crawlspacehvac
The home I purchased has a crawlspace below an addition that was put on to the original structure. The HVAC contractor that did the work ran 2 long runs of flex-duct to the 2 registers in the room of the the crawl space.
Is this acceptable? Do I need to be concerned about the elements or possibly animals getting into the crawl space and chewing holes in the flex duct?
Yes, bringing the crawl space into the conditioned space is generally recommended as a way to prevent crawlspace moisture problems (I assume this is what you mean by encapsulate).
This means:
This will prevent humid outside air from coming into the crawlspace and condensing on cold surfaces, and prevent/reduce moisture from coming up through the dirt floor or walls. Your AC will also deliver cold air more effectively. Good site drainage is also key.
There are many good references on how to do this properly:
If the cinder blocks are empty, a standard masonry drill bit in the 3/4 inch (19 mm) range plus a sawzall (which can be inexpensively rented, but you'll have to buy a blade).
Trace a duct end onto the blocks where you want the hole: it is best that the edges of the hole be at least an inch (3 cm) away from cinder block edges and mortar but can go through them.
Drill the 3/4 inch pilot hole inside but near the circle's line. Use care to get it square (perpendicular) all the way through and press lightly as it passes through the opposite face. (If you drill the hole right on the line, there will be an unsightly gap to deal with later.)
Place sawzall into the hole and—if you haven't used one before, practice by cutting toward the center of the circle—cutting slowly to avoid fracturing the brittle material. Until you get a feel for how much chipping it does, stay safely away from the line—an inch should be enough at first. (See example video.)
The hole need not be big enough for the full height of the sawzall blade. It can be started in about half its full width.
When cutting through the block edges and mortar, angle the saw as shown. Repeat from other side to finish cutting through.
Best Answer
I would not use flexible duct in a crawl space. It is like a 4 lane freeway for animals and bugs. Rigid duct is very easy to piece together. Even long runs might take you an extra few minutes.