Attic Ventilation Project with potential addition of solar attic fan (gable/peak)

doohic
doohic Registered Users Posts: 10 ✭
in Solar Beginners Corner #1
Hi all, I'm going to use this thread to post everything about the attic ventilation project I am about to endure. Just a quick background, Ive been lurking about here and there learning a little about solar and a little about attic venting practices. And I myself am a geek by trade and a want-to-be DIY master. (currently building my first screened in porch enclosure)

After doing a bunch of reading for my Attic ventilation project I've found I first need to do some adjustments to my soffit system. I'll be making sure I have all of my soffit chutes
Add-Attic-Vent-10-ss.jpg

Ive read that the aluminum soffit systems may not allow enough air to pass in (those tiny little holes), and to install 8"x12" vents every 8 feet or so.. however, here in FL, I'm not sure thats the best idea with heavy wind and rain. Those larger openings could result in more exposure.
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  • doohic
    doohic Registered Users Posts: 10 ✭
    #2
    Re: Attic Ventilation Project with potential addition of solar attic fan (gable/peak)

    after the chutes I need to figure out how to vent up and out. My original plans were to put gable vents at each end of my home, and then do a single ridge vent in center of my house near the peak and use a fan to vent it, and potentially have that fan be battery powered and battery charged/maintained by a solar panel (and use a thermostat). Another idea was to just use gable fans on each end. I believe I still need more venting near the ridge though. My house currently only has two ridge vents and they are at opposite ends of the attic (nothing in the middle).

    NOW, after some reading, I am not to sure about the solar powered fans, but in more dismay over gable vents. Ive read about people loving them (although mostly if they have a powered fan). Ive read about people blocking them back off because the ridge vents start to pull air IN from the ridge vents, instead of the soffits cooler air. And simply a statement that says Gable vents do not work at ALL (I assume unless fan powered appropriately). AND I should say, on the basis that gable vents will only work passively if your in a constantly breezy area, therefore, not really working passively.
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  • doohic
    doohic Registered Users Posts: 10 ✭
    #3
    Re: Attic Ventilation Project with potential addition of solar attic fan (gable/peak)

    I will be sure to get some pictures and diagrams up of my thoughts. But primarily I need to properly vent my attic space. It's insanely hot up there in summer here in FL. After I show you guys some images you'll know why (also my home gets NO shade (WIN for solar, FAIL for heat)). I just wanted to get the ball rolling and see what you guys had to say.

    Here was what I believe was some good information left by a new member here (but you never know if it was just self promotion.. ya know)

    http://www.savenrg.com/venting.htm
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  • halfcrazy
    halfcrazy Solar Expert Posts: 720 ✭✭✭
    #4
    Re: Attic Ventilation Project with potential addition of solar attic fan (gable/peak)

    I think you will be ok with the vented soffit you have and depending on the age of the house it may have ridge vent already installed. A couple gable vents wont hurt though. I come from the other end of the spectrum here in Maine we have to vent any warm moist air in the winter or it will freeze and then we build ice in the attic. We typically use vinyl soffit that has a bunch of little small holes and either ridge vent or a gable vent on both ends.

    Also I admire your desire to be more efficient. That is the best money spent by far any thing we can do to make our homes more efficient will pay back rapidly.
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  • System2
    System2 Posts: 6,290 admin
    #5
    Re: Attic Ventilation Project with potential addition of solar attic fan (gable/peak)

    Let me share with the class what I've gleaned from over two decades venting attics. I consider myself an expert since I manufacture products that make attics hotter...much hotter and therefore have been involved in venting attics correctly and have tested every type, kind, size and brand of powered and static venting products.

