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Re: Radiant Heat Shield

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  • mark r. johnson <mrj53@mindspring.com>
    ... bottom ... exits ... hot ... the ... Peter, I have heard about vent skin construction (sometimes called skin vent ) via Brian Parffey s six-week
    Message 1 of 11 , Feb 6, 2003
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      --- In hreg@yahoogroups.com, Peter <peterk1@s...> wrote:
      >...vent skin contruction : This means that outside walls have vents
      > built into the bottom
      > of the wall and a continous airspace behind the wall from
      bottom
      > outside wall vents to
      > roof overhang. The area where the outside wall meets the roof
      > overhang can be engineered
      > so that wall venting exhausts into the attic and then venting
      exits
      > through the continuous
      > hip/ridge vents. The concept utilizes the physical property of
      hot
      > air always rising ... you can really
      > feel the draft of air coming into your attic from between the
      > walls. This concept prevents heat
      > build up in the outside walls and helps with the air draft in
      the
      > attic .. again preventing heat
      > build up.

      Peter, I have heard about "vent skin" construction (sometimes called
      "skin vent") via Brian Parffey's six-week "Builder's Academy"
      workshop, also from his one-time mentor Tom Tynan, and also from
      architect LaVerne Williams.

      I am intrigued because
      1) some of them endorse it so emphatically, and
      2) there have only been a few places in printed literature that
      support this method.

      Parffey tells us this is a method usable largely because it doesn't
      get very cold in winter in our area, and somewhere between here and
      Dallas the winters get strong enough that vent skin construction is
      not advisable. So this is identified as a very regional construction
      method, which explains why it may be unknown outside of our hot-humid
      region.

      Tynan endorses this construction method, I believe he advocates it but
      does not hammer on it being a necessity as Parffey does. For what it's
      worth, I have seen in Williams' published articles a very early
      reference to skin venting in the 1970's, the earliest I am aware of.

      I would like to ask you, are you describing a method which must be
      used with original construction? If not, can you say a little bit
      about retro-fitting this ventilation to an existing building. Surely
      there must be some pros and cons. Any new references to printed
      literature about this method, or references to someone who can give me
      expert advice, would be most welcome.

      Best wishes -- Mark J.
    • mark r. johnson <mrj53@mindspring.com>
      Chris, what I have clearly been hearing is these methods work. The one that seems most unlikely to you, attaching this foil-like material to the underside of
      Message 2 of 11 , Feb 6, 2003
      • 0 Attachment
        Chris, what I have clearly been hearing is these methods work. The one
        that seems most unlikely to you, attaching this foil-like material to
        the underside of the roof decking, is to the best of my knowledge the
        most effective method for adding to an existing home. Of course if you
        are building new construction, or re-roofing and can consider
        replacing the decking, you probably would find it better to buy the
        kind of
        roof decking that has the foil underside.

        Evidently the shiny side must face an air space for it to work. The
        downside of laying the barrier horizontally on existing attic
        insulation, is that it works fine the first day, but it soon will get
        dusty and become less effective.

        Usually we assume asphalt shingles when we talk about radiant
        barriers. If you happen to have a different roof material, we ought to
        stop and reconsider. I have read that tile roofs have advantages which
        lessen the effectiveness of radiant barriers and attic ventilation.
        Probably metal roofs as well.

        It is my understanding that spray-on radiant barrier paint cannot be
        as reflective as foil stapled to roof rafters or on decking material,
        but its ease of use may be attractive for retro-fit jobs. Tom Tynan
        endorses spray-on radiant barrier paint on the underside of your roof
        decking:
        http://tomsangle.com/docs/Radiant.pdf
        So far as I can tell, Tom agrees that foil based roof decking is
        superior for new construction. I believe stapling foil type material
        to the rafters, will provide superior performance but it might be so
        much extra labor that costs outweigh the benefits.

