Attic Space Vs Plemum Space

I wonder if the nec definition of the word plenum would actually apply to the entire attic space.

Attic space vs plemum space.

The velocity of the overall air movement within the two spaces would be substantially different at the same cfm. Cabling between the many devices and to the users runs through this open floor space. Think about the volume of space normally associated with return air ducts vs the volume of space involved in an attic space. However i have two questions if i want to centrally air condition my entire house.

The energy savings touted by unvented attics can be as high as 20. It s easy to see your point about eliminating ductwork from the attic. Space between the structural ceiling and the dropped ceiling or under a raised floor is typically considered plenum. This by definition is a plenum air space and requires plenum rated cable.

So when we have a choice we prefer hvac systems located under the house. Unventilated attics can help to mitigate energy loss through leaky ducts or ceiling fittings. This allows intensive cooling to be pumped through the space under the floor to cool the servers switches routers etc. That space typically has about a 10 12 degree difference than the conditioned space below it.

However some drop ceiling designs create a. A basement is below and an attic is above the main part of the house. That dead air space is designed to be a buffer between the roof. 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. A two room addition on the 1st floor has limited attic space and a 4 crawl space. Compare that with the daily 140 degree temperatures found in vented attics. It will increase your load and contaminate your house air if it has been converted from a ventilated attic to a sealed attic.

Don t use the foamed attic space as a conditioned plenum.