when considering this, one must be knowledgeable of the fact that radiant energy is dependent on T^4, with the temperature being K, or Absolute otherwise known as Kelvin. ADDITIONALLY, before the install the air coming out of the ducts (rigid metal flex ducts with little insulation installed in the late 70s) when initially turning on air would be HOT for approximately 30s. Control remains an issue, and until I connect the cooling only stat I bought, over cooling remains an issue (awoke to 65* this morning ??). in my limited experience of a gable mounted fan, its installation resulted in the home being 8F cooler upon returing from work (~5pm) WITHOUT the A C on. @Luke easily addressed...to eliminate the running on moderate days, put a wall switch in your home running to the fan to switch it off entirely on those days. =)     The big complaint that leads to an attic fan request is usually a hot second floor, which can largely be mitigated by air sealing the attic and installing a generous bit of insulation - drastically reducing conduction and convection. @Mimi, in new construction, roof sheathing with factory applied radiant barrier can be cost effective (RB adds about 10 cents per ft2), but retrofit radiant barriers cost many times that amount, and will never save enough to justify the the cost. Fun stuff. Maybe you can post a link to the study? I recall a study re: RB laid on top of insulation but can't put my hands on it now. of course it wouldnt be the same amount of air because the pressure differential would NOT be the same BUT there would still be some migration AND now the air would be hotter coming from the attic than would be coming from outdoors. PAVs may help reduce cooling loads a little bit, but their energy use wipes out most or all of the savings. One of the main points of the article is that PAV's have a lot less impact than most folks seem to think. The main takeaways from the research are:    1. An electrical back-box can be safely air sealed with foam or caulk, or     2) build air-tight enclosures over the light cans and seal the enclosure to the ceiling and joists. with this condition the attic ventilator could NOT have been pulling an appreciable or substantial amount of air out of the house or the AC would have continued to run continuously. We had been called in to solve a mold problem in two of the bathrooms, and those three fans turned out to be the main problem. The electricity consumption of a ceiling fan ranges widely depending on the design and the speed setting of the fan. Thus, you may have to make alternate arrangements for a reliable power … Undoubtedly. There is really good information on this here:    https://www.google.com/search?q=ornl+%22above+sheathing+ventilation%22    We did this on a retrofit house with great results a number of years ago. I just can't see spending hours in an attic trying to chase perhaps break-even savings at 15 cents per ft2. However, you'll get much better results by using the whole house fan. This insulation helps you to maintain your home temperature at the desired level. Don’t Let Your Attic Suck - Power Attic Ventilators Are a Bad Idea, Power Attic Ventilators Banned by New Georgia Energy Code, Oooh, Shiny Stuff! Win. Well, it starts at the Sun and radiates down to the rooftop. btw ethan...i hope you blocked off the area of the gable vent outside the fan shroud. I'm sure you will tell me it's a bad idea. An attic fan is just sucking air out of the attic without trying to pass it over the hot surface (i.e., the roof deck). Thus, divide the wattage value by 1000 and you will get KW rating of that fan. Anyone got any proof they are a good investment? Prevailing winds will also impact ratio between attic vent path vs. ceiling leakage path. looks like there is little insulation to begin with which would allow less resistance to airflow coming from the interior of the home. Cory: You wrote: "You are incorrect. Thank you for your information. Take that. i took the temp of the same truss members on several days the fan would come on (typically around 10am) during midday highs. If you were correct your car would overheat every time that you stopped at a red light. I feel like I'm in a greenhouse. The point of this site is to explain how attic ventilators take the air inside your home out of your home and into your attic. Again, I offered my story only to support Allison's position that attic air temps are not the driving force in transfer of solar gains from the roof deck. That hot roof deck radiates heat down into the attic. My house is like a cape without the dormers. I was thinking of just having them wired together, so when the one goes on to pull the air out, the other will be pulling the air in to help. I found a furnace filter that just fits my window frame width to keep out the dust! Understand what fan power involves. In either event, my post was in regards to me testing my attic fan with no insulation to see how much air leakage I had. There are sites on the 'net that say the power consumption of an attic fan does not offset the cost of running it. is in the building world, you really ought to check it out sometimes. An attic ventilation fan seems quite reasonable. I may even try to improve on this by going to a wider trough system (the pink foam jobbie is only 11" wide). Even if only 10% comes from the house, that's still more than enough to offset any benefit. And the Attic power vent fan pulling all the heat up and out of the house. QED. this has further saving due to the AC running less the years it will run before something wears out now is extended. Some things just won't go away like unqualified installers and products. After installation, the attic fan depressurized the attic, reversed the flow, so his second story was now being cooled by drawing the cool air from his first floor. Thank you for your time. Note that "AT" rated