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Homeowner Forum / Home Automation / June 2005Cooling attic (and home) by spraying water on roof (shingles) - good/bad?
It's a mostly sunny day here (SW Ontario) and the mid-day outdoor conditions are about 87 degrees and 50 to 55% relative humidity. I have new shingles (100% asphalt, relatively light in color) on a roof (pyramidal) with a 4:12 pitch covering an area that's about 36' x 40'. Large vent fan and 3 passive vents near the peak. Soffits are 2 foot wide on all 4 sides (but ventaliation is only good along 1 side for the moment). Small fan is jury rigged in the attic space to provide forced air circulation of the attic space and is powered with the main roof fan. Temperature sensor is positioned 1/2 inch from the underside of wood deck - so I can read the air temp immediately under the decking but not the actual deck or exterior shingle temperature. Around 1 pm today the attic temperature read 120 degrees. I rigged up some garden sprinklers on the roof and adjusted the flow to achieve maybe 1 gallon per minute total flow. Naturally, the water exiting the roof through the downspouts was warm to medium hot to the touch (didn't measure the temp). Within about 15 to 25 minutes the attic air temp was about 100 degrees, and it's almost 4 pm as I type this and the temp is 98.4 degrees (outside temp is about 87). I'm sure I don't have total coverage of roof with water spray. Since I'm currently re-working the soffits (adding pot-lights, speakers, cables for CCTV, etc) I'm going to be running stuff into the attic from the basement. I'm thinking that maybe it might be "cool" to run a copper water line as well and permenantly mount a couple of sprinklers that would give proper coverage to the roof and I could turn on manually or automatically. Is there anything written up about residential roof cooling with water spray? Are the benefits (reduced interior cooling load and increased shingle longevity) outweight by (maybe) shingle dammage by water spray if the water is used on the hottest, sunniest days in the middle of the summer? What is your reason for spraying water on your roof? > It's a mostly sunny day here (SW Ontario) and the mid-day outdoor > conditions are about 87 degrees and 50 to 55% relative humidity. [quoted text clipped - 36 lines] > water is used on the hottest, sunniest days in the middle of the > summer? "Some Guy" > Are the benefits (reduced interior cooling load and increased shingle > longevity) outweight by (maybe) shingle dammage by water spray if the > water is used on the hottest, sunniest days in the middle of the > summer? Funny thing is that a coworker tried this. He said it made his shingles look really old quickly and didn't really do a whole lot other than that. Perhaps you are good (or bad) at math. You might start by looking at the accuracy of your thermometer. Only a few I know will discern accurately the 1.6 degree drop in temp you say, and they are expensive. In other words, the temp could well have gone up with the measurement error added in. Another thing to consider is the heat capacity of the water, and where that BTU capacity is best used - perhaps not cooling your roof. Did your living space get cooler? Probably not. Would a $50 attic fan do a 50x better job? They do seem popular. I suspect there is a reason the world isn't equipped with roof sprinklers. - Nate > "Some Guy" > [quoted text clipped - 11 lines] > discern accurately the 1.6 degree drop in temp you say, and > they are expensive. The thermometer I'm using is similar to this one: http://tinyurl.com/d2u7x It's an older version of the one on that page, except mine is temperature only (so it shows simultaneous temps of both the sensor in the unit and a remote sensor on the other end if a wire attached to the unit). Mine also shows the temp with 1 decimal place resolution. When the remote sensor is brought close to the unit and left to equilibrate for 10 minutes both readings agree with each other to within about 0.5 degree. Whether or not it is off by a few degrees compared with a calibrated thermometer is not really the point. If it shows a daytime attic temp of 120 degrees and then later 74 degrees at night, and if other sensors I have are telling me that it really is 74 degrees outside, then I think I can rely on it. > Did your living space get cooler? Probably not. Hard to judge, given the fact that my thermostat is on the main floor and is regulating the AC based on the temp it is seeing on the main floor. It seems obvious that an attic with an air temperature of 100 degrees would present a much better thermal load on the air space of the house below it vs 120 or 130 degrees in the attic. > Would a $50 attic fan do a 50x better job? > They do seem popular. This is with an attic fan going. > I suspect there is a reason the world isn't equipped with > roof sprinklers. Houses aren't equiped with a lot of things - today or 10 years ago or 30 years ago. My house was build in 1976 and (as I have discovered) has 1/2 inch drywall panels directly behind the aluminum siding on the second floor (no foam-board or styrofoam insulation panels). But