Rooftop units are direct expansion refrigeration systems that condition a building. They contain a condensing and air-handling unit section and have several noise transmission paths, including radiated noise, fan supply and return in-duct and break-out noise, structure-borne noise, and re-generated noise. However, traditional sound attenuators alone address only a few of these paths. We take a holistic approach when designing standard and acoustic-modeled solutions to ensure they can handle all the noise transmission paths while minimizing the impact on the unit’s efficiency, expertly manufacturing them according to your precise specification requirements.
Scroll down to explore our noise and vibration solutions for rooftop unit systems.
Fan Noise
Some fan types generate higher sound levels than others, but all supply and return air fans will generate sound that travels in duct to diffusers servicing occupied building spaces. Fan noise is often the primary transmission path except when RTUs are located directly above the space they service where the radiated path may dominate. Pay attention to frequency octave band data to address fan blade passage tones.
Radiated Noise
Radiated noise is the sound radiating from the unit cabinet through the roof deck inside the RTU curb confines Radiated noise is most significant in RTUs with DX cooling having a condensing section with compressors and cooling fans. In-curb acoustical treatments addressing the radiated path should include provisions for sealing around duct drops.
Structure-Borne Noise
Any structure that vibrates radiates airborne sound. Structure-borne vibration if not isolated at the unit by the RTU curb can excite building structural components. Rood steel, metal decking and gypsum board partitions are very efficient transmitters of vibration. Ductwork inside the building must also be isolated from structure.
Duct Breakout Noise
Breakout noise is sound passing through the walls of ductwork and silencer casings. It is a function of the component shape and size. Breakout noise is the reason to place sound attenuators as close to the unit as possible. Breakout noise is unusually greatest in the first elbow and 10′ to 12′ of ductwork directly below the RTU in a downflow Supply Air (SA) / Return Air (RA) configuration.
Fan Noise
Some fan types generate higher sound levels than others, but all supply and return air fans will generate sound that travels in duct to diffusers servicing occupied building spaces. Fan noise is often the primary transmission path except when RTUs are located directly above the space they service where the radiated path may dominate. Pay attention to frequency octave band data to address fan blade passage tones.
Radiated Noise
Radiated noise is the sound radiating from the unit cabinet through the roof deck inside the RTU curb confines Radiated noise is most significant in RTUs with DX cooling having a condensing section with compressors and cooling fans. In-curb acoustical treatments addressing the radiated path should include provisions for sealing around duct drops.
Structure-Borne Noise
Any structure that vibrates radiates airborne sound. Structure-borne vibration if not isolated at the unit by the RTU curb can excite building structural components. Rood steel, metal decking and gypsum board partitions are very efficient transmitters of vibration. Ductwork inside the building must also be isolated from structure.
Duct Breakout Noise
Breakout noise is sound passing through the walls of ductwork and silencer casings. It is a function of the component shape and size. Breakout noise is the reason to place sound attenuators as close to the unit as possible. Breakout noise is unusually greatest in the first elbow and 10′ to 12′ of ductwork directly below the RTU in a downflow Supply Air (SA) / Return Air (RA) configuration.
Regenerated Noise
Regenerated noise is noise attributable to obstructions and discontinuities that create turbulence in the otherwise smooth flow of air in duct systems. Probability for turbulence and regenerated noise is greatest at the first duct drop elbows. Regenerated noise transmits in duct downstream and also radiates through the breakout path.
Outdoor Noise
Outdoor noise is the radiated sound path to nearby community receptor locations. The sound pressure level at a given property line location is a function of the decay rate for a given distance and site influence of nearby grade, roof and/or building wall reflecting places. Outdoor noise is of greatest concern for RTUs with DX cooling that incorporate a condensing unit section containing scroll compressors and condenser cooling fans.
DEC
Deck
The Hushcore® Deck System™ is an in-curb, multi-layer treatment used to attenuate rooftop equipment curbs. We provide a high level of transmission loss for equipment curbs installed overtop noise sensitive spaces, and offer a quick and easy installation without sacrificing acoustic performance. Whether plenum or non-plenum style, BRD offers a variety of DECK system models depending on your noise sensitive project.
