Where should I block off my unused register's....

dcd22

About 1 year ago I added a 2nd forced hot air HVAC unit in my attic for my 2nd floor. The register's for the upstairs rooms are in the ceiling.

The original HVAC unit is in the 1st fllor utility room. THere is a main trunk in my crarl space that has branches coming off of it, up the outside wall cavity and to the upstair's rooms. The installed did not close these off from the main branch, rather he just glued some sheet metel in the room register's and closed the vent's!

Will I be better off going into the crawl and capping the main trunk for the run's I do not need?

jogr

If these abandoned ducts are in an outside wall, I would think you would want to disconnect them from the trunk and put insulation in the wall. Otherwise you have no insulation in that space and when the blower shuts off you'll have cold air convecting downward into your trunk which will be the first air blown out when the furnace kicks on again.

redline

Why two units?

Clutchcargo

1. That's really the only effective way to get two zone hot air heating. Zone dampers on a furnace causes the efficiency to go down the toilet.
2. Saves floor space because you don't need to run a large trunk from the basement to the second floor.

__________________

dcd22

ok, so closing them off in the crawl is easy. Filling the outside wall cavity with insulation, not so much!

I am wondering if I can fill the metal dust with insulation? If not, how would I fill that cavity?

I did two units for a few reason's. I added an 18x18 two story addition. When I did that it was either upgrade my current to be large enough to handle the new space OR add a second unit upstair's. THe 2nd unit gives me beter temperature control and add's some redundency if one goes down.

jogr

I would seal the bottom and use the blown in stuff.