When do I use a subduct?
Subducts are simple alternative to fire/smoke dampers when penetrating exhaust shafts in multi-story buildings. A subduct is commonly used for clothes dryer exhaust penetrations where local or state codes do not allow the use of fire/smoke dampers. However, subducts can also be used for bathroom and kitchen exhaust shaft penetrations. A single fire/smoke damper can cost up to $1000 installed so the use of subducts significantly reduces the installed cost of the building's exhaust systems.

What material is the subduct?
Section 716.5.3 of the 2003 International Building Code (IBC) requires "steel exhaust subducts [to have a] wall thickness of 0.019 inch." The LSR is constructed of 26 gauge galvanized steel to exceed the requirements of the strictest building codes.

What are the advantages of an LSR over a conventional round subduct?
When designing multi-story exhaust shafts, it is paramount to minimize the pressure drop between the closest and farthest penetrations in the exhaust system. This minimization alleviates balancing issues between the floors. The use of an LSR results in lower velocities and less restriction in the exhaust shaft, which allows the exhaust shaft to be smaller. In a 10"x10" shaft, the flow area is over 50% greater when using two LSR04s in lieu of two conventional 4"ID subducts. In addition, securing the LSR within the exhaust shaft is much easier than conventional round subducts. Furthermore, the low profile and flush mounting of the LSR significantly lessens the possibility of lint or dust accumulation.

What is the pressure drop through the LSR and conventional round subduct?
The LSR has a slightly higher pressure drop than a conventional subduct: The LSR is equivalent to 10 feet whereas a conventional round subduct is equivalent to about seven feet.

Where is the LSR located in the exhaust system?
Section 716.5.3 of the 2003 IBC requires the subduct to be installed within the exhaust shaft. See Figure 1.

Section 716.5.3 of the 2003 IBC requires subducts to be at least 22 inches tall; where is this dimension measured?
The 22 inch dimension is measure from the top of the duct penetrating the exhaust shaft to the top of the subduct. See Figure 2.

Is the LSR suitable for clothes dryer exhaust? Yes, the LSR was specifically designed to accommodate multi-story clothes dryer exhaust systems. The LSR's female duct connection is expandable to provided easy access to and cleaning of the LSR.

How is the LSR connected to the exhaust shaft?
The LSR is mounted flash against the exhaust shaft. The easiest, most common method is sheet metal screws or rivets; however, clothes dryers require a specific direction for the sheet metal screws or rivets. For clothes dryer exhaust, the sheet metal screws or rivets are installed from the inside of the shaft so that the ends do not protrude into the main shaft.

Is the LSR made in the United States?
Absolutely, LSR is proudly made in the State in Texas.

Where can I get more information about the LSR?
Subduct Riser Manufacturing OEMs with several manufacturers, but also has a growing distributor network across North America. Please email sales@subductriser.com or call 888-379-7622 ext. 701 for more information.

Always check your local codes.