Bitchy Builder - air ducts

[Jeff Eastman]

...........

[Dom D'Agostino]

I think it's time you invested in code books.

Try here:

2006 IBC Code Books - Page 1 (http://www.iccsafe.org/e/prodcat.html?catid=C-B-06i1&pcats=ICCSafe,C,I-C-06,C-B-06i&stateInfo=ccejngijlndbibjG6158|4)

[Ed Ochs]

I think it's time you invested in code books.

Try here:

2006 IBC Code Books - Page 1 (http://www.iccsafe.org/e/prodcat.html?catid=C-B-06i1&pcats=ICCSafe,C,I-C-06,C-B-06i&stateInfo=ccejngijlndbibjG6158|4)


Isn't there a way to exclude Dom's commentary, I would be happy to block his comments.....

[Dom D'Agostino]

Block away, Ed. I don't mind.

[Dom D'Agostino]

Jeff,

Ignore the Dom.... He is one of few that really isn't helpful on this board and has serious issues with himself. He just likes piping up and making dumb or smart alec comments. 98% of people on this board are usually very helpful and I for one like the questions you post. Anyways, I don't want to digress too far on the "DOM", might make me puke.



You're the one with serious issues...

[Ed Ochs]

Isn't there a way to exclude Dom's commentary, I would be happy to block his comments.....

I found it
Go to top of page Members list > find name click on it and add to ignore list...


Things are looking up....:)

[Scott Patterson]

This is a good article out of the ASHI Reporter on flex-duct
A Home Inspectors' Guide to Flexible HVAC Duct Installation | ASHI Reporter (http://www.ashireporter.org/articles/articles.aspx?id=41)

A good guideline on flex-duct and other types as well
http://www.toolbase.org/PDF/DesignGuides/doe_airdistributionsysteminstallation.pdf

[Jerry Peck]

Go here ( http://www.flexibleduct.org/download/ADC~Inst.pdf ) and download the installation instructions.

[Scott Patterson]

Again, no mention of not allowing them to lie on or in the insulation.

Yes it can lay across the joist. It really depends on the manufacturer of the the duct if it is flex-duct.

Jeff, I think you might have a hard time backing up this statement of yours.

[DavidR]

I wrote up: "Air ducts not properly supported above insulation which can cause condensation on the air ducts as well as crushing and displacing the insulation, reducing the insulations’ R value."

He wants to see code or manufacture requirements. Anyone have them handy? Thanks!

Not trying to start an argument here but how does an improperly supported duct cause condensation on the ducts?
If it's raining off the ducts there are other issues at play here.

Crushed insulation & reducing R values I am with you 100% as well as ducts that don't deliver the volume of air that they are capable of.

[Jeff Euriech]

If the flexible ducts get cold enough, and if the humidity is high enough, you will have condensation. I would suspect it depends on the "R" rating of the ducts and how much ventilation is in the attic. Out here for the most part we have R-6.0 insulated ducts with a couple of the cities switching to R-8.0. However, I have not seen any problems with condensation.

Fritz
Anytime you compress insulation, the "R" rating will go down. Something to do with not having as much air in the insulation. While the ducts do not weigh that much, they will compress some insulation more then others changing the "R" values.

From the Owens Corning web site:

Frequently asked questions (http://www.owenscorning.com/around/insulation/faq_general.asp)
What happens when I compress fiber glass insulation?

Fiber glass insulation works on the principle of trapped air pockets. By compressing fiber glass insulation, you decrease the amount of air trapped in the material, therefore reducing the overall R-value.

Jeff Euriech
Peoria Arizona

[Phillip Stojanik]

The greater problem is when we have ducts that are in substantial contact with each other. The probability of the contacting surfaces reaching the dew point (and thus forming condensation) is much greater. Any subsequent crushing of the insulation between the ducts just serves to exacerbate the problem.

This is because insulation serves to slow, but does not prevent, the transfer of heat energy and works best in a standoff situation standing between two extremes of temperature. In this case the dew point is reached within the insulation itself but because of an associated vapor barrier, a supply of condensable moisture is not available.

When the insulation stands between two similar temperatures however it will assume that temperature itself eventually. If that temperature happens to be below the dew point of the surrounding environment, then condensation will form on the "exposed" surfaces.

This is true even though there is little actual moisture laden air flow between the contacting ducts because there is no effective vapor barrier present to prevent enough air flow to avoid at least some condensation.

If you are in a hot humid attic and see flex ducts in contact with each other, run your hand between them. You will very likely pull back a wet hand.

[Jeff Euriech]

Fritz
No, I do not call it out in our area. I was only trying to explain a possible reason for not having ducts on top of the insulation. I also have never seen a problem with two ducts contacting each other. Maybe I should pay closer attention to that as we go through our monsoon season with the higher humidity.

