Roof Venting

darren

Hi
I am in the process of insulating my attic and my first step i thought was going to be to put in the extensions for the soffits. SO I went up in my attic and it looks like I don't have any soffit vents. I have a vent in each gable and two (roughly 4"square) roof vents. My house was built in the 50's and I am sure it has been this way since then and i notice no problems in the attic. Is this normal and should i worry about soffits and just use the gable ends.

Thanks
Darren

Grumpy

If you install soffit vents, you will want an exhaust like a ridge or mushroom vents. The problem with gables is most are undersized. And gable vents only work effectively when they have some help, either from a power fan or a direct wind blasting through. Depending on the size of your attic space the current venting may be ok, or undersized. There are mathematical formulas used to determine adequate ventilation, and the ammount of ventilation required varies from house to house, based on size and shape etc...

Don't mix ventilation systems. If you go the route of a ridge vent you must cover over your gable vents and you must also install soffit vents. In addition you must have about 1" at the bottom of the roof deck fre of insulation so air can pass from the soffit to the ridge (such as in the case of finished attics).

747

The roof of your house sounds exactly like mine. Meaning before my new roof i had two gable vents ridge to ridge and two square roof vents. When i re did my exterior about nine months ago decided to finish with a new roof. There are now six square roof vents brown to match new roof. Also all the plywood soffits were ripped down and replaced with the aluminum soffitts that have the little slits in them. So i now have outstanding soffit ventalation and those 6 new roofs vents and the gable vents which were replaced in white vinyl to match the white trim. Because when i had them do the vinyl siding i told them i wanted the corner trim on the house and garage done in white and the soffits also. I'm not a roofing expert like grumpy but you might be able to replace those two square roof vents with two whirly birds until your ready to drop the money to put a new roof on. Figure 3500 for a new roof. I think mine was around 33-3400. But they had to remove two layers of asphalt shingles. This was for a 40 year shingle.

Grumpy

I was with you on everything you said up until the above quoted comment. BOO HISSS

There are too many variables involved in quoting a price for a roof over the internet. The roof sounds exactly like yours? Wow man, I thought the orignal post left alot to my imagination, which is why I didn't give a specific formula about the ventilation... I just didn't know enough about the roof.

For the same reasons that I didn't quote ventilation specifications, I also can not agree what his roof would cost. I only bring this up because I do not want the original poster to think his roof will only cost $3500 if it might possibly cost more.

copusbuilder

Like Grumpy said!
I had an older home in Houston with gable end vents. I installed ridge vent and soffit venting and it was a remarkably cool attic in the hot Texas summers (still warm), Like Grumpy said there are mathematical equations but add some ridge and soffit and spend your savings on beer Just make sure your soffit vents can breathe...No insulation blocking air flow..

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AaronB.

I have gable vents on my house and it is a wind tunnel with the slightest breezes. Nice and cool and dry, too.

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copusbuilder

I really like the gable end vents
I agree with the breeze issue

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AaronB.

Most times when the attic is too hot, and gables vents are in place, no matter how small they are (inhibiting proper volumes of air flow), even roofers will sometimes say "Gable vents are crap." What they should be doing is checking to see if there is enough net free vent space to allow iar into and out of the attic space.

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Thunder1

The FHA recommends a minimum of 1sqft of venting per 300sqft of attic area (I prefer twice this amount). This assumes intake and exhaust venting are present. One huge vent will not do the job even if it has an electric fan

In order of my own preference. Eave to Ridge, Eave to Roof, Eave to Gable, Gable to Ridge, Gable to Roof and Gable to Gable. When I install a roof, proper ventilation is required and included in my estimate. I have lost jobs because the two or three other bidders invariably say it doesn't matter and could save the HO some money. (If there are any roofers on this forum that don't think venting is important I would be interested in hearing your opinion)

Excessive attic heat is detrimental to ALL types of roofing. Venting to the limit acceptable by the building code and insulation requirements will ensure the longest life for your roof. It is also important that air enters and exits your attic at the vents ONLY. When there is excessive heat and/or insufficient venting the hot air forces its way through your roof at weak points, doing damage on the way. When new roofing is installed all hips, ridges (without "ridge vent") and large penetrations should be sealed as tightly as possible against air as well as water. The best way to determine YOUR venting needs should be done by a LOCAL professional who is familiar with the climate and building code.

Call an HVAC or Roofing pro and be wary of any attempts to sell you on costly upgrades. Tell them to use the K.I.S.S. method. "Keep It Simple Stupid"

Remember that all damage from age is proportional to heat and moisture so you should store your house in a cool dry place.

copusbuilder

Great response...I like your thinking

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Grumpy

Gable to ridge should never be a consideration. Each and every ventilation manufacturer makes it a point to mention this. The lower portions of the roof, under the gables, will be incredibly underventilated. The gables essentially become and intake and the ridge an exhaust, and what's left... the majority of the cubic attic space left unvented.

In cases where gable vents must be used as intake, such as you mentioned gable to ridge, the ridge vent should be excluded and some type of static roof vent (like mushrooms) installed.

An alternitave you forgot to mention is a fascia vent. Most metal prefab fascia vents are crap IMO, because most displace the gutter. One that sits under or behind the gutter is a more logical choice and will provide the same intake as a continuous soffit vent.

There are some situations when venting is not important such as in the case of these new type attics which are fully enclosed. Teetor knows more about these than I do to be honest but from my breif research I know basicallyw hat they do is use a sprayed on foam and cover the entire underside of the roof deck surface. There is no intake or exhaust ventilation. Usually there is some kind of tile, or non asphalt, roof product used.

Thunder1

I agree Grumpy, but in my area the average roof pitch is about 4-5 in 12 so most decent sized gable vents sit pretty low. Also as you can see I put that option near the end of my list and this implies I have been left with few alternatives. When the customer can't afford to have proper eave vents installed or a thick layer of stucco makes it impractical I will (as a last resort) install mushroom/eyebrow vents at the eave to improve circulation. I didn't mention it before because it looks bad and I hate doing it.

Generally speaking, if a HO wants no vents added because he already has Gable to Gable venting I can assume two things. 1 He doesn't trust my professional opinion and 2 that distrust will cause him to blame me when his roof fails. I don't need that kind of work.

AaronB.

Gable vents do not fail if you have sufficient net free vent space. Most custom homes nowadays arent built in a configuration to allow gable vents AND sufficient net free vent space.

I like old school gable vents that are truly venting the size of the shape of the vent.

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Grumpy

Aaron, you said most homes today are not build to allow gable vents. To this I agree. I willa dd most older homes were not built with large enough gable vents! I know you have seen them too... 2 8" gable vents for a 30 square roof?

Shoot the architect!

These are the roofs that need the gable vents covered and the ridge/soffit system installed.


I do agree if the gable vents are large enough they CAN work. My father has a house with 25 square roof, probably only 1500 square feet of attic foot print, and I will tell you now his 1'x 2' gable vents ARE NOT ENOUGH. I have never felt a breeze and I used to use the attic as a sauna when I was young.

I never felt a breeze in hsi attic even when his gable fan was turned on. The point I am tryign to make is that although gable vents can work I don't have as much faith in them as you seem to have. Based on the laws of physicis, hot air moves verticle not horizontal, I can not see how they would work without some kind of forced air.

AaronB.

Im talking like the big 3' round vents with full air flow. Not in accordance with the vented siding type.

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