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Re: Passive solar

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  • LarenCorie
    Posted by: Chelsea vetcw3@hotmail.com ... Hello Chelsea; I am the designer, who David mentioned. I have partially written responses to the other posts
    Message 1 of 22 , May 1, 2008
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      Posted by: "Chelsea" vetcw3@...

      > How would you suggest sizing a sunspace?

      Hello Chelsea;

      I am the designer, who David mentioned. I have partially
      written responses to the other posts (including one on another
      forum, for David), but they are very long, so will take some
      proof reading and editing. Yours is fairly short, simple, and
      straight forward, so I think I can get it written and proofed
      in one setting.....we will see ;O)

      The sizing of a sunspace will depend on several factors,

      1) The desired extent of Solar heating. I usually start with
      theoretical 100% heating during the toughest Solar heating
      month. However, since winters vary, naturally, by about
      20% either way, that should not supply quite 100% during
      50% of winters. I call that (and anything fairly close to it)
      "Virtual 100% Solar heating" There is always a certain
      amount of heating from normal living (cooking, electricity,
      hot water, body heat, etc) Hopefully, you can supply the
      remainder with sunlight and maybe burning your junkmail
      and burnable trash. It might take an occassional stick in
      the wood stove, or I am beginning to use small portable
      heat pumps to draw additional heat from the heat storage.
      2) The heating demand of the house, including heat losses
      and the interior generated heat mentioned above.
      3) Weather data for the building location, including historic
      and current Solar data for monthly averages, and number
      of likely overcast days, in a row.
      4) From there, I size the sunspace glazing area, for the
      desired percentage of Solar heating. Though the initial
      thought might be that a lower percentage, could be more
      economical intially, that is often not true, because a larger
      Solar percentage, can mean the complete elimination of an
      extensive heating system, reducing the cost of the house.
      There is still backup heating, but it can be a much less
      costly system.

      > or the extra storage?

      Beyond the basic need for thermal mass to be able to absorb
      one day of heating, during one day of sunshine, there is the issue
      of multiple overcast days. Bringing even two days of heat into
      the living space, in about five hours of sunshine, will overheat
      the space. So, the simple solution is to isolate the room that
      overheats.That is what a sunspace does. I may even go a step
      further, using what we call, "interceptors" so that the heat gain
      does not even overheat the sunspace, and only a narrow flow
      of air, away from the 'people space' is super-heated, as it rises
      to a heat storage (Therma Attic) which is also isolated from
      both the heat loss of the sunspace glass, and the living space,
      so that it can get much warmer than mass in the living space,
      ever could. I also use water, for the storage medium, in nice
      2-liter mylar bottles, which happen to be what they sell soft
      drink in. They are just about a perfect contain, with excellent
      surface area for fast heat exchange. They are stacked in big
      "bottle racks" so they work like a heat filter. All this is done
      passively. No fans. No electronic controls. No dampers.

      www.ThermalAttic.com

      > Looking at Shapiro's Greenhouse and Sunspace book it
      > sounds like for our 900 sq ft strawbale house, with earth
      > floors, in a climate with 6,000+ hdd would require about
      > 70 sqft of glazing

      HDDs are not as important as the available sunshine
      in the particular climate. For instance, Detroit MI and
      Colorado Springs CO have very similar HDDs, but
      Detroit would need over twice the sunspace, to get
      the same percentage of winter Solar heating, as the
      identical house in Colorado Springs. I recently did
      a house in northern Indiana, which is at about 6000
      HDD. The house is only about 600sqft (plus the
      20x16 attic and a catwalk/loft , but we decided to
      under insulated the walls, to gain an additional closet
      area, in the small house. The additional heat, during
      the coldest months is just a few sticks in the wood
      stove. The sunspace has just under 150sqft of glass.
      The house has only one window that is not inside
      of the sunspace.

      This house does not have strawbale walls, but that
      does not effect the Solar heating/cooling strategy.
      http://www.flickr.com/photos/10072493@N08/1831385217/

      > (in addition to 36 sq ft of windows directly into the house).

      Code minumum is usually around (guessing at room sizes)
      50% more than that. Put as many windows as you can,
      facing south, inside of the sunspace. Facing south will
      allow them to give you optimal winter daylighting, and
      inside of the sunspace, will shield them from the wind,
      winter heat loss, and shade them in summer.

      > Would I up that number if I was going to add on more
      > storage in the attic for colder days?

      The size of the storage is not so much a matter of
      colder days, as it a matter of the desire amount of Solar
      heating, and the number of expected overcast day, in a
      row. The mass in the attic is sized to do the same thing
      that mass in the living space, tries to do. If the collector
      (sunspace glass area) is sized to meet virtually 100% of
      the mid winter heating, then the storage needs tobe sized
      to last through the maximum expected overcast days,
      during the coldest month. After that, there are variables,
      like the "Solar Source heat Pump" which can be used
      to downsize the heat storage, somewhat. Other factors,
      are the physical space that the storage takes up, and
      sometimes the support structures for the weight of the
      storage. It is generally no heavier than the loads that
      we get used to dealing with for floor and roof loads,
      but it is a significant weight (as the other are) so
      it can be a limiting factor.

      -Laren Corie-
      Natural Solar Building Design Since 1975
      www.ThermalAttic.com

      Read my Solar house design articles in:
      -Energy Self-Sufficiency Newsletter-
      www.rebelwolf.com

      Home base:
      LittleHouses YahooGroup
      http://groups.yahoo.com/group/LittleHouses/
    • Chelsea
      Laren, Thanks for the reply. I also found a reply you had previously made when I asked a very similar question. I am just going to make sure I have this
      Message 2 of 22 , May 1, 2008
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        Laren,
        Thanks for the reply. I also found a reply you had previously made when I asked a very
        similar question. I am just going to make sure I have this straight.
        So I need to size my solar space taking into account
        1) desire percent heating: 100%
        2)Heating demand of the house (not sure how to figure this out)
        3)Weather data (as many as 11 day with out sun, only 40% of days are sunny)

        Sizing storage: This can be built up as I find more bottles. Is it possible to have too much
        storage in a thermal attic?