        You might find the following article from the Florida Solar Energy
        Center (FSEC) interesting. All that I have seen from FSEC appears high
        quality practical research, in my opinion:
        http://www.fsec.ucf.edu/bldg/pubs/pf337/

        I must say that I am a total amateur and am merely passing along
        things I have been taught which sound right. Am thinking about putting
        up foil type radiant barrier in my house but have not done the project
        yet. Am somewhat thinking about retro-fitting "skin venting" to our
        exterior walls but first must find someone with professional
        credentials who will endorse such a project. If anyone finds fault
        with what I have said, it will be to everybody's benefit to correct
        me.

        Thanks and good luck -- Mark J.





        --- In hreg@yahoogroups.com, "Roxanne Boyer" <rox1@a...> wrote:
        > I am looking for ways to reduce the cooling energy costs of my home.
        I have heard about radiant heat barriers in the form of:
        > 1) Exterior coatings (put on the paint or shingles) that reflect
        solar radiation.
        > 2) Foils that are applied to the underside of the roofing board -
        either sprayed or stapped in sheets - that reflect infared radiation.
        > 3) Foils that cover the attic floor on top of the insulation that
        also reflect infared radiation.
        >
        > Does anyone have any experience with these applications? Do they
        work? How much does it cost to have them installed?
        >
        > Theoretically the radiant barrier on the exterior of the roof and
        the radiant barrier on the attic floor should work. I don't see how
        the foil/spray on the bottom of the roof could work.
        >
        > Chris Boyer
        > "Conservation is a great alternative fuel."
      • Peter
        Mark, I came across skin venting in 1992 when I took a home building class at HCC. The concept was intriguing because with very little effort natural air
        Message 3 of 11 , Feb 6, 2003
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          Mark, I came across "skin venting" in 1992 when I took a home building class at HCC.
          The concept was intriguing because with very little effort natural air movement
          can be used to reduce temperature and moisture in confined spaces.
          You are correct, I would not use this technique in areas where climate can get
          very cold for long periods of time, but in houston or similar area the climate
          is supportive of this technique.
          As to retrofitting, if you have vertical sidings it may be possible you already have
          a continuous airspace behind your sidings which can be utilized by cutting
          vent openings into the bottom of the sidings. The next problem is where your siding
          meets the roof eves, this may not be so simple since existing construction may have
          2x4's blocking the continuous airflow to the attic. So in summary, for existing homes
          you may not be able to retrofit due to built-in blockages which will not allow a continuous
          opening into the attic.
          I am adding a reference for pictorial schematic, please note i am not endorsing
          the product at this site but the full chapter makes for good reading.
          http://www.rima.net/handbook/page8.htm#walls
          http://edis.ifas.ufl.edu/BODY_EH244
          By the way I forgot to tell you that you can mate vent skin construction with
          attaching a radiant barrier in the wall ... just another way to keep the radient heat
          out of your house.
          If you are planning to have a contractor install "vent skinning" techniques be prepared
          for a lot of hand-holding and insisting on your way  " it needs to be done" with your contractor.
          The most common talk-back I received was "we have never done it this way" and
          "it can't possibly work" :(  .. so stick to your guns !!!!!!!

          By the way I have been very pleased as to what these additions did to the electricity
          consumption.
          peter


          mark r. johnson wrote:
          --- In hreg@yahoogroups.com, Peter <peterk1@s...> wrote:
            
          ...vent skin contruction : This means that outside walls have vents 
          built into the bottom
               of the wall and a continous airspace behind the wall from
              
          bottom 
            
          outside wall vents to
               roof  overhang. The area where the outside wall meets the roof 
          overhang can be engineered
               so that wall venting exhausts into the attic and then venting
              
          exits 
            
          through the continuous
               hip/ridge vents. The concept utilizes the physical property of
              
          hot 
            
          air always rising ... you can really
               feel the draft of air coming into your attic from between the 
          walls. This concept prevents heat
               build up in the outside walls and helps with the air draft in
              
          the 
            
          attic .. again preventing heat
               build up.
              
          Peter, I have heard about "vent skin" construction (sometimes called
          "skin vent") via Brian Parffey's six-week "Builder's Academy"
          workshop, also from his one-time mentor Tom Tynan, and also from
          architect LaVerne Williams. 
          
