The Reasons For Underlayments
There are a number of benefits of using roofing underlayments for metal roofing. There are a few purposes for three-dimensional entangled filament underlayments and roof underlayment composites. The leading purposes are providing an open ventilation space to allow accidental moisture to drain and allow evaporation to dry out. Most of the open construction of entangled filaments will help to dry out condensed water vapor from the structure’s interior. Low & Bonar underlayments offer each of these primary benefits. A significant secondary benefit from Enkamat 7010/7020 is reducing the impact of sound or noises on metal roof coverings caused by rain and hail and curtailing airborne noise levels.
Some sounds are considered unwanted noise. Unwanted noise is disruptive to the environment and usually created by human sounds. Other disturbances can be natural sounds that come in contact with building structures. This includes the drumming caused by rain or hail and sounds from airplanes and traffic that are disruptive to occupants of a building. Noises that interfere with the activities of the occupants can leave them feeling they have no control over the sounds. Exterior noises can disrupt various operations, loss of communication abilities, and affect the health of workers while reducing their efficiency. If there are elevated background noises in classrooms there can be a negative impact on students’ ability to learn.
Having a plan to reduce sound levels is important, especially in structures with metal roofs. The building industry claim that metal roofs do not increase the noise level any higher than other types of roofing material. That said, there have been many cases of noise caused by rain in buildings with lightweight metal roof construction that exceed 70dB which is like normal street traffic noises. The roof or ceiling assembly in structures with metal roof coverings can vary quite a bit and this has an effect on the levels of noise being transmitted. The sound from rain depends on several factors. First and foremost is the overall construction. A metal roof sitting over an open framing will be much louder than a roof installed over a continuous sheathing board. A metal roof over a concrete substrate will be much quieter. Unlike slate or tile roofing, rain striking a metal roof is much louder.
About Building Codes And Guidelines
There are very few building codes that require sound control for metal roofs. Some design guidelines from various organizations recommend noise isolation for specific building types. One example would be guidelines for churches. The guidelines for Orthodox churches include isolated noises from highways, busy streets, over-head aircraft, emergency services, rainfall, lightweight roofs, barking dogs, etc.
The American National Standards Institute (ANSI) and the Acoustical Society of American (ASA) have been working together to adopt a new voluntary standard for acoustics in classrooms. ANSI/ASA Acoustical Performance Criteria, Design Requirements, and Guidelines for Schools are the latest standards. Individual states and/or school systems can specify compliance with these standards. The maximum level of sound inside the classroom is set at 35dB. In order to meet the guidelines and requirements, there must be great care taken in roof assemblies that will reduce sound levels from environmental noise. Selecting materials that work together to reduce the impact from sound levels is critical for achieving the decline of noises both outdoor to indoor. Noise from roadway traffic, airplanes, railways, top mechanical equipment, and rainfall must be taken into consideration.
Low and Bonar Testing
L&B has conducted a number of acoustical tests in Europe on several different kinds of metal roofs. The roofs tested include zinc, copper, stainless steel, and aluminum. Roofs were also tested with varying underlayments. There are no standardized European rain tests for measuring the sound so an accepted hammer apparatus was used. This device is used to create the impact of noise for floor assembly sound testing. The tests were performed by WTCB Laboratory in Belgium which is a part of the Belgian Building Research Institute.
Sound levels were reduced from 9.5 to 13.5 decibels from Enkamat underlayment and composites in comparison to a metal roof over a weather barrier fabric.
Filament underlayments combined with a gypsum ceiling and thermal insulation, the reduction of sound increased by 21.5 decibels. Considering that sound reduction of 10 decibels is considered by the human ear as cut in half, a reduction well over 20 decibels is quite significant.
The Thermal Benefits Of Roof Underlayments
Roofing underlayments offer a number of benefits for metal roofing. There are several functions of three-dimensional entangled filament underlayments and roof underlayment composites. The main purpose is to offer an open ventilation space to let incidental moisture drain away and allow evaporation drying to take place. An open structure with entangled filaments helps dry the condensed water vapor from the structure’s interior. Low and Bonar underlayments offer each of the primary benefits. Another significant benefit of Enkamat 7010 and 7020 is the reduction of thermal heat gained by the metal roof substrate from the roof itself. Further info focuses on this patent-pending underlayment application and recent research involving thermal benefits.
Enkamat ASV helps with roof ventilation and sound mitigation
Overview Of The Test
A standing seam metal roof was constructed on a simulated roof structure to evaluate the effects of Enkamat underlayments on the temperature of the roof substrates from traditional construction and Structural Insulation Panels (SIP). Enkamat 7010, 7020, and EnkaTherm 5006 (Enkamat 5006 with an aluminum radiant barrier on one side) were tested.
