Duct Insulation

[psychro]

Hello!
I am looking for practical information regarding how to determine the duct insulation thickness for an air handler duct system. The information I have found so far is ambiguous since it determines the heat loss per foot for insulated and an uninsulated duct but the thickness is an input and not a result.
Thanks for your help.

 

[samv]

You can look at building codes and Ashrae Standards that have a minimum required Rvalue for several scenarioes.

Otherwise, Ashrae Handbook - Fundamentals has some suggestions on how you can go about estimating required insulation amounts to avoid condensation etc.

 

[imok2]

Duct insulation is rated in "R" values. The higher the "R" value the greater the insulating value. In a residential duct system for example you would use a value from R-6 to R-11 the colder it is exposed to the higher the "R" value

"R" = 1/C x thickness
"K" = Conductance =(Btu/Hr.Sq.Ft.*F)

 

[creamdust]

i have had the same problem once and i work with 'è ambient temperature and all ashrae and other reference state is R value and no mention of thickness
so u can check on

http://www.enginneringtoolbox.com

for related insulation thickness for variuos types and application
and u should also check the insitue of american insulation i forgot the web site mabe

http://www.naima.org

it has a lot of info on codensation control

 

[cubsfan]

R=5.6 or more is required by most codes. This is the minimum R value that will keep from condensation at 55F supply air. 2" batt will give you an R of about 6 or 7. Oh, yea--it doesn't matter what you have if you don't have a solid vapor barrier(standard batt comes with it, foil faced).

 

[rhino12811]

i see that this thread has not been adressed in quite some time but i thought it was worth chimeing in on. cubsfan is quite right a vapor barrier is an important part of insulating and insulation of materials ithought id add that a common misconception about vapor barriers is that two is better than one, ie.a kraft back insulation (paper backing) is the vapor barrrier. the mistake ive seen more than once is the use of visqueen (rolled plastic) or a barricade paper, housewrap ect... over the top of insulation with a kraft backing. the mistake comes into effect when the two vapor barriers trap condensation between themselves and a whole lot of problems can begin at that point. anyway i thought it may be helpfull to somebody, just thought i would say i am quite impressed with this web site and all the knowledge and expertise getting thrown around. i just found this site last night and i am in heaven. to see or read about problems and solution from others in the same field is great the old adage YOU ARE NOT AL0NE takes on a new meaning for me. all you guys & ladies are great!!! thanks and keep up the good work!!!