Comments on: Snakes in an Attic — The Ductopus’s Cousin Strangles Bath Fans

By: Jack

Jack — Sat, 27 Jul 2013 00:44:18 +0000

I'm from NJ (the land of
I'm from NJ (the land of eventual HVAC licensing) with 45 years in the business. I'm often called in after the fact. The "low bidder" did the ductopus installation, equipment sizing, duct sizing, and register sizing, by the WAG method & duct / return locations by the "this looks good" method. I make sure all of the residential property owners are there for my presentation as home improvement contractors in NJ are supposed to, and present my findings with facts and pictures.
I show them Manual J block and room loads, discuss their Average Daily life patterns, ask about unique problems in different areas of the home discuss the advantages of variable speed compressors and air handlers, zoning, outside air exchanging, empathy controlling vs. dry bulb temperature controlling... always being careful to stay within the realm of the customer's needs.
Initially, everyone's glad to see me. They almost always comment about how thorough I am, spending much more time measuring, inspecting, analyzing, etc. than the previous installer. ... and I do it all for a nominal pre set fee. Almost everyone says they wish they had me there before they signed with their contractor.

That's usually the end of the love affair. Most of the time, the homeowners understand there's major problems, but defend their installer like they are OJ's dream team.
I understand the phycology about people reluctant to accept they were scammed, and deal with it very delicately, never knowing who's son-in-law's best friend's cousin did the work, but I am getting very tired of fighting the uphill battle for the opportunity of cleaning up the other contractor's disaster because after all, the homeowner already spent $$$.

I'm extremely thankful for the few customers I'm fortunate enough to connect with every year that renew my faith in humanity.

By: J Foley

J Foley — Sat, 01 Jun 2013 22:19:22 +0000

I'm an HVAC contractor in
I'm an HVAC contractor in central Pa and see these octoposes all the time. Sometimes the ducts aren't even completely connected. Case in point just the other day I was at my local supplier cutting some 2" ductboard. I struck up a conversation with another contractor that was from out of town. I noticed he was grabbing some boxes of 16" flex R4.2 He commented on the 2" board as looking to be hard to work with which I said wasn't too bad after you get used to it. He went on to say that they did mostly residential work. He actually seemed proud of the fact that on most small ranch installs they used little trunk duct and flexed the rest. State College code where I'm at, adheres strictly to the IMC and IRC 2009 that dude would not make it around here. The max length of a duct connect (or flex duct) is 14' that they allow. Any longer conjoining length should be rigid. I must have a sign on my back because my son and I get calls all the time to fix stuff like this. The reputation does make for good business though. Knowledge is power we should never stop learning.

By: Bob

Bob — Sat, 18 May 2013 17:44:05 +0000

Making hard pipe for exhaust
Making hard pipe for exhaust fans a code requirement would eliminate many of these problems.

By: M. Johnson

M. Johnson — Sat, 18 May 2013 17:33:31 +0000

I think Gordon had one useful
I think Gordon had one useful suggestion when he said "smooth right angle bends". To use hard pipe means the flow capacity is greater than same size flex -- flex duct if used might be upsized from 4 to 5-inch to compensate.

For Gordon's question, I would refrain from telling the builder to peruse blogs. There is flow information in ACCA Manual D book, normally used for AC ducting but the principles are applicable here too. One thing it shows is all kinds of elbows and joints are equivalent to many feet of straight ducting. Based on that I would place more emphasis on minimizing elbows and joints, and less emphasis on the length of the run. I am no expert but these are some ideas which might be useful.

By: Curt Kinder

Curt Kinder — Sat, 18 May 2013 07:34:48 +0000

Normally I'm the guy quick
Normally I'm the guy quick with flippant remarks, but Martin took the cheese this time.

Gordon - there are scores of blogs here and at GBA (where Martin sleeps) concerning duct design and sound practice. Peruse those.

For starters, we use only hard pipe for bath fans whenever feasible. We also pair two 4" bath fans into a single 6" (using a wye) to minimize exterior penetrations and long runs of 4".

The pic illustrates a tradeoff - normally a roof exhaust provides the shortest run least likely to suffer future damage, but most clients understandably want the least possible number of roof penetrations.

By: Martin Holladay

Martin Holladay — Fri, 17 May 2013 23:50:43 +0000

Gordon,

Gordon,
You asked, "What is the language that a homeowner should put in his construction documents to avert this kind of disaster?"

This:"Make sure that the monkey fightin' ducts are installed right."

By: M. Johnson

M. Johnson — Fri, 17 May 2013 16:11:18 +0000
I lament the general fact
I lament the general fact people hesitate to measure with numbers. If they were to measure airflow at the vents, that would tell whether the design/installation is any good.

If they were to simply measure ESP (External Static Pressure) for the HVAC blower, that would head off a number of problems related to this. Such a measurement is cheap to do and in my mind hard to justify not doing. But some workers would rather not have true feedback on how they are doing.

In the absence of professional quality and pride, the buyer is the one who needs to ask for these tests.

By: Chris Brown

Chris Brown — Fri, 17 May 2013 15:30:18 +0000
$3 million is irrelevant! So
$3 million is irrelevant! So too is the untrained worker "just doing his job".
1.Home buyer does not know enough to question
2.Builder is more focused on "finished appearance" or visible upgrades and/or doesn't hold his trades accoutable
3.Builder shedule is out of whac...note damaged insulation as a result of running vent ducting after insulation was installed
4.Contractor that installed the ducting, whether that be the HVAC contractor, electrician or whomever, certainly does not understand airflow

Whats the common denominator?
Education! Man, we still have miles to go!