Our Deck Systems™ are an excellent alternative to traditional gypsum board treatments, and our STC-ratings range depending upon performance needs. Our systems outperform traditional methods and provide higher octave band transmission loss performance.
Sample Installation Images
Deck Highlights
PLUS
plus
PLUS Type P and Type V acoustic vibration curb systems address structure-borne, in-curb radiated, fan in-duct, and break-out noise from rooftop curb-mounted equipment. The construction of these fully adjustable and integrated curb systems features built-in springs with limit stops for wind and seismic events. They can serve as a blocking device during installation and have completely isolated top and bottom steel structural frames.
Sample Installation Images
plus Highlights
HIC-DS-41, HIC-DS-53
- Isolates structure-borne noise and vibrattion
- Reduces in-curb radiated noise
- Base System™ consists of Hush Curb™ with Deck System™ in-curb composite acoustical treatment
HIC-DS-38-E, HIC-DS-41-E, HIC-DS-53-E
- Isolates structure-borne noise and vibration
- Reduces in-curb radiated noise
- Addresses radiated, in-duct, and breakout noise
HPC-DS-49-P
- Controls structure-borne vibration, radiated noise and fan noise
- Plenum Vibration Curb with acoustical panel floor and offset SA and RA openings
- Ductwork connections to bottom of plenums can be field cut upon request
- Facilitates side by side SA and RA alignment
HIC-DS-41-V, HIC-DS-53-V
- Controls structure-borne vibration, radiated noise and fan noise
- Base™ System HUSH CURB™ with Deck™ System in-curb acoustical treatment and HUSH DUCT™ silencers
- Integrated in-curb HUSH DUCT™ vertical duct silencers and flex connectors
- Ductwork connections to downflow silencers
WHI
Whisper
WHISPER Type E is an acoustical curb system to control structure-borne vibration and fan noise of rooftop curb-mounted HVAC equipment into the building. Our Whisper Type P and Type E are fully adjustable and assembled plenum curb systems with completely isolated top and bottom structural frames that feature offset supply (SA) and return (RA) openings to facilitate side-by-side alignment. In addition, Type E feature integrated HUSH DUCT elbow silencers at supply and return curb openings below the roof deck.
Sample Installation Images
Whisper Highlights
HPC-DS-49-E
- Plenum Vibration Curb with acoustical panel floor and offset SA and RA openings
- Controls structure-borne vibration and fan noise
- HUSH DUCT™ Silencers at supply and return curb openings (below deck)
- Ductwork connections to bottom of plenums can be field cut upon request
ULT
Ultra
ULTRA is a plenum-style acoustical curb system and multi-path total noise control solution for rooftop curb-mounted HVAC equipment. The in-curb design features HUSH DUCT silencers and a solid bottom HUSH GUARD modular acoustical panel floor to facilitate side-by-side supply (SA) and return (RA) alignment. In addition, ULTRA includes an integrated, sealed, and pre-assembled vibration isolated curb with internal in-curb deck treatment. Snubbers help resist wind and seismic forces, and completely isolated top and bottom steel structural frames with a continuous flexible weather seal.
Sample Installation Images
Ultra Highlights
- Integrated In-Curb Design with recessed horizontal HUSH DUCT™ silencers, if unit size allows
- Multi-Path Total Solution
- Solid bottom HUSH GUARD™ HG-210 modular acoustical panel floor
- Ductwork connections offset in curb bottom panel from unit openings
- Ductwork connections can be field cut upon request
- Facilitates side by side SA and RA alignment
STA
2-4dB(A)
Standard
This is a treatment for the scroll compressor(s) on an RTU to address radiated noise.
Sample Installation Images
Standard Highlights
- Source Control using HUSH COVER™ removable sound blankets
- Model HC-500S-1 blanket construction
- “D” ring fastening bands with Velcro flaps
- The SL System treats only the scroll compressor to achieve a 2 to 3 dB(A) typical noise reduction
- The SC System treats chiller circuit parts, all compressors, suction lines, discharge pipes and oil separators to achieve a higher 4 to 5 dB(A) typical noise reduction
UNI
4-6+dB(A)
Unitary
The Unitary™ “SM” System is a top mounted, unit supported plenum style acoustically insulated stack constructed using HUSH GUARD™ sound panels. Condenser fan outlet noise can be reduced by 4 to 6 dB(A) with this treatment.