getting back to roof-mounted sprinklers, something like that will never become part of standard residential construction because if it's not done right it will more of a liability than an asset (freezing or bursting pipes or condensation in attic, need for a good control system, etc). There is no doubt that water-cooled roofs in industrial/commercial situations have been proven to be useful and cost effective (according to some google searches I've done). I can't find anywhere where they've tried it in a residential situation. Probably another reason why you don't see this in residential settings: Patent 4175703: Spray cooling system for gable roof http://www.freepatentsonline.com/patents/us/417/4175703/4175703.pdf In the USA, you can patent almost anything, regardless if it is similar to what is already in practice, or what is generally "known to those skilled in the art". In this case, the above patent (granted in 1979) at the time the use of evaporative roof cooling was well known for industrial / commercial flat roofs. How this guy got a patent for use on a gable roof is beyond me. The patent office is full of examples of things we don't see as consumers because some bone-head thought he could get rich by patenting something trivial and obvious. All he ends up doing is wasting his money on a patent. I would think that the patent has now expired. > Probably another reason why you don't see this in residential > settings: [quoted text clipped - 18 lines] > > I would think that the patent has now expired. BTW: In searching for the roof spray patent I found this: http://www.freepatentsonline.com/patents/us/417/4173930/4173930.pdf http://www.freepatentsonline.com/patents/us/417/4173930/4173930-002.tif That may be prior art that precedes one of the latest patents from NASA --- its for a golf ball that has aerodynamically more efficient ellipsoidal dimples. The wonder of socialism at work In America !!! ........ The water spray idea could be a nice product business where there is plenty of water. There may be room for some new inventions there. BTW, If you are working on an idea, write me, and I'll get you in touch with the right people. Do talk to your Patent Agent first or we'll help you to find one, and do not talk to others regarding your idea. Least of all on Usenet. No, you don't pay anyone to market your ideas - that's a scam. We help you to get your idea developed, drawn, patented, prototyped, and presentable. Sometimes we can help you to find capital for you for your development purposes, or more importantly, we are a self-help forum for technical ideas of all sorts. Ralph Hertle Vice President and Trustee National Society of Inventors "Some Guy" > Mine also shows the temp with 1 decimal place resolution. > When the remote sensor is brought close to the unit and left to > equilibrate for 10 minutes both readings agree with each other to > within about 0.5 degree. The readout doesn't mean anything. I'd bet you're getting 2 C max accuracy. > This is with an attic fan going. Pretty scientific test you had going there...not! Vent fans are tried and true energy savers. - Nate > The readout doesn't mean anything. I'd bet you're getting 2 C > max accuracy. I'm satisfied that when I bring that particular unit (with it's internal and external transducer) along with several other (different) units together in the same place, and see them display a temperature within 1 degree (F) of each other, that there's little chance that they're all out of whack by the same amount. > Pretty scientific test you had going there...not! My hypothesis was that spraying water on the roof would cause a decrease in attic air temperature. My temp display before applying the spray was showing 120+ degrees (f). Within 1/2 hour of applying the spray the temp went to 100 degrees and leveled off to about 98 degrees after an hour. This was scientific in that - I had reasonable confidence in my measurement device - I varied only 1 parameter during the study - there were no other variables that could have affected the results (like a change in outside temp, cloud cover, etc) During the entire time the roof-mounted exhaust fan was running. > > This is with an attic fan going. > > Vent fans are tried and true energy savers. I don't know what the temp would have been without the spray and without the fan running, but I agree that a vent fan (combined with proper soffit ventilation) is absolutely necessary to prolong shingle life and reduce the heat load to the house. > > The readout doesn't mean anything. I'd bet you're getting 2 C > > max accuracy. [quoted text clipped - 13 lines] > (f). Within 1/2 hour of applying the spray the temp went to 100 > degrees and leveled off to about 98 degrees after an hour. no suprise...sure water cooling works...did you say that was on an 85F day? so you cooled the roof to within 15 degrees. Venting with enough air would have taken the attic temp closer to the air temp that was used for venting. as a wild guess your load vs the cfm....90 deg F. maybe 98 or even warmer...depends on how big fan is and type of roof construction. again. its the temp inside the first 1/2 inch of attic