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tom1336 07-29-2012 11:59 PM

Insulating exposed roof top duct work
Part of my house has an add on with a flat roof. My central AC system is roof mounted. Part of the output is directed to the ducts for the "main" part of the house though a down draft configuration to the ducts. But the part to the add on with the flat roof, is though round ducts running exposed on the roof from the side of the AC unit to the two vents for the add on to the house. In summer I know the ducts are getting an extra heat loud.

What is a way that I as a DIY'er can add insulation to those ducts. They are "insulated" on the inside, but it is not much, and I'm in a very hot climate

Keep in mind they are exposed to the wind, rain, and so on.

Moving the ducts inside is cost probative.

scottmcd9999 07-30-2012 06:02 AM

You can always build a "roof" over them to protect them from direct sun - just a metal roof that is raised off the ducts a few inches, which allows some airflow and such.

Or you could box them in, and insulate the box. That would be the best way, most likely.

Either way, if they're wll insulated and well sealed, I'm not sure how much benefit you'll gain from this.

tom1336 07-30-2012 02:14 PM

High winds (45 to 95 mph) around here make "shading" them unworkable, as the cover would get torn off the roof, unless it was extremely substantial.

I have thought about building a box and insulating he inside of the box, but I am wondering if there is some add on insulation that works in an outdoor environment, other then say spry on closed cell foam.

Evstarr 07-30-2012 02:22 PM

Is it kosher to sleeve them inside larger duct?

scottmcd9999 07-30-2012 04:04 PM

Yes, the "roof" would need to be secured to the structure. We generally make 3 sided ducts around stuff like this (two sides and a top) and secure it to the structure.

We've also installed standard duct wrap and sealed it with several layers of roofing tar. It's a big mess, and I wouldn't do it for any big jobs.

Marty S. 07-30-2012 05:12 PM

They also make sheets of dense foam rubber for that. Never put any on myself but have been on plenty of roofs with it on the duct. It's coated with a shiny tin foil looking substance that has an adhesive backing. Sorry don't know the correct names of the products for you to look them up,just saying it's out there.

hvactech126 07-30-2012 05:33 PM

you can also contact an insulation company and they can spray foam the duct work and then the foam is painted white.

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