The Unitary™ “IM” System is an independently supported, wind load rated plenum style acoustically insulated stack constructed using HUSH GUARD™ sound panels. Condenser fan outlet noise can be reduced by 3 to 5 dB(A) with this treatment.
Unitary™ SM-SB Systems are available in both top mounted and independently supported constructions. This variation of the Unitary™ System design adds silencer modules to fit inside the HUSH GUARD™ plenum stack for increased performance and where noise sensitive receiver locations are elevated above the equipment. Baffle thickness, spacing and depth determine overall performance.
Sample Installation Images
Unitary Highlights
SM
- Source Control using HUSH GUARD™ modular acoustical panels
- Attenuates condenser fan exhaust
- 4 to 6 dB(A) typical reduction
- HGU panel construction
- Outperforms Low Noise Fans
- Minimal pressure loss impact
- Wind Load rated
IM
- Source Control using HUSH GUARD™ modular acoustical panels
- Attenuates condenser fan exhaust
- 4 to 6 dB(A) typical reduction
- HGU panel construction
- Outperforms Low Noise Fans
- Minimal pressure loss impact
- Designed to be bolted to and supported by the chiller
SM-SB
- Source Control using HUSH GUARD™ modular acoustical panels
- Splitter inserts for increased attenuation of condenser fan noise
- Attenuation can vary from 6 to 12 dB(A) depending on splitter configuration
- HUSH GUARD™ type HGU panel construction
- Outperforms Low Noise Fans
- Minimal pressure loss impact
- Available in both “IS” Independently Supported/Grade mounted and “TM” Top Mounted/Unit Supported configurations
LOU
5-7dB(A)
Louver
The Louver™ System uses high performance type HUSH DUCT silencers up to 36” deep for direct bolting to the chiller cabinet/frame. Typical reductions of the condenser inlet noise are 3 to 5 dB(A). Greater reductions can be achieved when combined with other source treatments.
Sample Installation Images
Louver Highlights
- Source Control using HUSH DUCT silencers up to 36” deep
- Direct mounting of louvers to upper side intake coil area and/or lower open framing
- Galvanized steel construction
- Range is 350 FPM (ideal) to 600 FPM maximum
- Additional Hush Guard (hard) & Hush Flex (soft) panel options for blanking off openings and Chiller ends to treat breakout noise.
SUP
7-10dB(A)
Supreme
Supreme System perimeter acoustic screens use HUSH SCREEN panels that attach directly to the unit, the curb, or can be independently supported depending on the wind loads needed for the application. Optimal system performance is for a screen that is 1-2’ taller than the equipment. Acoustical air intakes and discharge stacks may also be needed to manage the unit operating efficiency impact.” The HUSH SCREEN panels slide to allow access to the equipment, while maintaining a smaller footprint.
Sample Installation Images
Supreme Highlights
- Path Control Treatment
- 7-10 dB(A) typical reduction for floated Hush Guard perimeters and Hush Screens.
- HUSH SCREEN™ panel construction
- Panels can be installed without a crane
- Performance is based on variations such as enclosure/wall height, distance to unit, and noise receiver location.
SUM
10-12dB(A)
SUMMIT
The Summit System for rooftop units is a source-applied treatment of the intakes and discharge fans using Hush Guard panels and Hush Duct Silencers. Hush Cover removable acoustic jackets address vibration and breakout noise concerns from the RTU’s circuit components. These high-performance solutions do not require roof penetration for costly and extensive structural steel framing supports.
Sample Installation Images
SUMMIT Highlights
- Three-part source-applied treatments include Hush Guard panels, Hush Duct Silencers, and Hush Cover removable acoustic jackets
- Specialized unit mounting and attachment allow the source-applied treatment to be supported by a roof curb already needed to support the RTU
- The curb manufacturer must accommodate the extra weight so as not to void or affect the equipment warranty, but curb design modifications beyond a spring upgrade for vibration curbs are often minimal. Our system integration is coordinated with the equipment/OEM as to not void unit warranty when mounted to the unit direct.
- Absence of roof penetration helps prevent costly and extensive structural steel framing supports
- For RTU's up on dunnage, roof steel or platforms we can also provide Hush Guard panels to provide noise treatment below the units.