Attic Space Vs Plenum Space

Unventilated attics can help to mitigate energy loss through leaky ducts or ceiling fittings.

Attic space vs plenum space.

Space between the structural ceiling and the dropped ceiling or under a raised floor is typically considered plenum. Now this 2 foot space for return air is sealed off to the outside air and air tight for fire problems. Plenum trusses create a reverse bulkhead in the center of the attic space where ducting can be housed in an insulated area. Place 40 ft drainage pipe with holes across center floor of dirt crawl space attach this to duct line to attic space with an inline 90 cfm silent exhaust fan at the other end of attic run a 6 in.

A basement is below and an attic is above the main part of the house. Duct through corner of closet from attic back to crawl to circulate dry attic air and close the foundation vents. I wonder if the nec definition of the word plenum would actually apply to the entire attic space. A two room addition on the 1st floor has limited attic space and a 4 crawl space.

However it is ultimately up to the building owner or the goverment codes and regulations on whether or not to use plenum vs. However some drop ceiling designs create a. Think about the volume of space normally associated with return air ducts vs the volume of space involved in an attic space. A plenum space is a part of a building that can facilitate air circulation for heating and air conditioning systems by providing pathways for either heated conditioned or return airflows usually at greater than atmospheric pressure.

It s easy to see your point about eliminating ductwork from the attic. Space between the suppended ceiling and the insulted roof is the return. Insurance issues may also have an impact on the chose of plenum vs. The plenum truss bulkhead adds only the amount of inside conditioned space required to house the ductwork by modifying the roof framing to create a boxed in area in the otherwise unconditioned attic.

You will have a suppended ceiling showing in room then you have a fire wall sheeting covering the who attic area from the rooms and then the roof structure well insulated. The velocity of the overall air movement within the two spaces would be substantially different at the same cfm. Many projects will use non plenum cabling to save on costs.