Home>Discussions>INSULATION & HVAC>Ventilating and Insulating an Attic that has no Soffits or room for Soffits
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Ventilating and Insulating an Attic that has no Soffits or room for Soffits

We just recently purchased a home that is 29years old that we noticed has a little bit of mildew/mold growing on the sheathing. An inspector told us that it's most likely due to poor ventilation and insulation.
We only have gable vents installed on each side of the roof and no soffit vents or ridge vents. We don't even have any room for soffit vents so that's not even an option of adding them.
We were considering just remediating the mold,then replacing the insulation that's contaminated and adding new batts and making sure there are no areas exposed that could get warm air from inside the house, then adding an attic fan with a thermostat and humistadt to one of the gable vents. Would this provide enough air flow?
hope someone can advise!!

MLB Construction
Re: Ventilating and Insulating an Attic that has no Soffits or room for Soffits

***, did you open up a can of worms. this is a big debate among contractors, builders, home owners, etc.

my personal belief, and you're going to get a hell of alot of other opinions, is the following.

If you have gable end vents you don't need soffit and ridge venting. if you have sofit and ridge venting you don't need gable end vents. with that said, you can increase the size of the gable end vents if they're unusually small and add a roof vent on each side of the roof. you could also add a temperature controlled roof fan which kicks on when the temp goes above a certain temperature.

the ideal situation is to have the attic floor very well insulated so that heat from the house does not enter the attic. all holes from wiring should be filled, attic door or pull down stairs should be well insulated. now that you have prevented inside house air from entering the attic, the attic should always stay the same temperature as it is outside. it's all about air flow, gable end vents allow air to flow from one end of the attic to the other and out one of the vents. soffit and ridge vents do a better job by expelling all the hot air at the top of the attic ceiling and pulling fresh air from below through the soffit vents.

Re: Ventilating and Insulating an Attic that has no Soffits or room for Soffits

What MLB said.

I would add that you can calculate the amount of venting in square inches and square ft. by using the site below from Iris Communications to use the 1 in 150 rule, the 1 in 300 rule, or other applicable calculation; the video distinguishes between low & high vents; gable end vents are usually considered high vents, & you can always install a ridge vent along the very top of the roof; if you decide to install any roof vents thru the shingles (roof jack), install them in a location on the roof that is not visible from the street or front of the house to maintain good roof appearance; as noted in the Iris video, each & every attic vent or attic fan louver/vent MUST HAVE INSECT SCREENING as part of their installation----the bugs, bees & wasps will make you attic their home if you don't include a fine mesh insect screen with each vent installation.

Any electric vent fans must be quality units that have an automatic safety switch (thermal overload protector/Firestat) that will disable the fan in the event the unit overheats (due to shorts in the motor winding)---this will prevent an attic fire & most attic fans don't have this safety feature (cheap imports); this is in addition to an adjustable fan thermostat, which will turn the fan on only when the attic gets too warm (most attic fans have a T-stat); attic fans operate in high temperature conditions, & thus it is common for them to break down after being in service for several years; fire depts around the country have reported that an attic fire will be rapidly spread by an attic fan that doesn't have a thermal overload because it keeps sucking air into the attic to fan the flames of the fire.

Avoid restricting your search for a good attic fan to only the big box stores like HD/Lowe's or the local hardware store----these stores usually carry a very limited selection that includes unacceptable cheap imports that don't have adequate safety features; also Google "attic fans" to review a large selection of quality fans on the internet that have a thermal overload and sell for a competitive price, and sometimes include free shipping; also check out local Roofing/Shingle suppliers in the Yellow Pages; many/most of these dealers will sell to the homeowner.


Re: Ventilating and Insulating an Attic that has no Soffits or room for Soffits

Thank you both for your time in replying.
I have a few follow up questions.

Should we simply try to do the following:
Remediate mold
Then just have an insulation company add blown-in insulation for about 750 bucks?
Or would it be just as simple as a diy and just add more batts but perpendicularly (without the vapor barrier) to help seal out the air coming from inside the home?
Also, you both mentioned roof fans and well I was hoping to avoid that and just add an attic fan (w/thermostat/humidstat/firestat) by taking up one of the gable vent spots, do you think that would screw up the current airflow happening from vent to vent?

Should we just do the mold remediation and insulation part first and see how it goes, without the fan?

Thanks very much!!!

MLB Construction
Re: Ventilating and Insulating an Attic that has no Soffits or room for Soffits

i would remediate the mold, have blown in insulation installed, it will give you a higher R value and get into places that the batt insulation won't. make sure all penetrations through the attic floor are sealed and do something to improve the ventilation. any of the options we discussed will help even adding a powered vent in one of the gable vents.

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