Jeff Euriech
Peoria Arizona

[Phillip Stojanik]

Jeff,

I did not mean to imply that I would not write it up as a problem when I found it to be so. Suspending the ductwork is what I consider to be a "best practice" today but there was a point in time when it was not specified by many flex duct manufacturers and not otherwise required by code. It was perfectly acceptable to have a duct system laying across the rafter runs.

Subsequently, there are lots of older flex duct systems in my area that are just laid out in the attic rather than being suspended that have no sweating or other issues. I personally do not make an issue of that unless I see evidence that the lack of suspension is creating a problem in that particular case.

This brings us back to the age old argument among inspectors about inspecting all houses and all systems to currently accepted and expected standards. Codes, products and manufacturer installation specifications do change over time and what was once accepted may no longer be acceptable for new applications.

We do not however typically go back to the older houses and make it a point to update everything to the current standard each time there is a change in thinking unless that system happens to be getting a makeover anyway. That is when we expect things to be brought up to the current standards.

As a home inspector, it is not my purpose to compare the house I am inspecting to current standards in all detail. Frankly, that's just a near impossible task and the public (apparently) has no will to pay me to do that.

Having said that though, I do take issue with a fair number of specific items that I routinely encounter but these are reserved for where some threat to health and safety is concerned. Examples would include missing smoke detectors, missing GFCI protection, and the presence of dangerous stair geometry and so on.

I would however stop short of writing up an old unsuspended flex duct system that is not otherwise showing visible evidence of a problem.

[DavidR]

Ducts laying under blown-in insulation in an attic will perform better than those that are suspended with strapping hands down.

[Phillip Stojanik]

Philip,

Philosophical question:

If you agree that air ducts that lay on insulation will crush the insulation reducing its' effective R-value. Regardless if it is a 1950 ,2000 ,or 2007 home why would you not write that up for repair? Also does not your state require you to write up for repairs for insulation not at R30 rating (or whatever is the min in your state). The crushed insualtion would probably be less than R30?


Dan,

The TREC SoP says "... (10) inspect for the presence, and report the approximate depth of, insulation where visible;..."

There is no specific requirement to write up the lack of a particular R value but I very often find myself making the recommendation that additional insulation be added to increase the R value.

I do not however specify a particular goal as far as R value goes because I know that the insulation contractor will make their own recommendations about what to shoot for. This is typically above the code based minimum for my local climate zone and many insulation contractors locally push toward R 30 to R 38 which will exceed the code minimum R 26 shown in Table N1102.1 under ceiling R value for the climate zone in my predominant service area.

Getting back to the ductwork though. The kinds of older homes that I see with the ductwork laid out in the attic rarely have the ductwork sitting directly on top of the insulation. In these older homes the depth of insulation typically does not come up to the tops of the ceiling joists so there will be little or no contact as a general rule.

Now if additional insulation has been added to augment the original, and the ductwork is now partially submerged because it was not picked up and suspended first, I would take a closer look at it for signs of problems being created by that condition. If I find them, I write them up. If no issues are apparent to me, then I refrain from making assumptions and proclaiming that a problem exists.

Understand that I am trying to be careful with my explanation here because the rules are different in different parts of the country and folks from all over may be reading this. I don’t want to mislead anyone by making a declarative statement that something must be written up as a problem when in fact it may not be a problem at all (for others).

The point is that I happen to live in a very particular type of hot and humid climate that has its own set of psychometric conditions where building science is concerned. We can do things here that can not be done in other climates and other climates can do things there that are not advisable here. For example, a moisture vapor retarder for attic insulation is not required here but might be foolish to omit in some other climates.

People tend to love the "yes" or "no" type answers and no one likes to hear a "maybe" or "it depends" kind of answer because it requires more thought and further discussion. Sometimes though, the "maybe" or "it depends" answer is actaully the best answer to give under the circumstances.

The important thing (where the built environment is concerned) is to find out what is appropriate for your specific area and to be wary of seeking and embracing rules from other areas that may not match your own circumstances climatically or even geologically from either a code or a building science perspective.

We as home inspectors need to think on as broad a scale as we possibly can but we must apply what we have learned very narrowly and on a 'case by case' basis.

That is the essence of professional judgement in my opinion and that is what our client (and society) is convinced they are paying us to do for them when we are specifically hired.

Don’t disappoint them by failing to think broadly or by failing to apply narrowly to their specific benifit!

[Randy Aldering]

It seems the real issue that must be addressed is whether or not the ductwork is installed and operating according to design. Any reduction of the interior passage of the duct would be of primary importance. Damage to the insulation would also be important. These items can be noted as compromised, and that consulting an HVAC professional is suggested. As for the "bitchy builder", obtain the installation manual from the manufacturer. It will probably verify the concern. I also draw attention to the note in most of the installation manuals that state failure to properly install the product will usually void the warranty. Builders can complain all they want. I have even had them offer to pay me off. Makes not difference. It is what it is, and if its wrong, its wrong.