Instructions / Assembly

REQUIRED VENTING AREA
ForproperoperationofyourComfortCoolwholehousefan,itisCRITICALthatyourattichassucient
ventingarea;otherwisethehotaircannoteasilyescapeandcreatesback-pressurethatcansubstantially
reduce the performance of your new whole house fan.
The“net-free”areaofaventisthetotalventopeningminusthelosscausedbytheinterferenceofthe
screen, louver or grille covering the vent.
• TheCentricAir1.5requires a MINIMUM of 1.5 sq. ft. of “net free” venting area in your attic to allow for proper exhaust.
Thismeansthatitrequirestheequivalentofa2ft.by2ft.unobstructedhole.
• TheCentricAir2.0requires a MINIMUM of 2.5 sq. ft. of “net free” venting area in your attic to allow for proper exhaust.
Thismeansthatitrequirestheequivalentofa2ft.by2ft.unobstructedhole.
• TheCentricAir2.7requires a MINIMUM of 3.25 sq. ft. of “net free” venting area in your attic to allow for proper exhaust.
Thismeansthatitrequirestheequivalentofa2ft.by2½ft.unobstructedhole.
• The Centric Air 3.1 requires a MINIMUM of 4 sq. ft. of “net free” venting area in your attic to allow for proper exhaust. This
meansthatitrequirestheequivalentofa2ft.by3ft.unobstructedhole.
• TheCentricAir4.0requires a MINIMUM of 5.25 sq. ft. of “net free” venting area in your attic to allow for proper exhaust.
Thismeansthatitrequirestheequivalentofa2ft.by3ft.unobstructedhole.
Sincemostatticshavemultiplevents,oftenofdierenttypes,andsincemostventsarepartiallyobstructedbygrillesand/or
bug/animalscreens,you’llneedtodosomecalculationstomakesureyourventingissucient.Whileitisourexperiencethat
most properly constructed houses have the required venting, not all do. And because this is so critical to the proper operation
ofyourunit,itisimportantthatyouverifyit.Dierenttypesofventdesignshavedierentratiosofobstructioncausedby
grilles and screening and manufacturers typically publish these numbers. If this information is not available to you, a ratio of
50%isagoodruleofthumb.Forexampleatypical24”x24”louver,withagrossareaof4sq.ft.wouldhaveanetfreeareaof2
sq. ft.
Vent Length Width Net Free Calculation
Type Area (NFA%) L x W x NFA / 144
Louver 16” 16” 50% =16x16x0.5/144=0.89sq.ft.
RidgeVent 48” notused 13% =48x0.13/12=0.52sq.ft.
EaveVent 12” 4” 50% =12x4x0.5/144=0.16sq.ft.
•Inpractice,lessnet-freeareathanisrecommendedwilldecreasetheairowperformanceoftheunit.
•Ifyouareunsureastohowmuchnet-freeventingyouhave,pleaseconsultaroongprofessional.
•Net-freeventingareacanbeacquiredbyanycombinationofgable,eyebrow,sot,orridgevents,oranyother
means that provide ventilation to the attic space.
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