        Sizing glazing: In the other reply you suggested covering as much of the south face as
        practical, Is it possible for my sunspace to become too large? or will I just vent excess heat
        over the storage and out of the house?

        Thanks
        Chelsea
      • LarenCorie
        Posted by: Chelsea vetcw3@hotmail.com vetcw3 ... Hi Chelsea; Rather than an annual percentage, I aim for a certain percentage for a certain month of the
        Message 3 of 22 , May 13, 2008
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          Posted by: "Chelsea" vetcw3@... vetcw3

          > So I need to size my solar space taking into account

          > 1) desire percent heating: 100%

          Hi Chelsea;

          Rather than an annual percentage, I aim for a certain
          percentage for a certain month of the year. But, I find
          it advantageous to aim for 100%, either for an average
          year worst month, or 120% for that month to cover all
          years. When designing a house, if practical, you might
          as well go for getting all of the heating from Solar. The
          only reason that it is not usually done, is designs with
          inadequate control, as expressed earlier in this thread.
          Direct gain windows get appropriately downsized to
          reduce their nasty overheating while the sun is shining,
          and extreme heat loss, when it is not. Those situations
          do not exist when both the glass and the heat storage
          are outside of the primary living space, and well vented,
          so that the Solar collector area (sunspace glass) can
          be oversized, without jeopardizing the comfort of
          the living space. That is why there is an insulated
          wall between the sunspace and the living space.
          (though not as insulated as other exterior walls)

          When the primary living space is used as the Solar
          collector and storage (dirct gain), the system must be
          downsized to reduce its negative effects. That, of
          course, proportionally also reduces its capacity to heat
          the house. That design process seems very inadequate
          to me, since its goal is to deliberately not heat the house
          by Solar. Houses designed that way, today, are designed
          to waste energy for the next hundred years or more. I
          want houses that I desgin to waste as little as possible.
          Planning for efficient, comfortable, natural heating and
          cooling, is a lot better than planning to burn nasty
          fossil fuels for a century.

          > 2)Heating demand of the house (not sure how to figure this out)

          Calculate the heat losses of the building envelope, and the
          internal heat gains. Basically, the same can be done for the
          summer heat gains. Ehat is different from the heat loss/gain
          caculations for a standard house, is more detail, and the
          addition of caculating the internal generated heat. Standard
          HDD (heating degree days) still apply, because super insul-
          -ated house are comfortable at cooler temperatures But,
          it is easy to add or subtract HDDs, if the anticipated
          interior temperatures will be different.

          > 3)Weather data (as many as 11 day with out sun,
          > only 40% of days are sunny)

          You need HDD (heating degree day) and CDD (cooling
          degree day) data for each month, and Solar gain data
          for the south wall. it also helps to take a look at recent
          weather data, for climate change, and cloud cover patterns.

          > Sizing storage: This can be built up as I find more bottles.
          > Is it possible to have too much storage in a thermal attic?

          Only in that it can waste space, and weigh more than necessary.
          Though a weight of 8000 -12000 pounds is not large, in terms
          of primary building loads, it must still be dealt with, when sizing
          and specifying the structure, including for earth quakes.

          > Sizing glazing: In the other reply you suggested covering as
          > much of the south face as practical, Is it possible for my
          > sunspace to become too large? or will I just vent excess
          > heat over the storage and out of the house?

          As long as it is well enough vented, it is just a sunporch,
          and would be like having too much overhang in summer...
          ....no such thing ;O) In cold/cloudy climates, it is usually
          a matter of being able to find enough south face, for an
          adequate amount of glass. But, in sunnier and/or warmer
          climates, is usually easy to have enough area of glass.
          Since a sunspace may cover many of the house windows,
          there could be a situation, where an overwise adequate
          amount of ventilation or cooling, might not be enough,
          because of the warm sunspace, outside those windows.
          There are other solutions to this problem, besides just
          reducing the sunspace size, so I hesitate to say such
          a sunspace would be "too large" but there is potential
          as there is with every house ever built, for overheating
          during hot weather. The ideal house will never reach
          that point, that virtually all houses reach at some point,
          just as it should never need a furnace. This ideal is not
          only possible, for a cost, but is actually practical, for
          basically the same cost as a conventional house. How-
          -ever, and here is the caviot, since this is new territory,
          some of the bugs are still being worked out, so there is
          an element of exploration and experiementation. But,
          every custom home is just as much of an experiment,
          even if the experiement is a $10-15,000 ground source
          heat pump that will still create heating bills, or a poorly
          insulated house that will cost thousands every year, to
          heat. So, though we may aim for 100% but may get
          small heating and/or cooling loads, it sure beats the
          alternatives of planned higher heating/cooling bills,
          and/or the temperature swings of direct gain Solar.

          As far a summer cooling, sunspace roofs, or balconies
          inside two story sunspaces, can do an excellent job of
          shading living space windows, so as long as the house
          and sunspace are well vented, the sunspace can have
          a cooling effect on the living spaces. But, venting type
          windows can be expensive, and since a sunspace is
          essentially a porch, many people will not want to leave
          home with just locked screen doors, and their security
          doors open. This creates a financial balancing act
          between security and ventilation. There are very nice,
          and very low-cost, ways to build a sunspace (basically
          a porch with salvaged sliding glass door glass between
          the posts) so I find the summer vents to be the main
          limiting factor. I have designed/built (IIRC) sixty or
          more sunspaces, and have not found a perfect solution
          for this cost issue (basement windows can be a good
          solution). I am currently building a design for floor vents,
          that should cost a lot less than operable windows, but
          they are also more work to build, and as I always
          emphasize, labor is the most valuable commodity
          for owner builders, even if they might think that
          money will be.

