Wife and I bought a 1949 home that seems to be built pretty damn sturdy from what I can, but was missing a few things we thought were needed.

I installed an exhaust fan in the bathroom last month, and in the process of cutting a 4" hole in the roof, realized that there were ZERO vents for airflow to the outside. That hole I cut was like a hot hair dryer blowing right out from the attic. I took note that none of the vents existing were for attic ventilation. I have gable louvers and that is it.

I put a thermometer in the attic first, to see if the temp is even a problem. I was reading that if it is 100F out, it shouldn't be much hotter than 125-130F (at worst). I have no soffit vents and have been reading a lot about how to add airflow correctly. If I don't have enough proper intake surface area, a solar fan will end up drawing out cool air from the house.

Anyone have other ideas or suggestions? I should know this afternoon when I take a quick peak at the thermometer.

add soffit/ridge vent combo

I have a few questions about soffits and ridge vent combos though.

I suppose I need to go online and see how to retrofit them into existing homes. I've read the ridge vent process isn't terrible, but it does assume you have similar looking shingles available to attach on top. I

I'm just wondering with the louvered gables present, if t still makes sense to retrofit with ridge/soffits. It seems like I should be able to take advantage or the louvered gables being an intake. I just don't know if adding a solar powered exhaust fan is going to overpower the intake surface area.

130/135. Was inexact bc it was a meat thermometer.

What material are your soffits ?

Wood? Hardi ? Vinyl ?

Are you sure there are not any soffit vents ?

Can you post a picture of existing soffits ?

Without adding intake vents, ridge or whirlybirds won't do much


If you give me the square feet of the structure I will run the calculations for intake and exhaust surface area needed for proper for you.

There are no existing soffits.

House was built in 1949. It has louvers at each gable.

1250 sq feet. 1 ft per 150 right? 8.3 sq ft but that's exhaust + intake, no?

4.15 sq ft each intake exhaust. I read that I'd need to block my louvers if I want soffits to work correctly...

Martin Q. Blank said:

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add soffit/ridge vent combo

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Soffit + ridge vents and radiant barrier and you're done.

No pictures posted, but the first thing I though when you were saying a 1949 Craftsman, is a house with just the exposed rafter tails and no soffit. The gable vents was the venting of the time. If you are covered with trees, a radiant barrier will not do much good. Try a solar power vent at the gable vents.

Looking at Remington solar 1280 CFM sold through Home Depot! And yes, the gables are the only vents.

Looks just like this on opposite ends of our home.

Gable vents are acting similar to ridge vents. Letting the hot air out at the top of the roof.

Adding soffit vents should improve the airflow. Letting hot air out of the top while sucking cooler air in below.

Quote:

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To find out how many soffit vents you need to install:

• Calculate the total vent area needed: Multiply the length of the attic times the width in feet to find the attic area, then divide by 150 to find the total square feet of vent space needed. [(length x width of attic in feet) 150 = total sq. ft. vent area]
  Example: a 50 x 30 attic would have a total area of 1,500 sq. ft., divided by 150 equals 10 sq. ft. of total vent space needed.
• Calculate the soffit vent area needed: Divide the total vent area by two to determine the soffit vent area. [Vent space 2 = sq. ft. soffit vent area]
  Example: 10 sq. ft. vent area 2 = 5 sq. ft. soffit vent area.
• Calculate the area of each vent: When known, use the "net free area" supplied by the manufacturer of the venting you will be using, which takes into account the actual open area of the vent rather than the total vent size. For square or rectangular vents, muliply the length times width of the vent space in inches, then divide by 144 to convert into sq. ft. [(l x w in inches) 144 = area of vent in sq. ft.]
  Example: a 6 x 12 vent would equal 72 sq. in., divided by 144 equals an area of 0.5 sq. ft. per vent.
  For round vents, multiply the radius of the vent (half the diameter) times itself (squared), then multiply the total by 3.14 (pi) and divide by 144 to find the number of square feet [(r in inches x 3.14) 144 = sq. ft. area per vent].
  Example: a 6 diameter vent would have a radius of 3, multiplied times itself would equal 9, times pi (3.14) would give 28.26 sq. in., divided by 144 equals an area of 0.196 sq. ft. per vent.
• Determine the number of soffit vents needed: Divide the total soffit vent area by the area of each vent. [soffit vent area in sq. ft. individual vent area in sq. ft. = number of vents needed].
  Example: 5 sq. ft. soffit vent area divided by 0.5 sq. ft. vent area equals 10 soffit vents needed.