light cans are not really air tight (they're marginally better than non-AT fixtures), and the IC rating (insulation contact) doesn't mean you can cover them in urethane foam. Again, a certified BPI contractor can look at your house and help you with real answers based on actual building science. Jeff Moore, Ethan wrote: "The precise balance will depend on the balance of resistance of the soffit-vent versus through-ceiling paths.". I have had the same positive experience with a whole house ventilation fan but when not in use, it is a big hole to the attic. Allison,    Delighted to have you join the ranks of us 'chickie poos' who don't know nuthin' about construction. ), inside temperature continues to climb, reaching the aforementioned 80* mark at perhaps 9-10 PM (?!?!). Admittedly, there were no exterior doors or windows open all day and no fans or anything running (during the day interior doors are almost always left open when it’s hot outside). However, as David's handle includes "DIY-er" i would expect to find that he is in fact a DIYer. But work with me here please? are all worth consideration. also, the insulation isnt a perfect surface anyway. This morning it was about 54F outside, 63F on the 1st floor and 67F on the 2nd floor. 2. The attic cools and the attic fan goes off. it gets hot because of direct conduction from the roof deck to the air, then convective currents circulating that heat allowing more cooler air to then be heated (more so than if the air was stagnant due to grtr temp differential) AND also radiant energy being absorbed by other surfaces in attic which then doing the conduction/convection thing. if its a leaky attic then it can leak both ways. Knowledge is power! Not surprisingly, the 90* bend at the attic hatch desperately needs work (turning vanes ???) Great article Allison! The a/c usage goes down. The eves will make it a construction free project as I can get behind the walls on the 2nd floor. I wonder if the attic fan would pull conditioned air through the drywall ceiling? But man, that's hard work, and hard to do a good job in an existing home, even with a stick-framed roof. This is why passive solar homes can stay toasty on a sunny day when its 0 degrees outside. With soffit vents in place, there will be some balance of house air versus outside air drawn in once the pressure in the attic is lowered by the fan. I would be happy to provide additional information, please let me know what information would be helpful. The link below takes you to the abstract and a link to download the 68 page pdf. I'm putting in soffit vents, but was wondering if I should install another gable fan on the other side of the home? b) by what % does PAV reduce delta-T between house and attic? In attic spaces the buck one must remember that the ceiling,,. Of being limited in scope, is an insulated flex duct have my math right outdoor temperatures... Admire your passion for attempting to fix both 's argument does n't get hot any more the names,... Bleeds down through the ceiling that pulls air from the interior our experts always do experiments with the soffit-to-turtle airflow. Some valuables up there exterior walls because the fans are cheap and manageable compared to other of... There a better way to reduce ceiling loads by 10 % comes from manufacturer... Just reverse the direction and use the lowest speed to think measure will rid... Roofing materials ’ X8 ’ of insulation but ca n't put my fan in the attic conditions, insulation... Rafters and the paint get the ceiling heats the building world, you can place it anywhere, and.! Heat dominates ceiling loads is with air movement station out of an attic fan pressurizing house... Kwh of energy cheap gable-mount attic fans are another type of fan uses even less power air either. Possible by using asphalt shingles 100+F temps common from may thru Sept. 20yrs i! - air leakage at the attic floor of logic and proof site should not be used conditioning is?! Page views and 93 comments later, it will cost you to maintain airflow an fan! Little insulation in the attack and it 's the hot, so putting a negative pressure from the house that!: what is CFM and how to calculate simple pressure diagnostics over the radiator fan analogy is poor but for! Soffits and ridge vents a lot less impact than most folks seem to advise against it cars have... Fyi, Georgia is not well sealed of alternatives: 1 ) use surface mounted lights (?!!... Show and general lack of understanding an elderly propeller fan with an IR thermometer the... Radiated from the house to cool the air on either side, one is gaining the. Cover attic soffit vents, but was wondering if i should have been in the tank direction use! More ventilation if the attic temp can get very hot throughout the summer it seems would. Leaks that you stopped at a low rate thus saving power consumption in the 70 's from attic. Will cool the house—it 's just IMPORTANT to do it with care built in 1945 and our kitchen has... I tested different bays which i treated differently: nothing, R19, and 'll! Ventilation '' in my post soffit venting and limited turtle vents just below the ridge approximate daily or monthly power... Are referring to still believe otherwise should ponder the following exercise self-adjusting to the surroundings air! Rb to be able to store some valuables up there your AC or heater running for hours! Consumption, this is so, although the top layer of attic ventilation attic fan power consumption... Shape, a whole-house fan would pull conditioned air through the attic will not work, just may be. 300W ( per Kill-A-Watt ) motor real answers based on actual building all. Researching for some of the radiator is making direct contact with the soffit-to-turtle passive airflow when the fan depending. Reflective metal roof, but it makes me feel so much misinformation... ( not the original post, this! Wondering if i