Gary, / wall / ceiling / floor ... the V4A whole-house exhaust fan will provide you all the comfort and air quality you can expect from a low consumption, silent exhaust fan. @Mark, you are correct, my comment was intended for David-DIYer. Until I replace the roof (with an add-on, vented, light-colored metal roof a couple inches above the shingles) this will do very nicely. 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. However, you'll get much better results by using the whole house fan. The room also has a cathedral ceiling. maybe a separate blog topic? Otherwise it would defy physics. Ethan - when you replace your roof, DO NOT allow the old shingles to remain. Turn your fan off and monitor the temperature in your attic up unitl 2pm or something, then turn it on. If we were to build roofs like radiators, I'd agree with you that we could cool them with fans. the result...118F. Attic fan prices. So, I'm often at a loss for what to tell people who are concerned about storage in attic spaces. In these cases, the insulation and the paint get the job done with no batteries required. Some things just won't go away like unqualified installers and products. One of my ideas was to replace the insulation on the 2nd floor walls with a higher R-value maybe even spray foam. They're granular. My house is 2 floors but the second floor isn't a full second floor. without that set up much of the air exhausted by the fan simply bounces back off the louvres and into the attic. Its because radiation does not need air as medium to move so therefore air doesn't have a big impact on radiant loads. this was observed on numerous days following the installation. the air in the attic gets hot. But that radiant heat passes through the attic air and hits the solid materials. each succeeding night after that it switched off at 11pm no moatter if the daily temp high was 90 or 110. so there was at least a 4hr time period where the temps would have been 105+F (themostatically controlled switch was set at 105F). heat can and DOES transfer through the RB.... however it greatly retards that process. All exterior doors were replaced with low-E(all our doors are full lite doors) units as well and foamed. Have them stripped off, have the decking repaired/replaced as necessary, have new peel-and-stick weatherproofing installed, have furring strips installed over the roof joist lines, THEN have the standing seam light-colored metal roof installed. 660. d) multiply %'s from (a), (b) & (c) to get % reduction in total cooling load. My plan is to add thermostatic control to prevent over-cooling, as you described. You never mentioned where you live but it sounds like your problem is inadequate attic ventilation. If it's not in good shape, air sealing and insulation will save you more money and make your home more comfortable than power attic ventilators. the cost of running the fan was calculated at 30cents/day (running 13hrs at the $kW-hr we paid). Fish Tank. I remember them showing air entering the soffit vent on one side of the house and exiting the other side (windy conditions). If you set your pedestal fan at a low-speed level, it will not use as much electricity as when its at high speed. For some reason, the links were stripped from my last comment: Fan (Window) 200. Let us assume an attic fan is 300 watts and that fan is set at 110 degrees F. For the Chicago area, that would mean the fan would probably operate 700 hours during the cooling season. 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. so as temps rise in the attic, and hence less energy is convected off the insulation into the attic, the insulation on the ceiling is less and less effective, potentially by a LARGE amount. That's why pressure diagnostics is the only way to demonstrate the impact of the fan (or lack thereof) on house air changes. Luke: It's even more easily addressed than Mark says. one more thing that is flawed in your article. Jeff Moore, We have CA and ceiling fans in all rooms upstairs, but our second floor remains VERY hot throughout the summer. I went slightly off the reservation in discussing nighttime ventilation only to demonstrate an effect I observed in my home regarding Allison's thesis that attic temps are not a primary driver of occupied space conditions. Karen with the giant west facing window: You need to have a BPI certified contractor inspect your house. 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. Not to say that your very persuasive argument needs any support, of course ??. I have personally experienced immediate backdrafting and CO off scale when Jim Fitzgerald turned on an attic ventilator while I was testing a furnace in the house. What that tells me is that cooling down the attic actually will cool the house—it's just important to do it with care. Secondly, contact the manufacturer of that individual fan. again the critics will say "but then there is NO airgap" which is necessary for a RB to be effective. I would also recommend getting a BPI certified contractor to diagnose your house for you. I once had a house with R/H running in the 70's from an attic fan pressurizing the house. With the attic fan on, I tested the outlets and light switches in two rooms below the attic fan, and the smoke puffer didn't get pulled. However, studies have shown that typically this reduction is in the 5-10% range. Did you mean to say that your ceiling is not sealed? @Ethan, I realize there must be at least 100 comments posted here, but your situation has already been addressed more than once. Are you ready for this? In doing so, I have made an interesting observation in regard to the dynamic of my home's response to outside temperatures that I believe further supports your position that radiant heat from the bottom of the roof deck is likely the primary driver of solar gain entering the occupied space. clearl the testing didnt encompass all conditions yet you make recommendations for ALL CONDITIONS. For a DIY, I guess it depends on how much one values one's time. Big difference, just didn't know which one was the appropriate way to measure this. first...what gives a sunburn is UV. That's not what this article is about, as noted elsewhere in the comments. Would really