Looking at the cooling side only the additional load would be.
Commercial attic space over ducts.
According to rightsuite the software we use the supply ducts have about 560 square feet of surface area and the return ducts 101 square feet.
There can be moisture issues in the crawlspace but i would deal with that before choosing to put the ducting in the attic.
When hvac ducts are installed in a vented attic in a dry climate bury the ducts in attic insulation to protect them from temperature extremes in the unconditioned attic space.
They live in a townhome with no attic or basement or crawlspace of any kind.
R 8 duct insulation 5 227 btu hour.
They have been told that they need to replace all the ducts.
Ted has more than a few cobwebs in his attic.
Iv conditioned attic and more.
Your attic will probably be over 100 hotter than the crawlspace.
All the ducts are in the attic.
The unconditioned space also houses his hvac system.
Furnaces ducts and air conditioning ac equipment run throughout the attic spaces on all levels except the dormers and the space over the outside deck.
Duct sealing duct and pipe insulation and location lighting fixture schedule with wattage and control narrative location of daylight zones air sealing details scope construction documents section c103 the building thermal envelope shall be represented on the construction drawings.
When determining how to insulate this attic space various assemblies were taken into consideration and a hybrid combination of vented and unvented attic space was planned.
If the ducts must be located within a vented attic one option for protecting the ducts and helping to minimize heat transfer between ducts and the unconditioned attic is to lay the ducts on the attic floor and.
The duct insulation should include a vapor barrier cover.
Ii lowered ceilings in hallways.
Install ductwork so that it is in direct contact with i e laying on the ceiling and or truss lower cords.
Additionally some of the attic space is over an outside deck while other sections are over the house s interior space.
Obviously this means a lot of ripping and tearing etc.
You can get the air handler and ducts into conditioned space in several ways without needing a basement or crawl space.
If the ducting is not sealed well and insulated you will have plenty of problems because of the high attic temperatures.
Why put the ducts there.
My parents own a home about 40 years old and there is black mold coming from the a c ducts.
I lowered soffits around room perimeters.
Use metal flex or fiber board ducts that are insulated to code.
Shown below is an example of what not to do a grille cut into pull down attic ladder and an example of the right way to add a vent a register in the ceiling of garage that connects directly to a roof vent via a metal duct viewed from the attic.
Iii special trusses that create space below the unconditioned attic.
Part of the unit is inside and part is on the roof.