Main air duct size

[larrytbm]

We lost our house in a wildfire Sept. 4th. The site is cleaned up and I'm planning the rebuild. Metal building, house 30x44, garage 30x24 and RV garage 18x46. Not sure if we have the funds to finish the inside of the house, so we may be in the RV for awhile.

But before I lock-in the metal building height, I need to make sure there is room in the attic for the main A/C duct. The main duct will be a straight run of about 32 ft, six rooms, half cathedral, half flat 8 ft ceilings. With a 3/12 roof pitch, I will have a max. height of about 36 inches, dropping 3 inches for each foot of width. Can anyone tell me what cross-sectional duct size is needed? Too early for a full A/C plan, it will be another week before the RV slab is poured. Thanks if you can help.

[genduct]

!4" plus the height of insulation at the center and you're golden

[larrytbm]

Thanks so much, one less thing to have to worry about right now. Once I can get the sub contractor started on the building, I still have to re-run water, sewer and electric lines and get someone to recover the well pump since it dropped to the bottom of the well bore.

[newbehere]

!4" plus the height of insulation at the center and you're golden

If I read this right,,the cross section or is it diameter of the duct should be 14 inches??? how can that size be arrived at?? or did I not understand the question.

[genduct]

of the height as being important

[engineer2]

If you live in a hot climate zone have you given any thought to running your ductwork somewhere besides in the attic for better energy efficiency? What do other folks think about this? Starting from scratch leaves room for some other options I think. Where do you live?