Funny thing is, I was lying in bed last night and it hit me. The real solution IMHO is not more insulation (which is good, but which is solving a problem that would better be entirely avoided!) so even if the RB was perfectly flat, there is alot of space between many insulation fibers and the RB to give some effect anyway. The wattage that are stated for them are approximate and can vary depending on either model and brand or both. I am seriously doubting the efficacy of either the current practice of soffit/ridge vents or dual eave vents or any powered ventilation truly cooling the underside of the roof deck - which is where the true issue lies. They will give you the reading. So if you measure from the outside and it's 1" from the bottom of one louver to the top of the one below it, and the space is 10" wide, that's 10 square inches. skye, i may have the misconception i am attributing to you but i believe you are a guy... from what i can tell Allison is also a guy so maybe your marriage proposal is misdirected, @John, your question is valid. It is definitely sucking air upstairs, but after reading this article and viewing other pictures, I'm not sure if this is truly an attic fan. Due to your blog, I am now going to pass on all that :) Your logic makes sense. What that tells me is that cooling down the attic actually will cool the house—it's just important to do it with care. Use profanity and belittling when one runs out of logic and proof. Fan power measures exactly how much energy a fan must receive in order to be able to produce a specific amount of air flow. Larry, more likely your AC is running more because the fans are pulling air through your house. In simplest terms, you're measuring the holes. If the conditioned space to attic were perfectly sealed, this would not happen, but even in new construction in California we find: "51 percent of the house leakage area was between the attic and occupied space..." http://www.proctoreng.com/dnld/ECO_Report_CEC.pdf I also have to mention that since there is a leakage connection between the occupied space and the attic that depressurizing the attic can depressurize the conditioned space and the combustion zone space. Take that. I can't be convinced. Electric attic fans vs. He found that the average cost will vary between 7$ to 10$. I don't agree with the criticism nor perspective of this guy -totally. I just haven't found good retrofit option yet. The cooler roof radiates and conducts less to the attic. Just reverse the direction and use the lowest speed. the thermostatic switch may also be set a bit too low and comes on/off at temperatures not appropriate. Will you marry me? looks like there is little insulation to begin with which would allow less resistance to airflow coming from the interior of the home. the car radiator is using air to cool a engine block but is 2 steps removed (water cools block, fins cool water, air cools fins). He's not taking anyone's word for this. We're getting off topic, but here's a link to the Houston study: http://bit.ly/1m4W792. These are likely to be small with relatively low cfm ratings. R-value ratings are calculated at a temperature of 70F (possibly 75F, i forget). I'm sure I have described my situation before, very likely within the 93 comments you mention, but here goes: Diurnal temps here in NV, especially during spring and fall, can approach 35*, and by power ventilating during the night, I can often bring inside temp down into the high 60's by 6am, from a previous evening's high of perhaps 80*. David, In the summer months, a smart attic fan will prevent the attic from reaching scorching hot temperatures that, in turn, transfer into the living space below. It’s an affiliate advertising program designed to earn commission by advertising and linking to Amazon which helps us to maintain this website cost. Anyone have a good product suggestion for accomplishing that? Steve - to your point, I would also like to hear the experiences of anyone who has replaced their asphalt roofing system with metal (either standing seam or aluminum shingles) as metal is a much better radiant medium. However the affect of this roofing material change is remarkable elsewhere. We are in TOTAL sun. EW: That's a fair question, and I should have had that in this article from the beginning. Otherwise it would defy physics. Let's say your car is in the sun all day. We try to provide the best possible solution to survive during the hot summer season. Thank you David. Jump in anywhere, Allison. R30 at 130F is around R19 if i remember right. @Cameron, great point about impact of ceiling temperature on MRT and comfort. And it's part of the reason that my state, Georgia, has banned power attic ventilators (unless they're solar-powered, which was a concession needed to get the grid-powered fans banned). “Measure of power” A 1000 drill will need 1000 watts ( 1kw ) to make it work and use 1 kWh of energy in an hour, according to OVO energy. After I had the fan, my upper story doesn't get hot any more. Without the AC on, and with this fan going, my house does seem cooler, as if the cold basement air is getting turned up onto the main floor. Your comment will not appear below until approved. I've lived most of my life in Texas, Louisiana, Florida, and Georgia. Assuming again it has a 1500watt, which equates to 1.5 kWh, with 2019 electricity price then, 1.5 kWh would cost around 18 cents per hour. Until you address the hot surface created by the kneewall, blowing colder air into the room doesn't fix the problem. They are much more valuable when you have ducts in the attic and they make a bigger difference in an attic with little ceiling insulation. wind? Your website has lots of great insight and information, but I've read both your Canned Light page and this page, and I've read all the reasons we should not use canned lights or attic ventilators, but I haven't seen any solutions or alternatives. the RB bays produced the same floor interior temp as the R19. Or, is the measurement taken from the inside, the louvers are slanted, so from the top of one lover (can't start with the bottom of the