Ridge vent vs Gable vents - Attic exhaust help

thatguy · Mar 20, 2010

In our house we have an unfinished walk up 2nd story/'attic' (that could be finished at some point - the main floor ceiling/attic floor is insulated as an exterior wall).. We have a ridge vent and soffit vents all around the house (see pic below). I posted a question a while back about installing radiant barrier in the attic against the underside of the roof - so this may seem familiar..

Background info
Our attic seemed to get VERY hot in the summer (120 degrees due to a large roof, black shingles) so I added a electric gable exhaust fan on one side to try to get more air flow.. The gable ends seemed to me to have too much restriction for the fan to blow out (air pretty much blew down the wall instead of outside)..

I had a vinyl siding guy stop by today to give me a price for replacing the gable vents with something bigger/less restriction (possibly auto open/closing)..

Short story long - Here are my questions:

1) He said that since we have soffit vents and a ridge vents, the gable fan is disrupting the 'normal' air flow (in at the soffit out at the ridge).. Does that seem correct?

2) As you can see in the pic on we have the same 'hip' type roof all around the house. BUT when facing the house there are no open spaces in the attic walls for the soffit vents on the right/left side of the house to flow into the attic. (If you notice the side windows in the pic - the bottom of the window is waist high when in the attic) The plywood blocks off access to the side hip roof. He suggested possibly drilling some air holes in the plywood so that the soffit vents have place to vent. Does that make sense?

3) The vinyl siding guy thought that the ridge vent was undersized and could be replaced by a roofer.. our builders were meticulous in EVERY thing that was done, so I have a hard time believing that it is undersize. The house was built in 2006 if that matters.

4) Any other thoughts or suggestions?

thanks

Brian

buckeyefarmer · Mar 20, 2010

thatguy said:
In our house we have an unfinished walk up 2nd story/'attic' (that could be finished at some point - the main floor ceiling/attic floor is insulated as an exterior wall).. We have a ridge vent and soffit vents all around the house (see pic below). I posted a question a while back about installing radiant barrier in the attic against the underside of the roof - so this may seem familiar..

Background info
Our attic seemed to get VERY hot in the summer (120 degrees due to a large roof, black shingles) so I added a electric gable exhaust fan on one side to try to get more air flow.. The gable ends seemed to me to have too much restriction for the fan to blow out (air pretty much blew down the wall instead of outside)..

I had a vinyl siding guy stop by today to give me a price for replacing the gable vents with something bigger/less restriction (possibly auto open/closing)..

Short story long - Here are my questions:

1) He said that since we have soffit vents and a ridge vents, the gable fan is disrupting the 'normal' air flow (in at the soffit out at the ridge).. Does that seem correct?

2) As you can see in the pic on we have the same 'hip' type roof all around the house. BUT when facing the house there are no open spaces in the attic walls for the soffit vents on the right/left side of the house to flow into the attic. (If you notice the side windows in the pic - the bottom of the window is waist high when in the attic) The plywood blocks off access to the side hip roof. He suggested possibly drilling some air holes in the plywood so that the soffit vents have place to vent. Does that make sense?

3) The vinyl siding guy thought that the ridge vent was undersized and could be replaced by a roofer.. our builders were meticulous in EVERY thing that was done, so I have a hard time believing that it is undersize. The house was built in 2006 if that matters.

4) Any other thoughts or suggestions?

thanks

Brian

Your house looks very nice, matter of fact looks almost like mine, except I don't have the porch railings.

Normally you don't have gable fans with soffit vents and ridge vent, normally the air will draft out the ridge from the soffit. My room over my garage is not finished, like your upstairs, and it is hot also, but I am in the process of insulating it which I believe will keep it a lot cooler.

For question 2, if I understand the question, the gable side wall soffits do not vent into the attic, aren't supposed to. I think the idea of holes here into the attic is wrong.

I would doubt the ridge is undersized. Take a look from the inside, and check the size of the crack at the peak,should be a couple inches, or an inch down from the peak on each side.

get all those plants planted?

bornredi · Mar 20, 2010

The reason the attic is so hot is because the roof is so hot and no insulation to keep the heat out and cool in(insulation works both ways). There are fans that mount directly through the roof to vent hot air-thermostatically controlled etc., The point of soffit and ridge vents is to allow MOISTURE from the interior of the house to have a place to exit, so it doesn't condense/build up on the inside of the wood members of your house. They are not designed to COOL the attic. If the ridge vent was open enough to vent the attic of all hot air, it would also leak most likely in a heavy rain or blowing rain. In my last house, I had a fan in one end of the attic, and a nice sized vent in the other. In hot weather, the fan would pull hot air out, which would be replaced by cooler outdoor air.Larger gable vents will help, there are also solar vent fans that will go on when there is sun, that mount to the roof as well. In any roof penetration, just be sure it's installed right-water runs down hill. Hope this helps, Eric in Vermont.

thatguy · Mar 20, 2010

buckeyefarmer said:
<deleted text>

get all those plants planted?

I got about 100 more to get in the ground.. After last weekend we had about 300 that I kept moist and I got about 200 of them in the ground yesterday..

Brian

dave1949 · Mar 20, 2010

I take it there is no ceiling in the attic, you see the underside of the roof? If you were to 'finish' the attic space, would you add a ceiling or partial ceiling where height permits? I think how you go about cooling the attic depends on what/if you might do to finish it. Insulation is a big part of the solution, but how it is applied and what type depends on any future plans you have for finishing the attic space.

I used to have a 2 1/2 story house with a sloped ceiling on the sides of the 1/2 story rooms from a 4-1/2' knee wall until it reached an 8' foot height, then it transitioned to a normal flat ceiling. There were windows on the gable ends of the rooms. There was a short attic space above those ceilings about 4 foot tall with a gable vent on each end. I put Velux roof windows on the south-facing roof slopes thinking they would provide daylight and ventilation from a chimney effect by letting air in open windows in the stories below which could rise up the stairs.

The daylight worked out, and they never leaked, but the venting was poor. I came to the conclusion that the air on the roof exterior (brown shingles) was so much warmer than the air in the room, I lost the chimney effect of warm air rising. So, that didn't work the way I had hoped.
Dave.