Comfortable homes that save the world Sustainable Environmental Economic Development October 27,...
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![Page 1: Comfortable homes that save the world Sustainable Environmental Economic Development October 27, 2007 Don Otto dpoconstruction.com Don Otto dpoconstruction.com.](https://reader035.fdocuments.us/reader035/viewer/2022081519/56649e175503460f94b01f6c/html5/thumbnails/1.jpg)
Comfortable homes that
save the world
Sustainable Environmental Economic Development
October 27, 2007
Comfortable homes that
save the world
Sustainable Environmental Economic Development
October 27, 2007Don Ottodpoconstruction.com
Don Ottodpoconstruction.com
![Page 2: Comfortable homes that save the world Sustainable Environmental Economic Development October 27, 2007 Don Otto dpoconstruction.com Don Otto dpoconstruction.com.](https://reader035.fdocuments.us/reader035/viewer/2022081519/56649e175503460f94b01f6c/html5/thumbnails/2.jpg)
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 can’t 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
Conductive heat loss
Un-insulated basement floor (R-1, U=1.0) 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
The formula for heat flow through insulation, Btu/hr = U x A x ∆TFor 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 0°F, or year-round ground temperature of 50°
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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
That’s 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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QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
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QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
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QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
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QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
![Page 12: Comfortable homes that save the world Sustainable Environmental Economic Development October 27, 2007 Don Otto dpoconstruction.com Don Otto dpoconstruction.com.](https://reader035.fdocuments.us/reader035/viewer/2022081519/56649e175503460f94b01f6c/html5/thumbnails/12.jpg)
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
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QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
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QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
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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
• It’s 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