Register/diffuser

[robertee]

I have a duct calculator and have researched the internet but can't find any reference to register size. The house I'm working on had 2"x12" registers in all rooms even the ones supplied with 8" duct. I've replaced them with 4"x12" in all rooms except the bath rooms. How do you size registers to be matched to sq. ft. and duct size?

[duct dr]

Are these floor or ceiling outlets? Most bathrooms don't require anything larger than 4x8, some need 10x6. Depends on the sq ft of the bathroom and the and the required CFM to cool the room.

[hvac-tech-lane]

Grill manufacturer litrature will give you all info, flow face velocity, noise, throw, and recommended range.
2x12 how odd must have been on sale at wal-mart.

[schmuck]

4 x 12 = 48 / 144 = 3 x velocity = CFM's

[contactor]

2 X 12 floor very common. Lima register cal. Free sq. in. 16. face velocity 900. c.f.m.100, heating b.t.u. 9515, cooling b.t.u 2670 thro ft. 8 spread ft 14

4 x 12 Fre sq in.30.0 face vel. 840 c.f.m. 175 heat btu. 13320 cool btu 4805 thro ft. 13 spread ft. 24

[cem-bsee]

metal registers have much more free space than plastic ones -- I removed my new plastic ones, will use them as aux return grills from ea bdrm -- hallway side (sans sliding cover)

[robertee]

Thanks for the info. The old registers were 2x12 baseboard registers.