Cape Cod insulation problem with ductwork

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  #1  
Old 12-28-09, 08:06 AM
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Location: Michigan
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Cape Cod insulation problem with ductwork

Our house is about 9 years old. It is 1 1/2 stories with 2 bedrooms on the second story and a large open playroom between them. The ductwork for the bedrooms runs through the attic crawl space in the back of the house. There doesn't seem to be much insulation around the ductwork and the crawl space area is cold in the winter. There is some insulation on the kneewall and floor of the crawlspace but not enough to keep the ducts warm. This causes the bedrooms to be cold and the ice to build up on that back roof from the heat loss.

Should we just wrap the ducts somehow, spray in insulation or some other method? our main concern is the heat-loss and icecicles on the back of the house.

on another note we are thinking of installing some radiant barrier on across the roof-boards to keep the hot air out in the summer. not sure this will do any good in the winter but since we'd be working in there now with the insulation figured we might as well do both.

Any suggestions would be greatly appreciated!
 
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  #2  
Old 12-28-09, 09:47 AM
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Location: New England
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When you insulate the side attics of a cape you have a couple of choices. Floor, Kneewall, Slope, Upper attic space, with ventilation running from eaves to upper attic. OR: The slope from eaves to upper attic, spaced for ventilation all the way. Since you have ducts in that attic space, insulating the entire slope would be an advantage. Michigan is a bit on the cold side , so I would go with as much insulation as I could afford. I would avoid fiberglass, unless it is protected from the air flow. Some combination of rigid and possible mineral wool (more dense) could get you up above R=30. One of the most important issues will be air sealing inside from outside.

Bud
 
  #3  
Old 12-28-09, 11:38 AM
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So when you insulate the slope does that mean you can't use the radiant barrier? will insulating the slope with insulation alone help with the heat in the summer?

when you say air sealing inside from outside are you meaning the attic crawl-space from the outside world? Does that mean closing off the soffit vent?!

I'm sure my husband would understand this better than me. I was trying to help him with some of the research. He's tempted to have some contractors come in and give some quotes of what they would advise. I think he is capable of handling the work himself if we were just sure of what the right way to do it is.

Thanks for all your help!
 
  #4  
Old 12-28-09, 12:00 PM
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Location: New England
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When you insulate the slopes you can still use a radiant barrier (RB), facing the conditioned space or facing the roof deck. Radiant barriers work both ways.

Insulation alone will still help in the summer.

Air sealing refers to preventing warm air from leaking into cold spaces, or cold air from leaking into warm conditioned spaces. If you choose to insulate the slopes, you should now treat those attic spaces as conditioned spaces, so they must be sealed off from the eaves, and attic above. Cold air should be able to enter at the eaves and flow up under the roof deck and exit through ridge vents or gable vents, taking excess heat with it.

Soffit vents remain part of the process.

A more radical approach is referred to as a "hot roof", where all venting is sealed off, and spray on or blown in or other insulation is applied directly to the bottom of the roof deck. Advantages of more insulation, and no worries about venting. Disadvantages, unknown long term effects on shingles and roof deck. Hidden leaks will remain hidden and result in perhaps more damage. Time will tell.

There is a lot you and hubby will be able to do and lots of help here on the forum.

Bud
 
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