Attic Space Vs Plemum Space

Compare that with the daily 140 degree temperatures found in vented attics.

Attic space vs plemum space.

Space between the structural ceiling and the dropped ceiling or under a raised floor is typically considered plenum. The velocity of the overall air movement within the two spaces would be substantially different at the same cfm. Don t use the foamed attic space as a conditioned 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. It will increase your load and contaminate your house air if it has been converted from a ventilated attic to a sealed attic. Unventilated attics can help to mitigate energy loss through leaky ducts or ceiling fittings. Plenum trusses create a reverse bulkhead in the center of the attic space where ducting can be housed in an insulated area.

Cabling between the many devices and to the users runs through this open floor space. However i have two questions if i want to centrally air condition my entire house. A basement is below and an attic is above the main part of the house. 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.

This by definition is a plenum air space and requires plenum rated cable. 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 two room addition on the 1st floor has limited attic space and a 4 crawl space. The energy savings touted by unvented attics can be as high as 20.

So when we have a choice we prefer hvac systems located under the house. However some drop ceiling designs create a. However if moisture is able to enter the unvented attic space it may lead to roofing panel issues. Rarely will a sealed foam insulated attic deviate more than 15 degrees from the living space temperatures below it.

Think about the volume of space normally associated with return air ducts vs the volume of space involved in an attic space.