You need to run ducting from the vent down through the floor to the piping underneath. You just cant run piping under the cabinet that is not connected to the vent itself and expect it to work, and it could cause damage to the cabinet. Call an hvac person, they will have it fixed in just a short while.

You could simply connect the duct to the opening and use the cabinet as the duct. It is not a good practice but some HVAC installers do this to cut costs. It is unlikely that the warm air would damage the cabinet. I would however not store food items on the bottom shelf.

A better way to this is to install Toe Ductor Kit under the cabinet. If you are able to move the cabinet then installation is fairly simple. If moving the cabinet is not an option, then you may be able to feed the flexible duct through the floor opening and connect it to the duct work in the crawl space.

@mike_home The Toe Ductor Kit looks like a great idea, except I'm not going to be able to get underneath the island to install it to the opening. As for food in the island, no, it's just pots and pans

hmmm...Other option is I see if I can run some flexible duct through the hole, connect the two ducts in the crawl space, and then hopefully figure out a way to connect to the register.

As for calling an HVAC person, trying to avoid that cost. It actually looks like whenever the people in this house had AC installed, the installers went to connect the handler in the basement to this register and realized it was going to be tough, so they just left the duct exposed. Genius :)

It was done like that in our house before being renovated and I didn't see any problems.

@Seabornman When you say it was done like that in your house, are you speaking of air conditioning the crawl space or not using a toeduck kit, i.e. just air conditioning the bottom of the island and letting the air escape out the register?

Thank you!

Just connect the basement duct to the hole in the floor under your cabinet, as you proposed (that's how it was done originally). I would guess half of the toe-kick installs are done this way, as installers think no-one will go looking for their shortcuts and its a pain to connect ductwork under the cabinet!

Can you just cut a hole in the floor in front of the cabinets, or over in another location in the room, and extend the disconnected run to the new area, and just have a new floor vent? Existing holes can be patched under the cabinet, and also can be repaired in the toekick, or just leave the register in the toekick, even though it doesnt work.

@sktn77a Oh it was most definitely never connected. There's no fixture on the underside of the floor in the crawl space and the ducting is braced to the craw space ceiling and runs way past the hole. See picture. Hole is to the left in the (no insulation) spot. Its had to have been like this for over 5 years, probably 10+

@cat_ky I guess I could, but there aready is a floor register in the kitchen on a far wall, so might as well use this premade hole. As long as blowing air into the underside of the island won't cause damage, I think that's the best option.

OK, so there is a hole but the existing duct just blows past this into the basement(?) If you want to connect this duct to the toe kick space, just get a floor boot screwed into the subfloor where the existing hole is, loosen the flexduct from the joists and connect it to the new boot.

@sktn77a Yes, the ducting just blows cold air into the crawl space, so basically I'd be finishing the job of the HVAC people from about 5-10 years ago. I know it's at least five as the previous owners lived here that long and confirmed that the register didn't work, but they never investigated why.

But yes, that plan (connect duct to floor boot, which is attached to existing hole underneath island. blow air into space undeneath island and let escape out register) is what I was thinking. Thank you!

It is difficult to do much more than what you propose. However if you are looking for a better solution then this 10 in. x 4 in. to 4 in. Universal Register Box from Home Depot could work. If you are able to fit it through the opening of the toe kick then you may be able to connect it to a 4 inch flexible duct. Securing the register box to the toe kick may be a challenge. The register cover would cover any sins. You would also need something to couple the 4 inch duct to the existing 6 inch in the crawl space.

@Seabornman Thank you. I was hoping that would work, but just concerned about damage. Seems to be fairly common though

If you are worried about damage, you could glue some sheet insulation to the underside of the cabinet. On your belly work and some temporary props/ wedges to hold until the adhesive dries.

Or ledger strips and a nail gun.

@ci_lantro I like it... thank you