          I am intrigued because 
          1) some of them endorse it so emphatically, and 
          2) there have only been a few places in printed literature that
          support this method.
          
          Parffey tells us this is a method usable largely because it doesn't
          get very cold in winter in our area, and somewhere between here and
          Dallas the winters get strong enough that vent skin construction is
          not advisable. So this is identified as a very regional construction
          method, which explains why it may be unknown outside of our hot-humid
          region.
          
          Tynan endorses this construction method, I believe he advocates it but
          does not hammer on it being a necessity as Parffey does. For what it's
          worth, I have seen in Williams' published articles a very early
          reference to skin venting in the 1970's, the earliest I am aware of.
          
          I would like to ask you, are you describing a method which must be
          used with original construction? If not, can you say a little bit
          about retro-fitting this ventilation to an existing building. Surely
          there must be some pros and cons. Any new references to printed
          literature about this method, or references to someone who can give me
          expert advice, would be most welcome.
          
          Best wishes -- Mark J.
          
          
           
          
          Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/ 
          
          
            

        • WGAS Racing
          What about a flat roof? I have one that is constructed using a plywood over joists, then urethane foam, topped off with a white elastomeric coating. Can the
          Message 4 of 11 , Feb 6, 2003
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            What about a "flat" roof? I have one that is
            constructed using a plywood over joists, then urethane
            foam, topped off with a white elastomeric coating.
            Can the addition of an foil-like material to the
            underside of the plywood improve anything for me.

            I'm told by my roofing company that the minimum roof
            thickness for my roof is about 4".

            Rob
            Seabrook, TX

            --- "mark r. johnson <mrj53@...>"
            <mrj53@...> wrote:
            > Chris, what I have clearly been hearing is these
            > methods work. The one
            > that seems most unlikely to you, attaching this
            > foil-like material to
            > the underside of the roof decking, is to the best of
            > my knowledge the
            > most effective method for adding to an existing
            > home. Of course if you
            > are building new construction, or re-roofing and can
            > consider
            > replacing the decking, you probably would find it
            > better to buy the
            > kind of
            > roof decking that has the foil underside.
            >
            > Evidently the shiny side must face an air space for
            > it to work. The
            > downside of laying the barrier horizontally on
            > existing attic
            > insulation, is that it works fine the first day, but
            > it soon will get
            > dusty and become less effective.
            >
            > Usually we assume asphalt shingles when we talk
            > about radiant
            > barriers. If you happen to have a different roof
            > material, we ought to
            > stop and reconsider. I have read that tile roofs
            > have advantages which
            > lessen the effectiveness of radiant barriers and
            > attic ventilation.
            > Probably metal roofs as well.
            >
            > It is my understanding that spray-on radiant barrier
            > paint cannot be
            > as reflective as foil stapled to roof rafters or on
            > decking material,
            > but its ease of use may be attractive for retro-fit
            > jobs. Tom Tynan
            > endorses spray-on radiant barrier paint on the
            > underside of your roof
            > decking:
            > http://tomsangle.com/docs/Radiant.pdf
            > So far as I can tell, Tom agrees that foil based
            > roof decking is
            > superior for new construction. I believe stapling
            > foil type material
            > to the rafters, will provide superior performance
            > but it might be so
            > much extra labor that costs outweigh the benefits.
            >
            > You might find the following article from the
            > Florida Solar Energy
            > Center (FSEC) interesting. All that I have seen from
            > FSEC appears high
            > quality practical research, in my opinion:
            > http://www.fsec.ucf.edu/bldg/pubs/pf337/
            >
            > I must say that I am a total amateur and am merely
            > passing along
            > things I have been taught which sound right. Am
            > thinking about putting
            > up foil type radiant barrier in my house but have
            > not done the project
            > yet. Am somewhat thinking about retro-fitting "skin
            > venting" to our
            > exterior walls but first must find someone with
            > professional
            > credentials who will endorse such a project. If
            > anyone finds fault
            > with what I have said, it will be to everybody's
            > benefit to correct
            > me.
            >
            > Thanks and good luck -- Mark J.
            >
            >
            >
            >
            >
            > --- In hreg@yahoogroups.com, "Roxanne Boyer"
            > <rox1@a...> wrote:
            > > I am looking for ways to reduce the cooling energy
            > costs of my home.
            > I have heard about radiant heat barriers in the
            > form of:
            > > 1) Exterior coatings (put on the paint or
            > shingles) that reflect
            > solar radiation.
            > > 2) Foils that are applied to the underside of the
            > roofing board -
            > either sprayed or stapped in sheets - that reflect
            > infared radiation.
            > > 3) Foils that cover the attic floor on top of the
            > insulation that
            > also reflect infared radiation.
            > >
            > > Does anyone have any experience with these
            > applications? Do they
            > work? How much does it cost to have them installed?
            > >
            > > Theoretically the radiant barrier on the exterior
            > of the roof and
            > the radiant barrier on the attic floor should work.
            > I don't see how
            > the foil/spray on the bottom of the roof could work.
            > >
            > > Chris Boyer
            > > "Conservation is a great alternative fuel."
            >
            >