          -Laren Corie-
          Natural Solar Building Design Since 1975
          www.ThermalAttic.com

          Read my Solar house design articles in:
          -Energy Self-Sufficiency Newsletter-
          www.rebelwolf.com

          Home base:
          LittleHouses YahooGroup
          http://groups.yahoo.com/group/LittleHouses/

          WoodGas - Power from wood
          http://groups.yahoo.com/group/WoodGas

          Solar Power Corps - Spreading the Word
          http://groups.yahoo.com/group/SolarPowerCorps

          RefrigeratorAlternatives
          http://groups.yahoo.com/group/RefrigeratorAlternatives
        • Chelsea
          Thanks for the advice, so much to think about. It is good we have a few years before we start building. Chelsea
          Message 4 of 22 , May 17, 2008
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            Thanks for the advice, so much to think about. It is good we have a few years before we
            start building.
            Chelsea

            --- In SB-r-us@yahoogroups.com, "LarenCorie" <larencorie@...> wrote:
            >
            > Posted by: "Chelsea" vetcw3@... vetcw3
            >
            > > So I need to size my solar space taking into account
            >
            > > 1) desire percent heating: 100%
            >
            > Hi Chelsea;
            >
            > Rather than an annual percentage, I aim for a certain
            > percentage for a certain month of the year. But, I find
            > it advantageous to aim for 100%, either for an average
            > year worst month, or 120% for that month to cover all
            > years. When designing a house, if practical, you might
            > as well go for getting all of the heating from Solar. The
            > only reason that it is not usually done, is designs with
            > inadequate control, as expressed earlier in this thread.
            > Direct gain windows get appropriately downsized to
            > reduce their nasty overheating while the sun is shining,
            > and extreme heat loss, when it is not. Those situations
            > do not exist when both the glass and the heat storage
            > are outside of the primary living space, and well vented,
            > so that the Solar collector area (sunspace glass) can
            > be oversized, without jeopardizing the comfort of
            > the living space. That is why there is an insulated
            > wall between the sunspace and the living space.
            > (though not as insulated as other exterior walls)
            >
            > When the primary living space is used as the Solar
            > collector and storage (dirct gain), the system must be
            > downsized to reduce its negative effects. That, of
            > course, proportionally also reduces its capacity to heat
            > the house. That design process seems very inadequate
            > to me, since its goal is to deliberately not heat the house
            > by Solar. Houses designed that way, today, are designed
            > to waste energy for the next hundred years or more. I
            > want houses that I desgin to waste as little as possible.
            > Planning for efficient, comfortable, natural heating and
            > cooling, is a lot better than planning to burn nasty
            > fossil fuels for a century.
            >
            > > 2)Heating demand of the house (not sure how to figure this out)
            >
            > Calculate the heat losses of the building envelope, and the
            > internal heat gains. Basically, the same can be done for the
            > summer heat gains. Ehat is different from the heat loss/gain
            > caculations for a standard house, is more detail, and the
            > addition of caculating the internal generated heat. Standard
            > HDD (heating degree days) still apply, because super insul-
            > -ated house are comfortable at cooler temperatures But,
            > it is easy to add or subtract HDDs, if the anticipated
            > interior temperatures will be different.
            >
            > > 3)Weather data (as many as 11 day with out sun,
            > > only 40% of days are sunny)
            >
            > You need HDD (heating degree day) and CDD (cooling
            > degree day) data for each month, and Solar gain data
            > for the south wall. it also helps to take a look at recent
            > weather data, for climate change, and cloud cover patterns.
            >
            > > Sizing storage: This can be built up as I find more bottles.
            > > Is it possible to have too much storage in a thermal attic?
            >
            > Only in that it can waste space, and weigh more than necessary.
            > Though a weight of 8000 -12000 pounds is not large, in terms
            > of primary building loads, it must still be dealt with, when sizing
            > and specifying the structure, including for earth quakes.
            >
            > > Sizing glazing: In the other reply you suggested covering as
            > > much of the south face as practical, Is it possible for my
            > > sunspace to become too large? or will I just vent excess
            > > heat over the storage and out of the house?
            >
            > As long as it is well enough vented, it is just a sunporch,
            > and would be like having too much overhang in summer...
            > ....no such thing ;O) In cold/cloudy climates, it is usually
            > a matter of being able to find enough south face, for an
            > adequate amount of glass. But, in sunnier and/or warmer
            > climates, is usually easy to have enough area of glass.
            > Since a sunspace may cover many of the house windows,
            > there could be a situation, where an overwise adequate
            > amount of ventilation or cooling, might not be enough,
            > because of the warm sunspace, outside those windows.
            > There are other solutions to this problem, besides just
            > reducing the sunspace size, so I hesitate to say such
            > a sunspace would be "too large" but there is potential
            > as there is with every house ever built, for overheating
            > during hot weather. The ideal house will never reach
            > that point, that virtually all houses reach at some point,
            > just as it should never need a furnace. This ideal is not
            > only possible, for a cost, but is actually practical, for
            > basically the same cost as a conventional house. How-
            > -ever, and here is the caviot, since this is new territory,
            > some of the bugs are still being worked out, so there is
            > an element of exploration and experiementation. But,
            > every custom home is just as much of an experiment,
            > even if the experiement is a $10-15,000 ground source
            > heat pump that will still create heating bills, or a poorly
            > insulated house that will cost thousands every year, to
            > heat. So, though we may aim for 100% but may get
            > small heating and/or cooling loads, it sure beats the
            > alternatives of planned higher heating/cooling bills,
            > and/or the temperature swings of direct gain Solar.
            >
            > As far a summer cooling, sunspace roofs, or balconies
            > inside two story sunspaces, can do an excellent job of
            > shading living space windows, so as long as the house
            > and sunspace are well vented, the sunspace can have
            > a cooling effect on the living spaces. But, venting type
            > windows can be expensive, and since a sunspace is
            > essentially a porch, many people will not want to leave
            > home with just locked screen doors, and their security
            > doors open. This creates a financial balancing act
            > between security and ventilation. There are very nice,
            > and very low-cost, ways to build a sunspace (basically
            > a porch with salvaged sliding glass door glass between
            > the posts) so I find the summer vents to be the main
            > limiting factor. I have designed/built (IIRC) sixty or
            > more sunspaces, and have not found a perfect solution
            > for this cost issue (basement windows can be a good
            > solution). I am currently building a design for floor vents,
            > that should cost a lot less than operable windows, but
            > they are also more work to build, and as I always
            > emphasize, labor is the most valuable commodity
            > for owner builders, even if they might think that
            > money will be.
            >
            > -Laren Corie-
            > Natural Solar Building Design Since 1975
            > www.ThermalAttic.com
            >
            > Read my Solar house design articles in:
            > -Energy Self-Sufficiency Newsletter-
            > www.rebelwolf.com
            >
            > Home base:
            > LittleHouses YahooGroup
            > http://groups.yahoo.com/group/LittleHouses/
            >
            > WoodGas - Power from wood
            > http://groups.yahoo.com/group/WoodGas
            >
            > Solar Power Corps - Spreading the Word
            > http://groups.yahoo.com/group/SolarPowerCorps
            >
            > RefrigeratorAlternatives
            > http://groups.yahoo.com/group/RefrigeratorAlternatives
            >
          • peter van balen
            In many cases, a super-insulated house with direct gain windows, well-placed and calculated thermal in-house mass, in combination with a variable roof
            Message 5 of 22 , May 18, 2008
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              In many cases, a super-insulated house with direct gain windows, well-placed
              and calculated thermal in-house mass, in combination with a variable roof
              overhang, shouldn't overheat nor should it need much additional heating. And
              that what is needed needn't be met by fossil fuels: without a sunspace,
              there should be enough sun-facing surface left for solarpanels for DHW and
              hydronic floor/wall heating; and if that still doesn't suffice, a small high
              efficiency (>85%) woodstove or woodpellet-burner/stove,will do the job,
              especially those that give off most of their heat to the hot water tank (or
              direct into the floor/wall-heating). There are plenty examples of those
              types of houses (here in Europe). So, unless one has other reasons for
              building a sunspace, and I fully agree there could be many, one can often do
              without these oversized collectors that may, but often don't, add to the
              beauty of the design of the house.