like to see BSC or some other research group do more definitive/controlled analysis as I really think this is the root issue. I quoted Peter Yost in the earlier article, and in the comments, David Butler made a similar remark: "In a particular home, if a PAV truly reduces cooling costs enough to pay for itself (don't forget to consider the energy the fan consumes), then that tells me there are issues with ceiling insulation and/or attic venting.". etc    i know in my current house, 1-1/2 story home, the knee walls in the second story were insulated but the interior temp of the wall would still be hot enough in the summer months that leaving your hand on it for more than 5s was uncomfortable. The best way to reduce ceiling loads is with air sealing and insulation. Fan (Attic) 370. After sunset the attic temperatures continue this trend. here goes...while this information MAY be accurate it is also misleading. I don't even know what to search for on Google. David, If you were correct your car would overheat every time that you stopped at a red light. That heat then conducts down through the roofing materials. This is similar to having a hot kneewall radiate heat into a living space making the customer uncomfortable. They will give you the reading. "You cannot cool radiant surfaces with air. Likewise, a massive pedestal fan has a maximum output of up to 300w, whereas, a small one will range between 45w to 70w. Most ceilings aren't air-sealed well, so putting a negative pressure on the attic will do that. but there ARE times when a PAV can do the trick. The insulation is like s storage battery. New home owner probz. Now I know that heat radiating from the bottom of the roof deck and, to some extent all the trusses that have been baking in the attic all day, finally penetrates the R-40 attic insulation and turns my ceilings into radiant panels! I've lived most of my life in Texas, Louisiana, Florida, and Georgia. Take a look at all those cooling fins. Cory: You wrote: "You are incorrect. That still wouldn't solve the problem of pulling air from the house, wasting air conditioning money on cooling the attic and potentially backdrafting combustion appliances. as for your erroneous thought on cooling the attic. The attic is reasonably well insulated the ceiling is not well sealed. 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. on work days while gone we would NOT have the AC on. Energy Star and other efficiency programs require knee-walls to be fully encapsulated and air sealed (framed with top & bottom plates and fully backed). Prior to the fan, it took hours for the upstairs to cool down. And let us assume the cost per kilowatt is an outrageous $.14. By self-adjusting to the attic conditions, the fan is able to maintain an optimum year-round attic climate while minimizing energy consumption. So, it's natural to think of cooling the attic. as temps rise R-value goes down. How to Install a Roof Attic Fan? What do folks think about installing a reflective surface to the underside of the rafters as a solution to the radiant problem? Our problem is that the second floor is a Sharpe difference in temp than the 1st floor. The device includes a controllable temperature range of 60 to 120°F. I am a homeowner who was about to embark on paying an installer to repair/install new attic fans (electric) in a ceiling of the main house and a gable-mount in the guest house detached from the main house. I hope I've painted a clear enough picture of the layout let me know if I need to elaborate. People who think radiant barriers are magic: They're not. Another study by FSEC showed 12% average savings in older homes with crappy air sealing, leaky ducts, and poorly insulated ceilings. Continue that way with the rest of the openings, add them up, and that's your net free area. admittedly the radiator fan analogy is poor but NOT for the reasons you exclaim. My logic is that the 2nd floor is basically in the attic and that’s why it’s always so much hotter or colder up there. - Radiant Barrier Fundamentals, † My friend Mike Barcik gets credit for this analogy, except that when he tells it, you're lying naked in the sun. Imagine cooling your home without paying a dime extra on your utility bills! Now Since hot air rises and the living area is colder than the attic, how can this be true? Please help me to understand, that although the attic fan is on, there is no insulation in the attic, the attic isn't sealed, why is the smoke puff test not reliable in this situation? Bottom line: we should focus on building homes correctly to begin with and not rely on expensive band-aides. For me the equivalent area would be 4 hatches about 15 ft. long by 20 ft. high. Until you address the hot surface created by the kneewall, blowing colder air into the room doesn't fix the problem. The bearings are sealed and never need attention. Thank you for your time. at this temp, because of T^4, the radiant energy emitted is about 13W/sq.ft. There are soffits as I've mentioned and gable vents on either side of the 64’, no ridge vents. If you don't have AC, a PAV will help, but not as much as a whole-house fan that exhausts directly from the living space. We have a whole-house fan as well. hopefully this not not a "professional" job because it is pure hack. Power Consumption In another house I hooked a duct blaster up to the ducts (ducts in the attic) and I was getting pressure before I turned the fan on. Additionally, through time conduction/convection from the insulation surface to the air above is increased the GREATER the temperature difference between the insulation and the air. Like it or not, George Carlin was right, we humans collect a lot of stuff. Our bathroom is in the room opposite side of the huge window and there isn't a window in there to provide any cross ventilation. whereas they are both cooling, the example is poor. There appears to be far less radiant heat upstairs—it is always comfortable and just a few degrees warmer than downstairs, but no noticeable radiant heat. I suspect that the reason some have seen cooler attics when a reflective barrier is placed under the roof is because it traps air between the roof deck and the barrier, causing the air space to heat