DUCT?

[mgilbert]

Hey all,

I have decided to go it alone finally. I have put a few systems in and have done plenty of furnace swaps and AC upgrades. It's time to get into the mainstream and I have some duct questions. I'm bidding a house for a builder who wants all floor registers and supply duct in the crawl. I thought for a 2-story, ok. But this is a single story. I will do whatever the builder wants as long as the system integrity is not jeoprdized. Comments on this would be appreciated. The main question is ducting, 1. flex or ridgid. 2. square or round. 3. does it matter? And if ridgid(trunk), is flex supply runoffs standard. It may seem second nature to some of you, but I have spent the last 15 years in commercial refrigeration with emphasis on energy controls and now find AC ducting is very new and I understand the need to know. Any help would be great.

[md master]

An all rigid, properly sized, sealed, insulated and installed duct system is obviously the highest quality install. Flexible runouts will work ok if sized correctly, but imho it is a cheaper quality install. I wouldn't want flex in my crawl space, I've seen many a mouse living in them.
To compete here (MD) in the new construction field you'd better be able to use ductboard and flex, UNLESS you work/bid custom homes only. Good money in high end custom homes where you can keep quality first. Most new homes are complete trash installs.

[mgilbert]

Ooops, I didn't know I was posting in the 'Wall of Pride' area. When you mention ductboard, are you are reffering to the type of board that is 8x12 insulated board with facing on one side? I have used that material, primarily for plennum boxes and such. I guess my largest obstacle is tying to cross over to the HVAC side of the industry and learning which materials to use for different applications. My last two jobs were the 'Radial' style and I hear everyone refer to them as an 'octopus'. In my opinion, the system is ugly at best, but works. I dont want to be a hack in this industry. I've always managed to overcome obstacles and learn the best practices. I have been tops in my industry for years, however HVAC, outside of the service realm, is a bit overwhelming at this time. What do you think of the 'snap lock' round ducting material of galvanized. Is it cost effective and practicle?

[Dad]

.

[dash]

Correct sizing ,based on ACCA's Man.J load and Man. D duct design is more critcal then the materials,are you up to speed on these or in need of assistance?

[mgilbert]

I have been playing with a software program to handle the calcs and flow rates for me as well as duct sizing. I'm learning that what you say is common. Alot of under and over sized equip out there. Then we have to try to make them work some how. I have demo from Wrightsoft I am thinking of purchasing for duct layout and Manual J calculations. I'm learning that I'm at a loss for standard material knowledge. I see ALOT of flex but hear that is not the best choice. I understand there are factors to consider such as crawl space area and such. Any help would be great. I have both feet in and it's sink or swim!

[Jultzya]

Keep swimming, you'll do just fine! I know that because you care about your clients or you wouldn't be here. :)

[dash]

Metal,flex ,etc,can all perform well if designed properly,equivalent flex duct size will be larger than ,round metal size.


Builder work will eventually be all flex and ductboard,been that way in Florida for many years.

[docholiday]

Just a tip, but if your bidding 10-12 SEER stuff, you need to make sure its going to be avaialbe when its time to set the units. You wouldnt want to bid it and then find you cant get the equipment. Probably will not be an issue if the house is starting now, but if its going to be fall, you might want to check. It's a cheap phone call.

[mgilbert]

Thanks for your replys. I will take all of this information with me I as I move forward.

[airconman]

wow I thought I was havin a nightmare..... Somebody say ductboard??? NOT THE DUCTBOARD>>> STEP AWAY FROM THE FURNACE!!!
LOL
Good luck with your new venture.

[Edited by airconman on 05-04-2005 at 04:56 AM]

[lonnirat]

I myself do not use ductboard, but if I did it would not be in a crawl space where it might be exposed to creatures that like to chew.

[johnl45]

If the builder wants a supply in the crawl is this because it's properly insulated and considered a conditioned space?

[mgilbert]

The builder has been a drywall contractor for many years and has stepped up as a home builder. In his trade he has seen many situations with mold on walls, he feels that FLOOR vents would eliminate this condition and thus he would like the duct in the crawl to accomodate this. I prefer ceiling registers and ducting in the attic myself. Less critters and less crawling around on the ground. I choose ladder over dirt covered with plastic any day. The space will be vented to the outside and deemed 'un-conditioned'.

I have run the calcs and it looks like I will use two main perimiter trunks with round metal duct. Then after install I will have to wrap the duct with faced insulation wrap.

Again ducting is new to me, any prefference on material in this application?

[millerman]

Originally posted by mgilbert
I have been playing with a software program to handle the calcs and flow rates for me as well as duct sizing. I'm learning that what you say is common. Alot of under and over sized equip out there. Then we have to try to make them work some how. I have demo from Wrightsoft I am thinking of purchasing for duct layout and Manual J calculations. I'm learning that I'm at a loss for standard material knowledge. I see ALOT of flex but hear that is not the best choice. I understand there are factors to consider such as crawl space area and such. Any help would be great. I have both feet in and it's sink or swim!

I currently use the latest wrightsoft software and it is awesome. I have wright draw along with wright d, the cool thing is when you draw the building the software automatically calculates duct sizing and all the rest, the draw program is a drag type feature with point adjustments which you can get exact measurements into the calc program. I tried many differant load calc programs and nothing comes close. I have all the modules they offer, too many features to list. Good luck and stay away from duct board!