    RIDGE VENTS:
    "Run Forest Run!" Comes to mind whenever I hear of someone pondering a ridge vent (regardless of brand). Why? Before you classify me as a nutcase, let's look at the "obvious shall we? (and what most people, including architects/builders/DIY'ers are thinking)<br>
    <li> Hot air rises
    <li> Ridge vents are at the of the roof
    <li> Ridge vents are attractive
    <li> Being at the peak of the roof, ridges vents don't leak
    <li> Logic dictates this is the best venting system in the world

    Man, that sounds like the best of all worlds: Attractive, easy to install, doesn't leak and effective! Well, 3 out of 4 are correct. Effective? No, not at all.
    Putting "logic" aside, let's delve into a bit of physics: Let's see a show of hands for all those agreeing that hot air rises....ok, the entire room. Now then, ridge vents are at the top of the roof? Everyone agrees. Attractive...everyone nods. Ridge vents don't leak? How could they? they are at the top of the roof for heaven's sake. (edited by niel as we don't want to offend by religion here) But what about performance? Who cares if they look good, don't leak and are easy to install? THAT'S where the problem is, no one has ever taken the time to actually TEST a ridge vent to see if it actually works. Well we have and they don't. Here's why:
    Everyone reading this (if you are still with me), would agree that hot air rises. This is due to the lowered density compared to the air surrounding it. (think dust devils here in Phoenix, look how fast that hot air goes up!).
    So, let's take a cubic inch of hot air in the attic and follow it...
    <p>
    We watch it slowly gain heat (and lose density), against the hot roof deck and begin to slowly drift upward. As it continues to gain heat (and lose density) on the way up it picks up speed. By the time it gets to the very peak of the attic it's now joined by thousands of other cubic inches of low density, superheated air which are all accumulated at the TOP of the ridge vent. (here's where it gets good).
    Now that all these thousands of superheated cubic inches of air are wanting to go UP, they cannot because they are trapped at the peak of the roof. The only way OUT is DOWN and as we are all in concurrence, hot air rises, IT DOES NOT GO DOWN. Further, the reason hot air rises is due to its lowered density. So, would be safe to say that 145F degree attic air is less dense than 112F (and heavier) degree ambient air? So then, not logic but physics dictates that a cubic inch of superheated 145F degree attic air is not going to travel DOWNHILL (it's downhill from the peak of the ridge vent to the opening), and push air of a higher density (and weight) out of the way to get out. Won't happen. Don't take my word for it, do what I did and puff some tracer gas up underneath a ridge vent at 2pm and see what happens....

    Fact: In order for a ridge vent to work it would have to defy gravity and physics.

    But! They do look good and they don't leak...
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  • russ
    russ Solar Expert Posts: 593 ✭✭
    #6
    Re: Attic Ventilation Project with potential addition of solar attic fan (gable/peak)

    BPinspector - İ hope no one takes your word on this point as you are wrong. That is unless you are using klingon science or something quite different.

    The absolute peak may be hotter - that tiny V above the vent point. Natural stack action carries warm up and out - even if it has to make minor detours.

    Good insulation on the roof (mine is R49), vent it and it should be good. Gets quite warm here in the summer and our attic was perfectly comfortable on the hot days.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #7
    Re: Attic Ventilation Project with potential addition of solar attic fan (gable/peak)

    bpi,
    i'm not sure if i followed you rightly, but why would the warm air be trapped when there is a vent there? i do understand that there should be vents at the low points of a roof too to allow the hot air to escape easier by allowing the cooler air below it to replace it.
    as to hot air going down, yes it can. i have 2 chimneys that extend beyond the peak of my roof and when not forced out of my roof vents with fans it draws inward because of the chimney actions taking place in the chimneys. the air in the roof is lower in altitude and gets sucked down with the chimneys venting upward. i have the small holed soffits and they are useless in allowing the air to be sucked in from there.
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  • russ
    russ Solar Expert Posts: 593 ✭✭
    #8
    Re: Attic Ventilation Project with potential addition of solar attic fan (gable/peak)

    İ went to their site and it is - - - -?

    Statements like the following are made:
    "Installing energy efficient windows can drop your energy costs by 35%"
    "Set back thermostats can cut energy costs by 25%"
    "A high efficient heat pump can reduce your bill by 40%"
    "Attic fans curb energy costs, reductions of 29% are possible"

    Good - İ want the package to achieve the 129% savings. Who sends me the refund each month? Horizon Energy Systems?

    İ am sorry but far from being experts İ believe you guys are a fast talking bunch who are rather loose with the facts.