up even higher than without the barrier and causing a greater thermosyphon action to occur against the roof deck underside. It stores the heat all day long and at night it bleeds down through the ceiling into the living area. This mode of heat transfer is more effectively limited by 1) increased attic insulation, 2) a truss-mounted radiant barrier or 3) a white reflective roof surface that limits solar gain to the attic structure.". The insulation and air sealing keeps out the radiant heat, my interior home temp is fine. Sometimes your money will be better spent installing insulation, sometimes installing a radiant barrier. this made a BIG difference upstairs (i typically minimize air conditioning runtime and find other methods of cooling)    also, i installed RB in the crawl space of my gf's house. I found a furnace filter that just fits my window frame width to keep out the dust! Wind-powered attic fans are another type of green energy that reduces power consumption. The actual value of electric energy usage may differ significantly from the given. Regarding this point, Danny Parker wrote in a literature review of attic ventilation, "Detailed simulations suggest that the heat transfer in an attic to a residential building interior in mid-summer is dominated by radiative gains from the hot roof decking directly to the insulation surface. I'm not going to seal my ceiling **because I have a whole-house fan** and it would be difficult and expensive to do—refit everything, reinsulate everything, change the fan louvers, etc. We are working on a house right now where we used radiant barrier sheathing, included the normal soffit & ridge vents, installed the baffles throughout the entire roof, and then sprayed foam to the under side of the baffles. The table represents the approximate daily or monthly electrical power consumption of various household objects. but NOT always i understand. This will reduce electricity consumption… How to Calculate Electricity Consumption Of Electric Fan. Expect to pay between $50 to $400 and up for an attic fan, depending on the type and quality.. Passau . David E, I have seen research presented which supports what you're saying about where the air goes. When we are hot, we want the   feeling off of us, forget the damn savings or etc. You open the door, and the seats are hot. As long as they have at least as much net free area as the soffit vents, you don't need to install ridge vents. Some of that heat gets into the air above the hot materials on the attic floor, but the attic air getting heated up is a secondary effect. while doing the last step you might as well take the time to block off the area outside of the fan shroud so exhausted air doesnt bounce off the vent louvers and return to the attic. With the asphalt shingles, peak attic temperatures on days when outdoor ambient temperatures met or exceeded 100 degrees F would exceed 140 degrees F. The attic would remain above outdoor ambient temperatures well past sunset, imposing a heat load on the house HVAC as if the sun were still up. I recently discovered that my use of my attic fan has been extended a bit in that I recently installed a GeoSpring water heater. HOWEVER, energy WILL be conducted from the wood material to the air at the boundary of the two AND THEN convection currents will continue to transfer this energy to other parts of the attic space. 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! the energy density in the engine is MUCH higher. Knee-walls are a different story. Dropping the temp by 10°F would reduce the heat load to the second floor by 20% (of 750 BTU/h), so the attic fan reduces the conduction cooling load by 150 BTU/h, or 50W!! Your comment will not appear below until approved. And no, I do not recommend adding a second fan. How to Position Fans to Cool a Room – Learn Right! I'm sure you will tell me it's a bad idea. :). What would be wrong with replacing the power attic fan. It has automatic louvers—I don't know how well they seal, but I'm more worried about losing winter heat this way than summer cooling, since I use AC so little. That being said, what do you recommend that would help? Or if you live it for a long time? Sleeping with a Fan on – Wise Choice or Not? Those walls aren't like the normal exterior walls because the adjacent space is way hotter than outside. That's a whole 'nother topic. and you tell me it wasnt worth it. You could get a blower door test to make sure you've got it airtight. The 14" fan consumes 245 watts. Thank you for your information. I recall a study re: RB laid on top of insulation but can't put my hands on it now. Tower fans don’t cool the air, that’s why they use less electricity than any other cooling appliance out there. If this is so, I didn't really see any smoke being pulled whatsoever. you would be surprised how much air actually re-enters the attic without this blocking. And no - that's not me in the photo.). @Steve W, I fully concur with Allison re: radiant heat dominates ceiling loads. Our fan was installed in the upstairs hall ceiling blowing into the attic. the fact that the air in the atic gets hot in the first place, unbearably hot in fact, shows that energy transfer occurs from the solid surfaces to the air (and some of it actually is radiant energy from the surfaces to the air directly). There is no HVAC or dehumidifier; electric heat everywhere, and yes I LOVE it (I’m probably the only person who loves electric heat). We agree that professional installation is a deal killer for RB. Radiator FAN. 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. Thus allowing a higher AC setpoint at night the owner should get their money.! 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As the huge window, it 's even more easily addressed than mark says don. Observed on numerous days following the installation of an attic, the attic, how can this true... Flip open 60 to 120°F room – Learn right to impact a larger surface area make the two hard. Air isnt a perfect surface anyway vary between 7 $ to 10 $ to get the ceiling all. Many comments as possible a a minute of head scratching to realize that use. At night it bleeds down through the attic this would note be the best solution...