insulation thats most relevant. You have 'what works' confused with whats practical. Phil Scott > This was scientific in that > [quoted text clipped - 13 lines] > proper soffit ventilation) is absolutely necessary to prolong shingle > life and reduce the heat load to the house. >> Mine also shows the temp with 1 decimal place >> resolution. When the remote sensor is brought [quoted text clipped - 4 lines] > The readout doesn't mean anything. I'd bet you're > getting 2 C max accuracy. That may be true, but it's probably safe to assume that the temperature decrement which the gentleman read was not off by 2ºC. Even assuming the "before" and "after" temperature readings were off by a degree or two, the delta reading was probably accurate to within a small fraction of a degree. That said, I'm not sure this is an optimal use of natural resources. Where I live (southern Florida and northern Brazil at various times during the year) water is more expensive than electricity. A good fan can bring the attic temperature to within 5ºC of the outside air temperature. Operational costs are minimal. In Sarasota private well water cannot be used for this purpose for two reasons. First it's usually full of sulfur and iron deposits which would stain the roof horribly and stink like rotten eggs. Second, it's illegal. We have strict environmental laws here to keep anyone other than strip miners from wasting natural resources and destroying the ecology.  SignatureRegards, Robert L Bass =============================> Bass Home Electronics 2291 Pine View Circle Sarasota · Florida · 34231 877-722-8900 Sales & Tech Support http://www.bassburglaralarms.com =============================> > In Sarasota private well water cannot be used for this purpose for two > reasons. First it's usually full of sulfur and iron deposits which would > stain the roof horribly and stink like rotten eggs. Hoo boy, and does it STINK. I was appalled visiting a friend's place some years ago at how badly the water stank of sulfur. > Hoo boy, and does it STINK. I was appalled visiting a > friend's place some years ago at how badly the water > stank of sulfur. One of the worst things is getting hit with spray from a lawn sprinkler while bicycling. :( SignatureRegards, Robert L Bass =============================> Bass Home Electronics 2291 Pine View Circle Sarasota · Florida · 34231 877-722-8900 Sales & Tech Support http://www.bassburglaralarms.com =============================> >It's a mostly sunny day here (SW Ontario) and the mid-day outdoor >conditions are about 87 degrees and 50 to 55% relative humidity. [quoted text clipped - 36 lines] >water is used on the hottest, sunniest days in the middle of the >summer? Back in the days before ubiquitous A/C, and when 'skimpy' insulation was commonplace, "watering the roof" was a _common_ method of making things inside a bit more livable. The idea being to just wet down the roof, and have the water _evaporate_ to carry off the heat. evaporating water pulls off hundreds of times as much heat energy as does just warming the water up does. 'Evaporative cooling' is one of the most energy efficient cooling methods known. However, there are a whole bunch of limits as to how much cooling you can get that way. The higher the ambient 'relative humidity', the less cooling you can produce. The lower the temperature, the less cooling you can produce. And, of course, you have to have a means to 'discard' the 'used up' air. As a practical matter, you "don't care" how hot the attic air is _near_the_ _roof_, if the temperature just above the insulation to the inhabited space stays rational. Decent 'convection' air-flow, possibly with power-assist does a good job of _that_. Also, if you have 'good' insulation between the inhabited space, and the attic, a 'spike down' in the attic temperatures will -not- make a noticable difference in the inhabited space thermal load -- takes too long for the change to 'penetrate' all that insulation. I'd try putting some temprature sensors at, or even a little ways _into_ the top of the insulation at the attic *floor*, and see how bad the temperatures get there. And then try to optimize the air-flow to get those readings close to 'in the shade' outdoor temperatures. > >It's a mostly sunny day here (SW Ontario) and the mid-day outdoor > >conditions are about 87 degrees and 50 to 55% relative humidity. [quoted text clipped - 66 lines] > temperatures get there. And then try to optimize the air-flow to get > those readings close to 'in the shade' outdoor temperatures. Thats good advice Phil Scott > It's a mostly sunny day here (SW Ontario) and the mid-day outdoor > conditions are about 87 degrees and 50 to 55% relative humidity. [quoted text clipped - 31 lines] > Is there anything written up about residential roof cooling with water > spray? Its done very rarely but is a good idea in hot climates... especially as we are going to time of use billing on residential shortly... with roof cooling you could keep from running the AC so much under peak conditions and save a nasty demand charge billing. Using city water though leaves mineral deposits that embed into the roofing and are probably not real good for most roofs over time. thats why its not more common. If enough water can be used so that the roof stays wet and runs off then mineral deposits are less but its still an issue...some areas a big issue... others not. Poultry farms use 3000 psig water atomizer units (pumps as in pressure washers) to force water through tiny nozzels so it evaporates completely in the air...cooling the air and any mineral deposits come out as solid particles and land on the ground. You could cool your attic that way and get good results.. those are fairly expensive systems though. Or you could use an evaporative cooler to cool the attic. 