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whistlerdk

10:07AM | 05/17/04
Member Since: 05/16/04
2 lifetime posts
Bvroofing
I just had 3 power attic vents put into my new roof (U-shape house with one vent on each section). Summer in Texas is really hot.

Now I am reading some literature saying that those roof ridge vent can be even more "efficient" than power vents. My question is whether they are referring to roof ridge vent not having to use any electricity (thus energy efficient) or they can actually create more air flow than a power vent?


Piffin

09:20AM | 05/22/04
Member Since: 11/06/02
1281 lifetime posts
Much depends on other factors you have not mentioned such as whether you have soffit vents, vapour barrier, positive house air, cathedral ceilings, etc.

Excellence is its own reward!


Anonymous

06:27AM | 06/29/04
Good point, here are more data for a better comparison of options.

1. Single story ~2800 sq ft living area.

2. Roofing contract said 54 squares shingle.

3. Soffit vents under eaves, about 22 each measure ~6 x 18"

4. Ceiling is pretty much flat, I can stand up straight in about 90% of the high area in the attic.

5. No vapour barrier, just R-33 blown insulation. Regular recirculating AC.

6. Have relatively long ridge top for each section of the U.

7. House originally built with 1 power vent, thermostat set between 78~80 deg. Summer temp here sometimes get to low 100s for several days and my worst utility bill is ~$230. I think the old power vent is not bad so I am hoping 2 more will help lower the temp of other 2 sections of the attic.

If ridge vent in my case works better, then I will use them on my next roof. Power vents are not that quiet and adds a bit to my utility bill too.

whistlerdk

06:47AM | 06/29/04
Member Since: 05/16/04
2 lifetime posts
Good point. Here are more data for comparison between options.

1. Single story, ~2800 sq ft living area.

2. Roofing contract said 54 squares shingle.

3. Soffits under eaves, about 22 @ measure ~6 x 18"

4. Ceiling is pretty flat, I can stand up straight in 90% of high area in the attic.

5. No vapour barrier, just R-33 blown insulation. Regular recirculating AC.

6. Relatively long ridge top on each section of the U.

7. House originally built with 1 power vent,

thermostat set at 78~80 deg and summer temp gets up to low 100s for several days. Worst utility bill is ~$230 so old power vent is not bad. Hoping 2 extra will help lower temp for the other 2 areas of attic.

If ridge vent option can move more air for my house, then I will use them on my next roof. Power vents are not that quiet and they add to my utility as well.

Piffin

06:49PM | 06/29/04
Member Since: 11/06/02
1281 lifetime posts
Here is my professional opinion.

most venting specialists recommend one sq ft of vent area for every 100-150 sq ft of living area. That is passive venting.

That means that for your house, especially being in a hot location, and with 54 sq of roofing, you must have at least 4000+ sf of house. That would require no less than 40 sq ft of passive venting and probably more like 60.

Your soffit vents, depending on their configuration, provide only 10 - 15 sq ft.

Venting needs to be ballanced. in other words, if the ridge vents will allow 60 sf but the soffits allow ten, then you only have ten feet of effective venting. The outflow must equal the inflow. The air has to come FROM someplace befor eitr can ewxhaust heat.

The above refers to passive venting as with soffit and ridge vent balancing.

you have power vent exhaust hoods, which will propell more air out, but the soffit vents must stillll make up that air. They will have some gain due to pressure balancing in nature, but you do need more soffit vents before you need more exhaust vents. The first thing to consider is what the rated cubic feet perminute air flow is for those power vents. Then figure the CF of the attic and...

let's make this easy, see if you can double the amt of soffit vents you have for makeup air before you add passive ridge vents.

Excellence is its own reward!


BV012927

12:00PM | 09/20/16
I PRESENTLY HAVE 9 ROOF VENTS, WITH ONE OF THEM BEING A POWER VENT, AND MY HOME IS APPROX. 2300 SQUARE FOOT AND TWO ROOMS HAVE A 16 AND 18 FOOT HIGH SLANTED CEILING AND MY ROOF IS VERY SLANTED WHICH LEAVES QUITE A LOT OF AIR SPACE IN THE ATTIC.

MY QUESTION IS WHEN REPLACING THE ROOF USING RIDGE VENT SHOULD I/COULD I LEAVE THE ONE POWER VENT IN OR SHOULD I REMOVE IT? I KNOW THAT I SHOULD CLOSE OFF THE OTHER VENTS BUT WANT TO MAKE SURE BY LEAVING IT IN WOULD NOT BE COUNTER PRODUCTIV.

BV011721

09:43AM | 09/22/16
Unless your attic floor is completely air sealed, powered attic vents will suck conditioned air out of the house increasing the cooling costs at a much higher rate in cfm's then naturally vented attics.
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