Duct Insulation

First post! Huge fan of the site, and finally decided to register and join in on the fun. I am a first time home-buyer and budding DIY'er in search of direction and advice.

Not sure the cheesy intro was entirely necessary, but it seemed proper as I've been silently stalking the forums for over a year now.

Anyway, to the point. I have a 1900's ranch style home. On the large scale, my plan is to make the home more energy efficient. Insulating walls, attic space, etc. I am starting with the unconditioned crawl space.

I believe I have a fairly simple heating system, my trunk line runs the length of the house, with all branch lines running to appropriate room vents. With the exception of my return lines, all the duct work is in the crawl space and I feel I am losing efficiency to leaks, and lack of insulation.

As of right now all branch lines are 5-6" metal (unknown exact). My plan is to seal any leaks, and joints first. I have identified a major leakage issue on many of the lines where they make the connection to the trunk. I have enclosed an image of this. Please reference the shoddy duct tape job someone deemed acceptable.

1. What is the recommended method to sealing these areas and leaks? Should I keep the connections as is, or is there some type of fitting or collar that would be better to connect to the trunk.


I spoke with a gentleman at a local plumbing store. He advised I should replace all the branch lines with pre-insulated flex. I have mixed feelings about this as I know if not installed correctly, the flex ducting can create an air loss due to friction. This and the the system can be more susceptible to damage rodents and animals. Branch lines seem fine, and it seems it would be easier to insulate them rather than replace the lines.

2. What is recommended practice for this? Home depot carries a fiber glass insulation for this, but is only rated r-6. Is there a fiberglass roll in r-8? Where can I find this? Are the foil insulation rolls claiming r-8 worth a damn?


Thanks very much for any ideas/suggestions!