First off, an adjustable store bought roof curb requires no skill from the contractor. A good contractor will measure the pitch of your roof, measure your existing ductwork on the roof and have a sheet metal shop custom fabricate new metal.
Originally Posted by jason62082
The shingles need to be on top of the bottom flashing around the curb, otherwise when they tear out your existing roof jack and pull the duct up through the roof, you will have a leak. This is why you see in some pics, all the messy roof tar around the curb.
You will notice in a couple of those pics, the roof around the unit is shot. If I come accross something like this, I recommend that the HO replace the roof at the same time and most will.
I dont know what the norm is in Mesa Jason but in Vegas, the only people using these adjustable curbs are mostly hacks and that is so they can get in and get out quick. Like I said in my last post, they require no skill and I've yet to see one properly done here.
I've been told in the past on this site that I need to catch up or die. Well, I dont care if this new adjustable roof curb is the great new thing or not, I will not use one!
I will use an existing elbow and have a new stand made, it does not disturb the roof.
If a customer wants to go down shot, I will still use a stand and have a custom transition made and it still does not disturb the roof.
I'm guessing you mean the shingles should look like this: http://hvac-talk.com/vbb/showthread.php?t=89277
Originally Posted by sammy37
I also see in that thread that the contractor uses a custom curb and an adjustable curb in the second set of photos.
Yes, those look nice. I especially like the first one with the non adjustable curb.
Also, some residential units provide a little less airflow when mounted downshot. The Goodman GPG is the worst for that, the evap coil and drain pan sit right on top of the downshot opening.