Duct in Attic insulation.

[trouble time]

I am about to install my first Attic air handler and duct work. I know the duct has to be insulated. Is there a "standard" size to the insulation in R value? I will be using metal ducting. What other precautions should I take with this installation? Any suggestion are welcome. I have done far too many installations of furnace systems but have always stayed away from the attic jobs, leaving them to the younger guys. But this job is for family.
Thanks.

[hvacvegas]

probably 1 1/2" foil back is code minimum.

I'd go more if you could.

Take some furnace/bailing wire with you. Spin the duct in the wire after you wrap it. It relieves the stress on the tape, and helps hold it together longer.

[vstech]

R-8 is required in US.

it's 2"
also, all fittings, and duct seams must be mastic sealed.
also, the ductwork needs to be sized correctly by Manual J.

[pressordrop1]

if he is in Canada , you really need to consult some one who knows the R factor in Canada for your region. if you have to follow Canadian standards you should have some guidline to follow

[hvacvegas]

R-8 is required in US.

Not in my neck of the woods.

1 1/2" is code here.
Across the river, it'll be r-8 in july.

[ironpit]

3/8-1/2' bubble wrap is common here, or 1" fiberglass.

[genduct]

make sure that the duct is not buried in or even sittting on top of the attic INSULATION. I understand there is even RH in CAN.
Seems I remember some hot days in August competing in St Catharine's Henley Races

[trouble time]

probably 1 1/2" foil back is code minimum.

I'd go more if you could.

Take some furnace/bailing wire with you. Spin the duct in the wire after you wrap it. It relieves the stress on the tape, and helps hold it together longer.

Really good idea about the bailing wire..Thanks.
We do have heavy humidity here in the summer. A suggestion was made that the duct insulation should be the same as the attic insulation. In this case the attic will be insulated to R40. This seems to be the new standard for blown in insulation here.
I like the idea of the 3/8 bubble wrap insulation. Maybe on top of the foil-back and this would insure that the duct is properly insulated.
Anyone see any problems with that idea?
Thanks I appreciate the help.

[second opinion]

[QUOTE=trouble time;12651451]Really good idea about the bailing wire..Thanks.
We do have heavy humidity here in the summer. A suggestion was made that the duct insulation should be the same as the attic insulation. In this case the attic will be insulated to R40. This seems to be the new standard for blown in insulation here.
I like the idea of the 3/8 bubble wrap insulation. Maybe on top of the foil-back and this would insure that the duct is properly insulated.
Anyone see any problems with that idea?
Thanks I appreciate the help.[/QUOTE

If not sealed air tight between the two vapor barriers it can condensate.

[JPJ13]

In my neck of the woods the air handlers are in the attic about 70% of the time. Our code was changed in 2010 that all ductwork, regardless of location, has to be insulated to a value of R8.

I definitely would check with the mechanical code for your area in Canada first. Im sure they aren't going to want you to go to R40 like the attic is. If so I'd move somewhere else instead of trying to wrap duct with 10" insulation.

I also wouldn't put another layer of insulation over your original layer because it will trap moisture between the layers and present possible issue.