How I Build Duct Board Boxes in a few steps.

[@craigwh1000]

How do you calculate what size duct board plenum you need for an air handler(1200cfm)?

[@Builtwithtools]

Get a duct calculator. Or find one on line. It will tell you the pipe size per cfm. Rule of thumb. 400cfm per ton. 100cfm per register. Reduce your trunk size as you lose cfm with long trunks. A professional will tell you to do a manual j, then manual d. but honestly, Rule of thumb has worked every time. Haha.

[@craigwh1000]

I have the supercool slide ruler but don’t fully understand the rectangular metal duct part that mentions larger dimension on top and smaller on bottom. Does that mean if my length is 24” and width is 22” then 24 on top of slide ruler and 22 on bottom? What about height/depth for cubic volume? Lastly, what about calculating triangle duct board that connects flex duct trunk to branches?

[@Builtwithtools]

@@craigwh1000lol. I feel like you’re messing with me. Don’t make a triangle duct. Use duct board collars to connect flex.

[@craigwh1000]

I’m not. The builder used them to connect the supply side 12” flex’s from the plenum box to the branches. They did the same on the return plenum too. I think both sides are undersized and that’s why I was asking about how to calculate for rectangular plenums using duct board and for the triangle duct boards to feed the branches.

[@Builtwithtools]

@@craigwh1000I don’t know about sizing triangle. But to answer your question. 24x22 is the rectangle size. The volume doesn’t really matter unless outs an extremely long run. Because the trunk will come under pressure. More than likely you’ll have something tired in before that factors in.

[@davidater9]

Nice work!

[@Builtwithtools]

Thank you!

[@mohdnadeem-cx2jr]

Is This fibre glass duct board???

[@Builtwithtools]

Yes it is

[@coreascoreas3747]

@@Builtwithtools It is safe for breathing?

[@connordelano7945]

Would’ve went without the mastic myself and just used metal tape but really good box

[@Builtwithtools]

Thank you!

[@edwinfanai1979]

What is that tool?

[@ugh3012]

Yeah. I am trying to find one.

[@edwinfanai1979]

@@ugh3012 let me kow where u get it?

[@Builtwithtools]

I’m sorry I never saw your comment. They are called fasgroov tools from malco

[@Builtwithtools]

@@ugh3012 I’m sorry I never saw your comment. They are called fasgroov tools from malco

[@JoseHernandez-g2b]

What’s the name of that tool ? The one that you are using to cut the board.

[@rrhistorian8828]

It’s made by Malco, it’s a v-groove cutter.

[@Whit_Siever]

I need to replace distribution boxes, online can only find triangles (need at least 2 of those) but as far as 18" cubes no one seems to have those so guess i need to find duct board and cut away

[@LifeBloodMarketing]

Did you ever make one or find one?

[@Whit_Siever]

@@LifeBloodMarketing not yet but found a supply house in Houston TX that says they can custom cut, may reach out to them

[@adercroft2275]

Please stop using ductboard…. For anything…

[@Builtwithtools]

Why?

[@logans3365]

@@Builtwithtoolshe must not like having well insulated ducts lol

[@Builtwithtools]

@@logans3365haha maybe not.

[@drivebyok6709]

I don't see nothing wrong with this...

[@ryankramer]

I'm building a theater, need materials that won't rattle (Sheet metal and giant subwoofers don't mix), and all of this will be contained within a conditioned space. (HVAC is all contained on the inside of the room within a room design.) Be careful when you say "for anything," there's always an edge case!