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2854RE: [hreg] Solar Attic Fans OPPS

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  • Andrew McCalla
    Dec 15, 2004
    • 0 Attachment

      Oops,

       

      Sorry folks.  I didn’t read down far enough to realize that LaVerne had already done the research…………..

       

      http://www.fsec.ucf.edu/bldg/pubs/pvfan/  This is the kind of documentation I like.....

       

      http://www.advancedenergy.org/buildings/knowledge_library/ventilation/solar_powered_attic_ventilation.html

       

       

      Sorry about the repetition.

       

       

      Andrew H. McCalla

      Meridian Energy Systems

      2300 S. Lamar, Ste. 107

      Austin, TX   78704

       

      Voice: (512) 448-0055

      Fax:    (512) 448-0045

      www.meridiansolar.com

       

       

       


      From: Environment Associates Architects [mailto:laverne@...]
      Sent: Monday, December 13, 2004 11:16 PM
      To: hreg@yahoogroups.com
      Subject: Re: [hreg] Solar Attic Fans OPPS

       

      Hi Steven:

       

      UhOh.  I see that there is a misunderstanding about what I said in my email.  Where you got that I said or even implied that a return on investment did not exist for solar power is beyond me. 

       

      I stand behind everything I said.  All I am asking for is proof verifying what is being claimed.  Actual studies that verify that solar powered attic fans work better and are a better investment than passive solar ventilation systems like continuous ridge vents with balanced soffit venting.  As I stated in my email, provide the proof and I will be an advocate of the technology.  So far I haven't seen or heard any proof, just what seems like sales talk and literature by manufacturers and resellers that sounds convincing on the surface.  I know the PV cells will outlast the life of a composition shingle roof, but what about the fan?  How long will the fans actually last in an environment having elevated temperatures?  Can replacement fans be easily purchased?  What is the cost to remove and replace the fans? 

       

      I am sure there are lots of applications where solar attic fans may be a good solution.  One of these may be where it may not be cost effective to install continuous ridge vents is on a ten year old composition shingle roof, because the ridge vents will have to be ripped off in 5 years or so (Houston climate conditions) and replaced because the roof will need to be replaced.  Another application may be very complicated roof shapes.

       

      Everything has its application.  As an advocate for solar energy applications since the 70's (along with being a founding member of TXSES & TREIA, I was one of the founders of another non-profit solar energy society that predated both TXSES & TREIA), I want to see solar power shine as much as anyone else does.  But I need verification of the claims that are being made.  I think it is best for the long term interest of Complimentary Energy Systems.  (UhOh, I'm sure to get comments on this!!!!!)

       

      Here are a couple of web sites that may be of interest to those following this discourse:

       

      http://www.fsec.ucf.edu/bldg/pubs/pvfan/  This is the kind of documentation I like.....an actual study on the viability of PV powered attic ventilators.  By the way, FSEC also advocates white roofs that may work well in Florida but most will mildew here (Houston) (It's that grayish black stuff that covers composition shingle roofs of all colors here, but shows up most on those that are the lighter colored.  If you can find composition shingle roofing having lots of zinc granules, the leaching out of the zinc will kill mold spores before they can grow like below most vent pipes and turbine ventilators where they poke through composition shingle roofs here.  Manufacturers' make such roofs, but in the past no one was willing to order a box car load (minimum order) of them to sell in Houston .) 

       

       

       

      LaVerne A. Williams, AIA, LEED AP
      architect & building ecologist
      LaVerne@...
      ENVIRONMENT ASSOCIATES, Architects & Consultants
      5828 Langfield Road
      Houston , TX 77092-1429
      713.528.0000
      866.815.2527 toll free
      www.environmentassoc.com
      30 Years of Leadership in Healthy, High Performance Homes / Green Architecture
      Design Counseling / Consulting / Architectural Design / Construction Documents / Construction Administration Services

       

       

       

       

      ----- Original Message -----

      Sent: Monday, December 13, 2004 12:15 PM

      Subject: Re: [hreg] Solar Attic Fans OPPS

       

      Laverne,

       

      Considering the power source for any solar product is Sun energy that we don't pay for, how can you say the return on investment does not exist for using a solar product in this application or any application?  It seems to me that if a solar fan runs for five, ten, fifteen years then the return of investment would be realized several times.

       

      SBT Designs
      25581 IH-10 West
      San Antonio , Texas 78257
      (210) 698-7109
      www.sbtdesigns.com

      ----- Original Message -----

      Sent: Sunday, December 12, 2004 10:25 PM

      Subject: Re: [hreg] Solar Attic Fans OPPS

       

      John:

       

      See my comments in green below.  Also, what most people may not realize is that I don't sell any construction products, building equipment, solar, alternative or conventional energy products, so there is no vested interest in the recommendations I make.  In other words, I don't make any profit from the sale of the stuff I recommend.  Nor do I accept any "referral fee"  compensation from those who do manufacturer or sell the products I make in my recommendations.  I do this because I want all of my clients to know I am looking out for their best interests, not how much money I might pocket from what I recommend for their particular situation.  If for some reason you don't think I am up to date with what is available out there, please educate me, as I would want my clients (and subsequently you) to benefit from superior technology and design. 

