Sunday, December 11, 2011

LEED Certification: Gold

Rating Achieved: Gold
Home Size Adjustment: -8
Number of points: 67
Total Cost: $8,360.13 (Rough estimate, not including tax or shipping)

Biggest point contributions:

(1) Sustainable Site -Taking steps to minimize the constructions impact on the site gained 18 points.  This includes planting non-invasive plants, installing a light colored, high albedo permeable driveway, and having a compact development.

(2) Location and Linkage - Choosing the right site gained a lot of LEED points for little cost.  The site had to be on previously developed land, near a water line, near community resources, and near but not on to of a park.  By assuming the house was built on this kind of site, the project gained approximately 11 virtually free points.

(3) Reduced Water Need - Drought tolerant plants (ground cover - carpobrutus edulis), low flow rate toilet and shower, and reduced irrigation need accounted for 12 points.

(4) Environmental Quality - Reducing exposure to pollutants by not having a fireplace, using MERV 13 filters, carbon monoxide detectors, and not building a garage added 12 more points to the total.

(5) LEED Education - Educating the team, the public and home owners through manuals, newspaper articles, workshops, and open houses got 6 points.

LEED Certification Cost Sheet


Friday, December 9, 2011

Geothermal System In Phoenix Arizona

GeoComfort GCT036 Geothermal Heat Pump
  • 38,900 Btu/hr Cooling Capacity
  • 28,500 Btu/hr Heating Capacity
  • Desuperheater for Hot Water Heating
  • 1000 CFM Airflow Rate
  • 2.68 kW at Full Load
  • 6000 Btu/hr, 24 GPH Water Heating Capacity
  • 4 Feet Head Loss

Vertical Ground Loop
  • 1200 Feet HDPE 1.25" Piping
  • 6 - 100 Foot Deep Bore Holes
  • 7 GPM Flow Rate
  • 73 Degree Fahrenheit Ground Temperature
  • At Full Load, Loop Temperature
    • 108 deg F Incoming Temp
    • 97 deg F Outgoing Temp
  • 45,000 Btu/hr Heat Dissipated in Loop
  • 10 Feet Head Loss
 Wilo-Stratos ECO 16 F Pump
  • 120 Watts
  • At 7 GPM, 24 Ft of Head Loss

Energy Use
  • Heat Pump -- 2.68 kW
  • Pump -------- 0.12 kW
  • Total --------- 2.80 kW

  •  Heat Pump Price -------- $10000
  • Ground Loop Price
    • at $15 per foot ---- $9175
  • Pump ---------------------- $500
  • Total Cost ----------------- $19675
  • Cost With 30% Rebate -- $13773
  • Annual Costs with Geothermal ------------- $350 
  • Annual Costs with AC and Water Heater- $ 1502
    • Payback Time --- 9.4 Years

      Sunday, October 30, 2011

      Other Energy Uses

      While heating and cooling represent a significant amount of the energy used by households there are many other areas of energy consumption.  These have been broken down into several groups and can be seen in the following figures.



      Ventilation Rate

      The number of air changes per hour in a building is the number of times the entire volume of air within the building is replaced in one hour.  The recommended number of air changes per hour for a standard home is 4.  To get the ventilation rate of the home, the number of air changes per hour is multiplied by the volume of the home:

      4 x 8000 ft^3 = 32,000 ft^3/hr = 533 CFM

      Assuming the air density is close to 0.075 lbm/ft^3, the mass flow rate for the home is approximately 40 lbm/min.


      Heating and Cooling Degree Days and Heating and Cooling Needs for Phoenix Arizona

      The table below shows values used in the calculation of heating and cooling needs in Pheonix, AZ.  The calculation is based on the standard ventilation rate of 2000 CFM which can be converted to a mass flow rate of 150 lbm/min.

      Using data from October 2010 to September 2011, and the constants listed above, the approximate heating and cooling needs are summed up in the table below: