Roof vent

[Walter Cohen]

I have a small unfinished walk-in attic in my house in NY. It shares a wall with an upstairs bedroom as well as part of the hallway. There is a small double-hung wooden window at the far end of the attic space that I keep partly open for ventilation purposes. The walls and ceiling (which is the underside of the roof) had foil-faced insulation put in between the joists by the previous owner (for whatever reason). I have black roofing tiles on and the inside temperature during the summer months is quite high. Sometimes I even put a dual fan in the attic window for a few hours (on a thermostst) to exhaust the inside air.

I was thinking of maybe putting in a roof vent or even one of those turbine fans on the roof.

Any thougths?

Thanks, Walter

[jimmy]

Put up a turbine. A decent 12" one with ball bearings will do a great job.

[Tony Hwang]

If you want to do it properly just installing turbine may not be enough. If you wnat to exhaust, you have to inhale. Simple law of physics.

[CJT]

If by turbine you mean those gadgets that spin in the wind, I disagree; they seem pretty useless to me.

[Robert Gammon]

They get installed on LOTS of homes along the Gulf Coast for that very reason, to help pull air OUT of a HOT attic. For Attics, ridge and soffit vents seem to be a better solution to that problem,

In NY, you will need a way to wrap the turbine in the winter, and/or put up a interior barrier to keep the cold winds out.

[Robert Gammon]

They get installed on LOTS of homes along the Gulf Coast for that very reason, to help pull air OUT of a HOT attic. For Attics, ridge and soffit vents seem to be a better solution to that problem,

In NY, you will need a way to wrap the turbine in the winter, and/or put up a interior barrier to keep the cold winds out.

[HeyBub]

"Depending upon the diameter of the vents and the wind speed outdoors, the turbines can expel vast quantities of humid air...

"A small 12 inch diameter turbine vent with a constant wind speed of 5 miles per hour (mph) can remove 347 cubic feet of air per minute (cfm) from the attic space. A single 14 inch diameter turbine vent that is subjected to 15 mph winds can expel up to 1,342 cfm of air!

"If the winds are still, the vents still allow air to drift up and out of the attic space..."

A roof turbine operates at no cost, requires zero maintenance, and lasts for many, many years.

In order to exhaust the air, there has to be some way for fresh air to enter. You can't have too many soffit vents.

A whole-house attic fan needs to exhaust 4000 cu ft / minute (for a 1500 sq ft) house for most efficient operation. A mere THREE 14" turbines would be sufficient to air out a whole house (at an ambient wind speed of 15mph). Obviously, then, turbines are a cheap, easy way to prevent the attic from turning into an oven.

[jimmy]

The OP says he has an open window in the room. That will do quite nicely.

[Walter Cohen]

Thanks for the suggestions!

Walter

[rob]

Well yes and no. As another poster said, for winter, you will have to have a way to cover it or cut off the circulation so the cold air doesn't get in.

I've had some (turbines) on my Gulf Coast homes and I can't say they are that great. I suppose they helped to some degree but my attics still got hot (in every home that had them). Now I see more new home construction using ridge vents with soffit vents instead of the turbines.

Just in case, if his neighborhood has a home owner's association, he might have to check to see if the deed restrictions allow turbines. It happened to me once where the restriction allowed it as long as it was not in view from the front. I don't believe this is common tho.

[jimmy]

LOL! Nonsense. We have 35 below winters and I have never seen a turbine covered. If it's venting an unheated space blocking it is down right dumb. It still removes moisture from the space during the winter.

[rob]

Funny but I HAVE seen them covered on the outside and it's possible that even those not covered might have had some covering / blockage from inside (dunno because I can't see the attic of course). I agree that if you don't care about cold air getting inside, then no need to do anything. And usually moisture isn't a problem in winter for unheated areas.

[jimmy]

You can rot the roof off a house if the attic isn't vented in winter. I've seen a half inch of ice on the underside of roofs where the soffit vents were blocked.

[Moisés Nacio]

You are misinformed about moisture not being a problem in the winter. When heat escapes from the thermal envelope into an attic, it must exit, or you get condensation in the attic. It is simple physics of when cold meets warm. Take for example a glass of ice cold liquid, sitting on a coffee table at room temperature, it's not leaking fluid from the glass, but sweats (condensation).

I have seen instances where homes had power vents and that's all. The problem is, they don't come on in the winter. This caused thousands of dollars worth of damage to the roof deck, insulation & wallboard.

Never block venting during the winter, unless you want condensation, rot, and mildew.

This link will provide you a better explanation on how a house breathes.

[CJT]

That's how they get sold, but I've never seen any indication that they work.

For Attics, ridge and

[CJT]

I have no idea who you're quoting -- perhaps somebody who sells 'em?

[HeyBub]

"Ventilating attic spaces in winter months is often more important than venting them in summer.

"Water vapor from the inside of a home can drift up and into an attic space. If this water vapor is not quickly exhausted to the exterior atmosphere, it can often condense upon the cold roof framing members and the underside of the roof sheathing.

"It can get so bad that water can drip from the underside of the roof and when the temperature gets low enough, frost can actually form up inside the attic. Moisture conditions such as this can lead to wood rot and mold growth..."

My house has both: A ridge vent AND four 14" turbines (3000 sq ft).

[rob]

I agree and I should have said it differently.

I was thinking that usually you wouldn't bother to cover up the venting unless you had a heated (finished) attic so moisture shouldn't come about unless the venting was inadequate in either case.

[rob]

Agreed. See my reply given in this thread a minute or so ago.

[mm]

For the record, I live in the tiniest valley. The stream is only 1 or

2 feet deep and only 6 feet across most of the time, and the valley is only a half mile to a mile wide and 30 feet deep, I think, so it is pretty shallow. There are big trees on two sides of me.

And I get almost no breeze most of the time.

Before relying on wind to turn the turbine, check if there is wind.

If the turbine costs so much money, wind may cost extra.