Is it okay that spray foam is applied to this exhaust flue?
No!
Even B-vents require 1" to combustibles… not to mention Toxic combustibles!
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Thanks for the confirmation Jeff, had a hunch.
It’s about as non-combustible as gasoline. That ***, even the orange stuff, burns like candle wax.
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Hmmm, OK, where are they obtaining the combustion air for the unit since they appear to have moved the envelope to the roof decking?
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From what I recall, building codes typically require 1" inch of free space clearance from metal flues and 2" inches or free space clearance from masonry flues 'to any combustible materials, which includes combustible insulation."
Look closely at the metal flue, were the spray form is the thinnest. It appears there is a reaction to the foam caused by the heat. Enough to cause combustion or to off gas toxic fumes?
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The other one is even worse
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There are 2 exhaust flues?
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I found another! 
Water heater?
Apparently 2 furnaces, Brian. Likely zoned.
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Two things. The number of systems is no indicator if it is zoned or not. A second flue is not more likely to be an additional furnace vs water heater one way or the other.
So, if he found a second flue…he should know exactly what it was for or find out!
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It’s a furnace. He called me.
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Cool… 
How many inspectors/posters are onsite?
Exterior tankless
Where are you located?
So the exterior tankless water heater has a flue routed through the attic?
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Texas
Oh sorry misunderstood, no these are furnace flues
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Are you and @mschneider5 working together on this project,? because the two of you posting about the same thing is confusing the hell out of me.
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