              Peter van Balen
              France

              In SB-r-us@yahoogroups.com, "LarenCorie" <larencorie@...> wrote:

              > Direct gain windows get appropriately downsized to
              > reduce their nasty overheating while the sun is shining,
              > and extreme heat loss, when it is not. Those situations
              > do not exist when both the glass and the heat storage
              > are outside of the primary living space, and well vented,
              > so that the Solar collector area (sunspace glass) can
              > be oversized, without jeopardizing the comfort of
              > the living space. That is why there is an insulated
              > wall between the sunspace and the living space.
              > (though not as insulated as other exterior walls)
              >
              > When the primary living space is used as the Solar
              > collector and storage (dirct gain), the system must be
              > downsized to reduce its negative effects. That, of
              > course, proportionally also reduces its capacity to heat
              > the house. That design process seems very inadequate
              > to me, since its goal is to deliberately not heat the house
              > by Solar. Houses designed that way, today, are designed
              > to waste energy for the next hundred years or more. I
              > want houses that I desgin to waste as little as possible.
              > Planning for efficient, comfortable, natural heating and
              > cooling, is a lot better than planning to burn nasty
              > fossil fuels for a century.
            • RT
              ... well-placed and calculated thermal in-house mass, in combination with a variable roof overhang, shouldn t overheat nor should it need much additional
              Message 6 of 22 , May 18, 2008
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                --- In SB-r-us@yahoogroups.com, "peter van balen" <peter@...> wrote:
                >
                > In many cases, a super-insulated house with direct gain windows,
                well-placed and calculated thermal in-house mass, in combination with
                a variable roof overhang, shouldn't overheat nor should it need much
                additional heating.

                > In SB-r-us@yahoogroups.com, "LarenCorie" <larencorie@> wrote:
                >
                > > When the primary living space is used as the Solar
                > > collector and storage (dirct gain),

                > > That design process seems very inadequate



                I'd have to agree with Peter (but not necessarily with the "variable
                overhang" part) and disagree with Laren.

                The approach Laren describes strikes me as being rather confused and
                unnecessarily complicated -- more of a reactive solution to problems
                that were created by having too much glass and not enough
                incorporated mass in the first place.

                Perhaps we can discuss this further at some time in the future, on a
                point-by-point specifics basis rather than in these sweeping general
                terms.

                === * ===
                Rob Tom
                Kanata, Ontario, Canada
                < A r c h i L o g i c at chaffY a h o o dot c a >
                manually winnow the chaff from my edress in your reply
              • Chelsea
                I think, in my case at least, the sunspace is a response to the issue of cloudy winters and a desire to have 100% solar heating. Where we are building we can
                Message 7 of 22 , May 18, 2008
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                  I think, in my case at least, the sunspace is a response to the issue of cloudy winters and
                  a desire to have 100% solar heating. Where we are building we can have as many as 11
                  days without sun and a period of 3 or 4 days without sun is quite common. The
                  sunspace with thermal storage is to provide heat for that 3rd or 4th (or 5th...) day with
                  little or no sun. You are in Ontario correct? I don't know much about the climate there so
                  perhaps you have the same problem and are able to solve it with direct gain?
                  However I have little experience myself with super insulated houses. I don't think our
                  current house actually has any insulation in most walls at all.
                  Chelsea

                  --- In SB-r-us@yahoogroups.com, "RT" <archilogic@...> wrote:
                  >
                  > --- In SB-r-us@yahoogroups.com, "peter van balen" <peter@> wrote:
                  > >
                  > > In many cases, a super-insulated house with direct gain windows,
                  > well-placed and calculated thermal in-house mass, in combination with
                  > a variable roof overhang, shouldn't overheat nor should it need much
                  > additional heating.
                  >
                  > > In SB-r-us@yahoogroups.com, "LarenCorie" <larencorie@> wrote:
                  > >
                  > > > When the primary living space is used as the Solar
                  > > > collector and storage (dirct gain),
                  >
                  > > > That design process seems very inadequate
                  >
                  >
                  >
                  > I'd have to agree with Peter (but not necessarily with the "variable
                  > overhang" part) and disagree with Laren.
                  >
                  > The approach Laren describes strikes me as being rather confused and
                  > unnecessarily complicated -- more of a reactive solution to problems
                  > that were created by having too much glass and not enough
                  > incorporated mass in the first place.
                  >
                  > Perhaps we can discuss this further at some time in the future, on a
                  > point-by-point specifics basis rather than in these sweeping general
                  > terms.
                  >
                  > === * ===
                  > Rob Tom
                  > Kanata, Ontario, Canada
                  > < A r c h i L o g i c at chaffY a h o o dot c a >
                  > manually winnow the chaff from my edress in your reply
                  >
                • peter van balen
                  @ Rob Tom What I mean by variable overhang is a basic overhang (to protect the walls, in our case 4ft as we ll have earthplastered straw bale walls), which
                  Message 8 of 22 , May 19, 2008
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                    @ Rob Tom

                    What I mean by variable overhang is a basic overhang (to protect the walls,
                    in our case 4ft as we'll have earthplastered straw bale walls), which
                    defines the max height of your 100% solar-gain winter-sun-facing windows and
                    a (very simple, cheap to make, near-horizontal) variable extension for
                    adding additional shading depending on season, bottom height of windows and
                    need for solar gain.