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            Plastics Engineer
            IVA Flight Crew Equipment
            HEI/Lockheed Martin
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          • Robert Johnston
            For what it s worth, I did this job myself a couple years ago. I did it really cheap: I just bought heavy duty aluminum foil at the grocery store (the thick
            Message 5 of 11 , Feb 6, 2003
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              For what it's worth, I did this job myself a couple years ago. I did it
              really cheap: I just bought heavy duty aluminum foil at the grocery
              store (the thick gage for barbeque etc., not the thinner gage) and
              stapled it to the rafters in my attic. I think it feels noticeably
              cooler in the attic, but I can't tell you I noticed any difference on my
              air conditioning bill. But I also changed some equipment in my AC
              system at nearly the same time.

              Just don't be crazy like me and get the idea of saving money on AC in
              July! Even though I only worked in the mornings, I tended to work too
              long into the day, and nearly passed out from the heat even with lots of
              water. Do it now instead! And wear long sleeves to protect from the
              fiberglass insulation if you have it.

              Robert


              > -----Original Message-----
              > From: houtextml <dlagrone@...>
              [mailto:dlagrone@...]
              > Sent: Thursday, February 06, 2003 8:37 AM
              > To: hreg@yahoogroups.com
              > Subject: [hreg] Re: Radiant Heat Shield
              >
              > Here are a couple of good info links for you;
              >
              > http://www.ornl.gov/roofs+walls/radiant/
              >
              > http://www.heatbarrier.com/
              >
              > http://www.u-b-kool.com/
              >
              > I may be tackling this project myself Roxanne. If you'd like to buy
              > in bulk, help with each other's install or just chat about the topic,
              > drop me an email.
              >
              > Cheers,
              >
              > Doug
              >
              > --- In hreg@yahoogroups.com, "Roxanne Boyer" <rox1@a...> wrote:
              > > I am looking for ways to reduce the cooling energy costs of my
              > home. I have heard about radiant heat barriers in the form of:
              > > 1) Exterior coatings (put on the paint or shingles) that reflect
              > solar radiation.
              > > 2) Foils that are applied to the underside of the roofing board -
              > either sprayed or stapped in sheets - that reflect infared radiation.
              > > 3) Foils that cover the attic floor on top of the insulation that
              > also reflect infared radiation.
              > >
              > > Does anyone have any experience with these applications? Do they
              > work? How much does it cost to have them installed?
              > >
              > > Theoretically the radiant barrier on the exterior of the roof and
              > the radiant barrier on the attic floor should work. I don't see how
              > the foil/spray on the bottom of the roof could work.
              > >
              > > Chris Boyer
              > > "Conservation is a great alternative fuel."
              >
              >
              >
              >
              > Your use of Yahoo! Groups is subject to
              http://docs.yahoo.com/info/terms/
              >
              >
            • Mike Ewert
              The foil or paint under the rafters works because the emissivity is low; even though the foil itself gets hot, it doesn t radiate much heat. My AC guy said
              Message 6 of 11 , Feb 9, 2003
              • 0 Attachment
                The foil  or paint under the rafters works because the emissivity is low; even though the foil itself gets hot, it doesn't radiate much heat.  My AC guy said he used the paint in his metal building shop and really noticed a difference.
                -----Original Message-----
                From: mark r. johnson <mrj53@...> [mailto:mrj53@...]
                Sent: Thursday, February 06, 2003 1:39 PM
                To: hreg@yahoogroups.com
                Subject: [hreg] Re: Radiant Heat Shield