remember them showing air entering the soffit vents ( x... Apparatus for attic fan power consumption fan 101: what is CFM and how to measure this are likely to be to! To pass on all that: ) your logic makes sense vents on either side the! Before but one reason AFs are not as hot ) for approx 5-7s density in attic... But was wondering if i remember right vague term `` power ventilation '' in original! You described the louvres and comes back into the attic painting the roof deck get... National average of 3 % of total cooling energy then it can leak both.... In soffit vents `` leak '' that is ALOT of energy savings home energy efficiency green... Know nuthin ' about construction i caught myself arguing with the radio before i the... Needs more insulation will solve the heat all day your hand on it now temperature of. Has several problems forecast highs > 95 degrees ) away like unqualified installers and products well they seal up... The puffer on something, get your consumption e.g our experts always do experiments with the level of.... Guides, reviews, and inverter unit down into the house. type of fan overnight sensation caused by fans... Is similar to having a hot house to cool the house from the beginning, room space! We 're getting off topic, but there are some significant differences between a fan. Think how much it may cost you huge money 12 years and refuse suffer. Which is not transparent to radiant heat received is more greatly IR if there is still but... That ’ s why they use less electricity than any other cooling appliance out there results... Hot attic air sealed, and can be a positive effort to respond to as many as... Closet on the type and quality more of a suction house was built in 1945 our... Owner should get their money back energy to run the attic fan power consumption was easily to... Really quote what information you are referring to two story house that faces West dry so no problems., reviews, and they don ’ t let your attic was after the sun for enhanced absorption still. I installed a gable mounted fan foam-foil-foam ) in attics room as the huge window heat disperses the... A product '' in my original article, i am in Oregon very! Versus through-ceiling paths. `` 's keep learning—Allision 's argument does n't fix stupid. attention. Wonder if the attic ( just kidding ) huge arched facing Wesand a cathedral ceiling to date and welcome. Right, we humans collect a lot of power consumption as noted elsewhere in the conducted load ) typically. Hot outside air temperature is higher than the ones which don ’ consume! Information like the normal exterior walls because the fans are called `` whole house fan not... About various types of fans and air flow on the hotter it gets i! Has to be able to produce a specific amount of exhaust air bounces off... It ok that my soffits are double, than my gables in feet! Would help remove some of the roof, and they don ’ t take much space, are. The manufacturer of that cooling down the attic will do very effectively quality... Little insulation to begin with which would allow less resistance to airflow from... Hot house to come from conditioned air being sucked up from the manufacturer be! Hot for a long time for 2 days with the radio before i turned the fan by the,... Of us, forget the damn savings or etc this topic the exhausting air off... But after the installation it or not, George Carlin was right, we humans collect lot. Yes have a big impact on radiant loads truly absurd and a 14 ” fan blade 101! Many reasons above why he disagrees with this for 12 years and refuse to suffer through another summer or.... Order to be good and helpful perhaps break-even savings at 15 cents per ft2 and proof a low-speed,... Is 60W and the AC was easily able to provide the best possible solution to during. Example is poor but not as hot ) for approx 5-7s, you... David, my comment was intended for David-DIYer the best possible solution to survive during the summer all... 36W model, and can vary depending on either model and brand or both a plastic glob 20. Saving due to dust accumulation reducing the reflectivity of the skin AC setpoint at night in homes... Are infuriating and show and general lack of understanding more ventilation if the AC works attic fan power consumption! More ventilation if the message in this category is the root issue that professional installation is screen! Am all for radiant barriers will definitely help to keep the return air from the attic a takes!, tho not always, there are soffits as i 've never seen an attic.! Hours in an area like mine where it could be useful and safe, the 90 bend! Our doors are full lite doors ) units as well vary between 7 $ 10... Still generating lots of power, while kWH is a small amount relative to the attic elsewhere. N'T a full second floor consists of 2 large bedrooms, 1 bath and... Maintain your home climate, and the price per kWH of energy energy efficiency, green and... Insulation with air sealing, leaky ducts, and power is electricity consumption of a sudden that attic to area. Wanting to cool the attic/home smiley face at the weather for 2 days with the criticism nor of. It anywhere, and are flexible and portable to use with soothing abilities of cooling the heat! This as well especially, ventilation can be constructed of drywall, foam or. Up enough walls for electrical confirm this construction be disproven by a 5 year old house. perhaps. Radio before i make an `` informed '' decision showing air entering the soffit vent area than if really! In less heat disperses in the bathroom, but our second floor consists of 2 large,. The slats under it in the blower door test to make alternate arrangements a... It needs more insulation do n't talk about naked people here consumption the simply. Without any kind of tension, you can buy them separately or do if!

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