Yes, I've had another contractor experience, and once again it's the usual Two Step dance.
It's been over a year since I had my Imperial range hood mounted by my carpenter and electrified with a dedicated circuit by my electrician. Neither would do the job of ducting the range hood to the outside. They told me I would need to find an "Appliance Installer." They did not recommend any, but suggest I check with appliance dealers such as places where range hoods are sold.
Last year, I had lined up an "Appliance Installer" through some free internet app. I called 3 such handymen, and only one returned my call. Actually this was before I had even ordered the Imperial hood, and at the time I thought I would be installing something much less expensive (which later turned out to be under-cabinet only, not free standing as I had planned, leading me to discover the Imperial and other pricey hoods). He came out and we simply discussed the issue, he seemed knowledgeable and nice. I emailed back two months later after I had the hood actually mounted and electrified. He told me he'd need to come out again to re-do the estimate, which had been based on the cheaper range hood, but he was busy on another job and wouldn't be available for awhile. Then I went on vacation, and I was tied up with other projects for a month. Then it was a very hot summer, and I decided to call back in September for this attic work. Finally when I emailed again, he said he was busy on another job out of town. That happened a second time in November.
Finally, this year, I decided I need to try someone else. So this time I went to Home Depot, who does sell range hoods. Home Depot said they only listed contractors for convenience, and they were screeened, but I would deal directly with the contractor and they would be responsible for all work performed. I said OK so they gave my phone number to 3 contractors.
One of them called but left no message. Another never called, as far as I could tell (though I never answer spam calls, so I might have missed). Finally, the 3rd contractor left a friendly message, so I called them. They told me a flat rate of $350, and could do the job next Tuesday at 9am. Later by phone text we changed the appointment to Monday afternoon at 3pm, or earlier. Texting first, they actually showed up at 1:30.
I showed them the hood with the 7" stub duct which I said was required, and my 7" end cap. They asked if I had the ducting and I said no. So they went to Home Depot to get the ducting and other stuff.
They arrived with a reducer which would reduce the piping size to 6 inches. That would be connected to a ceiling plate, and the ceiling plates were not available in the 7 inch size. Then, they would fit the pipe to my 7 inch end cap with duct tape.
I said this was unacceptable. I insisted that the pipe needed to be 7 inches from end to end, it needed to attach to the stub pipe on top of the hood, but could go through the ceiling without a ceiling plate. So they went back to Home Depot a second time.
This time they did the installation. I was very unsure about this, but they used "semi-rigid" aluminum piping which Home Depot had said was suitable for "Bathroom and Kitchen ventilation." I was also unsure about their using Duct Tape, but they insisted it was suitable for ducts.
After the installers had left I decided to check this all out. I immediately discovered that semi-rigid aluminum ducting is not legal under the International Building Code my city references as the basis for it's building codes. The code specifically requires ducting with a smooth interior. It also requires galvanized steel, stainless steel, or copper. Obviously semi-rigid aluminum fails on both counts.
The building code does not give a rationale, but the issue is discussed on many forums where it is said that if the inside of the ducting has grooves--as all flexible and semi-rigid ducting does--it can build up with enough grease to catch and carry fires.
The code also doesn't specify how the pipes need to be sealed, but in many discussions it is clear that duct tape is unacceptible also. What is needed is either mastic (reinforced with mesh if covering some area) or aluminum foil tape with UL 181 rating. Duct tape is not fireproof, and it is not even permitted on fire rated flexible ducts in California.
Here is one inspector discussing all the range hood issues.
Here is another discussion about HVAC in general; cloth tape unacceptible, metal tape or mastic preferred, screws required, it specifices #8 screws. Also: mastic is generally preferred to tape, should be applied at least as thick as a nickel, 3 screws per duct connection up to 12 inches.
But, are screws OK in range hood ducts? The above code inspector showed one side screw, most pictures had mastic applied so thick you couldn't see screws, or were marked down because "no fasteners." The code guy didn't discuss what might be desireable fasteners. Are clamps OK???
Here's a discussion about range hoods in particular on a San Francisco site. It isn't official, it's some sort of journalism, but San Franciscans should know; it's a place of a lot of cooking. They specify using mastic inside before connecting, then screwing with 1/4" screws, the taping with metal tape.
Here's my attempt to link the actual building code for ventilation of all kinds.
Metal tape seems popular. I think that's because it's much faster to apply. My concern that it hides the seam, you can never know how good it is. There may be hidden gaps underneath the metal. With mastic, you observe the seam itself, which should basically not be visible in the least. I think this is why building inspectors, and Martin the Energy Nerd, always seem to prefer mastic. And the code guy above definitely seems to lean that way without saying as much.
However perhaps because the outside gap of a connection may exceed the "1/16 to 1/8" size that must be pre taped, it might be a good idea to simply fiberglass tape each seam first, then apply thick mastic to cover up the tape.
