Fiberglass insulation on rigid ductwork???

Reply

  #1  
Old 11-15-03, 08:46 AM
bobbyo8
Visiting Guest
Posts: n/a
Fiberglass insulation on rigid ductwork???

I cannot wrap my basement forced air ductwork comletely around it with the foil-wrap insulation, so I would like to stuff that framed soffit with regular fiberglass insulation (probably R13 or so)...

Is that ok to do with the ducts getting hot and all????

Thanks in advance!
 
Sponsored Links
  #2  
Old 11-16-03, 01:06 PM
Member
Join Date: Nov 2001
Location: USA
Posts: 1,873
Yes, you can install insulation in those areas, the heat from the ductwork is not that hot. What you need to careful in this application is leaky ductwork. If the ducts are leaking in those areas and you put insulation over them, condensation will form inside the insulation. Usually the ductwork will leak where there is a seam or joint in the duct. Where possible, try to tape or use mastic over the joint, this will seal the joint. Then you can insulate over the ductwork.
 
  #3  
Old 11-16-03, 01:20 PM
Ed Imeduc's Avatar
Member
Join Date: Aug 2002
Location: Mountain Williams Missouri
Posts: 18,389
Duct work

If this duct is in the basement and you are heating and cooling the basment I dont see why the insulation here. ED
 
  #4  
Old 11-17-03, 04:33 AM
bobbyo8
Visiting Guest
Posts: n/a
Insulating because I'm going to have a gas fireplace heat the basement on it's own separate thermostat. I don't want to lose any "upper level" heat to air space in soffits, that's why I want to insulate them.
 
  #5  
Old 11-17-03, 11:27 AM
Ed Imeduc's Avatar
Member
Join Date: Aug 2002
Location: Mountain Williams Missouri
Posts: 18,389
Question insulation

I hope this gas fireplace has a vent to the outside of the home. . You did put insulation in all the joist there on the sill plate and all around the belt board. Now we look at it as any warmth you get to the floors above is not lost its still in the home. Have found also that a warm floor makes a happy wife???????????? ED
 
  #6  
Old 11-17-03, 11:44 AM
bobbyo8
Visiting Guest
Posts: n/a
Fireplace is direct vented though what used to be a shoe-box type of window in the concrete. Sills are all insulated.

I really don't want to "insulate" the upper level from the lower in terms of heat and cooling.... Maybe you can help me here if I provide more detail:

My #1 concern is soundproofing the basement from the upper level, and soundproofing the duct work too. The idea of insulating the duct work was in case I was losing some of the heat because it is radiating into the basement. That's not a problem now, in an unfinished basement. But when I enclose the ducts in a big soffit, then I'm losing the radiant heat to....what, heating the soffit???? That seems like a waste: but I don't know if it will help me to insulate the ducts (would the air coming out of the long runs to their registers be ANY hotter?), or would it be more trouble then it's worth?
 
  #7  
Old 11-17-03, 04:15 PM
Ed Imeduc's Avatar
Member
Join Date: Aug 2002
Location: Mountain Williams Missouri
Posts: 18,389
Wink Duct work

When the duct work is in a basment this way we let it alone and dont use like duct board or such cause the rooms its in have heat and A/C. ED
 
  #8  
Old 11-18-03, 04:28 AM
bobbyo8
Visiting Guest
Posts: n/a
Gotcha. I'll leave it alone.....
 
  #9  
Old 11-19-03, 12:37 PM
brickeyee
Visiting Guest
Posts: n/a
Insulation slows the movement of heat when a temperature difference exists. If the basement is heated the temperature difference is already getting small reducing any heat loss or gain. The payback for insulating the exterior walls can often be many years with the large temperature differences encountered. Insulating for noise reduction may be worthwhile, but only because the payback is not measured in dollars but in comfort. I know one person who had an extra return installed in a basement rec room with a wood stove in the same room. He closes the upstairs return for heating season and opens the basement return. A fire in the wood stove heats the entire house.
You will not save any money by insulating ducts that are in conditioned space already.
 