                    Peter
                    ========================
                    Posted by: "RT" archilogic@...
                    Sun May 18, 2008 3:29 pm (PDT)

                    > I'd have to agree with Peter (but not necessarily with the "variable
                    > overhang" part)
                    ....................
                    > Rob Tom


                    @ Chelsea

                    Our winters can also be quite cloudy, with sometimes a week (or more)
                    without sunshine, so I wouldn't bet on having 100% solar heating - you (we)
                    need a back-up heating system for that (3rd, 4th) 5th day etc. And if you
                    don't have any insulation in most walls, you may need that back-upsytem for
                    day 1, 2, 3 as well... In that case I'd start there: insulating is often the
                    most cost-effective way of lowering your heating bill, especially if you
                    have no insulation to start with.

                    Peter

                    > Posted by: "Chelsea" vetcw3@...
                    Sun May 18, 2008 8:03 pm (PDT)

                    I think, in my case at least, the sunspace is a response to the issue of
                    cloudy winters and
                    a desire to have 100% solar heating. Where we are building we can have as
                    many as 11
                    days without sun and a period of 3 or 4 days without sun is quite common.
                    The
                    sunspace with thermal storage is to provide heat for that 3rd or 4th (or
                    5th...) day with
                    little or no sun. You are in Ontario correct? I don't know much about the
                    climate there so
                    perhaps you have the same problem and are able to solve it with direct gain?
                    However I have little experience myself with super insulated houses. I don't
                    think our
                    current house actually has any insulation in most walls at all.
                    Chelsea
                  • David Neeley
                    Rob, It s actually very simple. If you have numerous days in a row that are so cloudy the effective solar heat gain is zero, you need to accumulate sufficient
                    Message 9 of 22 , May 19, 2008
                    • 0 Attachment
                      Rob,

                      It's actually very simple. If you have numerous days in a row that are
                      so cloudy the effective solar heat gain is zero, you need to
                      accumulate sufficient heat during the days that are sunny to carry
                      you through *IF* you want 100% solar heating.

                      However, if you store that heat in thermal mass within the living
                      envelope, you will be much too warm for comfort in the meantime.

                      What's so complex about that?

                      Laren's system solves that problem by getting the heat storage out of
                      the living space entirely, and by collecting a maximum amount of sun
                      energy in a sun space, then channeling it to the storage. Later, it
                      works passively with no power to provide that heat into the living
                      areas of the house--although you may prefer to boost the effect with a
                      small fan, perhaps a computer fan IIRC.

                      Others are speaking of having back up heat for the "3rd, 4th, or 5th
                      days without sun." If all you want is to collect adequate heat for a
                      single cloudless day, using such a back up system for extended periods
                      without sunlight, then it would indeed be perfectly reasonable to
                      share your living space with the thermal mass. If you want to store
                      more, in many climates you would not be happy with the result with
                      that mass in the space with you, nor *could* you collect sufficient
                      solar energy through reasonably small windows to do so to begin with.
                      That is why the glass walls of a sun space can pay such big dividends
                      in such periods.

                      Remember that Laren lives and works in Upper Michigan, which is among
                      the most challenging winter climates in North America...and his
                      objective is to have a house that is very nearly 100% solar heated in
                      all circumstances (although I believe he also burns junk mail and the
                      like for an extra boost from time to time).

                      So--there needs be no argument, I think. Simply define your objectives
                      before you determine what makes the most sense for you. If you have
                      extended periods without usable sun, and if you are shooting for
                      sufficiently near 100% solar heating that you are effectively
                      backup-free, then your system will become a tad more elaborate than a
                      simple high-mass living area because of the more stringent
                      requirements for comfort in all conditions.

                      Thus, it makes no difference to "agree" or "disagree" with any of
                      these folks until you first define what the goals are for the house.
                      If you cannot agree upon those goals, the discussion is relatively
                      useless for you are speaking at cross-purposes.

                      Of course, if you design a sun space carefully, you'll have an all
                      weather porch that can quickly become an absolutely delightful spot in
                      all seasons, particularly by using removable glass panels that can be
                      replaced in clement weather by screens. If your design avoids the
                      "tacked on" look that some have, and if it instead is designed for
                      such a space to be an integral part of the finished design, you may be
                      pleasantly surprised at the results.

                      David

                      On Sun, May 18, 2008 at 5:29 PM, RT <archilogic@...> wrote:
                      > I'd have to agree with Peter (but not necessarily with the "variable
                      > overhang" part) and disagree with Laren.
                      >
                      > The approach Laren describes strikes me as being rather confused and
                      > unnecessarily complicated -- more of a reactive solution to problems
                      > that were created by having too much glass and not enough
                      > incorporated mass in the first place.
                      >
                      > Perhaps we can discuss this further at some time in the future, on a
                      > point-by-point specifics basis rather than in these sweeping general
                      > terms.
                    • LarenCorie
                      Posted by: peter van balen peter@tentotwo.net ... Hi Peter; The problem with large overhangs on south facing windows is that with the sun s noon time
                      Message 10 of 22 , May 21, 2008
                      • 0 Attachment
                        Posted by: "peter van balen" peter@...

