Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > HVAC

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Reply
 
Thread Tools Search this Thread Display Modes
Old 04-16-2010, 09:36 AM   #1
Member
 
Join Date: Jan 2010
Location: houston, tx
Posts: 37
Share |
Default

double walled ductwork question(s)


A recent fire put a lot of smoke in a rental house we intend to retire to in a few years. I've been told by some that is difficult-to-impossible to clean ductwork to the point that the odor won't reappear when the ductwork warms up. The suggested solution, of course, is to replace it. The problem is that what I have is rectangular metallic ductwork with internal insulation ... I presume this means double walled but I'm not sure. If I have to replace the ductwork I would like to replace it with what is there now. Is this still available (the house was built in 1957) and affordable? It is easy/difficult to install? Thanks,

Peyton

peyton is offline   Reply With Quote
Old 04-16-2010, 09:47 AM   #2
fabrk8r
 
fabrk8r's Avatar
 
Join Date: Feb 2010
Location: Iowa
Posts: 849
Default

double walled ductwork question(s)


What you have now is just called "insulated duct".

"Double-wall" duct has an inner and outer layer of metal with insulation in between. The inner wall is usually, but not always, a perforated metal.

As far as ease of installation, single wall insulated duct is pretty straightforward and relatively easy to do. Most residential duct is connected by what is called "slip and drive" connections and hung by 1' wide hanger-strap attached to joists with screws. The seams, tap collars and register boots should be sealed with mastic (Pro-Seal is one brand) to keep leakage to a minimum.

You can simply measure your old duct dimensions and lengths and have a local sheet metal shop fabricate it for you.

Let me know if you have any questions.

__________________
"The physician can bury his mistakes, but the architect can only advise his clients to plant vines." -- Frank Lloyd Wright
fabrk8r is offline   Reply With Quote
Old 04-16-2010, 10:17 AM   #3
Member
 
Join Date: Jan 2010
Location: houston, tx
Posts: 37
Default

double walled ductwork question(s)


Quote:
Originally Posted by fabrk8r View Post
What you have now is just called "insulated duct".

"Double-wall" duct has an inner and outer layer of metal with insulation in between. The inner wall is usually, but not always, a perforated metal.

As far as ease of installation, single wall insulated duct is pretty straightforward and relatively easy to do. Most residential duct is connected by what is called "slip and drive" connections and hung by 1' wide hanger-strap attached to joists with screws. The seams, tap collars and register boots should be sealed with mastic (Pro-Seal is one brand) to keep leakage to a minimum.

You can simply measure your old duct dimensions and lengths and have a local sheet metal shop fabricate it for you.

Let me know if you have any questions.
Thanks Fabrk8r,

I assumed it was double walled to support the insulation. How is the insulation held in-place in "insulated duct"?

So this is not an off-the-shelf product, it is fabricated as needed?

Peyton
peyton is offline   Reply With Quote
Old 04-16-2010, 10:30 AM   #4
fabrk8r
 
fabrk8r's Avatar
 
Join Date: Feb 2010
Location: Iowa
Posts: 849
Default

double walled ductwork question(s)


The insulation is applied with spray-on glue. It can also be brushed on if necessary.

You can buy standard sizes of duct at most home centers, but it will be uninsulated. Most Plumbing supply outlets carry standard size duct as well.

Your fastest, easiest and cheapest route will be to have a shop fabricate and insulate it for you. If you have any questions on installation I'm sure they would be happy to show you how that's done as well.

As far as fittings, such as tap collars,register boots, and insulated flexible duct,you can usually get those cheaper at Menard's.
__________________
"The physician can bury his mistakes, but the architect can only advise his clients to plant vines." -- Frank Lloyd Wright
fabrk8r is offline   Reply With Quote
Old 04-16-2010, 12:41 PM   #5
An old Tradesmen
 
Join Date: Oct 2008
Location: PA
Posts: 24,531
Default

double walled ductwork question(s)


Contact a fire restoration company.