  #10  
Old 11-19-03, 06:07 PM
bobbyo8
Visiting Guest
Posts: n/a
Interesting....

Originally posted by brickeyee
Insulation slows the movement of heat when a temperature difference exists. If the basement is heated the temperature difference is already getting small reducing any heat loss or gain. The payback for insulating the exterior walls can often be many years with the large temperature differences encountered. Insulating for noise reduction may be worthwhile, but only because the payback is not measured in dollars but in comfort. I know one person who had an extra return installed in a basement rec room with a wood stove in the same room. He closes the upstairs return for heating season and opens the basement return. A fire in the wood stove heats the entire house.
You will not save any money by insulating ducts that are in conditioned space already.
That must be some blower installed on his wood stove.... either that or he uses the fan from his furnace to circulate the stove's heat? I was going to try to do the same thing with my gas fireplace to augment the existing furnace, but the blower in the fireplace is not strong enough to circulate the heat through the ducts. So I will install one external vent to my existing return duct and have my furnace fan turn on when the fireplace is trying to heat the house. It's kind of complicated because I'm limited in what I can do to heat my basement I guess (I'm adding either registers or diffusers to existing duct branches, which probably isn't ideal, but it is the only thing I can do).

Anyway, if insulating the ducts provides any sound deadening at all, it will be worth it. I have to get rid of alot of old insulation, so that might be a good place to start...

thanks again, this newguy really appreciates all the help/advice. My first house at 28 yrs old ... and I'm learning something new all the time!!!!
 
  #11  
Old 11-20-03, 08:10 AM
brickeyee
Visiting Guest
Posts: n/a
The wood stove does not have a blower. Put the fan on the forced air heat to 'ON' and it runs all the time. The return in the room just pulls in the heated air and the system distributes it.
 
  #12  
Old 11-20-03, 08:40 AM
bobbyo8
Visiting Guest
Posts: n/a
Originally posted by brickeyee
The wood stove does not have a blower. Put the fan on the forced air heat to 'ON' and it runs all the time. The return in the room just pulls in the heated air and the system distributes it.
Makes sense. That's the same setup that I am looking to do, except I'll run a turn-on lead from the furnace blower to the fireplace so that the furnace blower comes on automatically when the fireplace comes on - without doing it manually. I think I'll put in an override option too.
 
  #13  
Old 11-20-03, 09:06 AM
Ed Imeduc's Avatar
Member
Join Date: Aug 2002
Location: Mountain Williams Missouri
Posts: 18,389
Lightbulb Heat

Now dont get carried away here . So you have the furnace blower pulling back down on that gas fireplace into the home. That what was told on a wood stove in a basement is right . BUT--- they dont have a diverter on them like a gas stove or gas fireplace has where it could pull back down the gas flue into the home ED
 
  #14  
Old 11-20-03, 09:37 AM
bobbyo8
Visiting Guest
Posts: n/a
OK, looks like I'm in for a lesson....

Educate me. Please expand on that last post! Not sure what you mean.

Here's my plan:
The model gas fireplace that I'm going to install has two additional duct hookups that can supply forced hot air to either registers or the existing return duct run to either 1) assist the furnace, or 2) use the furnace's blower and have that hot air circulated around the home, both methods using the existing duct system.

Correct me if you think I'm wrong on this plan.
 
  #15  
Old 11-20-03, 10:35 AM
Ed Imeduc's Avatar
Member
Join Date: Aug 2002
Location: Mountain Williams Missouri
Posts: 18,389
Exclamation hot air

As I cant see just what all you have in duct its hard to say for sure. But when it was said about the wood stove ,it just made the basement warm. So with a large return grill down there in the basement and turn the furnace blower on it would take this warm air into the rest of the home not by duct work from the stove.
Yes I have ran duct work from wood burning fireplaces that had a steel heatilator in them and pick up the hot air right there with the furnace blower and put it all over the home. BUT this was all done as the home was being built and we could put the needed dampers in at that time.
Now for what you have if Im right. Just put the gas fireplace in. The fans in it will take the cold air in the basement heat it and blow it back there in the basement. You dont want to hook this up to the furnace duct.Now on another wall or some where in the basement put a large return grill to the furnace. Now when you turn on the furnace blower it will pick up the warm air in the basement for you and take it through the home ED
 
  #16  
Old 11-20-03, 10:52 AM
bobbyo8
Visiting Guest
Posts: n/a
Ok, now I understand what the install with that stove was all about.

