1. Episode 27 – Wall materials for efficiency

Show Notes:

Ryan Mitchell

Macy Miller

Show Notes:

Episode 27 – Wall materials for efficiency

  • Todays topic: Efficient wall materials
      • its ALL regional
      • Wall assemblies
      • most important factor of efficiency (Insulation value)
          • Insulation Value (r-value) High is good
        • door and openings/glazing quality
          • U-Factor (inverse of r-value) low is good. (heat transmittence – The rate of heat loss is indicated in terms of the U-factor (U-value) of a window assembly. The lower the U-factor, the greater a window’s resistance to heat flow and the better its insulating properties.
            High-performance double-pane windows can have U-factors of 0.30 or lower, while some triple-pane windows can achieve U-factors as low as 0.15.
          • SHGC-The SHGC is the fraction of solar radiation admitted through a window.  SHGC is expressed as a number between 0 and 1. The lower a window’s solar heat gain coefficient, the less solar heat it transmits.  WHEN WOULD THIS BE GOOD?
        • Vapor barrier
          • Wam side of the wall, different regionally
        • Moisture barrier
        • Radiant barrier
          • Perforated or not
      • Roof and Floor assemblies
        • most heat is lost through the roof, insulate better than walls
        • instal roofing material properly with proper slope
        • Insulate/skirt floor, this is where you will FEEL heat loss first.
        • Caulk meeting points of floor and wall.
    • Materials!
      • Dark vs light
        • Dark absorb heat, good in cold places
        • Light reflect hear, good in hot places
        • Design for worst case (IE green roof)
      • Thermally massive materials (Cob, Earthbag, tile, concrete) help regulate temperatures by slowly absorbing and dissipating heat.
      • Aluminum does not retain heat but most metals are good conductors
      • Insulative paint additives (I have never EVER heard anyone say they ‘work), lots say they don’t.  NASA is working on a version, I have more faith in it… but still.
    • Roofing
      • slope and material
        • SRI (solar reflectance index, SRI)  Low is light)
          • TPO roofine (low slope, less direct rays, light and dark color)
          • Metal roofing, most manufacturers require 3:12 slope or more, lightweight, any color.
          • Shingles thermally massive, retain heat, durable but not in wind conditions
    • Outside envelope creates efficiency, there are things you can do on the interior but its the envelope that counts most.
  • Current Builder Callout:
  • 704650-9260



Leave a Reply