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ratfacemcdougal said:

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No pictures posted, but the first thing I though when you were saying a 1949 Craftsman, is a house with just the exposed rafter tails and no soffit. The gable vents was the venting of the time. If you are covered with trees, a radiant barrier will not do much good. Try a solar power vent at the gable vents.

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If that is the case, you could do this:

Plus good screens and a clear airflow path in the attic.

TexAg1987 said:

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ratfacemcdougal said:

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No pictures posted, but the first thing I though when you were saying a 1949 Craftsman, is a house with just the exposed rafter tails and no soffit. The gable vents was the venting of the time. If you are covered with trees, a radiant barrier will not do much good. Try a solar power vent at the gable vents.

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If that is the case, you could do this:

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Hope you don't have squirrels or you're asking for trouble by just drilling holes...

I checked the eave; doesn't look like any gap into the attic, so drilling a hole effectively goes right up through the roof. I could be wrong! I will take a much closer look if there is some entry into the attic. I must confess: not well informed/educated on old-school construction...or new-school.

Now that is what I thought you had. Try the power gable vent first. The next level would then be solar power vents on the roof deck. Then the next level would be cutting holes, or even removing the filler boards and adding soffit and ridge vent.

Out of curiosity, do you agree with the sentiment that attic temps shouldn't be much more than 20 F warmer than ambient? Yesterday was damn hot, but I'm pretty sure I can get the temp lower than 130-135F.

Google edge vents also. Similar to a ridge vent that is installed at the lower part of the roof.

Gary79Ag said:

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TexAg1987 said:

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ratfacemcdougal said:

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No pictures posted, but the first thing I though when you were saying a 1949 Craftsman, is a house with just the exposed rafter tails and no soffit. The gable vents was the venting of the time. If you are covered with trees, a radiant barrier will not do much good. Try a solar power vent at the gable vents.

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If that is the case, you could do this:

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Hope you don't have squirrels or you're asking for trouble by just drilling holes...

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All soffit vents are just holes to the attic. You are always going to have to do screens for rodent/insect control.

If you do ridge vents with soffit vents, then you should close the gable vents. The soffit and ridge work together to create a convective current that flows up the underside of the roof deck. Having an opening in the gable messes up the flow of the current. There is a careful formula for the balance between the 2 openings. If you have it wrong, then you end up with a slower current that can cause the flow to go the wrong direction.(more or less)

Lots of people install ridge vents and then leave the gable vent. It seems like the right thing to do because it means more vents but it actually is counter-productive. Also, convective currents work very well to move air without the need for fans.

I bought a cheapo wireless temp sensor with humidity. I am going to put it up in the attic, check again the temps, throw up a $15/$20 box fan and rig it next to the gable vent.

Based off of what I see happen with that will determine if I proceed with a $275 solar 1200 CFM gable fan.

Adding ridge-vents and soffits in my own may not be the right solution given the age and construction.

evan_aggie said:

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I bought a cheapo wireless temp sensor with humidity. I am going to put it up in the attic, check again the temps, throw up a $15/$20 box fan and rig it next to the gable vent.

Based off of what I see happen with that will determine if I proceed with a $275 solar 1200 CFM gable fan.

Adding ridge-vents and soffits in my own may not be the right solution given the age and construction.

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If you can pull air across the house from gable to gable that is probably your best bet right now. Ridge vents are best to install when you are re-roofing. Try blocking off the area that is not covered by the fan case also when you install the box fan.

That's what I'm going to try! We shall see.

You are going to have to seal off the rest of the vent for the fan to work.

Otherwise you will just be circulating the air right around the vent.

http://www.savenrg.com/venting.htm

What ended up working? We are in this exact same place, except we do not have gable vents, just a few roof vents.

I ended up installing a 1000 CFM gable fan. It isn't solar but was $100. The difference in electricity vs price would have taken many years to pay off.

The attic temp dropped pretty substantially. But keep in mind I had gable vents and enough surface area inlet to likely not suck air from within our air conditioned home.


https://www.homedepot.com/p/Master-Flow-1000-CFM-Weathered-Wood-Power-Roof-Mount-Attic-Fan-ERV4WW/302778609

I have a similar issue. Depending on how handy you are and how much work you want to do, the below product could be an option.

They have some solutions for tight spaces. I'm actively retrofitting and was able to order direct.

https://www.cor-a-vent.com/s-400.cfm