1/6 hp fan motor... would save about 3/4 hp of cooling load. No mineral depost issues... but then you have a swamp cooler to maintain. Phil Scott > Are the benefits (reduced interior cooling load and increased shingle > longevity) outweight by (maybe) shingle dammage by water spray if the > water is used on the hottest, sunniest days in the middle of the > summer? > Is there anything written up about residential roof cooling with water > spray? Besides the glaring fact of WASTING WATER? Do the math on your water bill (or the electric to pump your own well water) and you'll probably find it's a helluva lot cheaper to just leave the roof alone. If anything, put in an attic vent fan. Water's not as harmless a material as one might imagine. The various minerals causing deposits, the likelihood of algae other mold/fungus growth and even it's weight are all factors to consider. Enough that unless the roof was designed with in mind would make it not only a bad idea but a potentially dangerous one at that. -Bill Kearney Jim Baber's comments: >>Is there anything written up about residential roof cooling with water >>spray? >> > >Besides the glaring fact of WASTING WATER? Bill has a point here, but if you were to use misters (like I do between my solar panels and my roof), you might see the same kind of drop in attic temp that I have had. My roof that has my solar system is a 6:12 pitch facing due south. I have noticed a 10 degree reduction in the attic temperature just due to the shading by my solar panels, down from 160 to 150 deg. on a 100 degree day. I installed those commercial cooling misters for patios and yards, behind my solar panels to cool the panels themselves, figuring that I did NOT want mineral deposits on the front. I was not to worried about roof deposits, because I intended to only run the misters on days over 90 when I had measured a drop in power generated by the panels because of temperature degradation above 95 degrees. This supposedly only uses about 2 gal. an hour per the Mfg. claims, and has not deposited significant or noticeable minerals in 2 years of operation. The roof does get damp sometimes but not usually, since there is considerable convection air flow upwards behind the panels that evaporates most of the mist before it wets the roof. I do use a demineralizing cartridge in the supply line, and they are available where I got the misters. When I turned on the misters behind the solar panels the temperature dropped an additional 30 degrees in the attic to 120 degrees. This isn't cool by anyone's idea, but I noticed that the A/C has reduced the number of minutes the it runs each hour by about 15% on those 100 degree days we have too many of here. By the way the misters also accomplished what I wanted in the first place, I got back the 0.83 kW of peak solar production I had lost because of the solar cell heating. (that's about $1.62 for any day over 90) All in all I found it to be a very worthwhile effort since we had 67 days over 90 last year for an additional estimated $108.00 worth of power we produced. I have not estimated how much the reduction in A/C time was worth but I could from the cost of running it vs not running it. >Do the math on your water bill ............ > At 10.8 gal. a day for 67 days that's not much water, but I can't put a value on it since we are not metered at all. You could put a value on it at your cost, but I can't even make a guess as to that. >........ (or the electric to pump your own well water) and you'll probably find it's >a helluva lot cheaper to just leave the roof alone. If anything, put in an [quoted text clipped - 6 lines] >-Bill Kearney > I can't see how it would be dangerous, in fact in So. Calif. some people do this for protection from brush fires, and I would do it here if I still had a shake shingle roof. > >Besides the glaring fact of WASTING WATER? > > > Bill has a point here, but if you were to use misters Doesn't a mister waste water by atomizing it and then the wind will blow it away? I would think the ideal way to cool something with water would be to completely wet the surface of something you want to cool with a low volume of flowing water. That would avoid staining from minerals in the water. The heat you're taking away is the difference between the inflow and outflow temp multiplied by the volume flow rate. Some evaporation will also happen. I know that water can cool best if (all of) it evaporates, but that will leave mineral stains, and also it probably won't get you down to the