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Thread: Attic Venting

  1. #1
    Join Date
    May 2012
    Location
    New Jersey
    Posts
    3

    Default Attic Venting

    Hello all. First time poster, long time reader.

    I'm trying to figure out how to properly ventilate my attic. Just some background info, I've lived in a small cape cod in New Jersey for about 3 years now. My attic is nothing more than a crawlspace above the 2nd floor of my home. The ceiling in the attic is about 3 feet high at the peak of the roof, 30 feet long, and about 6 feet wide at the floor. In the summer, the 2nd floor gets unreasonably hot. Not only does it get hot, but there's no air movement whatsoever. Even with a 12000BTU air conditioner running in our bedroom, you can still feel the heat radiating downward from the ceiling.

    The prior owner had a powered roof vent installed but the electricity to it was cut long before we moved into the home. I don't know how well the powered roof vent would work anyway. I'm not quite sure where the unit would pull fresh air in from. There is no soffit space so installing soffit vents is not going to happen.

    So to those much wiser than I, what are my options for getting rid of all that hot, stale air?

    Thanks in advance!

    Allan

  2. #2
    Join Date
    Jan 2009
    Location
    Needham, MA
    Posts
    559

    Default Re: Attic Venting

    are you sure that there's no room for sofit vents? let's assume that there isn't. what you have to do is to, ideally, install a ridge vent running the length of the house then find a way to get fresh air into the space behind the kneewalls. above the angled ceiling along the bottom of the roof sheathing you have to install baffle vents in all the rafter bays and the insulation should sit on top of the ceiling. this will allow air flow from the knee wall space to the "attic" space up at the peak of the roof. the air will escape through the ridge vent. now you have to get fresh air into the kneewall space otherwise the ridge vent will be useless. if you can't install sofit vents then you could install a gable end style vent on the gable ends of the house, two in the front and two in the back which could let air into the kneewall space. there are lots of vents to choose from that you could install so stop by the lumber yard to see what they have. just remember that the most important thing is to get the air in down low, give it a path to the ridge and vent it out the top.

  3. #3
    Join Date
    Jun 2012
    Posts
    6

    Default Re: Attic Venting

    Depending on your budget, you may want to consider adding a radiant barrier as well. This will keep heat from "radiating" into your living space. You can also look at getting powered gable vents, either solar or ac powered.

  4. #4
    Join Date
    Feb 2008
    Posts
    175

    Default Re: Attic Venting

    I would also add that an AC powered small fan should help considerably; most of them these days come with an automatic temperature switch which can be manually set; if possible it should draw the coolest air in from the NORTH side of the house & exhaust it out the SOUTH side of the house or EAST IN WEST OUT, depending on your house's orientation; I would also insist on a manual ON/OFF switch in the living quarters to shut the fan off when no one will be in the home-----a number of attic fires are caused by failed attic fans after they've been in service for a number of years; don't ignore the EXTERIOR WALLS of the 2nd floor------they may not have ANY insulation in them; you will have to check by hiring a service that takes an infrared reading of the walls to see if excess heat is coming in; consult the Yellow Pages under "Infrared inspection service", or call a local insulation company; a DIY trick is to unravel a steel hanger & drill several 1/8" holes at various points around the 2nd floor in inconspicuous places; attach a small amount of glue to the hanger end & rattle it around inside the exterior wall cavities to see if you come up with any insulation fragments.

    One of the best homeowner investments going is to have cellulose insulation BLOWN IN by a local insulation service company----they work completely from the exterior of the building (usually in one day), removing a small piece of exterior siding here & there, drilling a 3" hole & blowing in the insulation & resealing the hole----even houses that originally had insulation installed experience settling over the years so a topping off is always worthwhile.
    Last edited by Dobbs; 06-18-2012 at 06:48 PM.

  5. #5
    Join Date
    Dec 2007
    Location
    Tennessee
    Posts
    1,381

    Default Re: Attic Venting

    How much work are you willing to do? This can turn into a very big project.

    First, do you have access to the space behind the knee walls? If not, are you willing to cut holes to get into this space? You need to get into this space to see if there are any soffit vents.

    You should have insulation on the back side of the knee wall and the floor of this crawl space. The insulation should go up the roof rafters that form the angled wall and you should be able to see if there is a gap between the insulation and the roof sheathing. The insulation should continue to the floor of your attic.

