I am installing a Takagi tankless water heater which calls for a “class III” flue. My local HD carries something called “type B” gas flue. What’s the difference? By the way, the Takagi literature specifies an “airtight” installation. Any suggestions on what materials lead to an airtight seal? Thanks. I am an advanced, adventurous DIYer, so I can handle the truth!
Thanks,
Steve K
To prevent moisture buildup and improve performance, install a continuous air barrier—such as drywall or specialized membranes—under tongue-and-groove boards or other interior wall paneling.
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Replies
You're screwed. Category III flue is airtight stainless steel. Try to find a brand called Pro-Tech, which is available through more comprehensive HVAC and sheet metal places. I have met very good experienced HVAC installers who have never even seen the stuff. It's hard to come by (or was when I needed some about a year ago) and incredibly expensive. We vented a Takagi about 40 feet with $1000 worth of pipe. If at all possible you should mount your unit so as to direct-vent. If that can't be done then you need the Category III material. B-vent is a totally different animal.
Thanks for the information David. I found a supplier in my area that carries Pro Tech and you are correct...it's pricey. Still, I have only about 10 feet to run, so it should work out. Again, thanks.