Comfortable homes that save the world Sustainable Environmental Economic Development October 27, 200

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Comfortable homes that save the worldSustainable
Environmental Economic Development October 27,
2007

• Don Otto
• dpoconstruction.com

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What Works Sure, it works in practice, but does
it work in theory?

• The physics of how buildings live in the
  environment
• Convection, Conduction and Radiation
• Some math formulas you cant live without
• Design planning spaces that meet your needs with
  the fewest square feet
• Testing each home for performance--the whole
  heating system, too
• Financing finding an appraiser who values EE

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Some details of how I do it
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The science math of energy flow

• Heat crosses the building envelope in only 3
  ways conduction, convection, radiation
• Conduction (insulation) roughly accounts for 1/3
  - 1/2
• Convection (air flow) also accounts for 1/3 - 1/2
• Radiation (electromagnetic) accounts for the rest
• Heat flow, (in Btu/hr) through insulation depends
  on conductance (U), sq. ft. area (A) and
  temperature difference from inside to outside
  (?T)
• Btu/hr U x A x ?T
• Heat flow by air movement depends on air flow
  rate (CFM), temperature difference inside to
  outside (?T), and correction factor (1.08)
• Btu/hr CFM x ?T x 1.08

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Some real-world examples
The formula for heat flow through insulation,
Btu/hr U x A x ?T For a 1-story,1,000 sq ft
house, (a 32 x 32 house walls also 1,000 sq
ft) an inside temperature of 70 and cold outside
winter air temperature of 0F, or year-round
ground temperature of 50

• Conductive heat loss
• Un-insulated basement floor (R-1, U1.0) 1,000 x
  1.0 x 20 20,000 Btu/hr
• (the temperature below grade is about 50, so the
  difference is only 20, not 50)
• But what if we installed insulation under the
  floor to R-10?
• R-10 (U 0.1) 1,000 x 0.1 x 20 2,000
  Btu/hr

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How much energy do we lose by air leakage?

• (Air flow Btu CFM x ?T x 1.08)
• For 5 air changes per hour (ACH) and 1,000 sq ft
• 1,000sq ft x 8 x 5 ach/60min 667 CFM. 667
  CFM x 70 x 1.08 50,350 Btu/hr
• Current ventilation standards (ASHRAE 62.2, 2004)
  recommend 7.5 CFM per person plus 1 CFM per 100
  sq ft. For a three-BR house, a couple with 2
  kids, per 1000 sq ft
• 40 CFM x 70 x 1.08 3,024 Btu/hr
• Thats saving 94 of the energy we waste to heat
  the winter sky
• If we installed an energy recovery ventilation
  system, we could even recover 60 to 80 of that.
  Minnesota already requires one in all new homes.

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Photos of the science applied
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Design- meeting your needs with the fewest
square feet
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Sight lines and focal points

• Diagonal views are the longest possible. Focal
  points, like light from windows, attract the eye,
  making the space feel larger than it is

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Does doing all this make a difference?

• A home in Solon costs 180 a year to heat
• It keeps 36,000 lbs of CO2 out the air
• Its comfortable all the time
• The benefits will last the life of the house

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How many ways do homes lose energy? How much?
Where?

• Inadequate insulation
• Air leakage
• Poor windows
• Inadequate ductwork
• How do you know what to fix?

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Performance testing

• Building envelope leakage w/ blower door
  Infra-Red camera
• Entire heating system performance
• Furnace A/C or heat pump
• Ductwork, airflow delivery
• As well as windows and insulation
• (the whole test costs between 300 - 400)

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Financing energy upgrades

• Banks need appraisers who place a value on energy
  efficient features in order to include them on a
  loan.
• I know of one such appraiser
• JIM POTTER, Preferred Appraisal,
• 319-373-6746

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THANKS This presentation will be on my
Website, dpoconstruction.com