[11thHourZero]

I am converting part of my attic into a rec room. I am sure many people run into the same pradicament that I am in. What the heck do I do with the gable vent. My roof is designed with continuous soffit vents, static roof louvers (close to the ridge on the aft side of the roof), and two gable vents on either side of the house. In an ideal situation, I would like to replace the gable vent with a window. If I do this, would the other gable vent, along the louvers, be adequate exhaust? Also, I am going to use channeling to go under the insulation along the roof so as not to plug the airflow.

If I can't replace the gable vent, I will start my ceiling below it. Does anyone have a clue what I should do to keep the dang thing from leaking all over my new ceiling? When it rains hard and with the right wind directing the gable vent is useless in stopping rain.

Thanks!

Oh ya, I am located in middle TN, if that gives you an idea of climate.

 

[kevinmcl]

I would:

a) close off that gable vent

b) install a ridge vent

You are reducing the volume of the attic (by bringing some of its volume inside the house envelope), but you are not reducing the roof area that gets heated by the sun. Now there will be even less opportunity for air to get from soffits to high-roof exit vents.

Are you going to insulate around the new room(s)?
Be sure to leave space between each pair of rafters for air to get from eaves to ridge.
Having a properly baffled ridge vent is the best passive solution. You won't have one side of your roof unvented. You won't leave alternate rafter pairs unvented (as you would if you installed only a mushroom vent in every second rafter channel... and you weren't even planning to put in that many... were you?).

The combination of full soffit venting and a full ridge vent (with no obstruction between the rafters) will give a great result, look better, and need no maintenance or electricity.

Some folks sidestep potential venting problems with storey-and-a-half houses and with cathedral ceilings by running two or three continuous lengths of central-vac pipe from soffit to ridge-vent between each pair of rafters (under both slopes of the roof). This is not as good as a completely open channel between each two rafters, but it's a dependable air-flow channel and allows them to be less careful where the insulation gets stuffed, or sprayed. The "air pipes" go between the insulation and the roof deck. That's another situation where a ridge vent is, by far, the better exhaust vent solution.

 

[orson]

I'm not sure if I'm looking at the picture right but why do I see one collar tie left in that attic? Did you remove them?

The collar ties on a stick framed roof are a structural element of the roof framing, you can't just remove them without considering how you're affecting the roof framing and altering the overall framing design of the house to compensate for the removed collar ties.

 

[11thHourZero]

I'm not sure if I'm looking at the picture right but why do I see one collar tie left in that attic? Did you remove them?

The collar ties on a stick framed roof are a structural element of the roof framing, you can't just remove them without considering how you're affecting the roof framing and altering the overall framing design of the house to compensate for the removed collar ties.

Orson,

Thanks for your concern, but I haven't removed any of the collar ties. You must not have been looking at the picture right. The lighting is way off on the picture, so maybe you couldn't see them. They are all still there (at least the ones that were there when I started). I have given it much thought and I intend on incorporating them into my new space with encasing. Thanks again for your reply to my question.

Jordan

 

[Gary in WA]

Does your local Building Department accept unvented roofs? You'll need a permit for this attic conversion anyway....
http://www.buildingscience.com/documents/digests/bsd-149-unvented-roof-assemblies-for-all-climates

The vac ducting is worthless for removing hot, humid attic air unless leaving an open gap between them as required with baffles;
http://www.adoproducts.com/duro.html

Check with them on the collar ties as well; http://www.finehomebuilding.com/how-to/qa/removing-collar-ties.aspx
Remember to air seal first, install Tyvek on attic side of knee wall, insulation block under k.w., insulate the access doors, ADA with the drywall, etc......

Gary

 

[kevinmcl]

Durovent with insulation...

Very true about the permit. Getting it will tell you what you need to do to get the space up to code.

Not getting it will be problematic when it comes time to sell.

The Durovent (or any similar product) is great when there's space to insulate.

I don't see where he's going to have that space.

The knee wall is not inset from the rafters - I think he's going for maximum possible living space at the expense of the insulation (judging by the picture); that's going to be one hot room every summer - so there's only the width of each rafter for both insulation and some kind of air channel. In a space that small, about the only way to get decent R-value is spray-foam. Durovent will collapse when foam expands against it.

If he insulates the knee walls and the top ceiling of the room, that leaves the slanted part of the ceiling (each side), and the junction/corner where kneewall meets rafters with little or no insulation. Last I heard, TN was warmer than where I live (Ottawa, Canada) and _my_ attic is currently 140+ Fahrenheit, so the original poster (a thousand miles south) must have a _really_ toasty attic room there. My house is a loft bungalow, so the loft is a big dormer kinda dropped into, and poking out of one slope of the overall gable roof. On top of the box that is the loft dormer, I've got at least three feet of blown-in fiberglass, and some extra batts around the walls (inside the attic). The insulation helps, but what's going to help a lot more is the ridge vent I'm getting in a few weeks.

I'd go for slightly less living space and bring both the knee wall and cathedral at least six inches inward from the rafters so he has enough gap to insulate well and still leave plenty of room for airflow up between those rafters. If he does that, the Durovent (or equivalent) would work.

- kevin