       

      LaVerne A. Williams, AIA, LEED AP
      architect & building ecologist
      LaVerne@...
      ENVIRONMENT ASSOCIATES, Architects & Consultants
      5828 Langfield Road
      Houston , TX 77092-1429
      713.528.0000
      866.815.2527 toll free
      www.environmentassoc.com
      30 Years of Leadership in Healthy, High Performance Homes / Green Architecture
      Design Counseling / Consulting / Architectural Design / Construction Documents / Construction Administration Services

      ----- Original Message -----

      Sent: Sunday, December 12, 2004 5:30 PM

      Subject: Re: [hreg] Solar Attic Fans OPPS

       

      Mike, we install lots of SOLAR powered attic fans and I can tell you that they do save you money because they have no ongoing cost to run and reduce the attic temperature of homes from 20 to 30 degrees.(But there is initial cost and lifecycle cost issues.  What is their life span?)  Show me the tests that prove this much temperature drop along with acceptable life cycle costs and I will become an advocate of solar powered attic ventilation fans.)    I don't see how this cannot save you money on cooling your home in the summer.  It also helps reduce moisture in the attic which can cause other problems. (Let's think about this.  Generally, let's hope the air outside the attic is more humid than the air already in the attic, (an exception perhaps being after a dry cold front comes through) otherwise there is a basic construction or operation problem here.  So I don't see how bringing in more humid outside air is going to make the attic less humid.)  Soffit vents to create bottom to top air flow are essential.  My experience with ridge vents and soffet vents is that if there is not a suction or motor pulling the air out they do very little good. (That's the beauty of passive ventilation systems.  They work by creating a laminar-like flow below the roof deck that is spread out over a large area.  Plus it is removing the hottest air....the air right below the roof deck.  It's not like measuring the concentrated flow of air near a fan. Passive ridge vents don't require any generated energy to run them, solar or otherwise, other than the heat of the sun on the roof to create a thermal chimney effect, i.e., hot air rises to create a draft.  This draft is enhanced when there is a breeze and the flow of the breeze over the ridges creates a suction throught the Venturi effect.)   Take a cigarette in the attic and check air flow before and after attic fans, it is a good way to test real world conditions.  (When I did smoke a long time ago, I could always show my clients how the draft was working with ridge & soffit vents.  The only time it didn't was when the ridge and soffit vents were not installed properly.......or it was nighttime.)

       

       It is common sense and I don't know if they were talking about attic fans that ventillate from the living space or from the attic in the mentioned study but if you have a 130 degree oven (your unventillated attic) over your living space and most homes have their AC vents running through this hot space that this heat transfers to your living space and to your AC.  I personally have measured the temp of the air coming out of AC vents in attics and have seen a 2 to 3 degree difference within hours of installing solar attic fans.  (2 or 3 degrees?  You said 20 to 30 degrees in your 1st sentence.  Which is it?)

      I have also had customers tell me that they used to keep thermostats at 74 and now, with attic fans and a cooler attic can keep their thermostat at 77.  Several repeat sales.

       

       Not sure that solar attic (crawl space) ventillation units were around in the 70's so not sure what was included in the aforementioned study 35  years ago but I have hundreds of customers that will testify that they are a good investment and have reduced their electric bill, especially in the summer. (They weren't available then.  Especially if there is a moisture problem with a crawl space, this is a good application.  However, the source of the moisture should be addressed and eliminated if possible due to health concerns)  We put thermostats on the solar attic fans to cut on at 80 degrees and cut off at 70 to save heat in the winter.   You be the judge. 

      I agree that radiant barrier is a good investment as well, keep the heat out in the first place and keeps your heat in. 

       

       

      Solar hot water can interface with existing water heaters by adding a preheat tank that captures the hot solution from the roof panels (located in the sun) and preheats the cold water going into your existing water heater.  It is better to add a new tank as well but that is not necessary.  (I concur.  I especially like passive solar water heating systems that include the storage tank.  No freeze concerns as long as the solar collector has a drain down provision.  They do present some structural concerns and may require some additional support.  I do not, however, recommend mounting any type of solar system on a composition shingle roof, because of the roof will have to be replaced long before the solar system and removing and reinstalling a solar system is too costly for most folks.  This is the main reason why you don't see any solar systems from the 70's & 80's still on rooftops in Houston , as there were tens of thousands, if not more, installed.)

       

      We have units in stock if you are interested contact me offline they are easy to install yourself if needed.  Houston is an ideal market for this as it is hot 8 months out of the year.  (Did you purchase David Sawchak's stock?)

       

      regards

       

       

      John Miggins
      Harvest Solar & Wind Power
      "renewable solutions to everyday needs"
      www.harvest-energy.com
      Phone/Fax 918-743-2299
      Cell: 918-521-6223

      ----- Original Message -----

      Sent: Sunday, December 12, 2004 1:06 PM

      Subject: Re: [hreg] Solar Attic Fans OPPS

       

      Opps.    Please see my correction/comments below in GREEN to my original email.