    RBS chips - blown in reflective foil? Does much good? NO! That ain't how insulation works or is used.

    TCM - thermal control membrane - a fancy way to say radiant barrier? İ guess maybe you can charge more for TCM?

    İ believe the web site is generally misleading!
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  • doohic
    doohic Registered Users Posts: 10 ✭
    #9
    Re: Attic Ventilation Project with potential addition of solar attic fan (gable/peak)

    russ, that was kind of my thoughts, sure, hot air may not vent above the top of the gable vent (gable, not ridge) but you would think hot air stacked below the top of the gable vent would make its way out.

    It appears that BPI wanted to tell us about Ridge vents. Which to me, are those vents that follow the entire peak of your house. Ya know saw the tip off your roof and nail down the ridge vents and cover with shingles. I actually believe (to a point) that those vents don't work very well. if you think about one of those pet water dishes that auto feed, no more water can go into the dish until something physically removes the exposed surface of water (the cat/dog drinking). I think this would be true for the ridge vents, Unless air was moving across the vents, physically (if you will) pulling out the hot air. (I am def no expert though).
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #10
    Re: Attic Ventilation Project with potential addition of solar attic fan (gable/peak)

    You need enough inlet air at the eves, with no restrictions, to allow the hot air to flow out the ridge. Then the hot air will push the air above it, past the labyrinth.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

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  • doohic
    doohic Registered Users Posts: 10 ✭
    #11
    Re: Attic Ventilation Project with potential addition of solar attic fan (gable/peak)

    The first image is the aerial view of my house. You can see I only have two roof vents (I believe way under vented for my roof). The second picture is the style soffit I have. I do not have gable vents on either end (you can see obviously on the south end I do not have one)

    arial.jpg

    211_c7de5_large.jpg
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  • doohic
    doohic Registered Users Posts: 10 ✭
    #12
    Re: Attic Ventilation Project with potential addition of solar attic fan (gable/peak)

    Some great little videos..

    http://roofingcontractorreview.com/Roofing/Attic-Ventilation/Roof-Ventilation-|-Powered-Attic-Fans.html

    http://roofingcontractorreview.com/Roofing/Attic-Ventilation/Static/Passive-Venting.html

    It appears to me that this website has some good information with some experiments to back it up.

    http://roofingcontractorreview.com/Roofing/Attic-Ventilation/Roof-and-Attic-Ventilation.html
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  • solarvic
    solarvic Solar Expert Posts: 1,071 ✭✭✭✭
    #13
    Re: Attic Ventilation Project with potential addition of solar attic fan (gable/peak)

    There is a ceiling vent fan that vents out your attic everynight. I first saw it on This old house program on PBS tv channel. The brand is Tamarack. I am thinking of putting one in my house. If you do a google you can find it. You can buy it directly from the manufacturer. There is a youtube movie that shows how to install one. Vic
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  • doohic
    doohic Registered Users Posts: 10 ✭
    #14
    Re: Attic Ventilation Project with potential addition of solar attic fan (gable/peak)

    thanks vic, I'm off to look for that and check out the video. I just got done watching this company's video on their own ridge vent:

    http://www.youtube.com/watch?v=beQoz4s7QTc

    I think the key in this experiment, is in the baffle, or the dam, that prevents wind coming up the roof directly into the ridge vent, in their design it hits the baffle and is pushed up, which creates the low pressure in the ridge vent, pulling out the hot air.

    The other units he uses as comparison have no baffle and the air from the fan is just pushing itself in the ridge vent and out the soffit.
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  • russ
    russ Solar Expert Posts: 593 ✭✭
    #15
    Re: Attic Ventilation Project with potential addition of solar attic fan (gable/peak)

    The Roofing Contractor site is a good one!

    You have to make it possible for air to move up through the attic to the vent. Somewhere there has to be an inlet at a slightly lower elevation.

    Hot air rises - law of science! Providing there is somewhere for it to go - meaning vents at the proper locations.

    The night cooling is good for an area with cooler night time temperatures. İt can be used for the attic and possibly the whole house.

