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Is attic venting necessary in St. Louis, Missouri?

iL4A4Er2ak | Posted in General Questions on

The house is approx. 15 years old and additional insulation was added. The Insulation Contractor used Owens Corning R-13 faced batt insualation and loose blown in insulation.

The picture I have sent you represents the owner’s house. There is a gable vent in the open attic area and a ridge vent in the knee wall living space area. There is also soffit vent through out the house exterior. In the knee wall section of the house the insulation contractor used your product and installed it in between the roof trusses and put it tight against the roof sheating with no baffles. They also isolated the knee wall attic area from the open attic area with insulation.

My concern is that since there is no ventilation in the knee wall section of the attic that we have a potential moisture/mold problem. To recap the situation, the knee wall is insulated with R-13 faced batt insulation (existing), in between the floor joists is insulated with loose blown insulation(added additional), and they installed new R-13 faced batt insulation in between the roof trusses, tight against the roof sheating (NEW).

The attic is also unconditioned. I have talked to a Licensed Architect and respected insulation contractors and they all said we have a potential problem and money was wasted on the insulation added in between the roof trusses.

Can you please comment on this situation? The Insulation Contractor said he does this type of insulation practice all the time.

I was unable to print the picture, can you please go to the energy star site listed and refer to 1.2 Locating Air Leaks for the picture reference.

Thank you for your time,

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  1. user-741168 | | #1

    Is attic venting necessary? There are two answers to the question.

    The correct answer is no. There are hundreds of square miles of roofs out there with no venting and they have no more than the usual problems, most of which are associated with leakage. It’s possible to screw up a roof that’s not vented, but any tradesperson worth their salt can deliver an unvented roof system that will work just fine. Most codes have been changed to permit these roofs.

    The old official answer is yes, ya gotta vent The argument goes something like this: if you don’t vent you’ll get moisture and if you get moisture you’ll get mold and if you get mold you might just get that black toxic mold that causes babies in their sleep to strangle on their own blood.

    You can tell a lot about a person depending on their attitude toward venting. It takes a little of the contrarian, of the outlaw, to say, sure, let’s go with unvented. And builders usually have that streak in their blood. I’ve never heard of an outlaw architect.

  2. GBA Editor
    Martin Holladay | | #2

    There are several references in your question that are unclear -- especially the reference to "your product" (my product? GBA's product? what is it?).

    However, it seems that you have two questions:

    Question 1. If I have insulation on the attic floor, does it make any sense to also put insulation between the rafters?

    Answer 1. No.

    Question 2. If I want to install an insulated unvented roof assembly, can I install fiberglass batts directly against the roof sheathing?

    Answer 2: No.

    For more information on unvented roofs, you may want to study code requirements for conditioned attics (see section R806.4 of the 2006 IRC). You may also be interested in the information in one of my blogs, Creating a Conditioned Attic.

  3. iL4A4Er2ak | | #3

    Martin and Bill,

    Thank you for the responses.
    When I referenced "your product" I meant the Owens Corning R-13 faced insulation.
    Thanks again.

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