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Radiant Heat Shield

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  • Roxanne Boyer
    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
    Message 1 of 11 , Feb 5, 2003
      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
      roxanne, radient barriers (reflect the radiant portion of the heat back to the roof shingles) underneath your roof decking absolutely does work and It cools
      Message 2 of 11 , Feb 5, 2003
        roxanne, radient barriers (reflect the radiant portion of the heat back to the roof shingles)
        underneath your roof decking absolutely does work and It cools your attic significantly.
        I do not know the cost but building supply stores sell the stuff already attached to plywood
        decking or in sheet that you can stick up yourself on the underside of the roof decking.
        Several other great techniques for cooling attics.
        1:  continuous soffit vents in combination of continuous hip/ridge vents give you a constant airflow
             from soffit to hip/ridge in your attiic.
        2:  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.
        3:  for extra measure you can wrap the inside of  the house wall  with radiant barrier material
             this only helps in exposed south/west/east walls where you have significant exposure to direct sunlight


        Roxanne Boyer 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.

      • houtextml <dlagrone@houston.rr.com>
        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
        Message 3 of 11 , Feb 6, 2003
          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."
        • 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 4 of 11 , Feb 6, 2003
            --- 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 5 of 11 , Feb 6, 2003
              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 6 of 11 , Feb 6, 2003
                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 7 of 11 , Feb 6, 2003
                  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."
                  >
                  >


                  =====
                  George (Rob) Rowland, Jr.
                  Plastics Engineer
                  IVA Flight Crew Equipment
                  HEI/Lockheed Martin
                  x-31393
                  281/527-3736 (pager)

                  __________________________________________________
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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 8 of 11 , Feb 6, 2003
                    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 9 of 11 , Feb 9, 2003
                      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 10 of 11 , Feb 9, 2003
                        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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                      • 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 11 of 11 , Feb 9, 2003
                          -----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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