low temps you can reach by continuous flowing water. My tap water comes from lake Huron and is probably around 50 degrees (f). I pay 3.86 cents (CDN) per cubic foot (3.165 USD). I think that's about 0.516 cents (CDN) per US gallon (or 0.423 cents USD). I pay 5 cents (CDN) per kWh for the first 750 kWh (per month) and 5.8 cents per kWh after that. That's about 4.1 and 4.8 cents USD respectively. > At 10.8 gal. a day for 67 days that's not much water That's 5.6 cents (CDN) per day, or $3.74 (CDN) for 67 days ($3.06 USD) > > The various minerals causing deposits, the likelihood of algae > > other mold/fungus growth and even it's weight are all factors > > to consider. Deposits, yes - but perhaps negligable if the water is not allowed to evaporate. Mold/fungus - I'm thinking no because this would only be used on mostly sunny days for maybe 1/2 hour to maybe 2 hours of the day. When the water is turned off, the roof will dry up and I wouldn't think that would give any mold or fungus any ability to grow given that the shingle temp would probably climb back to well over 100 degrees. A thin layer of flowing water on the roof is equivalent to a gentle spring or fall rain shower and nowhere near the weight of the snow loads we see during the winter. PS: Given gasoline costs at $2 to $3 per gallon (or $1 CDN per liter) what are the costs to generate electricity (on a kWh basis) using a gasoline powered generator? PPS: Are there gasoline or propane-powered AC units, and are they more economical to run vs electric? PPS: What are the pro's and con's of immersing your outside AC condensor coil in your swimming pool (and therefor doing away with the cooling fan) ??? Heat your pool and remove heat from the coils much more efficiently? > > >Besides the glaring fact of WASTING WATER? > > > > > Bill has a point here, but if you were to use misters > > Doesn't a mister waste water by atomizing it and then the wind will > blow it away? The latent heat of evaporation for water is somehing like 970 btu's per lb... one gallon of water is 8 lbs...so its about 7800 btu's of heat required or the equivalent amount of *sensible heat removed from the air to evaporate a gallon of water. Thats equivalent to about 3/4 of a ton of airconditioning (average home takes about 3 tons). So you would have to evaporate about 4 gallons of water an hour to cool the average home in a very dry climate... say 10 hours a day.. thats 40 gallons a day,..or 1200 gallons a month. The average home uses about 500 gallons of water a day the bill is say 25 dollars for that 15,000 gallons a month. So the water used in 100% evap cooling sells for around 3 dollars a month. or lets say 10 dollars max. Cooling the house with refrigerated HVAC will cost 200 to 300 dollars a month or more. The cost of a gallon of city water is less than a cent...so its a very good deal cost wise.. and ecologically much better than running a one HP motor (approx HP required to deliver 3/4 ton of cooling if you count the fans). That power is generated by burning foscil fuels in most cases. Evaporative cooling would be limitlessly popular if it did not add an equal amount of humidity in the form of 'steam' to the air it was cooling to *sensibly lower termperatures. There is sensible heat, measured with a thermometer, and Latent heat thats water vapor in the air..it takes about 100 times as much heat to create steam as it does to raise the same amount of water 1 degree F. So latent heat is a big deal in humid climates... in dry climates you can use evap cooling to take advantage of the situation. The human body feels both this humidity and the sensible temperature as one...so evaporative cooling only works in very dry climates where an acceptable rise in humidity fits well with human comfort requirements. It will become a lot more popular in commercial buildings in the south west shortly..as fuel prices go up. Right now its straight refrigerated air. > I would think the ideal way to cool something with water would be to > completely wet the surface of something you want to cool with a low [quoted text clipped - 30 lines] > given that the shingle temp would probably climb back to well over 100 > degrees. Thats about right. A thin layer of flowing water on the roof is equivalent to a > gentle spring or fall rain shower and nowhere near the weight of the > snow loads we see during the winter. [quoted text clipped - 10 lines] > cooling fan) ??? Heat your pool and remove heat from the coils much > more efficiently? That would be what is called a 'ground water sourced heat pump system' those work very very well. And are popular. For some reason you dont see them piped to pool water very often. But its workable....to a limit. Depending on the size of your pool, in the summer the system would warm the pool...but you wouldnt want it to go over 85 degrees or so...then it would have to switch back to air cooled or a ground loop. In the winter you would be cooling the pool while heating the house... the pool temp would then drop to 40F or so and start absorbing heat from the surrounding ground in most climates... and if the pools was large enough and had a pool cover .. it would