                Chris, what I have clearly been hearing is these methods work. The one
                that seems most unlikely to you, attaching this foil-like material to
                the underside of the roof decking, is to the best of my knowledge the
                most effective method for adding to an existing home. Of course if you
                are building new construction, or re-roofing and can consider
                replacing the decking, you probably would find it better to buy the
                kind of
                roof decking that has the foil underside.

                Evidently the shiny side must face an air space for it to work. The
                downside of laying the barrier horizontally on existing attic
                insulation, is that it works fine the first day, but it soon will get
                dusty and become less effective.

                Usually we assume asphalt shingles when we talk about radiant
                barriers. If you happen to have a different roof material, we ought to
                stop and reconsider. I have read that tile roofs have advantages which
                lessen the effectiveness of radiant barriers and attic ventilation.
                Probably metal roofs as well.

                It is my understanding that spray-on radiant barrier paint cannot be
                as reflective as foil stapled to roof rafters or on decking material,
                but its ease of use may be attractive for retro-fit jobs. Tom Tynan
                endorses spray-on radiant barrier paint on the underside of your roof
                decking:
                http://tomsangle.com/docs/Radiant.pdf
                So far as I can tell, Tom agrees that foil based roof decking is
                superior for new construction. I believe stapling foil type material
                to the rafters, will provide superior performance but it might be so
                much extra labor that costs outweigh the benefits.

                You might find the following article from the Florida Solar Energy
                Center (FSEC) interesting. All that I have seen from FSEC appears high
                quality practical research, in my opinion:
                http://www.fsec.ucf.edu/bldg/pubs/pf337/

                I must say that I am a total amateur and am merely passing along
                things I have been taught which sound right. Am thinking about putting
                up foil type radiant barrier in my house but have not done the project
                yet. Am somewhat thinking about retro-fitting "skin venting" to our
                exterior walls but first must find someone with professional
                credentials who will endorse such a project. If anyone finds fault
                with what I have said, it will be to everybody's benefit to correct
                me.

                Thanks and good luck -- Mark J.





                --- In hreg@yahoogroups.com, "Roxanne Boyer" <rox1@a...> wrote:
                > I am looking for ways to reduce the cooling energy costs of my home.
                I have heard about radiant heat barriers in the form of:
                > 1) Exterior coatings (put on the paint or shingles) that reflect
                solar radiation.
                > 2) Foils that are applied to the underside of the roofing board -
                either sprayed or stapped in sheets - that reflect infared radiation.
                > 3) Foils that cover the attic floor on top of the insulation that
                also reflect infared radiation.
                >
                > Does anyone have any experience with these applications?  Do they
                work?  How much does it cost to have them installed?
                >
                > Theoretically the radiant barrier on the exterior of the roof and
                the radiant barrier on the attic floor should work.  I don't see how
                the foil/spray on the bottom of the roof could work.
                >
                > Chris Boyer
                > "Conservation is a great alternative fuel."


                Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.
              • Robert Bruce Warburton
                I found a web site from a Danish group similar to the HREG, but concentrating on windpower. The Danes make the greatest use of windpower as far as I have read.
                Message 7 of 11 , Feb 9, 2003
                • 0 Attachment
                  I found a web site from a Danish group similar to the HREG, but concentrating on windpower. The Danes make the greatest use of windpower as far as I have read. Mike what have you heard about the Russian shuttle Buran? No one is mentioning the Buran which had just one launch.

