of your home or building to reap the ongoing energy savings of a DECRA stone-coated steel roof warrantied to last for a lifetime please don’t hesitate to contact the roofing experts at DECRA today.
*Download the full study here.