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Old 07-22-2013, 11:55 AM   #1
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Insulating air ducts in basement


What's the difference between using these items for insulating air ducts in my basement? Would 2,3,4 be useable as alternatives to 1?

1) http://www.homedepot.com/p/Master-Fl...0#.Ue1hWtLVDmc

2) http://www.homedepot.com/p/Reflectix...4100/202851855

3) http://www.homedepot.com/p/Reflectix...4100/202851863

4) http://www.homedepot.com/p/UltraTouc...1475/100656747

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Old 07-22-2013, 12:56 PM   #2
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Insulating air ducts in basement


The obvious answer is the main difference is price. As far as their use insulating existing ductwork, it appears that all of them will do that. I would go with what seems easiest to work with and what your wallet will tolerate.

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Old 07-22-2013, 01:03 PM   #3
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The obvious answer is the main difference is price. As far as their use insulating existing ductwork, it appears that all of them will do that. I would go with what seems easiest to work with and what your wallet will tolerate.
Cool, I just wanted to make sure that the products marked "air duct insulation" don't have some special feature that the other stuff don't have. If it is just marketing, I'd go with the cheaper product that gets the job done. Thanks!
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Old 07-22-2013, 01:28 PM   #4
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Insulating air ducts in basement


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What's the difference between using these items for insulating air ducts in my basement?
Is the basement currently a raw & unfinished space without heat or AC?
If so... do you have any plans to remodel down there so it will be finished with heat and AC?
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Old 07-22-2013, 03:31 PM   #5
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Insulating air ducts in basement


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Originally Posted by TarheelTerp View Post
Is the basement currently a raw & unfinished space without heat or AC?
If so... do you have any plans to remodel down there so it will be finished with heat and AC?
Currently, it is unfinished, without heat/AC/insulation.

Eventually, which can be a long time, it will be finished with heat/AC ...
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Old 07-22-2013, 04:10 PM   #6
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Insulating air ducts in basement


I would not waste my money on the insulated ducts, is my opinion. Find out if your unit will supply at least two supplies and at least habdle one, maybe two returns in the basement.

Make sure any leaks are sealed, rim & sill joist bays along tenperemiter are insulated (Does not matter if it is Batt or foam board), you will quickly find your heating & cooling bills go way down.

All you are doung right now, is just throwing money away.
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Old 07-22-2013, 05:39 PM   #7
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Insulating air ducts in basement


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Originally Posted by saimike View Post
What's the difference between using these items for insulating air ducts in my basement? Would 2,3,4 be useable as alternatives to 1?

1) http://www.homedepot.com/p/Master-Fl...0#.Ue1hWtLVDmc

2) http://www.homedepot.com/p/Reflectix...4100/202851855

3) http://www.homedepot.com/p/Reflectix...4100/202851863

4) http://www.homedepot.com/p/UltraTouc...1475/100656747

2 if double wrapped will be close to 1.
3 is only single reflective, so not quiet as good as 2.
4 is not an insulating product per say.
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Old 07-22-2013, 07:01 PM   #8
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Insulating air ducts in basement


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Make sure any leaks are sealed, rim & sill joist bays along tenperemiter are insulated (Does not matter if it is Batt or foam board), you will quickly find your heating & cooling bills go way down.
I agree with Greg. I took out the supply registers in the basement, sealed up the duct leaks, and all it got me last winter was colder floors in the non carpeted areas.
Now I'm bringing the basement up to code (sealing and insulating the sill) and beyond (insulating the exposed basement wall) and I'll put at least one of the registers back. (the other register was in a trunk that doesn't have any airflow to spare)

Last edited by taxmantoo; 07-22-2013 at 07:29 PM.
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Old 07-22-2013, 07:24 PM   #9
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Insulating air ducts in basement


taxmantoo, I just took the one duct that was in the floor of our Kitchen, due to it is going away once we are done remodeling, and placed that over the laundry area, also have a damper vent in the trunk on the opposite side for that end of the basement.

Have a return vent on the front of the house in the return duct, return vent on the back of the house on the back face, not the bottom like I did for the front.

My basement is only 825sqft, same as upstairs, but the unit was sized to serve both basement & main floor, when we had it installed.

It keeps both at a comfortable level, but during Winter, it gets around 58-62 down there, which I do not mind, upstairs stays around 68-69 depending on how cold it is outside (no insulation in the walls, but well sealed around windows, doors, outlets), so radiant cold & heat is not a problem, due to the air in the cavity actually helps to insulate some, and there is a radiant barrier under the siding, so that also helps.

Older homes are fun when it comes to bringing them up to better standards, so you are not wasting energy.

I personally do not know what happened with my last month's bill, but I have an idea of who caused it to go up more for electric & water (16 y/o son), same as my fuel bill for the Trailblazer that he is driving, when I come home from work, so he can use it to go to work.

Keep up on air sealing, insulating, watching use on electric, water heater, etc., and find a median point. Also how old are we talking for the hvac equipment?

When you do the ductwork, do it how it will be when you finish the basement, so you do not have to put money into redoing it all over again, when you go to finish the basement. You can use dampers to close off those extra supplies that you will not be using, same as returns, and that would help to still keep air upstairs. Now if you add in a 2 zone system, that basement is one, upstairs is another, and a way to also pull cooler air through from the basement into the system, to help cool upstairs, that helps.

