Author Topic: Judgement call on A/C and ductwork replacement  (Read 5118 times)

thestudent

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Judgement call on A/C and ductwork replacement
« on: July 16, 2014, 09:52:39 AM »
I'd like to thank anyone that has opinions/advice ahead of time for their input. 

My current air handler-heat pump combination is approx 25yrs old and since my wife is stay at home and pregnant with twins I am going to replace it as preventative maintenance.  It has already needed repair a few times over the past three years.  Plus a new unit would probably save me $30-$50/mo w/ better efficiency.  I was in the attic for another unrelated issue I found that some of the ductwork is separating from the points where the airflow splits off into separate rooms.  Explains why the bedroom has felt warmer lately. 

Here's the question:
Replace the ductwork at a cost of around 1500.  The repair guy said my ductwork is probably an R value of 4.  New ductwork would be 6 or 8. 
-or-
Simply patch the ductwork. 

On the surface it sounds simple - patch it and move on, but my concern is that we will eventually be doing blown insulation that will bury part of the ductwork.  If we had to go in and do more repair work later seems it would be messy, and an additional expense.  I also wonder how much the better R-Value might save me on just the ductwork.   

Rollin

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Re: Judgement call on A/C and ductwork replacement
« Reply #1 on: July 16, 2014, 12:45:18 PM »
That's a tough one to answer, but you say your "repair guy" gave you the quote.  Is he also the AC contractor?  Mine would likely say repair it, as a 2 to 4 increase in R value may not help you recover $1,500 in your lifetime.  Of course, the overall system will be more efficient so you'd need to factor that in.  A good AC guy/gal should be able to run the calcs for you.

What you may want to look at in more detail (if you have a warm room) is the intakes.  If they are down the wall they are only as wide as the wall cavity (no matter how large the vent plate is).  We improved our cooling efficiency greatly by adding a few around the house through the ceiling.  Of course, it was based on the fact that the pressure at the air handler was off (as measured by my AC contractor) and a lot of moisture was building up on the coils, causing corrosion on a 7 year old system.

Also, you may see better than $30-50/month savings from a 25 year old system.  I replaced one that old at my rental (1 person living there) and they saw $75 less per month (in central Florida during the summer months).

I guess I'm saying that there are ways to determine what the correct path should be without guessing.

zolotiyeruki

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Re: Judgement call on A/C and ductwork replacement
« Reply #2 on: July 16, 2014, 01:32:24 PM »
It sounds like your air handler is in your attic, with flexible insulated ducts running throughout the attic.  Is that right?

If so, then go ahead and patch it.  If you're planning on blowing in more insulation later, the R-value of those ducts won't mean much, as they'll be buried in several inches of fiberglass or cellulose.

If you want to replace the ducts, it can definitely be a DIY job.  Flex ducting is readily available at your local big box home improvement retailer, and pretty easy to install yourself.

Numbers Man

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Re: Judgement call on A/C and ductwork replacement
« Reply #3 on: July 16, 2014, 01:41:21 PM »
If you're saying that the ducts have small gaps so the airflow escapes then I would use Duct Tape to close of the gaps. This happened to me and the HVAC guy charged me $20 to duct tape the gaps. It made a huge difference in the coolness of the areas that were impacted.

thestudent

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Re: Judgement call on A/C and ductwork replacement
« Reply #4 on: July 16, 2014, 01:54:05 PM »
Awesome replies so far!

I'm in north FL, the air handler is in a closet in the hallway but all the ductwork is in the attic.  There are also no return vents, just one big one  on the wall opposite of the hallway. 

I'd like to think the AC guy could run numbers, but I get the feeling he's not that inclined to.  Good Angie's list rating, and he's a good neihbor too, but hasn't impressed me as a numbers guy.  He is giving me a good deal on the handler/heat pump though.  ~3500 for a 2.5 ton unit installed. 

I had wondered too if the additional savings on just the ductwork would be worth the $1500. 

Rollin - if I can save $75/mo I'll be dancing in the streets. 

Milspecstache

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Re: Judgement call on A/C and ductwork replacement
« Reply #5 on: July 16, 2014, 03:02:27 PM »
Be sure it is metal as much as possible.  I've had mold grow on cheap ducting before which is expensive to then replace.

Also, check ac prices on www.acwholesalers.com before buying through a company.  I've used them a couple of times now to save quite a bit of money.  They also have periodic sales (like black Friday for instance).

zolotiyeruki

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Re: Judgement call on A/C and ductwork replacement
« Reply #6 on: July 16, 2014, 04:00:56 PM »
In addition, if you're going to replace all the ductwork and cover with insulation, I would highly recommend you go with all-sheet-metal ducts, rather than the flexible ones, for the reason Milspecstache mentions--mold.  It's been a while since I priced out the flexible ducting, but my recollection is that the straight sheet metal ducts are cheaper per foot.  Sheet metal ducts also have less air resistance than flex ducts.

Rollin

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Re: Judgement call on A/C and ductwork replacement
« Reply #7 on: July 22, 2014, 05:28:29 AM »
Awesome replies so far!

I'm in north FL, the air handler is in a closet in the hallway but all the ductwork is in the attic.  There are also no return vents, just one big one  on the wall opposite of the hallway. 

I'd like to think the AC guy could run numbers, but I get the feeling he's not that inclined to.  Good Angie's list rating, and he's a good neihbor too, but hasn't impressed me as a numbers guy.  He is giving me a good deal on the handler/heat pump though.  ~3500 for a 2.5 ton unit installed. 

I had wondered too if the additional savings on just the ductwork would be worth the $1500. 

Rollin - if I can save $75/mo I'll be dancing in the streets.

$3,500 is not a bad price as long as it is a higher SEER.  I paid about that for a 13.5 SEER (2 ton?).  If you are going to be in the place a bit longer you might want to go with a 15 or 17, depending on the extra cost.  Mine was a rental.  Had I lived there myself I'd have gone with a 17 SEER.

In my current home the previous own regularly had $3-400 a month bills.  My highest was $225 so far, and that is with 5 occupants (previous own lived alone).  That's what a new variable speed pool pump, my newer fridge, LEDs, better intakes on the AC, and foaming the underside of the rafters will do (now my AC unit and duct work is in "conditioned" space).