The thicker underlayment, Enkamat 7020, offered the best protection. All three offered a thermal break and ventilation that showed reduced temperatures throughout the simulated roof structure.
The Procedure For The Test
The model roof was constructed using SIP panels contained in a 2x4 frame. The dark standing seam metal roof panels were temporarily locked in place to the roof with various Enkamat layers placed under the metal roof panels. The IR lamp assembly was suspended 8-inches above the metal roof surface. The temperature of the IR lamps and the roof temperature were controlled by an IR sensor pointing at the roof surface. Other temperatures, with the exception of the inner SIP, were measured and recorded by the surface mount thermocouples connected to an Omega USB converter that was controlled by Omega software.
The temperature of the attic was measured inside the roof structure and the ambient temperature was measured at a remote location away from the influence of the IR lamps. For the sake of the experiment, the temperatures were recorded every 10 seconds. Before the IR lamps were turned on, the temperatures were measured and recorded every one minute. Then, the temperatures were recorded every 6 hours to simulate a full day of sun exposure on the roof. For all the experiments, the roof temperature was constant at 90 °C (194 °F).
The Results Of The Research
Research showed an increase in temperature under the roof panel, regardless of the addition and kind of underlayment spacer. It also showed a rise in temperature inside the SIP. The under-deck, attic, and ambient temperatures were not affected by the IR lamps which were essentially constant. Some cyclic behavior could be observed in the temperature profiles, attributed to the cyclic behavior of the laboratory air conditioning system.
Figure A showed the comparison between the over-deck temperatures affected by the test spacers. The temperatures are in Fahrenheit and the roof temperature is included for reference. Enkamat 7020 offered the largest temperature difference with others offering slightly less.
Figure B showed the temperatures as a function of time and the spacer inside the SIP and included the roof surface temperature for reference. Compared to the earlier graph, the temperatures are closer inside the SIP. The insulation minimized the effect of the spacer installed under the metal roof panels.
Figure C showed how close the curves fall with 7020 offering a maximum of approximately 10 °F lower internal temperature. The inner surface and the attic temperatures did not change significantly throughout the experiment. The 6-inch thick SIP was filled with rigid foam insulation and regardless of the roof covering the panel offered sufficient insulation to maintain a constant temperature at the two locations. The differences in temperature were obtained by using the various spacers and summarized in the Underlayment Comparison tables. The values in °F were obtained from the average temperature over the last 60 minutes of the experiment.
The first chart showed the real differences between the roof surface and decking temperature. The second chart is normalized by subtracting the effect of the conductive roof panel represented by the drop in temperature observed in the control experiment. The use of Enkamat 7020 offered a 33 °F temperature difference on the roof decking, and a 12 °F difference inside the SIP. The differences seen with the other substrates were not as dramatic, all were within a few degrees of each other. The others offered at least ten degrees and as much as 15 degrees difference on the roof decking temperature.
The reduction in energy used in buildings and residential structures using a thermal break and a ventilated air space in the roof assembly is quite important for both environmental and energy cost savings considerations.
Sheathing Ventilation (ASV) improves the insulating effect of the entire roof system. Testing at the Department of Energy in Oak Ridge, TN has shown that vented space under a metal roofing can cut heat transfer over 70% when compared to an asphalt shingle roof. Other research at the Oak Ridge National Lab showed the airflow between the roof sheathing and the rood material provided a more effective heat gain barrier than a reflective surface. L&B will continue to research in order to better understand the thermal benefits of the above Sheathing Ventilation such as Enkamat roof underlayments mats.
About Low & Bonar Underlayment Products
The patent-pending application for thermal underlayments uses a range of L&B products including Enkamat 7010 and 7020 three-dimensional multi-use mats made of continuous nylon filaments fused at the intersections. They can be used in both metal and ballasted roofing applications where the spacing of the roof will offer ventilation, drainage, and thermal separation are needed for long-term service life.
The nylon filaments will not fail under the load of the roof and the tough operations of a construction environment including construction traffic. The space between the roof membrane or weather barrier underlayment and ballistic/metal roof will allow moisture to move away or evaporate. This is required under zinc roofs to prevent white rust that can be caused by condensation on the under-side. EnkaTherm 5006is a unique blend of fused and entangled nylon filaments formed in a 0.5-inch button pattern and heat bonded to an industrial pure aluminum foil The combination of the radiant barrier is designed to insulate, ventilate, and drain roofing and wall applications and create a rain screen for minor moisture. The material can double as a weather or vapor barrier and is available in perforated and non-perforated versions for use in various climates.
Organizations and leaders in the industry will continually research and test products and environments to guarantee standards and requirements are staying ahead of the game.