They will have a sealer they can use on the insulation to prevent the odor from returning.
beenthere is offline   Reply With Quote
Old 04-16-2010, 02:30 PM   #6
Member
 
Join Date: Jan 2010
Location: houston, tx
Posts: 37
Default

double walled ductwork question(s)


Quote:
Originally Posted by beenthere View Post
Contact a fire restoration company.

They will have a sealer they can use on the insulation to prevent the odor from returning.
I've talked to a couple but they talk about cleaning rather than sealing. I'll ask them about sealing. Thanks

Peyton
peyton is offline   Reply With Quote
Old 04-18-2010, 06:48 PM   #7
Newbie
 
Join Date: Apr 2010
Posts: 8
Default

double walled ductwork question(s)


Quote:
Originally Posted by fabrk8r View Post
The insulation is applied with spray-on glue. It can also be brushed on if necessary.

if done correctly, after the glue is applied and the insulation is set in place, small disks with stems in the center are inserted through the insulation and spot welded to the ductwork to create a permanent hold, should the glue fail. it really would be in your best interest to have this fabricated at a local shop.
PA_DIY'er is offline   Reply With Quote
Old 04-19-2010, 09:09 AM   #8
Member
 
Join Date: Jan 2010
Location: houston, tx
Posts: 37
Default

double walled ductwork question(s)


Quote:
Originally Posted by PA_DIY'er View Post
if done correctly, after the glue is applied and the insulation is set in place, small disks with stems in the center are inserted through the insulation and spot welded to the ductwork to create a permanent hold, should the glue fail. it really would be in your best interest to have this fabricated at a local shop.
Thanks, I've wondered about that. I really wasn't planning to try to fabricate or insulate the ductwork myself but was, rather, trying to understand how it was done.

Next question(s): what kind of insulation is used? boards, bats, etc. Is it faced and, if so, does it face the interior of the ductwork?

Peyton
peyton is offline   Reply With Quote
Old 04-19-2010, 10:02 AM   #9
fabrk8r
 
fabrk8r's Avatar
 
Join Date: Feb 2010
Location: Iowa
Posts: 849
Default

double walled ductwork question(s)


We use a product from Johns Manville called Linacoustic RC. It is a flexible fiber glass duct liner and it is treated with antimicrobials. It comes in 250'- 300' rolls in various thicknesses and widths. For residential duct we usually use 1/2" thickness. One side is faced with a reinforced coating (RC) to keep the fibers contained.

As PA DIY'er said, the duct liner is usually attached with glue and then "pin spotted" to make sure it doesn't come loose.

On a side note, about the only reason we ever insulate residential duct is for noise control. We usually just insulate the return plenum within a few feet of the furnace or air-handler to keep the noise down. This is because the duct is usually in the conditioned space anyway, so there isn't much concern about sweating. If the duct is in an attic or crawl space then you would want it insulated it's entire length.

If you are concerned about exposure to airborne fiberglass particles you can have the duct wrapped on it's outside surfaces, which leaves only the metal exposed to the conditioned air. This is something that makes future duct cleaning easier. If this is something you'd like to do you will have to contact an insulation specialty company because most tin shops contract this part of the job out.

__________________
"The physician can bury his mistakes, but the architect can only advise his clients to plant vines." -- Frank Lloyd Wright
fabrk8r is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Finishing basement, had a few questions about ductwork... Wyjeep Plumbing 12 04-27-2010 09:27 PM
Questions about ductwork for kitchen range hood ilyaz HVAC 11 12-09-2009 12:16 AM
Double Check Valve installation (and a few other questions) secutanudu Plumbing 0 04-17-2009 07:42 AM
questions on sealing slab , underlay pad, double padding under laminate pauls Flooring 8 02-21-2009 01:10 PM
Ductwork install questions smcmurrey HVAC 4 07-24-2008 05:36 PM




Top of Page | View New Posts

Copyright © 2003-2014 Escalate Media. All Rights Reserved.