make a good heat source for winter heating...but of course then too cold to swim in.. so for that reason pipes burried in the ground are common. The engineering and install can screwed up easily and often is..then its a mess. If done right its a very good deal. On the attic temps though the poster who mentioned temp at the top of the insulation had the best response.. myself in your case I would not wet the roof. I would ventilate the attic with a fan. Phil Scott Mech Engr HVAC contractor since 1829. >Phil Scott >Mech Engr HVAC contractor since 1829. Evaporative cooling must do wonders for longevity. > > Doesn't a mister waste water by atomizing it and then the > > wind will blow it away? > > The latent heat of evaporation for water ... I still don't see an effective way to arrange a residential cooling system based on the evaporation of water. I don't think you can concentrate and deliver a substantial amount of heat to a surface you can cool via evaporation. Evaporative cooling would be effective if the heat inside a house could be brought to an out-door device who's surface temperature is well above boiling and the application of water would result in evaporative cooling. > Evaporative cooling would be limitlessly popular if it > did not add an equal amount of humidity in the form of > 'steam' to the air it was cooling to *sensibly lower > termperatures. So what you're saying is to mistify the air circulating in a house in order to cool it. I don't think that would work once you've saturated the air (ie humidity > 75%) not to mention the effects of saturated air on items in the house, the wood, the machinery, etc. I think only the roof makes a workable item to cool with a water cooling. It's designed to get wet, to collect runoff, and gets very hot in the summer, and cooling it can lead to reduction in cooling requirements of the house. The only thing that makes more sense is a temporary tarp or canopy to cover the roof during the summer (to be taken down during nasty weather, storms, etc). > > > Doesn't a mister waste water by atomizing it and then the > > > wind will blow it away? [quoted text clipped - 19 lines] > the air (ie humidity > 75%) not to mention the effects of saturated > air on items in the house, the wood, the machinery, etc. I am a mechancal engineer doing these sorts of calculations and systems for over 40 years.. and you are entirely correct if the humidity is say 50% and the outside air is 90F... you can cool the air to 75 or so but the humidity is then up into the 80% range and all the problems you mention manifest. Thats why evaportive cooling is not used in many cases. However in areas where the relative humidity is in the 20 to 30% range, and the outside air is over 90F... then the supply air can be cooled to 70F and 50% relative humidity..that works very well/ > I think only the roof makes a workable item to cool with a water > cooling. It's designed to get wet, to collect runoff, and gets very > hot in the summer, and cooling it can lead to reduction in cooling > requirements of the house. Its workable...but there are problems ..its seldom used because of those problems. You get to do whatever you wish though its yer house. Have fun. > The only thing that makes more sense is a temporary tarp or canopy to > cover the roof during the summer (to be taken down during nasty > weather, storms, etc). Oh please. Phil Scott Don't cooling towers use evaporative cooling? > > > > Doesn't a mister waste water by atomizing it and then > the [quoted text clipped - 63 lines] > > Phil Scott > Don't cooling towers use evaporative cooling? Yes they do... but they discharge 100% relative humidity air...but its outside so its fine...the water in the process is cooled and that cool water is used to cool most often the condensers on large tonnage refrigerated AC systems. that water typically runs 65 to 80 degrees F... sufficiently cool to cool condensers but not cool enough to be used directly for conditioning air (below 40F is required) Phil Scott > > > > > Doesn't a mister waste water by atomizing it and then > > the [quoted text clipped - 63 lines] > > > > Phil Scott > > Don't cooling towers use evaporative cooling? > [quoted text clipped - 7 lines] > > Phil Scott Well you really lost me now. Hasn't this suggestion of water ON the roof been about water on the outside of the house? So the humidity created by a watered roof would be outside, just as with a cooling tower. Chas Hurst > > > > > > Doesn't a mister waste water by atomizing it and > then [quoted text clipped - 84 lines] > > > > > > Phil Scott > > > Don't cooling towers use evaporative cooling? > > [quoted text clipped - 10 lines] > Well you really lost me now. Hasn't this suggestion of water ON the roof > been about water on the outside of the house? > So the humidity created by a watered roof would be outside, just as with a > cooling tower. correct...thats why your plan WORKS....that is...it is VIABLE....in other words...you are NOT wrong.... said another way...your plan to cool the roof and thus reduce attic temps will fly like an eagle... its FLAWLESS.... to elaborate... water cooling works GREAT... your plan it