Attic Vs Crawl Space

In a crawlspace you have to worry about critters and duct losses.

Attic vs crawl space.

A two room addition on the 1st floor has limited attic space and a 4 crawl space. It s easy to see your point about eliminating ductwork from the attic. Expanding the conditioned space doesn t require you to condition an entire attic or crawl space. You can expand it just enough to accommodate the ducts.

Knowing the disadvantages of attic install and the crawl space install. Insulate and air seal the floor with open cell foam put ductwork and mechanicals in the attic install a radiant barrier and mastic seal the ducts. Compare that with the daily 140 degree temperatures found in vented attics. So when we have a choice we prefer hvac systems located under the house.

In the attic you have worry about heat gain and duct losses. Strap ducts out of insulation with 3 ductstraps per specifications. Seal supply boxes with mastic. My vote would be the crawl space if there is sufficient room and easy access for service.

If there were a way to eliminate the possibility of critters i would prefer the cooler location for ducts. If you have vaulted ceiling then you will need to install some registers near the ceiling on one of the walls. The attic would be fine if the equipment and duct work were installed in conditioned space. Rarely will a sealed foam insulated attic deviate more than 15 degrees from the living space temperatures below it.

This is a big deal and has the potential to add significant cost to air sealing insulating crawl space encapsulation and all those things we do in confined spaces. An attic crawl space is an area on the top level of a house that is not tall enough to be used as a living area and is often unfinished. For homes with eight foot ceilings you can get special roof trusses called plenum trusses that are designed to accommodate ductwork and create a chase in the attic floor. With new construction i would look for a way to have them in conditioned space.

If it applies to energy auditors and raters too that could really be difficult because many times they go into a house on their own. As a great deal of heat can escape through the attic of a house it is common for this area to be insulated.