    If all this is in place, then you can simply add gable end vents at the top of the gables on each end. If the fan is still there, you could check it, but if someone cut the power to it years ago, it probably doesn't work anymore. Replace the fan and run new wires as needed. Follow Dobbs advice on this. With the fan and the gable end vents, you should be OK. If you can add soffit vents, it will be even better.

    If all this is not in place, or you do all the above and are still not satisfied, then plan on ripping out the sheetrock on at least the angled wall. Insulate the rafters along the angled wall with batts that are at least 1" less thick than the rafter size. For example, if the rafters are 2x8, then use 6.5" or 6.25" thick batts. If 2x10, then use 8.25" thick batts. Staple the flange of the batts to the bottoms of the rafters, not to the sides as you see walls done so often. You want the gap above the insulation, not below it.

    Before putting up new sheet rock, use 1" thick foam boards on the bottoms of the rafters. This will help stop heat conduction through the rafters that bypasses the insulation. Just 1" will make a big difference, 2" would be a little better, but the biggest difference comes with that first inch.

    Then put enough insulation in the attic to cover the joists by at least 4". Then in the knee wall, add more insulation over the studs, You will probably have to use foam boards for this too but if you can figure a way to hang batts from the studs, that will work too. This is where the least amount of heat is getting into your room so you want to minimize your costs here.

    If you removed substandard batts from the angled wall, you might reuse them here. Lay them horizontally along the wall, paper side in toward the studs, staple the flange to the ends of the studs. These can be laid like clapboards with each batt over hanging the batt below it by an inch or two.

  6. #6
    Join Date
    Feb 2011
    Posts
    2

    Default Re: Attic Venting

    Quote Originally Posted by MLBSF View Post
    are you sure that there's no room for sofit vents? let's assume that there isn't. what you have to do is to, ideally, install a ridge vent running the length of the house then find a way to get fresh air into the space behind the kneewalls. above the angled ceiling along the bottom of the roof sheathing you have to install baffle vents in all the rafter bays and the insulation should sit on top of the ceiling. this will allow air flow from the knee wall space to the "attic" space up at the peak of the roof. the air will escape through the ridge vent. now you have to get fresh air into the kneewall space otherwise the ridge vent will be useless. if you can't install sofit vents then you could install a gable end style vent on the gable ends of the house, two in the front and two in the back which could let air into the kneewall space. there are lots of vents to choose from that you could install so stop by the lumber yard to see what they have. just remember that the most important thing is to get the air in down low, give it a path to the ridge and vent it out the top.
    I have a larger attic that some day we may turn into a loft but at the moment I would, like to improve the insulation and determine the best way to vent the space with future finishing in mind.
    It is a brick house build in 1930 with a slate roof, and currently no apparent ventilation. There are plaster ceilings below with some loose insulation and fiberglass batting over top. I live in Richmond VA.

    I can see the soffits from the attic and wonder if just adding soffit vents with out a ridge vent is a good idea, and if there is a standard of how much area of venting is necessary per volume of attic or size.

    I would like to inlay some reflective insulation in between the rafters with an air space below the roof, and possibly then more insulation under the roof. When it is complete I would like to slightly condition the space with a return and all.

    Thanks,
    David

  7. #7
    Join Date
    Jul 2012
    Posts
    3

    Question Re: Attic Venting

    I have a gable vent that failed. When I replace it, should I block up the opening so that the fan is 100% effective when running. The old one only covered half the opening, so that outside air could enter the attic right around the fan - not too efficient. I have a louvered opening at the opposite end of the house, so when the fan is running I'll get good air flow through the length of the attic.

    But, when it's off, there will be NO Circulation of air. Is this a problem in the winter?

  8. #8
    Join Date
    Jul 2012
    Location
    LA, CA
    Posts
    4

    Cool Re: Attic Venting

    You can do 3 things:

    * add insulation to the roof (radiation and heat insulation)

    * add insulation to the 2nd floor ceiling (radiation and heat)

    * re-establish the attic fan or maybe portable air conditioner with 2 vents, preferably.

    The last point depends on the temperature difference on the hottest days.

    What is the temperature outside vs. the attic temperature on the hottest of days?

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