water cooling the roof... very very good. Its just that an attic fan works better without whatever problems are incurred by wetting the roof...that is why so few people on planet earth, including the worlds best engineers use the strategy. Its workable you see.... just not practical in context with other approaches. Phil Scott > Chas Hurst > [quoted text clipped - 86 lines] > > > > > > > > Phil Scott > > I think only the roof makes a workable item to cool with > > water cooling. It's designed to get wet, to collect runoff, [quoted text clipped - 3 lines] > Its workable...but there are problems ..its seldom used > because of those problems. Would you care to mention what those problems are? > > > I think only the roof makes a workable item to cool with > > > water cooling. It's designed to get wet, to collect runoff, [quoted text clipped - 5 lines] > > Would you care to mention what those problems are? Water is a corrosive. Would mildly wear the roofing but with your limited use not much... Mineral deposits with your limited usage would be minor but still a negative factor. The net benefit of water cooling the roof would be close to the benefits of attic air ventilation..attic air ventilation would not have that set of minor problems though. Your suggestion is workable just not the optimum as I see it. It would be optimum however say in the deep south west with air temperatures over 110 in the shade... but then mineral content of the water is higher there and could be a very significant problem one would have to look at... it is typically not done. I might be inclined to put a spray misting system in the attic air make up stream. that would work. However misting companies will not sell into a high mineral content water area because the minerals destroy their PD pumps and clogg the micro nozzels....thus...we see swamp coolers used in the south west. Phil Scott > ... The average home uses about 500 gallons > of water a day... Are you sure about that? I use much less than that, even with lawn sprinklers and a 15,000 gallong in-ground pool to maintain. > the bill is say 25 dollars for that 15,000 gallons > a month. Where I live it's a good deal more costly than that. SignatureRegards, Robert L Bass =============================> Bass Home Electronics 2291 Pine View Circle Sarasota · Florida · 34231 877-722-8900 Sales & Tech Support http://www.bassburglaralarms.com =============================> > > ... The average home uses about 500 gallons > > of water a day... [quoted text clipped - 3 lines] > > > the bill is say 25 dollars for that 15,000 gallons a month. 15000 gallons is about 2005 cubic feet. It would cost me $77 CDN ($63 USD) for that much water. > Where I live it's a good deal more costly than that. http://www.azcentral.com/specials/special26/articles/0122drought-waterrates.html Cheap water could become thing of past as supplies dwindle The Arizona Republic Jan. 22, 2003 "It may not seem like it when you write the check to pay the bill every month, but water is cheap in the West. Not only do Arizonans pay some of the lowest residential rates in the nation - in one survey of big cities, only San Antonio charged less - the state's farmers tap into reliable, subsidized sources that allow them to survive a shifting economy. The Salt River Project collects about $10 per acre-foot from its municipal customers, a rate that hasn't changed much in years. The Central Arizona Project, a $4 billion canal that brings water to Phoenix from the Colorado River, charges cities about $105 per acre-foot. An acre-foot is about 326,000 gallons, or enough to supply a five-person household for one year. Tribes have been reluctant to talk price publicly, but one attorney told a group of city officials that the cost could start as high as $1,100 per acre-foot." $10 per acre foot is practically free. Are there no carrying or pipe-line charges? That wouldn't even support routine maintenance. An acre-foot is 326,000 gallons, or about 43580 cubic feet. $100 per acre foot is 0.23 cents per cubic foot. $1000 per acre foot is 2.3 cents per cubic foot. That's still almost half of what we pay (but then some of our costs include sewer surtax). So what does the average home owner in San Antonio pay for his water? > PPS: What are the pro's and con's of immersing your outside AC > condensor coil in your swimming pool Corrosion. Air doesn't eat at the coil nearly as bad as chlorinated pool water would. > Jim Baber's comments: > [quoted text clipped - 38 lines] > power we produced. I have not estimated how much the reduction in A/C > time was worth but I could from the cost of running it vs not running it. Misting is a vastly under used technology... sounds like you have a great application there. Ive been trying to sell it to super markets with air cooled refrigeration for years... a tough sell..but it would save them a bundle and cut repair costs. There are commcl systems on the market for that application but they dont sell well. They sell for chicken ranches and misting public areas the desert mostly. Phil Scott > >Do the math on your water bill ............ > > [quoted text clipped - 15 lines] > do this for protection from brush fires, and I would do it here if I > still had a shake shingle roof. > Jim Baber's comments: Nice bit of explanation Jim. > I can't see how it would be dangerous, in fact in So. Calif. some people > do this for protection from brush fires, and I would do it here if I > still had a shake shingle roof. True, I suppose dangerous isn't the right word. I was thinking more along the idea of some DIY nightmare oversaturating the roof (somehow) and introducing problems well beyond the roof's design. Weight, saturation, downspout overflow, etc. Jim Baber's expanded comments: >>> Is there anything written up about residential roof cooling with water >>> spray? [quoted text clipped - 4 lines] > Several people including Phil Scott have made good comments here. I > feel I need to make 2 points I didn't in the earlier post. 1. The average humidity in Fresno CA is generally quite low in the daytime during the summer. Right now it is 8:30 in the morning the humidity is 66%, and the temperature is only 62.8 with an expected high of 92 @ 17:00 pdt. The humidity will probably drop to about 25 - 35% if it performs as usual. This is really ideal for misting as a cooling device. I just wish these temperatures would continue all summer, but we are supposedly going to hit 100's next week (the latest in several years by the way). 2. Wind does severely reduce the effectiveness of the misting as far as cooling, but one of the major problems with the weather in Fresno is the LACK of wind in the summer. At best we can maybe get a 3 - 6 mph breeze and that will usually be after 7 PM. I just looked at my weather station again, the highest wind speed over the pas 24 hr was a gust to 4 mph most of the rest at 2 - 3 mph. with long periods without any at all. Rather typical and boring. <> By the way, in the 5 min. I've been typing, the Relative humidity dropped to 62 and the temperature went up to 64 >> Is there anything written up about residential roof cooling with water >> spray? [quoted text clipped - 11 lines] > bad > idea but a potentially dangerous one at that. There's one method of using water to cool the roof/attic that can help. I use solar panels to heat my pool. The pool holds ~30,000 gallons. There are eight 4'x10' solar panels on the roof. Sunlight hitting them warms the pool -- not the attic. I've noticed a significant improvement in cool-down cycle (time it takes to get the house cool again after we've been away) with the pool heater running. Since the pool water is being circulated by the filtration pump during the day anyway, there's almost no *extra* cost to use the solar panels. SignatureRegards, Robert L Bass =============================> Bass Home Electronics 2291 Pine View Circle Sarasota · Florida · 34231 877-722-8900 Sales & Tech Support http://www.bassburglaralarms.com =============================> > There's one method of using water to cool the roof/attic that can help. I > use solar panels to heat my pool. The pool holds ~30,000 gallons. There [quoted text clipped - 4 lines] > filtration pump during the day anyway, there's almost no *extra* cost to use > the solar panels. The solar heating system should be a required part of any pool installation. It should be written into the code and rebates should be offered by the utility companies. But that would make sense... R > But that would make sense... True, so don't count on any incentives coming from the present administration either. :) SignatureRegards, Robert L Bass =============================> Bass Home Electronics 2291 Pine View Circle Sarasota · Florida · 34231 877-722-8900 Sales & Tech Support http://www.bassburglaralarms.com =============================> > > [quoted text clipped - 15 lines] > >R I really have to agree, but I feel the government already has too much to say in how I do things at my home. I can't even REPLACE a bad water heater without getting a building permit. Dealers will not sell the heater without the permit, and it is just a way to extract a $35 fee from the homeowner. Supposedly it is to provide inspections to insure proper installation, but when I insisted that the inspectors actually come out and inspect my installation they got very upset, and claimed it would cost them a lot more than the 35 would cover. The did come out, since I told them my next call was to the newspaper. > I really have to agree, but I feel the government already has too much > to say in how I do things at my home. I can't even REPLACE a bad water [quoted text clipped - 5 lines] > would cost them a lot more than the 35 would cover. The did come out, > since I told them my next call was to the newspaper. Given the risk of damage to property and loss of life due to improperly installed water heaters I'd say it's perfectly reasonable to insist a permit be issued. As for your permitting people being lazy, that's certainly worth a call to the newspapers. Call them anyway, if just to give the Metro section reporters something to write about. Jim, watch what you're doing. I don't need your posted response as an email with an attachment. Reading the newsgroup is just fine. R |
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