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Old 07-08-2009, 10:36 AM   #1
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Attic Ventilation in 1928 Bungalow

I apologize if this is the wrong section to post in... my issue deals with attic ventilation. I initially posted in the HVAC section, but that seems more geared towards HVAC equipment. I'm hoping someone here can help.

I have a 1928 bungalow in Houston, Texas (read: hot and humid). I'm in the process of replacing my ductwork, and wanted to improve the ventilation in the attic while up there. It's getting extremely hot in the attic, and I'd like to prolong the roof's life, while getting rid of some of the hot air that is zapping my nice cold air inside.

This is a rectagular, Southward-facing, A-frame attic. Originally, there were gable vents at the front and back (South and North) of the house. 12 years ago, a previous owner renovated the home. They took out the front vent, and replaced it with a piece of glass. When they replaced the roof, they also put in a ridge vent. There are no other roof vents. There are also no soffit vents, or air intakes entering at the bottom of the roof. In fact there are no soffits, as the rafters are exposed. As for insulation, the remodeler blew in insulation, and it has settled in to a height just above the joists.

My initial thought was to add several soffit intakes along what I guess you might call the fascia (the 1x6's in between the rafters). Although I'm not sure "fascia" is the right term, since it's moved up and in, towards the attic. Then stick some of the styrofoam baffles on the inside to hold the insulation back.

My questions:

1 Would I be better off just replacing the front glass with a vent, to get some cross-flow in the attic?

2 After adding soffit vents, is the rear gable vent going to hinder the proper airflow of whatever soffit & ridge system I am able to create?

3 Is there some sort of regional climate issue that I'm not aware... do soffit & ridge sytems not do well with hot and humid climates? I've seen some ridge vents in my neighborhood, but not mant soffits... are they hidden?

Thanks in advance... all advice is welcome!

This is what the overhang looks like... exposed rafters, no vent

This is the front gable... glass, no vent

This is the back gable... just a screened vent


stephensandlin is offline   Reply With Quote
Old 07-09-2009, 11:16 PM   #2
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The section of wood that you were referring to, which you called a "fascia", is actually called "Blocking".

Yes, you can install some intake vents in the blocking, but the size of the vents and the Total NFVA of Intake Air provided may still not be enough, since the vent sizes would need to be sort of large.

Mini-Louver circular vents provide hardly any NFVA, (Net Free Ventilation Area), and the rectangular ones need to be around 8" x 16" before they start giving decent NFVA numbers.

Check out Lomanco Ventilation and for further information about the totals that each vent style provides for more information for yourself.

Due to the duct-work inside of your attic, you have to be certain that there is no air leakage coming from any of the joints.

You may want to invest in a Home Inspector with Wind Movement measuring devices and/or smoke pots to see the current air flow and test for any leakage.

Normally, I do not recommend adding additional exhaust ventilation when there is already a performing exhaust system in place, such as your ridge vet, but in your case I might re-consider the potential pro's and con's and weigh in at choosing a Powered Gable Vent Fan creating air-flow from one end of the attic and discharging it out of the opposite gable side, therefor, requiring you to get rid of the window for the powered gable vent installation.

One more thing is that you should check to see if the current Ridge Vent is actually allowing air-flow to get exhausted through it from hot air thermal buoyancy. Many of the cheaper and less proficiently designed versions sold and installed do not function as stated, or do not get installed per the manufacturers specifications, totally negating any positive effect they should have had regarding the interior conditions and the cooling effect.

By the way, I apologize about the delay getting a response back to you, but I knew it would be necessary to be explicit and put it off for a while and then just noticed it again tonight.



Ed the Roofer is offline   Reply With Quote

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