Attic Space Vs Plenum Space

However i have two questions if i want to centrally air condition my entire house.

Attic space vs plenum space.

Space between the structural ceiling and the dropped ceiling or under a raised floor is typically considered plenum. I wonder if the nec definition of the word plenum would actually apply to the entire attic space. It s easy to see your point about eliminating ductwork from the attic. Think about the volume of space normally associated with return air ducts vs the volume of space involved in an attic space.

A two room addition on the 1st floor has limited attic space and a 4 crawl space. 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. Duct through corner of closet from attic back to crawl to circulate dry attic air and close the foundation vents. 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.

Plenum trusses create a reverse bulkhead in the center of the attic space where ducting can be housed in an insulated area. Unventilated attics can help to mitigate energy loss through leaky ducts or ceiling fittings. Many projects will use non plenum cabling to save on costs. 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.

A basement is below and an attic is above the main part of the house. Space between the suppended ceiling and the insulted roof is the return. However some drop ceiling designs create a. 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.

However it is ultimately up to the building owner or the goverment codes and regulations on whether or not to use plenum vs. However if moisture is able to enter the unvented attic space it may lead to roofing panel issues. The energy savings touted by unvented attics can be as high as 20.