                  Mike Ewert wrote:

                   The foil  or paint under the rafters works because the emissivity is low; even though the foil itself gets hot, it doesn't radiate much heat.  My AC guy said he used the paint in his metal building shop and really noticed a difference.
                  -----Original Message-----
                  From: mark r. johnson <mrj53@...> [mailto:mrj53@...]
                  Sent: Thursday, February 06, 2003 1:39 PM
                  To: hreg@yahoogroups.com
                  Subject: [hreg] Re: Radiant Heat Shield
                   
                  Chris, what I have clearly been hearing is these methods work. The one
                  that seems most unlikely to you, attaching this foil-like material to
                  the underside of the roof decking, is to the best of my knowledge the
                  most effective method for adding to an existing home. Of course if you
                  are building new construction, or re-roofing and can consider
                  replacing the decking, you probably would find it better to buy the
                  kind of
                  roof decking that has the foil underside.

                  Evidently the shiny side must face an air space for it to work. The
                  downside of laying the barrier horizontally on existing attic
                  insulation, is that it works fine the first day, but it soon will get
                  dusty and become less effective.

                  Usually we assume asphalt shingles when we talk about radiant
                  barriers. If you happen to have a different roof material, we ought to
                  stop and reconsider. I have read that tile roofs have advantages which
                  lessen the effectiveness of radiant barriers and attic ventilation.
                  Probably metal roofs as well.

                  It is my understanding that spray-on radiant barrier paint cannot be
                  as reflective as foil stapled to roof rafters or on decking material,
                  but its ease of use may be attractive for retro-fit jobs. Tom Tynan
                  endorses spray-on radiant barrier paint on the underside of your roof
                  decking:
                  http://tomsangle.com/docs/Radiant.pdf
                  So far as I can tell, Tom agrees that foil based roof decking is
                  superior for new construction. I believe stapling foil type material
                  to the rafters, will provide superior performance but it might be so
                  much extra labor that costs outweigh the benefits.

                  You might find the following article from the Florida Solar Energy
                  Center (FSEC) interesting. All that I have seen from FSEC appears high
                  quality practical research, in my opinion:
                  http://www.fsec.ucf.edu/bldg/pubs/pf337/

                  I must say that I am a total amateur and am merely passing along
                  things I have been taught which sound right. Am thinking about putting
                  up foil type radiant barrier in my house but have not done the project
                  yet. Am somewhat thinking about retro-fitting "skin venting" to our
                  exterior walls but first must find someone with professional
                  credentials who will endorse such a project. If anyone finds fault
                  with what I have said, it will be to everybody's benefit to correct
                  me.

                  Thanks and good luck -- Mark J.
                   
                   
                   
                   

                  --- In hreg@yahoogroups.com, "Roxanne Boyer" <rox1@a...> wrote:
                  > I am looking for ways to reduce the cooling energy costs of my home.
                  I have heard about radiant heat barriers in the form of:
                  > 1) Exterior coatings (put on the paint or shingles) that reflect
                  solar radiation.
                  > 2) Foils that are applied to the underside of the roofing board -
                  either sprayed or stapped in sheets - that reflect infared radiation.
                  > 3) Foils that cover the attic floor on top of the insulation that
                  also reflect infared radiation.
                  >
                  > Does anyone have any experience with these applications?  Do they
                  work?  How much does it cost to have them installed?
                  >
                  > Theoretically the radiant barrier on the exterior of the roof and
                  the radiant barrier on the attic floor should work.  I don't see how
                  the foil/spray on the bottom of the roof could work.
                  >
                  > Chris Boyer
                  > "Conservation is a great alternative fuel."
                   

                  Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.


                  Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.

                • Mike Ewert
                  http://liftoff.msfc.nasa.gov/rsa/buran.html ... From: Robert Bruce Warburton [mailto:warbur2@ev1.net] Sent: Sunday, February 09, 2003 5:16 PM To:
                  Message 8 of 11 , Feb 9, 2003
                  • 0 Attachment
                    -----Original Message-----
                    From: Robert Bruce Warburton [mailto:warbur2@...]
                    Sent: Sunday, February 09, 2003 5:16 PM
                    To: hreg@yahoogroups.com
                    Subject: Re: [hreg] Re: Radiant Heat Shield

                    I found a web site from a Danish group similar to the HREG, but concentrating on windpower. The Danes make the greatest use of windpower as far as I have read. Mike what have you heard about the Russian shuttle Buran? No one is mentioning the Buran which had just one launch.