BTW, what are you measuring for output and input temps at supplies & returns on your system currently? I get anywhere between 36-42 depending on how warm it is upstairs at that time (ie av system on for a hour or more, the amp and our plasma tv puts out some heat, so does the oven), but the running joke in our household, is that you can keep a six pack of beer cold in our supply if you wanted, due to it is that cold when running.

I basically had my system done to keep not only the house cool, but also keep electronics cool, so basically I have a system that would keep a server room cold enough, and keep up with demand, even though I have had some on here state that it is incorrectly installed, which it is not. It was designed on the a/c side for our use and demands that we place on it.
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Old 07-22-2013, 10:50 PM   #10
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Insulating air ducts in basement


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Originally Posted by taxmantoo

I agree with Greg. I took out the supply registers in the basement, sealed up the duct leaks, and all it got me last winter was colder floors in the non carpeted areas.
Now I'm bringing the basement up to code (sealing and insulating the sill) and beyond (insulating the exposed basement wall) and I'll put at least one of the registers back. (the other register was in a trunk that doesn't have any airflow to spare)
Code says (in my area at least) you need two supplies minimum in a basement, finished or unfinished.
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Old 07-23-2013, 11:59 AM   #11
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Insulating air ducts in basement


I haven't even thought about heating the basement, so this is all going over my head. Just out of curiosity, how is insulating the exposed air ducts in the basement now a waste of money? I see a lot of insulated air ducts, exposed or not, hence my plans to insulate.
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Old 07-23-2013, 12:33 PM   #12
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Insulating air ducts in basement


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Just out of curiosity, how is insulating the exposed air ducts in the basement now a waste of money?
Underground space does not lose heat as rapidly as above ground space.

If you insulate your ductwork from the basement and treat the basement as unconditioned space, you will lose "x" BTU/hr from your house to the basement through the floors even if you reduce duct losses to zero.

If you treat the basement as conditioned space (but still colder than the house), you will lose "y" BTU/hr from the basement, and you will lose "z" BTU/hr from the house to the basement, z being less than x. So it costs you y-z to heat the basement, but you saved x-z from your cost to heat the house because there's less heat loss through the floor.

So your net cost to heat the basement is y-x, y being the rate at which the heated basement loses heat to the outdoors, and x being the rate at which the house used to lose heat to the previously unheated basement.
In my case, y-x turned out to be a lot smaller than I guessed it might be, and I could save far more money by reducing heat loss from the basement than I could by reducing heat loss from the ductwork into the basement, and as a bonus I get a warmer dryer basement and a warmer kitchen and bathroom because the tile floors aren't so cold.

Last edited by taxmantoo; 07-23-2013 at 12:35 PM.
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Old 07-23-2013, 12:53 PM   #13
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Insulating air ducts in basement


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Underground space does not lose heat as rapidly as above ground space.

If you insulate your ductwork from the basement and treat the basement as unconditioned space, you will lose "x" BTU/hr from your house to the basement through the floors even if you reduce duct losses to zero.

If you treat the basement as conditioned space (but still colder than the house), you will lose "y" BTU/hr from the basement, and you will lose "z" BTU/hr from the house to the basement, z being less than x. So it costs you y-z to heat the basement, but you saved x-z from your cost to heat the house because there's less heat loss through the floor.

So your net cost to heat the basement is y-x, y being the rate at which the heated basement loses heat to the outdoors, and x being the rate at which the house used to lose heat to the previously unheated basement.
In my case, y-x turned out to be a lot smaller than I guessed it might be, and I could save far more money by reducing heat loss from the basement than I could by reducing heat loss from the ductwork into the basement, and as a bonus I get a warmer dryer basement and a warmer kitchen and bathroom because the tile floors aren't so cold.
If I understand this correctly, sounds like its a matter of framing the question.

Why is z<x? I presume the basement remains as is for every situation in your post, hence my puzzlement.
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Old 07-23-2013, 01:40 PM   #14
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Insulating air ducts in basement


It will really depend if you have a walkout, or how much of the foundationd sticks up above the ground, will be te factor.

Do the supplies and returns in te basement, you will find out that not only will the air smell fresher when you go down there, but main floor will feel warmer.

Keep airsealing the basemt and uptairs for any leaks, insulate the basement joist and sill bay, then later on you can do foam board over the foundation, then frame in your walls, go from there.

Also, again how large square footage is the basement and upstairs, how many tons is your a/c or heat pump, how many btu is your furnace?
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Old 07-23-2013, 03:43 PM   #15
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Why is z<x? I presume the basement remains as is for every situation in your post, hence my puzzlement.
Z being the heat loss from the ground floor living area to the semi conditioned basement and X being the heat loss from the ground floor to the unconditioned basement, right?

If you heat the basement 5 warmer than it was before, the heat loss through the floor will be less because the difference in temperature is 5 less.

If you raise the basement temp from 50 to 60 when the house is at 70, Z will be about 1/2 X.

You will probably have to do some insulating, at least in the areas above ground. 8" hollow block is about R2, 1.5" pine sill plate is even less. Modern code here in Michigan is for R11 in the sill/joist area IIRC. My 1976 house had no insulation there. I put R6.5 foil faced foam on the outside of the exposed block, but it's fragile and now I wonder if I need to put lattice or something over the foam to protect it.


Last edited by taxmantoo; 07-23-2013 at 03:47 PM.
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