Update:
I was pleasantly surprised that the Contractor came back and re-did the ducting using galvanized steel ducting that I had purchased, with adjustable elbows and UL rated mastic.
I just texted that I wanted it done to code and this was the code and they did it. No threats were needed.
A couple times, the contractor said it wasn't necessary, and I reiterated how I searched both the local government website (for modifications to the international code) and the 2015 international code itself.
This took far longer than the original flex duct--a couple hours of installation just on the pipe itself. However even at that it surprised me how quickly the handyman knocked it out. He had certainly done this before, and did a neat install with shallow angles on the only 2 adjustable elbows needed. I had purchased 4 elbows just in case.
There was one arguable weakness in my plan, and that was the mesh tape. The mesh tape that goes under the mastic for big gaps is not made with any UL listing. I looked very hard for such a thing, and there is none, either online or in any store I checked. None of the dozen or so accounts I read of the mesh+mastic installation metioned a UL rating for the mesh, but they always mentioned that the mastic should be UL 181 rated. What I ended up buying was the fiberglass mesh tape indended for drywall. That had to be relatively non-flammable, I figured, as resistance to fire is the reason drywalls are required for home interiors.
The contractor did in fact point this weakness in my plan. He said "You're breaking your own rules, not having the approved material." I told him to be sure the mesh was always covered with Mastic.
Later I obtained online (it was apparently not sold in any local stores) a fiberglass mesh tape indended for ducts. It was not UL rated either, but at least it gave ducts (it said nothing about special ducts, such as range hood ducts, just ducts) as the intended usage.
I performed flammability tests outside on little pieces of the fiberglass mesh tape actually used, and the one sold for ducts. They performed similarly, which made me consider this satisfactory, even though my tests were not definitive. Either one would resist fire from a lighter for a few seconds, then burst into flame. However the flame wasn't necessarily inclined to spread, would go out by itself, and leave some fiberglass remaining after burning. I think this is about the best that can be expected in any non-metallic building material, particularly with adhesive on it. A butane flame is up to 1400F and UL ratings are for far lower temperatures. I would really need to test in a wood flame, and perhaps allow time for the adhesive solvent to evaporate. Mesh is intended to be covered with UL rated mastic, and the assembly gets its rating from the covering, not what is inside. Inside of the mesh tape there may be even more flammable grease and stuff; if the mesh tape weren't there, the grease would be right up to the mastic in its place.
It's been over a year since I had my Imperial range hood mounted by my carpenter and electrified with a dedicated circuit by my electrician. Neither would do the job of ducting the range hood to the outside. They told me I would need to find an "Appliance Installer." They did not recommend any, but suggest I check with appliance dealers such as places where range hoods are sold.
Last year, I had lined up an "Appliance Installer" through some free internet app. I called 3 such handymen, and only one returned my call. Actually this was before I had even ordered the Imperial hood, and at the time I thought I would be installing something much less expensive (which later turned out to be under-cabinet only, not free standing as I had planned, leading me to discover the Imperial and other pricey hoods). He came out and we simply discussed the issue, he seemed knowledgeable and nice. I emailed back two months later after I had the hood actually mounted and electrified. He told me he'd need to come out again to re-do the estimate, which had been based on the cheaper range hood, but he was busy on another job and wouldn't be available for awhile. Then I went on vacation, and I was tied up with other projects for a month. Then it was a very hot summer, and I decided to call back in September for this attic work. Finally when I emailed again, he said he was busy on another job out of town. That happened a second time in November.
Finally, this year, I decided I need to try someone else. So this time I went to Home Depot, who does sell range hoods. Home Depot said they only listed contractors for convenience, and they were screeened, but I would deal directly with the contractor and they would be responsible for all work performed. I said OK so they gave my phone number to 3 contractors.
One of them called but left no message. Another never called, as far as I could tell (though I never answer spam calls, so I might have missed). Finally, the 3rd contractor left a friendly message, so I called them. They told me a flat rate of $350, and could do the job next Tuesday at 9am. Later by phone text we changed the appointment to Monday afternoon at 3pm, or earlier. Texting first, they actually showed up at 1:30.
I showed them the hood with the 7" stub duct which I said was required, and my 7" end cap. They asked if I had the ducting and I said no. So they went to Home Depot to get the ducting and other stuff.
They arrived with a reducer which would reduce the piping size to 6 inches. That would be connected to a ceiling plate, and the ceiling plates were not available in the 7 inch size. Then, they would fit the pipe to my 7 inch end cap with duct tape.
I said this was unacceptable. I insisted that the pipe needed to be 7 inches from end to end, it needed to attach to the stub pipe on top of the hood, but could go through the ceiling without a ceiling plate. So they went back to Home Depot a second time.