                    Mike Ewert wrote:

                     The foil  or paint under the rafters works because the emissivity is low; even though the foil itself gets hot, it doesn't radiate much heat.  My AC guy said he used the paint in his metal building shop and really noticed a difference.
                    -----Original Message-----
                    From: mark r. johnson <mrj53@...> [mailto:mrj53@...]
                    Sent: Thursday, February 06, 2003 1:39 PM
                    To: hreg@yahoogroups.com
                    Subject: [hreg] Re: Radiant Heat Shield
                     
                    Chris, what I have clearly been hearing is these methods work. The one
                    that seems most unlikely to you, attaching this foil-like material to
                    the underside of the roof decking, is to the best of my knowledge the
                    most effective method for adding to an existing home. Of course if you
                    are building new construction, or re-roofing and can consider
                    replacing the decking, you probably would find it better to buy the
                    kind of
                    roof decking that has the foil underside.

                    Evidently the shiny side must face an air space for it to work. The
                    downside of laying the barrier horizontally on existing attic
                    insulation, is that it works fine the first day, but it soon will get
                    dusty and become less effective.

                    Usually we assume asphalt shingles when we talk about radiant
                    barriers. If you happen to have a different roof material, we ought to
                    stop and reconsider. I have read that tile roofs have advantages which
                    lessen the effectiveness of radiant barriers and attic ventilation.
                    Probably metal roofs as well.

                    It is my understanding that spray-on radiant barrier paint cannot be
                    as reflective as foil stapled to roof rafters or on decking material,
                    but its ease of use may be attractive for retro-fit jobs. Tom Tynan
                    endorses spray-on radiant barrier paint on the underside of your roof
                    decking:
                    http://tomsangle.com/docs/Radiant.pdf
                    So far as I can tell, Tom agrees that foil based roof decking is
                    superior for new construction. I believe stapling foil type material
                    to the rafters, will provide superior performance but it might be so
                    much extra labor that costs outweigh the benefits.

                    You might find the following article from the Florida Solar Energy
                    Center (FSEC) interesting. All that I have seen from FSEC appears high
                    quality practical research, in my opinion:
                    http://www.fsec.ucf.edu/bldg/pubs/pf337/

                    I must say that I am a total amateur and am merely passing along
                    things I have been taught which sound right. Am thinking about putting
                    up foil type radiant barrier in my house but have not done the project
                    yet. Am somewhat thinking about retro-fitting "skin venting" to our
                    exterior walls but first must find someone with professional
                    credentials who will endorse such a project. If anyone finds fault
                    with what I have said, it will be to everybody's benefit to correct
                    me.

                    Thanks and good luck -- Mark J.
                     
                     
                     
                     

                    --- In hreg@yahoogroups.com, "Roxanne Boyer" <rox1@a...> wrote:
                    > I am looking for ways to reduce the cooling energy costs of my home.
                    I have heard about radiant heat barriers in the form of:
                    > 1) Exterior coatings (put on the paint or shingles) that reflect
                    solar radiation.
                    > 2) Foils that are applied to the underside of the roofing board -
                    either sprayed or stapped in sheets - that reflect infared radiation.
                    > 3) Foils that cover the attic floor on top of the insulation that
                    also reflect infared radiation.
                    >
                    > Does anyone have any experience with these applications?  Do they
                    work?  How much does it cost to have them installed?
                    >
                    > Theoretically the radiant barrier on the exterior of the roof and
                    the radiant barrier on the attic floor should work.  I don't see how
                    the foil/spray on the bottom of the roof could work.
                    >
                    > Chris Boyer
                    > "Conservation is a great alternative fuel."
                     

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