louver since I am now behind the it facing the screen) to the one below it is 3 inches. You could add one or two of those passive turbines. I'd love to hear your thoughts. But I don't see this as being much of a problem—I should just experiment and see what keeps the house cooler. This unit uses a heat pump as the primary heating source for the water in the tank. set point of t'stat could also make a difference. I am just worried if my roof and shingles will warp since the attic temp is high and the heat remains trapped in the attic. It would be better to reduce heat loading into the attic at all, which the new roof will do very effectively. He has assumed that, The output wattage of the fan is 60W and the price per kWh of energy cost is $14p. I've lived with this for 12 years and refuse to suffer through another summer. Is it drawing some conditioned air into the attic? Is there a better way to keep the return air from heating up other than control the attic temp. The electricity consumption of a ceiling fan ranges widely depending on the design and the speed setting of the fan. People will write anything these days. I added the soffit vents (16 x 4 vents), 10 on each side of the home, evenly spaced apart. An enclosure can be constructed of drywall, foam board or duct board. heat can and DOES transfer through the RB.... however it greatly retards that process. This creates a nice stack effect and moves air the hotter it gets. The power is adjusted and optimised to limit noise and energy consumption. David, Thanks for your comment! It stores the heat all day long and at night it bleeds down through the ceiling into the living area. For example, assuming your fan uses 60 watts output to the maximum and does not exceed, then take 60 and divide by 1000 (60 by 1000) = 0.06KW. So, we will teach you how you can calculate the energy consumption of an electric fan. Now I'm thinking radiant barrier and more insulation in my attic. It's funny that you posted this article this week because I was listening to the "At Home with Gary Sullivan" radio show this past weekend and a Homeowner called in wanting advice on how to improve her attic. Not to mention, 1/8 HP with 210W is a bit high power requirement, yet provides reduced power consumption that makes it best electric attic fan. And I agree with the additional energy costs, but my attic fan is a 1500 CFM @ 40 Watts. I've been in lots of attics. Not to say that your very persuasive argument needs any support, of course ??. The actual value of electric energy usage may differ significantly from the given. There's no way there was enough open vent area in that attic to supply all 8 of those fans. You open the door, and the seats are hot. Also, 1/8 HP with 210W is a somewhat high power prerequisite, yet it gives diminished power consumption that makes it the best electric attic fan. One of my ideas was to replace the insulation on the 2nd floor walls with a higher R-value maybe even spray foam. Most people think adding more insulation will solve the heat transfer from attic to living area but this is not necessarily correct. 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). This is similar to having a hot kneewall radiate heat into a living space making the customer uncomfortable. Could it be that although the attic is a little cooler, it is, in fact, drawing in more humid air from outside and, because the temp in attic is lower, the dewpoint is also lower? You can place it anywhere, and they don’t take much space, and they don’t consume much electricity. Just an example, but this is how you get to calculate. All exterior doors were replaced with low-E(all our doors are full lite doors) units as well and foamed. However, a ceiling fan in a room with attic exposure also acts to disrupt the air film, reducing it's R-value, which brings ceiling temperature closer to room ambient. We've definitely covered it in other articles and in comments, but if you'll look back at this article, I've just written an addendum with some advice on what to do instead of using PAVs. The reason is simple. Likewise, a massive pedestal fan has a maximum output of up to 300w, whereas, a small one will range between 45w to 70w. In this article, we are going to give you idea about various types of fans and their energy consumption. I have read many of the comments about how taking hot air out of an attic will not lower the temperature. Should I close some soffits to create more of a suction? I installed 2 attic fans last fall. PAVs can backdraft combustion appliances. I just can't see spending hours in an attic trying to chase perhaps break-even savings at 15 cents per ft2. But there's really a more fundamental reason that power attic ventilators won't help a lot, and for some reason, I didn't mention that in the original article. However, a whole-house fan would be a lot more effective if the objective is to avoid the use of A/C. Sleeping with a Fan on – Wise Choice or Not? as temps rise R-value goes down. I adapted it to my attic access hatch, used a GFCI and a timer for (limited) control. How to Install Window Fan (Easiest Method). Nor am I. here goes...while this information MAY be accurate it is also misleading. is in the building world, you really ought to check it out sometimes. I used a smoke puffer, and there was no air leakage. Did you mean to say that your ceiling is not sealed? This is why passive solar homes can stay toasty on a sunny day when its 0 degrees outside. Where my attic temperature sensor is located may be slightly affected by heat loss from the house whenever the attic temperature falls below indoor temperature, so the effect of night sky radiant cooling on the metal roof and attic coupling is to me not sufficiently measured. the AC ran considerably less after the fan was installed PLUS we had a better quality of comfort which is hard to put a dollar value on. Without any kind of tension, you can use any type of fan overnight. (Don't be scared; you can click the link without leaving the Energy Vanguard website and without seeing anything indecent.
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