attic vent

[JakeKohl]

Looks like all gable vent fan i see are for a full size house needing 600 square inches of intake air to work. I see they have a solar powered unit that only needs about what i can offer out of a gable vent, I may really not sure what my best route will be. Or i get a full size one and use basically a dimmer switch to slow the motor down but then i am sacrificing the life.

The specified sofit vents are just to get the rated air flow out of the fan. The fan will still work with fewer vents. The solar powered one recommends fewer vents because it's rated air flow is less. If you are trying to control the heat load in the space, more air flow is better. If you are trying to control moisture buildup any kind of air flow will probably be adequate.

 

[purevil115]

Ic. What about doing to mushroom vents low on the one side of the roof and on the other side high up by the peak put a fan powered mushroom unit so itll draw the heat upward.

 

[purevil115]

Anyone think this is a good plan?

 

[ilovevocs]

I didn't read the entire thread but if you have vented soffit and a power vent installing an intermediate roof vent will create a short circuit effect. Do not mix ventilation types as short circuiting will occur.

 

[purevil115]

i dont have soffits

 

[purevil115]

So after doing the research and asking around looks like my best bet is between gable vents powered or a mushroom style vent on roof itself. I can do mushroom vents very low on the one side and one powered mushroom highup on the other side of the roof this will give chimney effect up to powered unit. I can also get a motor dimmer to slow down fan if needed.

 

[purevil115]

What about ridge vents. How hard are these to install. I am thinking of a ridge vent at top and 2 box vents low on each side. since no soffits this will be next best thing.

 

[readhead]

I'll mention again that if you insulate under the roof you will get the insulation and as a bonus you will bring the furnace inside and if you store anything in the attic it won't melt or freeze. You won't have to cut anything. Think of it as a cathedral ceiling in a house. There is also a way to make this a cold roof and still insulate under the deck.

 

[tylernt]

I never recommend powered vents (unless you have some kind of flat roof where you can't get a chimney effect). A properly designed passive vent system works just as well, if not better, and has zero ongoing electricity costs. I would not want to add several dollars to my electric bill ever month... not to mention the fan will seize up after some number of years, and hopefully won't catch fire when it does (since you probably won't be there to see it).

Mushrooms near the eaves as intake, and a ridge vent for exhaust, would be ideal IMHO.

Readhead's idea isn't bad either. It's called a "hot roof" and while it can potentially degrade asphalt shingles, there's no issue with a metal roof.

 

[ilovevocs]

Insulating the roof would cause it to function like a compact roof assmbly seen in commercial applications. A dew point anaysis should be conducted to determine the need / placement of a vapor barrier before implimenting such a sulution to ensure that condensation doesnt become an issue. If the insulation is not sufficient warm moisture charged air will contact the roof substrait and condense creating mold and moisture issues during winter months, again this is assuming you live in a 4 season climate zone. Compact roof assmeblies in the absence of a vapor barrier are self drying during the summer months , however damage that occurs to the structure during winter months in cold climates as a result of condesation is irreversible.

Mark S. Graham NRCA's associate executive director of technical services has published countless articles on compact roof assmeblies and their functionality. I have included a link below to the NRCA's publication Professinoal Roofing, you can access current issues as well as their archives.

http://www.professionalroofing.net/

 

[maddawg1952]

Build a couppola and install a power vent in it.

 

[purevil115]

Ok after doing some shopping looks like mushrooms and ridge vent is the key. static so no electric and nothing to worry about after its done. The real question is with a ridge vent. I doubt i can match the shingles so should i just get a metal one that doesnt need shingled over. Im not worried about matching house. This is a detached garage so doesnt really matter to me. 2 box vents low on each side and a full ridge vent.