I will be replacing the HVAC system in 12 properties in March.

The oldest property is 1996 and the rest are 2001-2004. I'm installing 14 seer HVAC and 80,000 BTU 80% AFUE gas furnaces. All but 3 of the houses need 2.5 tons and the rest need 3. I'm comfortable with the sizes and the efficiency ratings.

Two contractors have told me not to bother replacing the ductwork and two have said replace it. One of the "don't" contractors has recommended a leak test to see if the ductwork needs sealing the other has said that is waste and that they can visually review the ductwork and connections and do repairs as needed.

Last spring I replaced my HVAC at home with 2-3 ton units but my ductwork had been replaced and rerouted 4 years before so it wasn't an issue I had to address at that time.

This is beyond my comfort zone especially with an equal split in opinions by the contractors.

I would appreciate your input.

Hum. You are lucky on one hand, your ducts are newer and don't contain asbestos lining. I would do a visual inspection first. On a ladder with a bright flashlight I would stick my head into the attic and view the condition of the old ducts. See if they are in good shape. If they are insulated. If they are strapped down and run efficiently as opposed to installed by a drunk mad man.

Second, if the look good, I would do a quick pressure check. while the system is just blowing air I would close a few vents and see if other have increased air flow. Or let a professional do a quick test.

Turn the fan to "on" and check out the ductwork with it running. You should be able to hear and see any air leaks. If you don't find any, check for the "bird poop" sealant on the metal joints. If they applied it (to the metal, not just the insulation covering the metal) I would not even consider replacing the ductwork.

Unless I am missing something. Why would you ever need to replace ductwork. What part do you think can go bad?

Unless it was installed wrong to begin with.

What is there to rot out or go bad?

From 1996 unlikely they would even be undersized.

Following. Interesting.

Is this property up in the mountains or closer to the coast? I am wondering exactly how much need really exist. An AC system down south - absolutely.......but the furnace and ducting? Today's high where I am at will be 18 with a wind chill at -10. I would be alright in most cases with a 20 year old furnace.

I never contemplated replacing the ductwork until the two contractors recommended it. I did tell them to include an estimate for checking/repairing any leaks and separations.

The properties all have insulated flex ductwork. I've never had a single complaint about uneven distribution of heat or air.

The properties are in Charlotte. Summers have always been oppressive with very high heat and humidity. 100 degree days are common from June - September. The past 3 yrs. winter temps are erratic. We go from the mid 60's daytime to 15 degrees the next day with a steady stream of 5-15 degrees at night and wind chill dropping into the minus range.

All of our houses have had extra insulation blown into attics, windows and doors have had new weatherstripping installed plus silicone caulk around all of the windows so that's not a problem.

To Ray's point there comes a point where the cost of replacement outweighs the constant cost of repairing. The furnaces have been fine but the HVAC need constant freon and tuneups.

A couple of questions to help clarify...

Where do the ducts run? Is that space heated/cooled?

Up here in the north, in a one story house, it is typical for the ducting to run entirely through the basement, with openings for registers and returns low on the walls, just above the floor. In cold areas with clay soils , it's important to heat the basement as well as the main level of the house, as those clay soils will frost heave, putting inward pressure on basement walls; heat in basement expands 'the balloon' , helping to hold those walls out. So, up here in the cold north, air leaks from ductwork in the basent isn't a bad thing. (Tenants often close the registers in the basement 'to save money' . Doesn't save me money when the walls start moving. I like heat leaking from the ducts in the basement.)

In areas of the country where ducting goes up into the attic, and then down from there, or, through a crawl space, it might be a totally different issue. Since the attic or crawl space isn't heated/cooled, having tightly sealed ducts would probably be very important. In that case, I am just wondering if it wouldn't be more cost effective to wrap the existing ducts in that foil-bubble wrap type insulation making sure the seams are well sealed?

I'm very much 'consciously Incompetant' when it comes to HVAC, so follow advice of more knowledgeable posters. I have, in fact, had all of the ducts on my houses redone, but, mine are 60-70 year old houses, and all of the heat registers were in the center of the house, in some instances, right next to the cold air returns. My houses had terrible trouble with hot and cold spaces. None of my registers could be replaced, except by the company that does custom sizes for about $80-120 a register, all were rusted. I had the ductwork run the way it would be run in a modern house, with heat registers under the windows, cold air returns in the center of the house. But, because all of my houses have basements, and heating the basements is a must to prevent failed walls (expansive clay soils,) my ducts are simply screwed with three-four screws per connection. Seams aren't sealed, ducts aren't insulated, except for the one pipe that goes through an un heated crawl space. All of that improved the comfort of my houses tremendously. And, on one house it greatly improved the smell. The ducts were very rusty on that house, I hate that smell!

BUSY:

Thanks for your response. Basements are an anomaly in Charlotte. It's a combined issue with the water level and clay soil. The few "basements" here are walkout ground level and you only find those in high end homes since the cost of construction is prohibitive.

The properties I'm referring to are starter homes. I don't think any sold for more than $150-160. All of them are built on a slab so all the ducting is in the attic.

I've had the ductwork in my home redone 4 times by supposed "top rated" HVAC companies and it still isn't right. We have a large home with an open floor space and 20'+ ceiling in some areas exasperated by an abundance of windows. There are only two rooms without wall to wall windows, the powder room and walk-in closets. The change in temperature from room to room has been a persistent problem. As a result I am acutely aware of the importance of ductwork.

It's amazing how much we don't know yet about conditioning the spaces in a house. Very interesting stuff. My husband has been tweaking the weatherization on our own home for the twenty years we've lived here, he now has our energy consumption at the very low end for a comparably sized house in our area, according to our power company. And we still have 19 windows and one exterior door to replace, so we'll see more good results in the future. We have a fairly modest house, with a lot of windows, all placed without regard to sun and wind back in the late 1950s . We've relocated a few windows, changed sizes on many already. Doing more this summer. One great thing about our house is the three foot overhang, all the way around. That overhang has taught me the importance of awnings on controlling heat gain in summer.

And then, there is the intersection of interior comfort with exterior landscaping. Properly placed and maintained trees make such an incredible difference, in both heat and cooling.

Good luck on your properties, and on your own house. 20 foot ceiling -I cannot imagine the challenge that presents!