Latest Discussions : Basement & Foundation


12:42PM | 03/13/01
Member Since: 03/12/01
40 lifetime posts
This is similar to another post.

Our home is over 50 years old. We have noticed there is a moisture problem in the attic. We also have water in our crawlspace.

The attic has 1/2 blown in insulation and 1/2 roll insulation. We put plywood done on the side with roll insulation, but put spacers between the plywood floor and joists to allow air movement. The bottom of the boards are moldy and the insulation is wet. And insulation not covered is also wet.

In the winter, the roof nails are frosty.

We rerouted our plastic bathroom vents to reduce pipe runs in our attic. The west and east side of the house has open louvers for air flow. There is a power fan in the middle which runs all the time. There are no soffit vents on the house. There are a couple of vents along the middle of the roof.

Once we get the crawlspace done this summer, we want to put in new insulation in the attic in the fall.
Any suggestions to what may be causing the moisture and what can we do reducing the moisture in the attic?

Thanks in advance.


09:39AM | 03/14/01
Member Since: 01/28/01
171 lifetime posts
If the insulation is wet, you have a very serious problem. Do you have a vapor barrier under the insulation? It is necessary to keep house moisture from migrating into the attic when the attic is cool or cold. Are you sure the vent runs are sealed and run all the way to an exterior vent? Given the wide spread nature of the moisture and the "wet" feeling, I lean towards needing much more ventilation at the level of the insulation and a search for roof leaks. Without seeing your attic, it sounds like all the air movement is up at the roof peak. You need soffit vents so air circulates throughout the attic. When you reinsulate, check the floor of the attic for leaks from the rooms below. Check the seal of any access hatches.

Another, though remote, possiblity is past roof leaks since repaired. The soaked insulation was never replaced and is very slowly drying.


09:44AM | 03/19/01
Member Since: 03/12/01
40 lifetime posts
The insulation seems to be damp on the top, primarily under the plywood boards.
The insulation sits ontop of the ceiling and has no paper backing.

I do have a moisture problem in the crawlspace, which are working on fixing this spring with a sump system.

We are also going to add some more vents below the louver vents on the west/east end of the house (this should be inline with your suggestion, too). There is no easy way to add soffit vents because of how the house was made.

The area in the attic is approximately 60 ft by 30 ft.

The bathroom vents are sealed and all run to the roof and exit out the roof.

I appreciate your time and if you have other suggestions on how to move more air around, please let me know.

Also - if we get the crawlspace dried out this spring, and the insulation finally dries out, do we need to replace the insulation or just put new on top?

Thanks again.


02:14AM | 03/20/01
Member Since: 01/28/01
171 lifetime posts
The insulation may be damp on top if the moisture migrated from the house to the attic and then condensed when it reached the cold attic air.

I would a) throw out the old insulation, since it may be moldy, etc. and lost its insulating structure.
b) lay one layer of fiberglass insulation, backing down or blown in with a layer of plastic film for a vapor barrier.
c) if using fiberglass, add a second layer across the first layer to cover gaps.

Others with experience with damp insulation may have other advise. You definitely need the vapor barrier.


03:58AM | 03/20/01
Member Since: 03/12/01
40 lifetime posts
Thanks for the info on the insulation.
I'd like to use the roll kind of insulation. Part of the attic has plywood floor. We used spacers to provide some air movement between the floor and insulation. I've heard I need 18inch in the attic. How do you get that much, when there is 6-8 inches between the insulation and plywood?

To get the vapor barrier, I need to place the insulation with the paper backing against the top of the ceiling?

What R-factor do I need?

I appreciate your assistance!


02:14AM | 03/21/01
Member Since: 01/28/01
171 lifetime posts
For figuring what you should have go to:
(all one line without any spaces)

Insulation levels are based on age of house, type of heat and zip code. My new house in West Virginia calls for R-49 in the ceiling.

I don't know other materials but fiberglass batts are R-3ish per inch of thickness. I have a layer of kraft faced R-30 (10 inch) layed along the joists, face down against the ceiling. On top I have unfaced R-19 (6 inch) layed across the joists to close gaps in the first layer.

Other, higher R materials would need thinner layers. Just make sure you have a vapor barrier and you close gaps as much as possible.


02:17AM | 03/21/01
Member Since: 01/28/01
171 lifetime posts
The website in my last post didn't display quite right. The last part should be:

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