    The big key is good insulation though. The kind people have heard of without the made up names! Made up names only allow for fancy prices and claims. The testimonials are meaningless - you can get them for a dime a dozen (probably less if outsourced to İndia).

    A natural draft through the house is wonderful. İ live in a hot area and with the assist of a small sea breeze air moves up through the house (4 floors) and out with no assistance. İn a new design this should be carefully considered.
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #16
    Re: Attic Ventilation Project with potential addition of solar attic fan (gable/peak)

    I don't have the photo anymore (that I know of) but I've mounted a $15 20" box fan, into the access hatch for the attic. I set it so it sucks air out of the house, and blows it into the attic, pressurising the attic, and forcing air out the attic gable vents. When run at night, it sucks cool air in the bedroom window you have open, and cools the house and attic down.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

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  • doohic
    doohic Registered Users Posts: 10 ✭
    #17
    Re: Attic Ventilation Project with potential addition of solar attic fan (gable/peak)

    yeah, i really like the cooling chimney effects, either it be a whole house fan or using a box fan, for my location during the summer (Orlando FL) It's not really an option. Were talking 80+ temps all day all night.

    So for me, the house fan is not on my plate. Like I said, my first step is making sure all of my soffit vents are clear and that I have all of my soffit chutes.

    My next biggest dilemma is what venting options to go with. I realize that gable vents are not the most efficient, but I've seen proof they will work passively. Until this week I was not really considering the ridge vent, now I am considering something like the venturivent, or similar with the baffle set-up.

    Another consideration was using dormer vents, although, from the construction I've seen may not work great in a highwind/hurricane situation. I could also try and track down the style vents that are currently on my house (have not been able to find them yet)

    And why I really started talking about this here.... potentiall doing a DIY solar attic vent, similar to the store bought one's, but I'd like to modify/build my own kit. If I go this route, the best idea I have had so far is to mount one attic vent near the center/middle of the roof and have that pull cool air from my soffits to push out the hot air. If I do this I would like to run the numbers on this and really come up with a good plan. I would want to leave this a 12v system (don't want to tie into the house/110), have a fan run off a battery and keep the battery charged using PV(s). I would also like this to be on a thermostat. Battery back-up would be key for me, here in the summer, the attic is still screaming hot even at night.
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  • dwh
    dwh Solar Expert Posts: 1,341 ✭✭✭
    #18
    Re: Attic Ventilation Project with potential addition of solar attic fan (gable/peak)

    I have personally installed these on a couple of houses, and they do a good job. They are made so that a second 10w panel can be added, and they really pump with two PVs, but they do a good job with just the single included panel.

    http://www.homedepot.com/h_d1/N-5yc1vZ1xhc/R-100548465/h_d2/ProductDisplay?langId=-1&storeId=10051&catalogId=10053

    If it were me, I would probably install a pair of gable end vents such as:

    http://www.homedepot.com/Building-Materials-Ceilings-Attics/h_d1/N-5yc1vZ1xhcZargr/R-100669485/h_d2/ProductDisplay?langId=-1&storeId=10051&catalogId=10053

    And then install the above solar attic fans behind them. The only issue is that the vent has to be blocked off around the fan housing to prevent air blowing back into the attic around the outside of the fan housing.

    I don't know what effect your existing roof vents would have on such a setup. Depending on the diameter of the existing vents, you might be able to just mount the solar power fans underneath them and exhaust the attic through the existing vents.
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  • n3qik
    n3qik Solar Expert Posts: 741 ✭✭
    #19
    Re: Attic Ventilation Project with potential addition of solar attic fan (gable/peak)

    I would check around before doing a continues ridge vent. During a hurricane/high wind event. Water may be pushed up the roof and into the ridge vent opening. This could cause a lot of water damaged.


    I have seen snow pushed up and into the attic with building using ridge vents.
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  • russ
    russ Solar Expert Posts: 593 ✭✭
    #20
    Re: Attic Ventilation Project with potential addition of solar attic fan (gable/peak)

    İ remember hurricane Hugo 10 years back - forced rain through the vent in a gable end of the house in Charlotte, NC.

    İt was raining flat!
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