Shop HVAC Ductwork Questions

[grsthegreat]

I'm not an HVAC guy, but I am a Remodel and Repair Contractor. I like your plan for a flat ceiling with insulation. That will allow the roof to vent and make it more affordable to max out your R value with insulation. Are you going to blow in loose insulation?

I also like the idea of putting your duct work in the attic. Unlike the others, I'm a big fan of flex line. It gives you a smooth run that doesn't come apart or leak like metal is famous for. I've been in a lot of attics. I've never seen flex line leak, but I've enjoyed the cool air coming out of metal ducts on just about every attic that I've been in!!!

I can't comment on 12 inches being the correct size for your main distribution line. I would base the size of that line on the size of the opening coming out of the unit.

Something an AC guy told me when deciding where to place the ducts was in dealing with the outside influence on that room. Windows let more heat or cold into a room then a solid wall. Place the duct to force air in that area.

With your big doors, that's where the ducts need to be. That's where you will have the most heat loss.

Depends where you live. In north Idaho, ive seen mice eat thru flex duct in attics. Also, here at least, the heat released by any duct into an attic can cause ice issues from snow. Not such an issue with metal roofs.

Also here, all metal duct is required to have flexseal coating around every joint.

 

[gstrom99]

No ductwork required.

https://www.supplyhouse.com/Modine-HDS75AS0121FCAN-HDS75-Hot-Dawg-LP-Separated-Combustion-w-Aluminized-Steel-Heat-Exchanger-75000-BTU

That's the one I have, but 100k. Works perfect.

 

[fidowanttobe]

Thanks for the replies, I appreciate the advice.
Since starting this shop from the dirt up, I've realized that I don't know/remember as much as I thought from my early hammer swinging days. I'm just a one man show so it's good to bounce ideas off of folks.

 

[fidowanttobe]

I'm not an HVAC guy, but I am a Remodel and Repair Contractor. I like your plan for a flat ceiling with insulation. That will allow the roof to vent and make it more affordable to max out your R value with insulation. Are you going to blow in loose insulation?

I also like the idea of putting your duct work in the attic. Unlike the others, I'm a big fan of flex line. It gives you a smooth run that doesn't come apart or leak like metal is famous for. I've been in a lot of attics. I've never seen flex line leak, but I've enjoyed the cool air coming out of metal ducts on just about every attic that I've been in!!!

I can't comment on 12 inches being the correct size for your main distribution line. I would base the size of that line on the size of the opening coming out of the unit.

Something an AC guy told me when deciding where to place the ducts was in dealing with the outside influence on that room. Windows let more heat or cold into a room then a solid wall. Place the duct to force air in that area.

With your big doors, that's where the ducts need to be. That's where you will have the most heat loss.

I was hoping you would chime in!
Yes, lots of blow in insulation, plenty of room up there with 6/12 pitch.
2x8 batts in the walls, 3) east facing R-18 garage doors, 1 north walk in and 1 west 36x54 window.
Reeeeaaally hoping I won't need AC, but I have to prep for it.
Still pulling wire, is it odd that I feel I should start keeping copper in my SAFE?? $$$$ WOW.

 

[gstrom99]

I feel I should start keeping copper in my SAFE?? $$$$ WOW.

I've seen home improvement stores that have it locked up.

 

[BlueKnife]

Depends where you live. In north Idaho, ive seen mice eat thru flex duct in attics. Also, here at least, the heat released by any duct into an attic can cause ice issues from snow. Not such an issue with metal roofs.

Also here, all metal duct is required to have flexseal coating around every joint.

Yeah, ducting in the unconditioned space of a building is a bad idea in a climate like ours (or really any climate, IMO). I agree with several of the other posters. Ducting for a shop with a fairly open floor plan doesn't need to be at all complicated, or even exist at all. The key is to properly insulate and vent the building.

 

[ultrarunner]

Depends where you live. In north Idaho, ive seen mice eat thru flex duct in attics. Also, here at least, the heat released by any duct into an attic can cause ice issues from snow. Not such an issue with metal roofs.

Also here, all metal duct is required to have flexseal coating around every joint.

Yep... if not going to be accessible then spiral wound and coated single lengths metal to the length not accessible.

Mice and rats will get into the flex and then what if concealed?