Comments on: Signs of a Bad Duct Installation

By: Clark morris

Clark morris — Wed, 21 Jun 2017 18:17:55 +0000

I just had a new heat and air
I just had a new heat and air package installed with all new ductwork. Some of my supply line and some of my flexible line is laying on the dirt under my house. Is this acceptable practice?

By: Jeff W

Jeff W — Wed, 28 Sep 2016 23:52:59 +0000

Allison, A newbie here,
Allison, A newbie here, still learning how to post.
Im a homeowner in the Pacific NW with a 1300 sf L shaped rambler. After a critter infestation (yep they got inside) I removed the duct work. Knowing things were just spec’d in with this 1960 house, I did some research and using my old Fire Science Hydraulics designed my system for max air flow according to room size, and friction loss. When I finished the design, and I had a few Furnace companies look at it, they all told me it was too much work, and a great design but not worth it, cuz it’s just a house… As a part of the design, Im running heat to the 434 sf that was electric heat.
Im now trying to upgrade the returns as well.

Thanks for the info here, it has been helpful.

By: Terje

Terje — Sat, 27 Aug 2016 02:24:11 +0000

Seems like it is time to come
Seems like it is time to come on the market with a "duct lube spray" that will smooth out any issued in in the system and provide flow like a proper laxative. Think l could make big bucks on such a product....:)

By: RJ

RJ — Sun, 21 Aug 2016 20:03:13 +0000

John, you should reread the
John, you should reread the last section of the article "How to Get it Done Right" and it's links. Cliff Notes version: Metal ducts with 100% mastic sealing and heavily insulated is the best if you don't want the gold standard which is to get the ducts into a conditioned space. In your case conditioned space probably means sealing the crawlspace. Flex duct is easy and may reduce noise in short runs but is also easy to damage and generate condensate.

By: John Aller

John Aller — Sun, 21 Aug 2016 04:11:57 +0000

Is the length of flex duct on
Is the length of flex duct on each run spec on HVAC design or is it installers (mis)choice. Is flex duct attahced to register boot the design choice for flow or vibe/noise isolation. The isulation sheathing on the flexduct is pretty cheesey. What right R rating is best for crawl space ducts in southeast? Is double wrapping the solution to prevent condesation or Should I just ensure there is 100% no leakage in any supply/return duct or both? We keep our house cool and AC runs a lot. Now the cral space ducts are dripping. Seems the only way to ensure success is for me to go over the duct inch by inch myself and ensure they are dry on outside, sealed and wrapped right.I have seen posts saying some of these leaks are saving overdesigned system from overpressurization or underpressurization. I had my ducts in vented crawl space replaced several years ago and they replace with similar lengths of flex duct. I have one run of about 20 ft (not very straight) flex (close to what was in the original install. If it is spec'd as flex what is impact if I replace the longer runs with metal duct? Do I need flex near boots to minimize noise/vibration. am I better with a 45 or 90 on the boot?attached to flex on the short runs to the terminals Also should register boots be extended when installing new flooring which is higher.

By: Craig Savage

Craig Savage — Tue, 19 Jul 2016 18:54:44 +0000

As I've watched the HVAC
As I've watched the HVAC tradespeople struggle with sealing ducts for at least the last 15 years here in energy-code-serious Title-24 California, I've often wondered why the manufacturers can't come up with fittings equivalent to PEX tubing plumbers use, or the "shark-bite" fittings that slip over and seal copper tubing.

By: Ray Austin

Ray Austin — Tue, 19 Jul 2016 15:44:23 +0000

There is a pretty big problem
There is a pretty big problem within the HVAC industry of having things done properly. Duct work can be one such area of concern. I think the reasons many of these problems exist is the nature of the beast in pricing the work that will be done.

People looking at a quote see “all visible duct work replaced” for $xxxx and then compare this to other quotes. If they get a quote or two with fancy terms thrown in there as to what will be done and the price is double maybe even triple from what the low ball quote is, guess who wins the job?

Duct work is boring to a customer, they know the conditioned air runs thru the duct to reach their habited space but other than that they will refuse to look much further.

What further complicates this is the condition of the housing market. There has been literally an explosion of house rentals over the past several years. The rental market (any rental) is in the business of counting beans. The landlord is not interested in duct blasting, air leakage, duct hung every 4 foot etc.

They are interested in the cheapest job they can find. That is the reality of this market. People can pretty much price duct work out themselves by going to home depot, so they can see the cost of materials what they don’t see is the labor intensive job in an attic many times that has nothing but rafters, which only adds more labor intensive attributes to an already labor intensive job.

Just a few days ago I got a call in which some home owner had bought equipment on line and he was calling me because his supposed friend who “that was licensed” didn’t have the tools necessary to do the job, so he was wanting to rent my tools.

All that and in the middle of summer. So the problems of the HVAC market run deep. You have people out there that want it done right, but the vast majority don’t want to pay for anything a professional has to offer.

PS: If you call me, I know you are not a licensed HVAC Contractor. A Licensed HVAC contractor would never call me, and if they did I would tell them to go break the gumball machine they got their license from.

By: RJPakrer

RJPakrer — Tue, 19 Jul 2016 15:22:33 +0000

1. Builders and architects
1. Builders and architects should take responsibility upfront including ensuring all ductwork is detailed in the plans and is installed within the envelope (no unseled attics and especially no crawlspaces)
2. Rigid ducts should be specified and installed
3. Flex should only be used for short connections to the registers
4. Testing should be almost redundant to good design

By: Charley Cormany

Charley Cormany — Thu, 07 Jul 2016 20:49:14 +0000

I have yet to meet a
I have yet to meet a traditional HVAC company (non Home Performance) that owns a duct blaster. In fact, I asked a person with 30 years in the HVAC trade about manometers, he didn’t own one. CA added duct testing to the inspection process several years ago and what happened? HVAC installers stopped pulling permits. Duct issues are huge – I would bet that enforcing duct testing would save more energy than many of the current rebate programs. Bottom line – get the ducts tested or find a different contractor.

By: Allison Bailes

Allison Bailes — Wed, 29 Jun 2016 15:07:01 +0000

Great point, Dave. I should
Great point, Dave. I should have mentioned that in the article, but here’s the best article on the topic of duct leakage in spray foam attics:

Cool Hand Luke Meets Attics, by Joseph Lstiburek, PhD, PE

http://buildingscience.com/documents/insights/bsi-077-cool-hand-luke-meets-attics