                        > basic overhang (to protect the walls, in our case 4ft as we'll have
                        > earthplastered straw bale walls), which defines the max height of
                        > your 100% solar-gain winter-sun-facing windows

                        Hi Peter;

                        The problem with large overhangs on south facing windows
                        is that with the sun's noon time altitude changing by 23.5° just
                        between Solstice and Equinox (3 month, over ¼°/day) with a
                        4ft overhang, that can be as much shadow line movement as
                        over 4½"/day, around equinox. The geometry for a four foot
                        south wall, so-called optimal, overhang ends up being pretty
                        weird. However, if you cluster your windows, in a section of
                        wall that has no strawbales to protect, you can downsize the
                        overhang, to a much more reasonable dimension, that will
                        not end up with a lot of shaded, heat losing glass area,
                        during winter, when you need it to be sunlit.

                        > and a (very simple, cheap to make, near-horizontal) variable
                        > extension for adding additional shading depending on season,
                        > bottom height of windows and need for solar gain.

                        Also be very concerned with the top height of the windows.
                        Adjustable overhangs are definitely an effective solution (though
                        not particularly convenient to maintain). Fixed overhangs are
                        simply not functional as shading devices, because the sun's path
                        across the sky does not match the seasons or the need for heat-
                        -ing and shade. Vegetation can do an excellent job, because it
                        does time itself to the seasons. I wrote an article on overhangs
                        for one of the 2005 issues of ESSN. It goes into a lot more
                        detail. Here is link to the article, on my website.

                        http://web.axilar.net/LarenCorie/OverhangsAndOversights.htm

                        -Laren Corie-
                        Natural Solar Building Design Since 1975
                        www.ThermalAttic.com

                        Home base:
                        LittleHouses YahooGroup
                        http://groups.yahoo.com/group/LittleHouses/

                        WoodGas - Power from wood
                        http://groups.yahoo.com/group/WoodGas

                        Solar Power Corps - Spreading the Word
                        http://groups.yahoo.com/group/SolarPowerCorps

                        RefrigeratorAlternatives
                        http://groups.yahoo.com/group/RefrigeratorAlternatives
                      • peter van balen
                        Hi Laren, Thanks for you advice and suggestions. Given that the overhang is 40cm (1ft3inch) higher than the top of the glass of my window (the eaves are
                        Message 11 of 22 , May 23, 2008
                        • 0 Attachment
                          Hi Laren,

                          Thanks for you advice and suggestions.

                          Given that the overhang is 40cm (1ft3inch) higher than the top of the glass
                          of my window (the eaves are horizontal, which facilitates easily-extractable
                          overhang extensions) we'll still have 60% of the glass surface for solar
                          gain at solar noon at equinox (and more, ofcourse, before and after noon);
                          if we'd downsize the overhang to 2ft that would increase to nearly 90% (and
                          if you'd lower the top of the window 10in it'd be 100%, but we'll take the
                          extra heat-loss to have more light and better views...).

                          Peter


                          Posted by: "LarenCorie" larencorie@...
                          Wed May 21, 2008 9:14 am (PDT)

                          Hi Peter;

                          The problem with large overhangs on south facing windows
                          is that with the sun's noon time altitude changing by 23.5° just
                          between Solstice and Equinox (3 month, over ¼°/day) with a
                          4ft overhang, that can be as much shadow line movement as
                          over 4½"/day, around equinox. The geometry for a four foot
                          south wall, so-called optimal, overhang ends up being pretty
                          weird. However, if you cluster your windows, in a section of
                          wall that has no strawbales to protect, you can downsize the
                          overhang, to a much more reasonable dimension, that will
                          not end up with a lot of shaded, heat losing glass area,
                          during winter, when you need it to be sunlit.

                          > and a (very simple, cheap to make, near-horizontal) variable
                          > extension for adding additional shading depending on season,
                          > bottom height of windows and need for solar gain.

                          Also be very concerned with the top height of the windows.
                          Adjustable overhangs are definitely an effective solution (though
                          not particularly convenient to maintain). Fixed overhangs are
                          simply not functional as shading devices, because the sun's path
                          across the sky does not match the seasons or the need for heat-
                          -ing and shade. Vegetation can do an excellent job, because it
                          does time itself to the seasons. I wrote an article on overhangs
                          for one of the 2005 issues of ESSN. It goes into a lot more
                          detail. Here is link to the article, on my website.
                        • peter van balen
                          Hi David, I m not sure it s that simple, at least not (to achieve) in our case (which is not at all extreme): * heating need for 24hrs on a typical sunless
                          Message 12 of 22 , May 23, 2008
                          • 0 Attachment
                            Hi David,

                            I'm not sure it's that simple, at least not (to achieve) in our case (which
                            is not at all extreme):
                            * heating need for 24hrs on a typical sunless winter day (0°C outside, 20°C
                            inside, strawbale walls, 30cm cellulose ceiling insulation, some floor
                            insulation, very low ventilation (0.2 aer), low-e glass with warm-edge
                            spacers, 120m² house): 45kWh (= rough calculation), roughly 150,000 BTUs
                            * to store (at 35°C - or would you get more out of your sunspace?) and
                            release (at 25°C, to get 20°C in your house) that energy in water takes 3857
                            liters (roughly 1000 US gallons); for comparison: a 15cm (6in) concrete slab
                            or earthen floor (of 120m²) would have to absorb 2-3°C to store the same
                            energy amount
                            * you'd need to multiply this for every additional sunless day you'd want to
                            store, so I/you'd need a swimming pool in your thermal attic !

                            Alternatively, you could store 45kWh in an in-house watertank that's heated
                            through solar panels - high efficiency ones should be able to cut down the
                            needed amount of "water storage" by 2 or 3, or store the heat directly in
                            the slab/floor/walls, as some hydronic systems do.

                            Peter
                            ps: hope I didn't make any miscalculations a/o conversion mistakes ;-)

                            ===================
                            Posted by: "David Neeley" dbneeley@... dbneeley
                            Mon May 19, 2008 3:56 pm (PDT)

                            Rob,

                            It's actually very simple. If you have numerous days in a row that are
                            so cloudy the effective solar heat gain is zero, you need to
                            accumulate sufficient heat during the days that are sunny to carry
                            you through *IF* you want 100% solar heating.

                            However, if you store that heat in thermal mass within the living
                            envelope, you will be much too warm for comfort in the meantime.

                            What's so complex about that?

                            Laren's system solves that problem by getting the heat storage out of
                            the living space entirely, and by collecting a maximum amount of sun
                            energy in a sun space, then channeling it to the storage. Later, it
                            works passively with no power to provide that heat into the living
                            areas of the house--although you may prefer to boost the effect with a
                            small fan, perhaps a computer fan IIRC.

