Hard or flaccid?
I am advising my friends on their 50s ranch upgrade with full basement. The house could never be made energy efficient unless it was completely torn down and rebuilt. They have a lower seer HVAC system that is a tad bit over-sized and runs like a top. Their GC wants them to completely rip-out the very accessible (full basement) hard HVAC duct and install a new system for 16k+ not including 18% markup (estimate with no manual J or D, to go by I might add), because their system is “too leaky” which he summarized by just eyeballing it.
I have nothing against Flex (which he suggested) but the hard duct is really in terrific shape and has control dampers for each run and I am arguing to peel off the fiberglass duct wrap and just mastic the ducts to death, then re-wrap new fiberglass and/or spray foam encapsulate them after a leakage test.
BTW the ducts currently “leak” into fully conditioned space. I estimate my retrofit with manual D included would be around $1000.
Am I thinking too cheap to my friends detriment?
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I am thinking your friend needs to go look for some new bids. Took me talking to a dozen contractors to find one who actually calculated ROI of all the work he was doing. He did Manual J BEFORE quoting me anything.
Leo,
Unless there is something wrong with the duct design -- the classic problem is undersized ducts -- galvanized ducts are always preferable to flexible ducts.
Several studies have shown that there is a negligible energy penalty from duct leakage when all of the ducts are located inside of the home's conditioned space. In spite of these findings, it is often helpful to seal duct seams, to ensure that the conditioned air is delivered to the rooms where it is being sent.
I think that your friends should find another contractor.