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  1. #1
    Join Date
    Dec 2012
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    Question Insulating ductwork?

    My wife & I purchased our first "real" house after living in a manufactured home during all of our married life.
    The house is a small, ranch-style house on a concrete block foundation. We were told it was built in the '40's, but if so it's built suprisingly well.
    My question is about the ductwork for the central heat & air. We recently put in a new gas heater & it seemed that when it first kicks on, cold air comes out of the registers. It eventually warms up, but it's not real hot. I contacted the company we purchased it from & they came right over & checked it out. He told me that the registers weren't insulated & that was the reason I was feeling the cold air initially. He stated that they need to be foil wrapped at the joints & foil "bubble wrap" around the ductwork. He stated that fiberglass insulation wouldn't last long. He gave me a quote of "about $1000" to do the job & that it would take a good days work to complete. I called to get a second opinion & he told me the same thing except that he wanted to use the fiberglass & that it holds up well. He climbed into the crawlspace & checked everything & said the ductwork was in good condition. He gave me a quote of $1290.
    The house is about 32'L x 28"W. I looked at insulation at Home Depot...the foil "bubble wrap" type. If I figured right, the insulation & foil tape would run about $400-500. Is this a job I could do myself or should I leave it to a pro?
    Also, while the crawlspace does have plastic sheathing on the ground, there is no insulation between the floor joists. Should there be some type of insulation there?
    Thanks for any help.

  2. #2
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    Default Re: Insulating ductwork?

    Replacing ducts is not easy, mainly due to space restrictions, so it's hard for us to tell you whether you can do it or not.

    The bids you got are right on the money.

  3. #3
    Join Date
    Dec 2012
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    Default Re: Insulating ductwork?

    Quote Originally Posted by dj1 View Post
    Replacing ducts is not easy, mainly due to space restrictions, so it's hard for us to tell you whether you can do it or not.

    The bids you got are right on the money.
    I'm not wanting to replace the ducts, i'm wanting to insulate them by wrapping them with whatever they need to be wrapped with.
    I'm also needing to know if the floors need to be insulated underneath.

  4. #4
    Join Date
    Dec 2007
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    Tennessee
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    Default Re: Insulating ductwork?

    If you think you can do it, then I think you can do it. Its not rocket science, but crawling around on your hands and knees in a very confined space it is very unpleasant work that not a lot of people are willing to do. The fiberglass is durable and probably less expensive but is even more unpleasant to work with than the foil bubble wrap. You should consider the R values of each as part of your decision.

    Be sure to use a foil tape for sealing as "duct tape" will not hold up. As for insulating your floors, that depends on your climate and the foundation construction. In moderate climates, it really doesn't save any where near as much energy as people believe.

  5. #5
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    Default Re: Insulating ductwork?

    Actually, replacing ducts with insulated ones will be easier than wrapping existing ducts with insulation...

    Do this:
    Go under the house, crawl around and stay there for 5-10 minutes. Then tell us how it felt.

  6. #6
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    Dec 2012
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    Default Re: Insulating ductwork?

    Quote Originally Posted by dj1 View Post
    Actually, replacing ducts with insulated ones will be easier than wrapping existing ducts with insulation...

    Do this:
    Go under the house, crawl around and stay there for 5-10 minutes. Then tell us how it felt.
    The price difference for replacing the ductwork vs. insulating was $1700.
    I know i'm not going to like crawling around under the house, but i'm just trying to save some money. I was just hoping an "expert" here could tell me if it was something that had to be done by a professional.
    As far as the insulation underneath the floors, the house is sitting on a block foundation & there's plenty of venting. There's a moisture barrier on the ground under the house. I live in So. IL so it's not like i'm going to experience too harsh of a winter (knock on wood). I do know that the floors are awfully cold (& I don't plan on installing carpet) so I didn't know if some type of insulation underneath would help or not.

  7. #7
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    Default Re: Insulating ductwork?

    Wrapping existing ducts with insulation is something a homeowner can do himself. No lic required.

    My previous point was:
    Do you want to do it?
    Do you feel comfortable working in confined space under the house?
    Can you work under tough conditions, space, breathing, lighting, etc.?

    I guess the only way to find out is to get started, isn't it?

    Just make sure you have your fully charged cell phone with you.

  8. #8
    Join Date
    Dec 2012
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    Default Re: Insulating ductwork?

    Quote Originally Posted by dj1 View Post
    Wrapping existing ducts with insulation is something a homeowner can do himself. No lic required.

    My previous point was:
    Do you want to do it?
    Do you feel comfortable working in confined space under the house?
    Can you work under tough conditions, space, breathing, lighting, etc.?

    I guess the only way to find out is to get started, isn't it?

    Just make sure you have your fully charged cell phone with you.
    OK...fair enough.
    In answer to your previous point:
    Not really
    Not really
    Somewhat



    To me, $500 in savings is alot of money.
    I guess I need to know what's best to wrap them with next.

  9. #9
    Join Date
    Aug 2007
    Location
    Maryland
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    Default Re: Insulating ductwork?

    The joists should be insulated. The floor will be more comfortable. Building codes require it. Doesn't southern IL get kind of cold? When I hear IL I think Chicago and the midwest, even though Chicago is north I know.
    It is a job you can do if you want. It depends how much you want to save $700 or so.

  10. #10
    Join Date
    Dec 2007
    Location
    Tennessee
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    Default Re: Insulating ductwork?

    You misunderstood dj1. What he was talking about with the insulated ducts was flex ducts. They are a flexible duct with about 2" of fiberglass insulation around them. They are cheap and easy to install, but if mice or other critters get under your house, they will tear them up. You can see this stuff at any of the big box stores like Home depot and Lowes.

    You might be able to buy the flex duct for about the same price or even less than the insulation alone and since each section is 25 or 30 feet long, you only have to deal with the connection at the main trunk and at each vent. You will need the widest strapping they have for this though as narrow strapping tends to cut into it.

    If you do this, make sure that your foundation vents are secure and that the screens are damaged. You might want to cover them with hardware cloth to make sure the critters don't get under your house.

    If you have cold floors, you could start with closing your foundation vents. That will warm up the crawl space, especially if your present ducts have any leaks in them. Insulating the rim joist around the perimeter will do more for you than insulating between the joists. If you do decide to insulate between the joists, the vapor barrier goes up and you don't need a lot of insulation.

    Just like the walls and the attic, the warm air in the joist bays will rise to the top, but unlike the walls and attic, warm air rising is a good thing as it gets trapped against the floor boards. The air under the floor stratifies and insulates, you just need enough insulation to keep air movement to a minimum.

    I live just a little south of you, I have those automatic foundation vents that close when the temperature drops below 40F that I reinforced with hardware cloth. My rim joists are doubled 2x10's plus a 1x10 cedar trim board outside that so my perimeter has about an R-5 rating. My joists are not insulated and my floors are plenty warm. But I also have that flex duct and I know there are a couple of holes in it, I have to replace runs every 10 years or so, so my crawl space is a little warm.

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