Loading ...
Sorry, an error occurred while loading the content.

Re: I'm constructing a 120sqft home, come follow along

Expand Messages
  • LarenCorie
    Posted by: David Neeley dbneeley@gmail.com ... Hi David; The so-called Larsen trusses (which many of us had built, way back in the 1970s-80s, before
    Message 1 of 9 , Feb 1 8:40 AM
    • 0 Attachment
      Posted by: "David Neeley" dbneeley@...

      > I mentioned the Larsen trusses for those who are building
      > in heating climates who may benefit from a super-insulation
      > approach.

      Hi David;

      The so-called "Larsen trusses" (which many of us had built,
      way back in the 1970s-80s, before whoever Larsen is, every did)
      are one way to retrofit an existing house, if it also needs new siding
      and windows. But, for new construction it is seldom an optimal
      cost-effective strategy. Double walls, I beam walls, and several
      other approaches (even SIPs) can be more cost-effective.

      For the "Northern California" (wherever that means) location,
      for such a small structure (interior space at a premium) the idea
      of 2x4s with foam sheathing is (IMPO) very good. However, it
      should be done in advanced framing, which means to place the
      studs and rafters aligned, 24" oc. However, since it is an earth-
      -quake prone area, the corners NEED a minimum of OSB or
      plywood, under the foam at the corners. Since the building is
      so small, it might as well cover the whole walls. It should be
      glued, and nailed, 4"oc, around the perimeter, and 8" oc in
      the center. Gluing the roof sheathing would also stiffen it up.
      Houses, in that region are required to be built with hefty
      shear walls at the corners. I would also build at least
      one interior wall, that intersects the 12ft exterior walls,
      as a shear wall (glued OSB or plywood).

      > As I said, though, the design sketch the OP shows has
      > a relatively large glass area for Winter heating through
      > insolation;

      I did not see that. I just saw a drawing of a window that
      might have been facing in any direction. How did you
      interpret that it was facing South? Did I miss something?

      > thus, he may be well advised to consider some sort of
      > shade for the glass for the Summer

      Even more so, if the window is facing East or West.
      South facing windows are quite easy to shade.
      (the sun is quite high in the southern sky, in Summer)

      > otherwise he could find it uncomfortably warm
      > without mechanical air conditioning-

      That would depend on the specific climate,
      which will vary widely in northern California.

      Posted by: "Dennis Otto" queenbeeandthehappydrone@...

      > The Idea of useing more rather than less insulation is not only
      > to insulate an warm interior from the outside cold, but also
      > insulate a cool interior from outside heat.

      Hi Dennis;

      Typically, in Winter we are looking at temperature
      differentials that are 5-10 time greater than in Summer.
      So, recommendations, for warmer climates, is not for
      thick walls, but instead to focus the insulation in the roof.
      This is even more important in very small houses, which
      will lose significantly more interior floor area to thick wall.
      Shading, particularly of windows, is far more important
      than wall insulation. Definitely, the roof appears to be
      under-insulated, but 2x4 walls with foam, are a good
      system, for that climate, and such a small house. This is
      coming from a professional designer, of super high
      efficiency houses, with 35 years of experience. In the
      northern climates where I do most of my work
      (currently in Minnesota, Michigan, Indiana, New
      York, Nova Scotia, and Massachusetts), I typically
      use foot thick walls, of dense packed cellulose
      (R40+). But, for this little house in such a mild
      climate 2x4s (advanced framing, 24"oc), fiber-
      -glass insulation (use R13 or 15 if you want a
      higher Rvalue, and can find it at a good price),
      and foam (R5+), is the formula that I feel is ideal.
      It was a good choice by the owner-builder.

      BTW....I did find the foundation to be very overbuilt,
      and wasteful of both materials and labor. It was typical
      of amateur designers, who are unsure of where to invest
      the resources, and where not to put them. Without
      having more details, I would likely have recommended
      building it on piers. There seemed to be no reason
      for such an elaborate foundation. Those are
      very expensive design decisions.

      -Laren Corie-
      Natural Solar Building Design and
      Solar Heating/Natural Cooling/Energy
      Efficiency Consultation Since 1975
      www.ThermalAttic.com

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

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

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

      Founder-RefrigeratorAlternatives YahooGroup
      http://groups.yahoo.com/group/RefrigeratorAlternatives
    • David Neeley
      ... The poster stated the double (sliding glass?) door and the large window are on the South for Winter solar heating. ... Easy to shade, yes...but again the
      Message 2 of 9 , Feb 1 9:37 AM
      • 0 Attachment
        On 02/01/2011 06:40 PM, LarenCorie wrote:
         


        > As I said, though, the design sketch the OP shows has
        > a relatively large glass area for Winter heating through
        > insolation;

        I did not see that. I just saw a drawing of a window that
        might have been facing in any direction. How did you
        interpret that it was facing South? Did I miss something?

        The poster stated the double (sliding glass?) door and the large window are on the South for Winter solar heating.



        > thus, he may be well advised to consider some sort of
        > shade for the glass for the Summer

        Even more so, if the window is facing East or West.
        South facing windows are quite easy to shade.
        (the sun is quite high in the southern sky, in Summer)

        Easy to shade, yes...but again the original drawing shows no roof overhang or other shading mechanism.

        > otherwise he could find it uncomfortably warm
        > without mechanical air conditioning-


        That would depend on the specific climate,
        which will vary widely in northern California.

        When it is 90 outside (not so uncommon in most of those areas), unshaded glass of that magnitude could make things much less comfortable.

        I would suggest in addition to a better-insulated roof that it be built with at least some overhang as well.

        David
      Your message has been successfully submitted and would be delivered to recipients shortly.