dryer vent in crawl space

[Lilah]

We are in the final stages of finishing our underground, south-facing passive solar home. We use the crawl space to circulate air from the green house through the house so it is relatively warm.

The dryer vent has to go down from the dryer, across about 15 feet of crawl space and outer wall, then up with a 90 degree turn (through soil) to the outside where there will have to be another 90 degree to face the vent flap out rather than up.

My questions:
1. Does anyone know why aluminum duct is recommended rather than 4" pvc? We can only find aluminum in two foot lengths which makes for a lot of joints and possible future problems.

2. If the two 90 degree turns at the end of the run are not going to work at all, please let me know. The only other possibility is to make a second cut through the outer wall which is two feet thick -- not an easy job and we don't really want to have to do it.

For those of you who wonder why we didn't plan ahead, we originally had the dryer vented directly out the one exterior wall but then a health change required a different bathroom layout and the dryer had to be placed in another location.

All suggestions, answers, and helpful hints gladly received. Thanks, Lilah

[metalhd2]

Lilah,

Universal code states a dryer vent has to terminate within
45' with each 90 degree turn equal to 10' of length. Your
configuration is okay in that the dryer vent fan will move the
air and lint to the outside. I would suggest 5' sections of
30 gauge galvanized pipe (4" diameter) until I reached the
interior wall. I would then install 4" PVC (Well Casing grade)
underground and up to a standard vinyl termination cap with flapper.
You might want to check with the local inspection authority on
the PVC section of your project but I think you will be okay.

Ed Tolbert
Hendersonville, NC