Ductwork

[spex1]

I am getting ready to have a 15+ year old gas furnace/split AC unit removed and and replaced with a packaged rooftop system in Phoenix. The home is 1500 sf, and 50 years old with original ductwork designed around a direct evap system.

As such, I have decided it is time to replace the ductwork, as well (the current system has a single, undersized return in the hallway closet, with the main supply trunk running down the hall -- there is really only one branch line more than three-feet long, which goes to the kitchen). As is typical in Phoenix, I'd like to have a single (properly sized) return installed in the hallway, with new ductwork going to new registers (but through the original openings) throughout the house.

I am writing a scope of work to go to bidders for the work, as I want to be able to compare apples-to-apples as best I can. I work in the HVAC industry and have a comfort level with equipment and duct sizing (while I don't plan to size the ductwork myself, I do want to specify that it be oversized appropriately to allow me to continue use of the evap cooler in a piggy-back fashion).

My question relates to how I should specify what I want (need) when it comes to ductwork. I'd love for all the new ductwork to be rigid (and properly sealed, sized, and insulated), but I suspect that is the Cadillac system (and is well into diminishing returns).

I have and am familiar with the Specification of Energy-Efficient Installation and Maintenance Practices for Residential HVAC Systems written for the Consortium for Energy Efficiency and the accompanying Duct Installation and Sealing Standards produced for Pacific Gas and Electric.

So my questions are:

- Is anyone who installs systems for a living familiar with these documents, and should I reference them?

- Does anybody leak test residential ductwork installations and should I consider this?

- What should I specify when it comes to ductwork as it relates to rigid versus flex, restrictions on use of flex, types of flex (e.g., insulation values available), connections, etc.?

- If the above referenced standard is not appropriate, is there a way to specify proper duct sealing?

Thanks in advance for all responses, and if it is not inappropriate for this message board, does anybody know anybody I should include on my bidders list?

[vapor_rush]

My question to you is: "Why don't you do it yourself?"

You sound like you have some knoweledge about HVAC...Maybe?

Not to take away from anything you've said, BUT, my take on this would be to:

1) Call a reputable company
2) Tell them what you want to do
3) Leave out the useless information that the sales guy doens't need to know
4) Supervise the installation...this may cost you more.

I would hope you would get more than one estimate on this job. Pick someone who will work with you, if it doesn't go how you want it, then bring up everything you know!!

[dash]

HVAC system to be sized by ManJ room by room,load calculation,duct worked to be sized by Man. D duct design,to deliver the cfms required by the Man.J,at .05 " of WC,or less,including filter.

If they design by Man.D,any flex duct will be properly sized.


When calling for estimates,save yourself some time,tell them what your specs are in advance,as this will likely eliminate 50% of those you call.Sad part is what you want/need is what everybody should be doing.

[spex1]

Thanks for the specification language, dash. I will use it verbatim.

I'm still uncertain about flex. Should I be concerned or is it just fine?

Thanks again.

[du mech eng]

as long as the flex is accounted for in the design and installed properly its perfectly fine.

[ct2]

Paysonhvac is our expert in your area

[dash]

We have flex duct systems installed over 20 years ago with no problem.

You want the "foil" look type of flex,go with Owens Corning,Certainteed or other major brand,with R-8 insulation,for that hot attic.

[spex1]

Thanks for all the help -- this gets me much closer.

I will try to look up PaysonHVAC, as well.

[dash]

Originally posted by spex1
Thanks for all the help -- this gets me much closer.

I will try to look up PaysonHVAC, as well.

That's his "screen name" here ,he doesn't ever say where he works as far as I know.Take a look in the wall of shame section here,he posts a lot of pictures of hack jobs in your area.