2nd judgement call: floor insulation and ductwork

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  #1  
Old 04-07-07, 08:16 AM
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2nd judgement call: floor insulation and ductwork

Ok, rd 2:

I feel silly for even asking, but I should make plans to add insulation under the floor of my 1-story house with a crawlspace, right? (small house in NC built in 1956 and has none right now).

I read about not wanting to insulate too much b/c I'd miss out on the benefits of the natural cooling in the summer, but I don't know if that really applies to North Carolina summers (hot, humid, etc).

IMPORTANT: I'm going to have all of my ductwork replaced soon. If I am going to add insulation under my first floor (6" joists, FYI), should I add insulation first and then get the ductwork guys out there or vice versa?

-Chris
 
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  #2  
Old 04-07-07, 08:34 AM
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Wink

You need the insulation on the walls there and a R 19 up in the joist space just on the sill plate . All around the home. Seal all vents. Put a 6 mil poly down on the ground over lap it 2 ft and tape all seams. No insulation in or on the heat ducts . Put 2 small registers in the duct to let air out and one small return down there.

Go to http://aboutsavingheat.com/crawlspace.html

This way the crawl space works as a heat sink for the home
 
  #3  
Old 04-07-07, 10:05 AM
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Wow, that's wild!!! I love the logic there! I didn't realize that the plastic was more than just something that kept me from getting dirty and a nominal vapor barrier.

I'm obviuosly not up to speed on the whole thing though, so:

First question: All houses with crawlspaces around here have approx 6" by 12" openings for those plastic-framed, screened vents. Doing what that link shows would cover those. Is 'that' (aka, the reason for those vents) taken care of by the fact that I'd have two registers and a small return down there?


Second question: If I follow this, then does that mean:

-no floor insulation needed
-don't need insulated, flexible duct (do they even make non-insulated flexible duct?)

Third question: I assume this doesn't interfere or compromise the cooling process for the summers?

Fourth question: If I told you I had a gas furnace under the house, would that change this recomendation (b/c I'm sealing off the outside air from circulating under the house) and on the same line is there are significant risk for gases rising from the earth getting trapped in my crawlspace and accumulating to bad levels (a process that wouldn't happen if I left my crawlspace vented as it is now)

Final set of questions: Is this fix a good candidate for a DIY job? Can I find that wall insulating material easily? I can see how to install along the walls where the joist is parallel with the brick wall, but for the walls where the wall and joists are perpendicular, is there an easy solution (like, pre-cut notches for the joists along the top edge)?

Thanks so much! I'm kind of childishly excited about this solution!
 

Last edited by Chrisatunc; 04-07-07 at 10:22 AM.
  #4  
Old 04-10-07, 09:43 AM
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Ed Imeduc, just checking to see if you shed some light on my questions about what you proposed.

Thanks!

-Chris
 
  #5  
Old 04-10-07, 01:48 PM
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We use all just sheet metal pipe and duct in the crawl works a lot better. better Cfm in the pipe not the drag of the flex pipe.There is a glue you can use to hole the insulation to the walls. If you dont have a 80%or 90% furnace you do need a make up air pipe to it is all .
 
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Old 04-11-07, 09:28 AM
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Gotcha.

So -

What about the foundation vents?

Does that mean that no floor insulation is needed?

I assume this insulation process doesn't interfere or compromise the cooling process for the summers?

The gas furnace is a 90+ furnace and has an air pipe going through the wall to the exteriorr. Not sure if that's the make up air pipe you're referring to or not.

Can I find that wall insulating material easily? I can see how to install along the walls where the joist is parallel with the brick wall, but for the walls where the wall and joists are perpendicular, is there an easy solution (like, pre-cut notches for the joists along the top edge)?

Thanks,

Chris
 
  #7  
Old 04-11-07, 11:14 AM
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A lot use the 2 or 3" polystyrene on the walls They have a glue for it. A R 19 in the joist space up on the sill plate all around the home .Paper to the crawl No vents at all close them and seal them up. You dont want that warm wet air comeing in on the cool ground there. That just makes water. No insulation in the joists

Did you go to http://aboutsavingheat.com/crawlspace.html

Dont forget 2 small registers in the supply duct and a small one in the return duct. Stay with steel duct and no insulated duct down there. it will give you a better job and the air can move better. Been doing them like this for over 30 years. This way the whole crawl space works as a heat sink for cooling and for heat.

significant risk for gases rising from the earth getting trapped in my crawlspace and accumulating to bad levels (a process that wouldn't happen if I left my crawlspace vented as it is now)
Yes it would.. Now if you think you have the gas in the ground. Some homes have like put just a pvc pipe with a fan in it that is sealed to a hole in the 6 mil poly and vent to the out side of the home . If you think you have Radon gas there Id check it out for sure and see if so or not t
 
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