Condo and High-Rise Vents
Unit branch ducts in shared-riser towers, cleaned with the building's own rules in mind.
More on Condo and High-Rise Vents →Know the rules
Dryer vent installation: the rules on Oahu
Moving a dryer, adding a laundry room or rerouting a duct? This is what the code Hawaii adopted requires of a new dryer vent, the length limits that catch most reroutes, and how the state treats the work.
The basics
What does a code-compliant dryer vent look like?
An independent duct of smooth metal, run as short and straight as the room allows, ending outside with a damper and no screen. The residential code Hawaii uses is the 2018 IRC, and the state's amendments leave its dryer exhaust section as written. These six points cover most of it.
- Own duct, never shared
- Ends outside, 3 ft from openings
- Damper cap, no screen
- Rigid metal, 4 in., No. 28 gage
- Supported every 12 ft
- Listed transition, 8 ft max
Length limits
How long can a new dryer vent be?
The code gives three ways to set the maximum length, and a reroute has to satisfy one of them.
- Method 135 feet from the transition duct connection to the outlet, minus a set deduction for each fitting.
- Method 2The dryer maker's instructions set size and maximum length; a copy goes to the code official at the concealment inspection.
- Method 3A listed power ventilator's instructions set the length.
- Over 35 ftA run longer than 35 feet equivalent needs a permanent label within 6 feet of the duct connection.
- Hawaii numberingIn the 2018 edition Hawaii uses, the length rule is M1502.4.5 with Table M1502.4.5.1.
Fitting deductions
What each bend costs under Method 1
| Fitting | 45 degree bend | 90 degree bend |
|---|---|---|
| 4 in. radius, mitered | 2 ft 6 in. | 5 ft |
| 6 in. radius, smooth | 1 ft | 1 ft 9 in. |
| 8 in. radius, smooth | 1 ft | 1 ft 7 in. |
| 10 in. radius, smooth | 9 in. | 1 ft 6 in. |
Planning
How do you plan a reroute that meets code?
1
Pick the exit
Choose an outside wall over the roof where possible; roof caps are harder to service and attract nests.
2
Measure the route
Add straight duct and fitting deductions, then compare against 35 feet and the dryer maker's chart.
3
Check the framing
Cavities must be big enough not to deform the duct, with steel shield plates where it sits close to the face.
4
Hire the right trade
Installing duct work sits inside Hawaii's C-52 and C-44 contractor classifications. We inspect and clean, before and after.
Hawaii law
Who can install a dryer vent in Hawaii
A contractor in the matching classification, in most cases. Hawaii's contractor law covers anyone who offers or undertakes to alter or improve a building, and installing duct work falls inside the written scope of the C-52 ventilating and C-44 sheet metal classifications. A small-job exemption exists, but it is lost whenever a building permit is required, cannot be used by splitting a job, and does not allow advertising as a contractor. Whether Honolulu requires a permit for a dryer duct reroute was not something we could confirm, so ask the City and County before work starts. Our part is the inspection and cleaning on either side of it.
Code rules spelled out
Length math shown
Contractor scope explained
We inspect and clean
Our services
Dryer vent services in Honolulu
We do not install vents. We inspect them before a reroute and clean them after.
Dryer Vent Inspection
A camera look and an airflow reading that show what the duct is really like inside.
More on Dryer Vent Inspection →
Bird Nest Removal
Nests and packed lint pulled from the outside cap so the damper can swing again.
More on Bird Nest Removal →
Commercial Dryer Vents
Multi-dryer exhaust for coin laundries, hotels and building laundry rooms.
More on Commercial Dryer Vents →
Dryer Vent Repair
Crushed connectors, foil duct and stray screws: what cleaning fixes and what it cannot.
More on Dryer Vent Repair →Dryer Vent Installation
Code length limits and routing rules to know before any duct is moved or replaced.
More on Dryer Vent Installation →01
Installation rules
The 2018 IRC that Hawaii adopted for homes, whose dryer exhaust section the state did not amend: metal duct, an outside termination with a damper and no screen, and a length within code or the dryer maker's chart.
No. The concealed run must be smooth-walled metal, at least No. 28 gage, 4 inches nominal. A transition duct is for the connection behind the dryer only, and it may never be concealed.
No. Dryer exhaust must be its own independent system.
Outside the building, at least 3 feet from openings unless the dryer maker says otherwise, with a backdraft damper and at least 12.5 square inches of open area. InterNACHI's guidance is to avoid roof terminations.
Under the prescriptive method, start at 35 feet and deduct for each fitting, from 9 inches for a gentle 45 to 5 feet for a tight mitered 90. The table above lists them.
02
Hawaii and our role
Code lets the maker's instructions govern if a copy goes to the code official at the concealment inspection. Brand limits vary widely by model, so read the manual for the exact unit.
No. Installing duct work is contractor work in Hawaii, and we do not advertise it.
We could not confirm the City and County's rule, so ask them. It matters twice: a required permit also removes Hawaii's small-job exemption from the contractor law.
A steel plate at least 0.062 inch thick, required where the duct sits less than 1-1/4 inches from the finished face of framing, so a nail or screw cannot puncture it.
A run test: the dryer on, exhaust leaving the cap, the damper opening freely. An dryer vent inspection can confirm the airflow on a new or rerouted duct.
Planning a reroute? Have the old run inspected.
Talk to us
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