                            Others are speaking of having back up heat for the "3rd, 4th, or 5th
                            days without sun." If all you want is to collect adequate heat for a
                            single cloudless day, using such a back up system for extended periods
                            without sunlight, then it would indeed be perfectly reasonable to
                            share your living space with the thermal mass. If you want to store
                            more, in many climates you would not be happy with the result with
                            that mass in the space with you, nor *could* you collect sufficient
                            solar energy through reasonably small windows to do so to begin with.
                            That is why the glass walls of a sun space can pay such big dividends
                            in such periods.

                            Remember that Laren lives and works in Upper Michigan, which is among
                            the most challenging winter climates in North America...and his
                            objective is to have a house that is very nearly 100% solar heated in
                            all circumstances (although I believe he also burns junk mail and the
                            like for an extra boost from time to time).

                            So--there needs be no argument, I think. Simply define your objectives
                            before you determine what makes the most sense for you. If you have
                            extended periods without usable sun, and if you are shooting for
                            sufficiently near 100% solar heating that you are effectively
                            backup-free, then your system will become a tad more elaborate than a
                            simple high-mass living area because of the more stringent
                            requirements for comfort in all conditions.

                            Thus, it makes no difference to "agree" or "disagree" with any of
                            these folks until you first define what the goals are for the house.
                            If you cannot agree upon those goals, the discussion is relatively
                            useless for you are speaking at cross-purposes.

                            Of course, if you design a sun space carefully, you'll have an all
                            weather porch that can quickly become an absolutely delightful spot in
                            all seasons, particularly by using removable glass panels that can be
                            replaced in clement weather by screens. If your design avoids the
                            "tacked on" look that some have, and if it instead is designed for
                            such a space to be an integral part of the finished design, you may be
                            pleasantly surprised at the results.

                            David
                          • brad723853
                            I was discussing the need for variable overhangs to control solar gain with my wife this weekend - specifically about the huge variability in need for solar
                            Message 13 of 22 , May 27, 2008
                            • 0 Attachment
                              I was discussing the need for variable overhangs to control solar gain
                              with my wife this weekend - specifically about the huge variability in
                              need for solar gain on a daily basis due to the weather extremes that
                              we experience at anytime of the year. She reminded me of an ad for a
                              local company that is selling an awning with adjustable louvers for
                              the slats. We don't have that ad anymore. I searched for it on line
                              but did not find the local company. I'll post it when I run across it
                              again.

                              I did find something similar that would meet the need.

                              http://www.pergolaland.com.au/pages.php?id=27#

                              We are looking to start construction in the next year or so of a SB
                              house that requires little or no energy to heat and cool.

                              Thanks to all on this list for your contributions!

                              Brad
                              Sahuarita AZ
                            • RT
                              ... gain with my wife this weekend Just wondering: If one uses simple fixed overhangs with horizontal extensions calculated in the usual manner to provide full
                              Message 14 of 22 , May 29, 2008
                              • 0 Attachment
                                --- In SB-r-us@yahoogroups.com, "brad723853" <bradtke@...> wrote:
                                >
                                > I was discussing the need for variable overhangs to control solar
                                gain with my wife this weekend


                                Just wondering:

                                If one uses simple fixed overhangs with horizontal extensions
                                calculated in the usual manner to provide full sunlight penetration
                                in winter and full shading in summer, wouldn't simple "variable"
                                shading devices (ie slatted interior window blinds or shoji-like
                                translucent panels take care of whatever else ?

                                (In my experience/latitude the answer is "Yes".)

                                === * ===
                                Rob Tom
                                Kanata, Ontario, Canada
                                < A r c h i L o g i c at chaffY a h o o dot c a >
                                manually winnow the chaff from my edress in your reply
                              • Brad Radtke
                                ... RT, In the area I live, the weather we get in March can vary considerably. There are days where we would want considerable solar gain and others days in
                                Message 15 of 22 , Jun 2, 2008
                                • 0 Attachment
                                  At 11:31 AM 5/29/2008, you wrote:

                                  >--- In SB-r-us@yahoogroups.com, "brad723853" <bradtke@...> wrote:
                                  > >
                                  > > I was discussing the need for variable overhangs to control solar
                                  >gain with my wife this weekend
                                  >
                                  >Just wondering:
                                  >
                                  >If one uses simple fixed overhangs with horizontal extensions
                                  >calculated in the usual manner to provide full sunlight penetration
                                  >in winter and full shading in summer, wouldn't simple "variable"
                                  >shading devices (ie slatted interior window blinds or shoji-like
                                  >translucent panels take care of whatever else ?
                                  >
                                  >(In my experience/latitude the answer is "Yes".)
                                  >
                                  >=== * ===
                                  >Rob Tom
                                  >Kanata, Ontario, Canada

                                  RT,
                                  In the area I live, the weather we get in March can vary
                                  considerably. There are days where we would want considerable solar
                                  gain and others days in the same week or two where we would not want
                                  any solar gain.

                                  In my limited experience, sunlight hitting our south facing windows
                                  will get quite hot to the touch even in March. The blinds I have
                                  seen will mitigate that heat being transmitted into the house
                                  somewhat. But blocking the sunlight from shining on the glass
                                  altogether seems like it will work even better. The best answer
                                  seems to me to use really well insulating blinds, plus full control
                                  over amount the sunlight striking the glass on any given day.

                                  In our situation, we have a great mountain view out our south windows
                                  that we would like to keep when we build our SB house.

                                  Oh, in my last post, I mentioned a company advertised in a local
                                  paper that offered a louvered roof solution. I found the ad. The
                                  company site is http://www.equinoxroof.com/.

                                  Brad
                                  Sahuarita AZ - expecting 103 F today :)
                                • LarenCorie
                                  Posted by: Brad Radtke bradtke@arizona.edu ... Hi Brad; Your weather is relatively consistent, compared to what those of us, in humid climates, experience.
                                  Message 16 of 22 , Jun 3, 2008
                                  • 0 Attachment
                                    Posted by: "Brad Radtke" bradtke@...

