1000 SE EVERETT MALL WAY BASE FILE 2025-10-22

Acoustical DesignReview-ff ,US Probation Court Off IV. BACKGROUND NOISE AND ROOM CRITERION (RCY Background noise levels, quantified as Room Criterion (RC), from HVAC. systems are required to meet an RC 30 per the product criteria and USCDG. Areas requiring a background noise level of RC 30 will require careful design of the HVAC system to make sure that spaces are not impacted by mechanical noise from sources such as diffuser noise, duct breakout noise, radiated equipment noise, and vibration from equipment and ductwork. The existing space is served by heat pumps with fans located above the ceiling. These units supply air to each space through duct work. The majority of noise in the current space is generated by the fans themselves. it was noted that a significant amount of noise was heard coming from the air intake filter on the unit. We recommend the following: Recommendations: • For in -ceiling fan units, install a sheet metal boot over the air intake filter that is at least 2' long and lined ctlth 1" duct the soundlaway fOrient the opening to rom the spaces belowhe boot on the top facing upward to red • For in -ceiling fan units, reinforce the ceiling the or backs of light fixtures in close proximity to units with a barrier to reduce noise breakout to the space below. This can t achieved by aeasti4g t beyondss to eback the union all dire tioling lles ns. oWextures for an re recommend area that extends at either of the following options: 2" or 518" GWB on the backside of ACT with 1" Option 1: Install a layer of 11 thick fiberglass on top. (Approx. 2lb/sf added weight) - Option 2: install a mass loaded vinyl ceiling tile backer product with built in insulation. Use Sound Seal NBCTC Model 1-1-1 for ACT and NBCT Light Fixture Covers. (Approx. 1lb/sf added weight) • Line the first 5 feet of supply and return duct from the unit with V duct liner. • For any new ductwork installed, rectangular ductwork is preferred over round ductwork given that it is more efficient at reducing duct -borne noise. • For all diffusers, use flex duct for the last 3 feet of duct before diffusers. Flex duct absorbs sound before it becomes noise through the diffuser. • if return grilles are not ducted, this will create a potential path for noise between spaces. install a sheet ry ntaadjacentrooms boot ovr non-ducted should of face toward each other. finer. Boots openings g • Equip fan units with vibration isolation to reduce structure -borne noise and rattling coming through the ceiling. implement the following mitigation: isolate units with a neoprene hanger with a minimum 0.35" static deflection. Use Mason industries Neoprene Hanger Type HD or equivalent. Hanger shall be sized to maximize deflection depending on equipment weight. For diagonal seismic bracing, use aircraft cable with a slight amount of slack rather than rigid angle brackets. Provide flexible connectors where ductwork attaches to indoor units. Use Ventfabrics Type Ventglas or equivalent. _.._ ......_ .._..._._...__.... ..... _... _.._...... _...... ._....... _..... w.._........ ._..... _...... _...... __.._...__.._._...._...__.._...... _.._....... .._....._.._ __._._........ _.... __...... -......... .__... ... _......... .��JG.��.. SSA acoustics