Attic Space Vs Plemum Space

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

Attic space vs plemum space.

Rarely will a sealed foam insulated attic deviate more than 15 degrees from the living space temperatures below it. I wonder if the nec definition of the word plenum would actually apply to the entire attic space. Space between the structural ceiling and the dropped ceiling or under a raised floor is typically considered plenum. 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.

A basement is below and an attic is above the main part of the house. 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. So when we have a choice we prefer hvac systems located under the house.

However some drop ceiling designs create a. That space typically has about a 10 12 degree difference than the conditioned space below it. The energy savings touted by unvented attics can be as high as 20. However if moisture is able to enter the unvented attic space it may lead to roofing panel issues.

It s easy to see your point about eliminating ductwork from the attic. Unventilated attics can help to mitigate energy loss through leaky ducts or ceiling fittings. A two room addition on the 1st floor has limited attic space and a 4 crawl space. That dead air space is designed to be a buffer between the roof.

This allows intensive cooling to be pumped through the space under the floor to cool the servers switches routers etc. It will increase your load and contaminate your house air if it has been converted from a ventilated attic to a sealed attic. Think about the volume of space normally associated with return air ducts vs the volume of space involved in an attic space. Compare that with the daily 140 degree temperatures found in vented attics.

Plenum trusses create a reverse bulkhead in the center of the attic space where ducting can be housed in an insulated area.