I also understand your suggestion for my install, and it is actually easier to do it that way than the way I had in mind. Thanks for expanding on that for me.

BUT, here is where I believe the conflict of info arises:

This is the fireplace I want to buy (see link below).
Why wouldn't I want to connect one of the fireplace's external hot air ducts directly to the (end) of the existing home return duct? The manufacturer lists this as a possible way to help heat my home.

It seems that by routing hot air directly from the fireplace to the return duct and turning on the furnace blower, I would be "skipping the middle man" which is what you described: having a return duct register in the basement that draws in heated air from within the basement room(s). That heated air would only be warm, whereas direct heat from the fireplace would be hot (or warmer at the least). Makes sense to me.

Here's the link (see Page 4 "Heat Duct" option):

www.heatnglo.com/brochures/6000.PDF
 
  #17  
Old 11-20-03, 12:17 PM
brickeyee
Visiting Guest
Posts: n/a
That actually looks like a good option since the unit has a fan. The only problem I see would be that you will need to inspect the fireplace unit carefully to make sure it never develops a crack or hole. Install a CO detector if you do not already have one for insurance.
 
  #18  
Old 11-20-03, 12:38 PM
bobbyo8
Visiting Guest
Posts: n/a
The CO2 sensors are a must, I agree.

I've heard something about that condition before, but don't know the reason why a crack or hole in the fireplace would be a problem? (I mean, I know they are supposed to be sealed, and stay sealed, is that what you are saying, or is it a catastrophe if it cracks over time?) Seems unsafe if they are prone to cracking.
 
  #19  
Old 11-20-03, 12:52 PM
Ed Imeduc's Avatar
Member
Join Date: Aug 2002
Location: Mountain Williams Missouri
Posts: 18,389
Exclamation fireplace

Ok Went there .Now 160 Cfm on the fan ,that wont blow 2ft out of the vent there I dont think.

Now dont know where you are . How about code there. You cant say put a hot air supply outlet into a cold air duct. A lot of the cold air duct in a home is not metal its in just the walls and is in panned joist for the return.Also by code the heat duct is 1" down from the joist. The cold air is right to the joist. Now with the heat pipe off the fireplace into the cold air duct now makes it the heat duct Will it pass code. The unit looks good on the www.Id say put it in warm the air and let the furnace help take it upstairs with the blower and its returns there. You can just let the basement door open all the time. ED
 
  #20  
Old 11-20-03, 01:03 PM
bobbyo8
Visiting Guest
Posts: n/a
Good points.... I'm in Mass.

All my ducts are metal: hot and cold. They look identical, from teh registers to the furnace, all the same.

Aaaah, the hot air duct must be mounted 1" below joists? oooh, I don't think mine was built that way, I'm going to have to check on that tonight after I make a quick run to Home Cheapo.
 
  #21  
Old 11-20-03, 01:05 PM
bobbyo8
Visiting Guest
Posts: n/a
Oh, and maybe that blower is just to get the heat "out" of the furnace towards the registers, where it will "radiate" out of, insead of "Blow" out of?
 
  #22  
Old 11-20-03, 01:49 PM
Ed Imeduc's Avatar
Member
Join Date: Aug 2002
Location: Mountain Williams Missouri
Posts: 18,389
Lightbulb heat

Thats Home DE------pot or Slowes

Check code there . And yes the ducts heat and return are metal but is the cold air also up in the joist metal or behind a return grill is that all sheet metal? ED
 
Reply

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


Thread Tools
Search this Thread
Display Modes