                                    > In the area I live, the weather we get in March can vary considerably.

                                    Hi Brad;

                                    Your weather is relatively consistent, compared to what those of us,
                                    in humid climates, experience. However, your point is well made,
                                    and is only reinforced by the fact that the sun's path in September is
                                    identical to that in March, even though the average air temperature
                                    may be 30-40­F warmer than March. Fixed overhangs simply are
                                    not adequate for Solar shading (on any exposure, though we are
                                    specifically discussing south facing glass).

                                    > There are days where we would want considerable solar gain
                                    > and others days in the same week or two where we would not
                                    > want any solar gain.

                                    You are fortunate to have that choice almost every day....
                                    It is a real problem with direct gain Solar heating. When the
                                    living space is between the glazing and the thermal mass, you
                                    are literally living inside of the Solar collector, so you are sub-
                                    -ject to the temperature swings of a Solar collector. However,
                                    in your very consistent, and fairly mild climate, that can be
                                    tolerated. In cold/cloudy climates, south facing windows can
                                    lose more energy during winter months, than they gain, even
                                    though they gain a lot on sunny days. It ends up being like
                                    living in a mild thermal torture chamber. That is why I always
                                    do my collection outside of the living space, in a sunspace,
                                    or with air panels, and also store most of the heat, outside
                                    of the living space.

                                    > In my limited experience, sunlight hitting our south facing
                                    > windows will get quite hot to the touch even in March.

                                    It should get that hot in colder months too. And, in September
                                    when it is hot outside.

                                    > The blinds I have seen will mitigate that heat being transmitted
                                    > into the house somewhat.

                                    Many of my clients tend toward reflective mylar shades, perhaps
                                    because they do not block the view. But, some use standard white
                                    shades, especially in sunspaces, which are well vented and can be
                                    isolated from the primary living spaces. Here is a picture of one of
                                    my sunspace remodelings, in mid-November (southern Michigan,
                                    average temp 40°F), when they only need a little of the sunspace's
                                    heating capacity, to warm the house, since it does not have any
                                    heat storage, beyond the thermal mass of the standard house
                                    interior (plaster walls, etc).

                                    http://web.axilar.net/LarenCorie/ESRemodeling.htm

                                    > But blocking the sunlight from shining on the glass altogether
                                    > seems like it will work even better.

                                    It works very well, but may require tending. Day to day fluctuations
                                    in Solar gain are much easier to live with when the additional heat is
                                    either stored, or vented, or both. Vegetation can provide a good
                                    degree of seasonal shading, and small overhangs, as well as the
                                    changes in the sun's angle to the glass, will also help. Again, I like
                                    sunspaces, because they provide a very big overhang (the sunspace
                                    ceiling) to block light from directly shining into the living space at eye
                                    level (glare) while still collecting the heat, which can be used to warm
                                    the house, stored for later use, vented to outdoors, or used to heat
                                    the domestic hot water.

                                    > The best answer seems to me to use really well insulating blinds,

                                    Yes, they can work very well, and if you are going to have a shade
                                    anyway, for light control, privacy, and sunlight blocking/reflectance,
                                    it might as well be able to serve as window insulation, too.

                                    > plus full control over amount the sunlight striking the glass on any
                                    > given day.

                                    That is the hard part. Trees and vegetation can work well.
                                    I have only used movable overhangs, once, on the outside
                                    of a house. They really take a beating in climates with a
                                    lot of cold weather percipitation. But, I have used the
                                    same approach inside of a tall sunspace, many times. That
                                    is, the use of wooden slats or deck boards, laid across
                                    beams, that can be stacked back against the wall, when it
                                    is desirable for the sunlight to pass. When the boards are
                                    against the wall, there are just bare beams. The same thing
                                    can be done, using roll blinds, horizontally over the beams
                                    instead of hanging behind or in front of the glass. Sunspaces
                                    are areas, outside of the house, so shading devices, in them,
                                    are outside of the living space. As long as a sunspace is
                                    well vented, it will function as a porch, during warm weather.

                                    > In our situation, we have a great mountain view out our south
                                    > windows that we would like to keep when we build our SB house.

                                    The nice thing about south facing windows is that it is never
                                    necessary to block the view, in order to block direct sunlight
                                    Snow/ice, extreme winds, and sun damage, are some of the
                                    factors that effect exterior movable overhangs, but your climate
                                    is probably as good as any for it. Mylar reflective shades are
                                    nice, because you can look right through them from the inside,
                                    while they reflect sunlight and provide privacy.

                                    Roll down awnings, like are used on RVs are actually a very
                                    good option, and also provide a nice area to sit in the shade. They
                                    can be motor operated, so that you can adjust them from inside the
                                    house. Shade cloth, and shade sails are also very nice looking and
                                    effective solutions.

                                    > Oh, in my last post, I mentioned a company advertised in a local
                                    > paper that offered a louvered roof solution. I found the ad. The
                                    > company site is http://www.equinoxroof.com/.

                                    There are many good solutions for your climate, that use
                                    the roof as a living space, with shades and low mass, materials.
                                    Roof shades could also work with thermal mass, to create some-
                                    -thing for not only heating, but also radiant night sky cooling. A
                                    simple, much less costly equivalant might be to use shade sails,
                                    simply hoisted, then lowered and furled, like sails on a boat.

                                    > Brad
                                    > Sahuarita AZ - expecting 103 F today :)

                                    -Laren Corie-
                                    Northern Michigan...expecting 90+ with 100% humidity within
                                    a week, even though it was below freezing less than a week ago.
                                    Natural Solar Building Design Since 1975
                                    www.ThermalAttic.com

                                    Read my Solar house design articles in:
                                    -Energy Self-Sufficiency Newsletter-
                                    www.rebelwolf.com

                                    Home base:
                                    LittleHouses YahooGroup
                                    http://groups.yahoo.com/group/LittleHouses/

                                    WoodGas - Power from wood
                                    http://groups.yahoo.com/group/WoodGas

                                    Solar Power Corps - Spreading the Word
                                    http://groups.yahoo.com/group/SolarPowerCorps

                                    RefrigeratorAlternatives
                                    http://groups.yahoo.com/group/RefrigeratorAlternatives
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