Tips for replacing air ducts in slab foundation home

Multiple broken joints may require rerouting system overhead

By Inman News Feed
Add Comment Add Comment | Comments: 0 | Posted Feb. 3, 2012

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Multiple broken joints may require rerouting system overhead

Paul Bianchina
Inman News®

Q: We have recently discovered that the air ducts in our slab are breaking down; and it was recommended that we consider rerouting the air ducts to the attic. What are the advantages/disadvantages of having air ducts in the floor vs. overhead?

Also we have heard that there are now several companies that can coat the inside of your air ducts in the floor with a paint-like substance that seals off any breaches in the system, therefore leaving the system in the floor vs. rerouting. Have you heard of this procedure, and, if so, is it something you would recommend?

We feel that rerouting the system is very expensive because not only would we have to pay for the new air duct system in the attic, but also we would have to purchase a new heating unit that can be placed horizontally in the attic. The rerouting also would have a "domino" effect in that we would need to consider replacing all of our flooring to cover the old register holes.

Another solution that was mentioned is a split system. What exactly is a split system, and what advantages/disadvantages are there in a split system? --Susan C.

A: You have a couple of different questions here, so I'll try to answer them in order:

1. Warm air rises and cool air falls through a natural convection process. So, ducts that are in the floor tend to be a little more effective in distributing heated air throughout a room. Ducts that are in a ceiling tend to be a little more effective in distributing cooled air throughout a room.

2. If your ductwork is breaking down under the slab, a coating is not going to do you any good. There are companies that can use thermal imaging cameras to pinpoint "hot spots" in the floor where a duct might be broken, allowing you to cut into the slab at that point and make a repair. But if you have more than one bad joint, that's probably not going to be cost effective.

Unfortunately, at this point your best bet is going to be to replace the ducts, and the most cost-effective way to do that is to reroute them overhead.

3. Your heating contractor can advise you on the best way to seal off the old ductwork. As to the holes in the floor, you can simply leave the old registers in place as camouflage until it comes time to replace your flooring.

4. A split system is simply one that has a furnace located somewhere inside the house, and an air conditioning unit located somewhere outside the house. The two share common ductwork, wiring, plumbing and other components, and are controlled by a common thermostat.

Split systems are very common for houses requiring both heat and air conditioning, but they do not offer an alternative to replacing your ductwork.

There are, however, through-the-wall units that combine both heating and air conditioning components and do not require duct work. These are the type of units commonly seen in hotel rooms. They are intended for individual rooms or zones of the house, and while not as convenient as central heating and air conditioning systems, they might offer you an alternative to a new furnace and duct system.

Q: My home, built in 1971, had 6 inches of loose-fill fiberglass insulation installed. This has compressed to about 4 inches. Knowing I needed more insulation in my attic, this past June, I contracted with a local contractor (licensed in Maryland). The workers installed about 1 to 4 inches of loose cellulose in my attic, over the existing fiberglass, totaling 6 inches of insulation, and covered it with a radiant barrier, which they call Attic Mirror. It looks like aluminum foil.

In the section of attic that is a storage area, they also installed this radiant barrier on the ceiling of the attic. They told me I needed a total of 12 inches of insulation for the R-38 factor, but they installed only enough to equate to 6 inches of insulation. They owe me 6 more inches of insulation.

I didn't like what I saw when I returned home, so I hired an inspector who was shocked at what they had done, and suggested that the radiant barrier be removed due to moisture concerns, and to install batts for the additional 6 inches of insulation.

I contacted the contractor, telling the company that the radiant barrier must be removed, and the remaining 6 inches of insulation due me is to be batts. The contractor told me the company does not have batts. I have paid in full for their service, and this problem is still unresolved. Do you have any suggestions as to what I can do here? --Catherine B.

A: First, you need to go back to your original contract with this company. They're a licensed contractor so they had a legal obligation to provide you with a written contract. Within that contract there should have been some specifications about what they were going to do.

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