Roof Ridge Vents / Insight on this?

[sosoe]

Ok good to know..
Ill double check today and see how its vented and if the front/back is also vented as the side. If so, I just might do the ridge vent and add some more insulation myself, since I want to add some to the top of the garage.

[lowfast]

Ideally you would have at least as much area of intake as venting, so figure out the square feet of each and compare. Does not really matter too much where the intake is located as long as it is lower than the vent. Of course evenly distributed along the eves/soffit would be ideal to get the best flow from low to high and probably would move the most air.

[black2002ls]

It is a combination of simple physics and the bernoulli principle. Hot air is less dense than cold air, meaning it weighs less. So the cold air falls below the hot air forcing it to rise to the top of the attic. So, the cooler air coming in through the soffit vents is forcing the warmer air up to the top of the attic and out of the vents at the upper portion of the attic. A venturi effect may also be noticed as the pressure difference between the outside air and the air in the attic can increase the velocity at which the air moves through the soffit vents/perforations. In this type of situation, that velocity would move the cooler air up the inside of the roof decking and could have a cooling effect helping to reduce overall temperatures.

In the case of ridge venting, if wind is moving perpendicular to the vent, it would cause a bernoulli effect, pulling the warmer air out of the ridge vent due to the pressure differential created by the wind.

This is my best attempt at a Strychnine type explanation. If he were around, he would probably point out the areas where I am completely incorrect. It's been a few years since I've had any real physics exposure...

[black2002ls]

Ideally you would have at least as much area of intake as venting, so figure out the square feet of each and compare. Does not really matter too much where the intake is located as long as it is lower than the vent. Of course evenly distributed along the eves/soffit would be ideal to get the best flow from low to high and probably would move the most air.

You would want intake to be more than venting. I think 3:1 is the preferred maybe.

[lowfast]

You would want intake to be more than venting. I think 3:1 is the preferred maybe.

Sounds good to me.

[juiceweezl]

It is a combination of simple physics and the bernoulli principle. Hot air is less dense than cold air, meaning it weighs less. So the cold air falls below the hot air forcing it to rise to the top of the attic. So, the cooler air coming in through the soffit vents is forcing the warmer air up to the top of the attic and out of the vents at the upper portion of the attic. A venturi effect may also be noticed as the pressure difference between the outside air and the air in the attic can increase the velocity at which the air moves through the soffit vents/perforations. In this type of situation, that velocity would move the cooler air up the inside of the roof decking and could have a cooling effect helping to reduce overall temperatures.

In the case of ridge venting, if wind is moving perpendicular to the vent, it would cause a bernoulli effect, pulling the warmer air out of the ridge vent due to the pressure differential created by the wind.

This is my best attempt at a Strychnine type explanation. If he were around, he would probably point out the areas where I am completely incorrect. It's been a few years since I've had any real physics exposure...

LOL I was wondering if someone would mention Matt. Nicely played.

You would want intake to be more than venting. I think 3:1 is the preferred maybe.

Yes. This for sure.

On a related note, does anyone know someone that does sprayed in insulation? I need to do something upstairs above the boys' rooms.

[Chuck_Finley]

This actually made my head hurt. "You have to hope the hot air decides to rise". Didn't pay attention in science class much?

As previously stated. You need to have enough "makeup air" from the soffits. My old house had the ridge vent and it worked great.

No 2 houses are the same. Assuming you even get enough heat rising out of the vent, are you getting sufficient volumetric airflow to actually keep the attic cool?

[black2002ls]

LOL I was wondering if someone would mention Matt. Nicely played.


Yes. This for sure.

On a related note, does anyone know someone that does sprayed in insulation? I need to do something upstairs above the boys' rooms.

I can give you a contact with our Vendor, that is the best I can do. We use garland insulating

[TexasPyro]

I had ridge vents installed back in 2012 when I got a new roof. My house is a POS Drees 1400' house with 3 small ridges. I fucking hated them, my attic temp in the summer would reach north of 160 degrees. My house with a brand new 17 seer A/C wouldn't cool below 80 degrees. I suspected that I didn't have enough soffit vents, checked one day, I have 18, more than enough. I gave in and put an electric fan up there, went with a standard cheap fan as a proof of concept before I dropped the $600 on a solar unit. The difference was nearly instant, my attic now hovers right around 10 degrees above ambient.

[mustang1200]

Sealed attics or give me death.

[lowfast]

I agree, sealed attic is best, but in a retrofit situation this is not easy or many times cost effective.

We are going with sealed attic on our new build. Never made sense to me to run duct work through a non-insulated space.

[mstng86]

It is a combination of simple physics and the bernoulli principle. Hot air is less dense than cold air, meaning it weighs less. So the cold air falls below the hot air forcing it to rise to the top of the attic. So, the cooler air coming in through the soffit vents is forcing the warmer air up to the top of the attic and out of the vents at the upper portion of the attic. A venturi effect may also be noticed as the pressure difference between the outside air and the air in the attic can increase the velocity at which the air moves through the soffit vents/perforations. In this type of situation, that velocity would move the cooler air up the inside of the roof decking and could have a cooling effect helping to reduce overall temperatures.

In the case of ridge venting, if wind is moving perpendicular to the vent, it would cause a bernoulli effect, pulling the warmer air out of the ridge vent due to the pressure differential created by the wind.

This is my best attempt at a Strychnine type explanation. If he were around, he would probably point out the areas where I am completely incorrect. It's been a few years since I've had any real physics exposure...

I wonder if you get some moisture in the attic, it can create a nice little thunderstorm.

[GhostTX]

Purpose of venting is to keep your attic moisture low. Yes, you want to keep it as close to ambient as possible, but you don't want to seal it.

http://energysmartohio.com/plan-your-job/attic-ventilation

[8mpg]

I had ridge vents installed back in 2012 when I got a new roof. My house is a POS Drees 1400' house with 3 small ridges. I fucking hated them, my attic temp in the summer would reach north of 160 degrees. My house with a brand new 17 seer A/C wouldn't cool below 80 degrees. I suspected that I didn't have enough soffit vents, checked one day, I have 18, more than enough. I gave in and put an electric fan up there, went with a standard cheap fan as a proof of concept before I dropped the $600 on a solar unit. The difference was nearly instant, my attic now hovers right around 10 degrees above ambient.

You sure thats really enough soffit vents? I have no clue on the calculations. Lots of houses these days are going with continuous soffit vents.

[sosoe]

I noticed yesterday when I was up there that, I had these baffles in my attic, and now I understand why. Air passage from the soffit vents across the side of the whole house.

http://ths.gardenweb.com/discussions/2594450/what-does-adding-baffles-for-an-attic-room-mean