Floor Trusses Hvac Chase

Ducts in a special roof truss.

Floor trusses hvac chase. Still commonly used is the panned floor joist. Floor trusses have built in openings which can be used to install hvac ductwork plumbing lines and electrical wiring. Hvac chases or duct runs may be designed into floor trusses to allow for plumbing and or heating and air conditioning ducts to be installed in the floor. Alpine engineered products now itw referred these to floor trusses as system42 trusses.

Open joist is a revolutionary open web all wood floor truss engineered with superior strength and load carrying capabilities. I specified open web trusses for my new house in part to simplify the installation of mechanical systems. Most truss manufacturers can produce custom plenum trusses that include an integral duct chase. Recently i discovered that the truss system would not support metal ducts.

See sbca s ttb floor truss fact sheet. There simply wasn t a way to get from the mechanical room to the other end of each floor using metal. Design criteria for the 4 x 2 floor system. Using floor joists as return ducts by panning can cause leakage because negative pressure in the cavity will draw air from the outside into the cavity through the construction joints of the rim area at the end of the joist cavity.

Stuart lewis from alpine engineered products tells us. This also reduces the need and cost for extra bearing posts beams and footings. Floor trusses go by many names and since parallel chord 4x trusses can be used in roof systems the term floor truss is not necessarily the most accurate term although it is the one in most common use. Maximum span to depth ratio of 1 to 20 example 14 truss should not exceed 23 4 span spacing may be adjusted to accommodate longer spans maximum 24 duct chase on flat wise trusses minimum duct chase offset from the bearing is of the span.

The resulting chase is variously called a raised hvac coffer and an inverted soffit. Floor trusses can span farther between bearing points than i joists allowing for larger open rooms. Open web design leaves plenty of room for mechanical systems hvac plumbing electrical to be installed within the floor frame. For a standard 4x2 floor truss meaning warren style webs with 30 inch panels with double cut webs the maximum round duct in the end panel is 5 625.

Are there charts illustrating allowable hvac duct sizes that can fit between truss chords for various truss depths. Hvac chases are typically 24 wide and as tall as the height between the top and bottom chords will allow.