This time they did the installation. I was very unsure about this, but they used "semi-rigid" aluminum piping which Home Depot had said was suitable for "Bathroom and Kitchen ventilation." I was also unsure about their using Duct Tape, but they insisted it was suitable for ducts.
After the installers had left I decided to check this all out. I immediately discovered that semi-rigid aluminum ducting is not legal under the International Building Code my city references as the basis for it's building codes. The code specifically requires ducting with a smooth interior. It also requires galvanized steel, stainless steel, or copper. Obviously semi-rigid aluminum fails on both counts.
The building code does not give a rationale, but the issue is discussed on many forums where it is said that if the inside of the ducting has grooves--as all flexible and semi-rigid ducting does--it can build up with enough grease to catch and carry fires.
The code also doesn't specify how the pipes need to be sealed, but in many discussions it is clear that duct tape is unacceptible also. What is needed is either mastic (reinforced with mesh if covering some area) or aluminum foil tape with UL 181 rating. Duct tape is not fireproof, and it is not even permitted on fire rated flexible ducts in California.
Here is one inspector discussing all the range hood issues.
Here is another discussion about HVAC in general; cloth tape unacceptible, metal tape or mastic preferred, screws required, it specifices #8 screws. Also: mastic is generally preferred to tape, should be applied at least as thick as a nickel, 3 screws per duct connection up to 12 inches.
But, are screws OK in range hood ducts? The above code inspector showed one side screw, most pictures had mastic applied so thick you couldn't see screws, or were marked down because "no fasteners." The code guy didn't discuss what might be desireable fasteners. Are clamps OK???
Here's a discussion about range hoods in particular on a San Francisco site. It isn't official, it's some sort of journalism, but San Franciscans should know; it's a place of a lot of cooking. They specify using mastic inside before connecting, then screwing with 1/4" screws, the taping with metal tape.
Here's my attempt to link the actual building code for ventilation of all kinds.
Metal tape seems popular. I think that's because it's much faster to apply. My concern that it hides the seam, you can never know how good it is. There may be hidden gaps underneath the metal. With mastic, you observe the seam itself, which should basically not be visible in the least. I think this is why building inspectors, and Martin the Energy Nerd, always seem to prefer mastic. And the code guy above definitely seems to lean that way without saying as much.
However perhaps because the outside gap of a connection may exceed the "1/16 to 1/8" size that must be pre taped, it might be a good idea to simply fiberglass tape each seam first, then apply thick mastic to cover up the tape.
Update:
I was pleasantly surprised that the Contractor came back and re-did the ducting using galvanized steel ducting that I had purchased, with adjustable elbows and UL rated mastic.
I just texted that I wanted it done to code and this was the code and they did it. No threats were needed.
A couple times, the contractor said it wasn't necessary, and I reiterated how I searched both the local government website (for modifications to the international code) and the 2015 international code itself.
This took far longer than the original flex duct--a couple hours of installation just on the pipe itself. However even at that it surprised me how quickly the handyman knocked it out. He had certainly done this before, and did a neat install with shallow angles on the only 2 adjustable elbows needed. I had purchased 4 elbows just in case.
There was one arguable weakness in my plan, and that was the mesh tape. The mesh tape that goes under the mastic for big gaps is not made with any UL listing. I looked very hard for such a thing, and there is none, either online or in any store I checked. None of the dozen or so accounts I read of the mesh+mastic installation metioned a UL rating for the mesh, but they always mentioned that the mastic should be UL 181 rated. What I ended up buying was the fiberglass mesh tape indended for drywall. That had to be relatively non-flammable, I figured, as resistance to fire is the reason drywalls are required for home interiors.
The contractor did in fact point this weakness in my plan. He said "You're breaking your own rules, not having the approved material." I told him to be sure the mesh was always covered with Mastic.
Later I obtained online (it was apparently not sold in any local stores) a fiberglass mesh tape indended for ducts. It was not UL rated either, but at least it gave ducts (it said nothing about special ducts, such as range hood ducts, just ducts) as the intended usage.
I performed flammability tests outside on little pieces of the fiberglass mesh tape actually used, and the one sold for ducts. They performed similarly, which made me consider this satisfactory, even though my tests were not definitive. Either one would resist fire from a lighter for a few seconds, then burst into flame. However the flame wasn't necessarily inclined to spread, would go out by itself, and leave some fiberglass remaining after burning. I think this is about the best that can be expected in any non-metallic building material, particularly with adhesive on it. A butane flame is up to 1400F and UL ratings are for far lower temperatures. I would really need to test in a wood flame, and perhaps allow time for the adhesive solvent to evaporate. Mesh is intended to be covered with UL rated mastic, and the assembly gets its rating from the covering, not what is inside. Inside of the mesh tape there may be even more flammable grease and stuff; if the mesh tape weren't there, the grease would be right up to the mastic in its place.
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