       

      LaVerne

      ----- Original Message -----

      Sent: Sunday, December 12, 2004 12:29 PM

      Subject: Re: [hreg] Solar Attic Fans

       

      Mike:

       

      Back in the 70's, a study was done in Houston by HUD (I think) regarding attic fans versus other types of attic ventilation and the results came back showing the energy saved (in air conditioned homes) by attic ventilation fans for removing heat didn't offset the amount of energy they used.  So this study showed there was no advantage to powered attic ventilation.  This would also apply to PV powered attic ventilation fans.  It clearly showed that when it came to ventilating attics in Houston , continuous ridge and soffit ventilation performed best.

       

      (Assuming you are using gas for heating** and that your furnace is located in the attic where it needs combustion air supply from outside), continuous ridge vents balanced with soffit ventilation proportionally located around the entire perimeter of your house is your best option.  If you have hip roofs, you will have to run the ridge vents down the hips.  I would use Cor-A-Vent for the ridge and hip vents, following details you can get from their website.  The soffits vents can be any kind (even galvanized  hardware cloth).  They must can be sized to balance the air admittance into the attic so that the free inflow air flow area is equal to or greater than the free exit area of the ridge vent area.  In other words, don't put twice as much soffit venting on the west side versus the east side of your roof.  It has to be evenly balanced around the house.  Otherwise, you can get water intrusion into your attic during blowing rains, not matter whose ridge vent system is used. 

       

      Also, be sure to include insulation baffles in your plans so that the air path from the soffit vents to the ridge vents isn't blocked by insulation.

       

      If your house is all electric, you may want to consider insulating at the roof and eliminating attic ventilation all together, as a lot of moisture is added to the interior of your house from having ventilated attics.  In this area of the country, approx. half of your air-conditioning bill comes from just removing the moisture for the air.  While all this moisture obviously doesn't just come through your ceilings, sheet rock and insulation are not going to stop attic moisture from diffusing down into the interior space.  So eliminating the moisture from this source will not only help reduce your energy bill, but can also provide a healthier indoor environment.  Since dust mites and molds thrive in high humidity environments, eliminating as many possible sources for humidity intrusion into the interior of our homes is prudent.  However, insulating at the underside of the roof will cost more initially.  

       

      Should you follow the ventilated attic path, if you haven't already stapled a radiant barrier to the underside of your rafters or considered some other means for adding a radiant barrier to the underside of your roof, it should be considered a major component in your strategy to improve your home's performance.  If you decide to insulate with spray-in foam insulation on the underside of the roof deck, then disregard the use of the radiant barrier.

       

      Hope this helps. 

       

      LaVerne A. Williams, AIA, LEED AP
      architect & building ecologist
      LaVerne@...
      ENVIRONMENT ASSOCIATES, Architects & Consultants
      5828 Langfield Road
      Houston , TX 77092-1429
      713.528.0000
      866.815.2527 toll free
      www.environmentassoc.com
      30 Years of Leadership in Healthy, High Performance Homes / Green Architecture
      Design Counseling / Consulting / Architectural Design / Construction Documents / Construction Administration Services

       

      **If the water heater is gas, make sure you don't eliminate it's outside air supply for combustion in your insulation /attic sealing efforts.

       

       

       

      ----- Original Message -----

      Sent: Saturday, December 11, 2004 7:20 PM

      Subject: [hreg] Solar Attic Fans

       

      Hello,

       

      I guess I have to start somewhere..So I will start with attic fans.

       

      I live up near Cut-n-Shoot in the woods and I don’t get enough wind to see the old style turbines spin on my roof. I have added more sofit vents and still doesn’t seem to get them moving. So instead of replacing the turbins with new ones, Im looking into changing them out with 2 solar powered attic fans to help cool down the attic. I’m trying to find small PV projects to start with and work up to the bigger ones later after I get the house better insulated.

       

      Right now this 2 story house is 2200 sq feet with the highest electric bill was at $134.00 this summer. I have been graphing my daily power usage and the highest was 82 KWh for one day. All the bulbs have been replaced with the Compact FL bulbs (60w version).  The attic has to have more insulation added. I was able to get insulation in 30% of the attic this summer. All the A/C ducts are in the way…will finish up this winter. The windows in this house are a step above the aluminum frame. They have double panes but are worthless….they will have to be updated soon. The good thing about this house is that the previous owner paid the money to have the interior walls insulated as well as the exterior but for some reason did a half rear job in the attic. The 30% I put in up there was to cover the corner that didn’t have any. After updating some appliances (washer/dryer, fridge and dish washer) I should be able to move up to the bigger projects.

       

      Some questions I have are:

       

      1. At what point (daily KWh usage) is a good point to start adding PV systems. Im thinking in terms of a hobby because off the A/C systems in Houston … you can’t really go off grid or can you? How does it work with the A/C power usage?
      2. Where can I get some quality attic fans? What CFM is a good flow to have here in Houston ?
      3. Any Ideas on how to hook up a solar water heater that has the water heater situated on the first floor in the middle of the house? Can I use a plain insulated tank in the attic or do I need to tie into another water heater?
      4. Anything else I’m missing?

       

      Thanks in advance for your time!!!

       

      Mike Schmitt

       

       

       

       

       

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