- Location of home is Iowa City
- 1000 sq ft, 2 bedroom, and no basement
- Found R-values based on good insulation, windows, and doors
- Degree Days
- Heating degree days = 7228
- Cooling degree days = 1270
- Manual J standard & Smith (1999) used for heating and cooling loads
- Total heat load = 32,000 Btu/h
- Total cooloing load = 16,650 Btu/h
Energy System for the home
- Geothermal heating and cooling system was chosen
- Iowa City not sufficient for solar irradiation
- Not enough wind to justify wind power
Heating
- Loop size & configuration
- Vertical loop due to lack of land space
- Higher up front cost but better longterm efficiency
- less disruption of landscape (can plant more trees etc.)
- 3/4" outer diameter Polyethyline pipe
- Required pipe length of loop = 730 ft
- Used 800 ft. (oversized for better performance)
- 3 bores at 250 ft deep spaced apart 20 ft
- Would require approx 50 ft^2 of surface space (Far less than horizontal)
- $200 more for the extra pipe but well worth it.
Formula used for sizing ground loop:
*Takes worst case scenario into consideration. Uses January temps & run hours
- Pump for fluid loop
- Dayton 5PXX4
- 1/8 hp
- 3/4" inlets and outlets
- 11 gallons per minute
- 15 ft of head loss
- Heat Pump
- 31,000 btu/h heating
- 1.6 Ton cooling
- Duct Work
- Max tons of AC = 2 tons
- 800 total cfm of air flow
- supply
- 2- 7" round for living room (300 cfm)
- 5- 6" round for the rest of the house
- 2-master bedroom
- 1-kitchen, bathroom, spare bedroom
- return
- 16" X 25" return opening for filter grate
- rule of thumb for return is 2 cfm per sq in of return grille size
- 8" X 10" - spare bedroom
- 8" X 12" - master bedroom
- 10" X 25" - living room
- none in kitchen or bathroom (odors)
- Economic Comparison
Annual return for the geothermal system is $960 per year
Capital cost to install natural gas furnace and conventional AC = $7500
(This includes the equipment, labor, and duct work parts & labor)
(Based on two estimates given by Family Heating and Cooling and Mr HVAC, both of the Quad Cities)
Geothermal Equipment:
Water Furnace by Envision
- Higher efficiency
- Less noise during operation
- Dual Stage system
- Higher upfront cost
- Uses less energy
- Model 026
- Heating-31,000 btu/h COP=5.5
- Cooling - 19,500 EER =18.6
Capital Cost
- Pipe = $2400
- Duct Work = $1000
- Equipment = $8000
- Labor = $2600
- Total Cost = $14,000 - 30% rebate = $9800
(Matched up with ballpark estimate for Iowa City on Geothermal sizing & cost ballpark figures)
(Figures based on cost estimate done by Family Heating and Cooling and Matt Burke)
Simple payback time
$9800 / ($1560-$600) = 10.2 year payback period
- The payback time did not meet the magic number of 7 years.
- Going with the conventional equipment would be more cost effective up front.
- Recommend considering geothermal if:
- prospective owner feels strong about conserving energy
- manufacture estimations are trusted
- 20 year life of equipment
- 50 year life of loop
- Possibility of 10 years of use after system has paid for itself
Description of LEED
LEED, or Leadership in Energy and Environmental Design, is an internationally-recognized green building certification system. Developed by the U.S. Green Building Council (USGBC) in March 2000, LEED provides building owners and operators with a framework for identifying and implementing practical and measurable green building design, construction, operations and maintenance solutions.
Details of LEED Certification
· Home Size Adjustment
o Apx. 1000 sq ft – two bedroom ( -9 pts)
· Innovation and Design
o 1.1 – Preliminary Rating – need 66 pts for GOLD certification
o 1.2 – Integrated Project Team ( 1 pt )
o 1.3 – Professional Credentialed with Respect to LEED for Homes ( 1 pt )
o 1.4 – Workshop for Green Strategies ( 1 pt )
o 2.1 – Durability Planning
o 2.2 – Durability Management
o 2.3 – Third-Party Durability Management Verification ( 3 pt )
· Location and Linkages
o 2 – Follow the rules of Site Selection ( 2 pt )
o 3.1 – 25% of perimeter borders previously developed land ( 1 pt )
o 4 – within ½ mile of water and service lines ( 1 pt )
o 5.1 – within ½ mile of bus stop (30 or more stops per day) ( 1 pt )
o 6 – within ½ mile of publicly accessible open space ( 1 pt )
· Sustainable Sites
o 1.1 – design and plan appropriate erosion control measures
o 1.2 – Minimize Disturbed Area of Site ( 1 pt )
o 2.1 – no invasive plants
o 2.3 – no conventional turf ( 3 pt )
o 2.4 – make 50% of plants drought tolerant ( 1 pt )
o 4.2 – plant 1 tree for every 500 sq ft of disturbed lot area ( 1 pt )
o 5 – meet all pest control alternatives ( 2 pt )
o 6 – build house on a 1/7 acre lot ( 2 pt )
· Water Efficiency
o 3.2 – average flow rate for lavatory faucets ≤ 1.5 gpm , average flow rate of showers ≤ 1.75 gpm , average flow rate of toilets ≤ 1.1 gpf ( 6 pt )
· Energy and Atmosphere
o 2.1 – 2.2 – install insulation that exceeds R-value requirements ( 2 pt )
o 3.1 – 3.2 – greatly reduce air leakage ( 2 pt )
o 4.3 – install exceptional windows , U-factor ≤ .28 ( 3 pt )
o 5.3 – install heat pump/duct system with minimal distribution losses ( 3 pt )
o 6.3 – install very efficient geothermal system ( 4 pt )
o 8.3 – install ENERGY STAR advanced lighting package ( 3 pt )
o 9 – install ENERGY STAR refrigerator, ceiling fans, dishwasher and clothes dryer ( 2 pt )
· Materials and Resources
o 1.1 – limit the overall estimated waste factor limit to 10% or less
o 1.2 – detailed framing plans for special architectural details ( 1 pt )
o 1.3 – create a detailed cut list and lumber order ( 1 pt )
o 3.1 – 3.2 – generate 2.5 lbs or less of waste per sq ft of floor area and divert 25% or more of the total waste from landfills and incinerators ( 3 pt )
· Indoor Environmental Quality
o 2.1 – meet combustion venting measures
o 2.2 – no fire place/wood stove ( 2 pt )
o 5.1 – exhaust systems in bathrooms and kitchens
o 5.2 – occupy sensor in every bathroom ( 1 pt )
o 5.3 – third party performance test for exhaust flow rate ( 1 pt )
o 6.1 – perform design calculations for system
o 6.2 – every room has adequate return air flow ( 1 pt )
o 6.3 – third party performance test ( 1 pt )
o 7.3 – install best air filters MERV ≥ 13 ( 2 pt )
o 8.1 – seal all permanent ducts and vents during construction ( 1 pt )
o 8.2 – install permanent walk-off grates (4 ft long) and a shoe removal and storage system ( 2 pt )
o 8.3 – preoccupancy flush ( 1 pt )
o 9.1 – 9.2 – protect EVERYTHING from Radon ( 1 pt )
o 10.1 – 10.4 – no HVAC in the garage + detached garage ( 3 pt )
· Awareness and Education
o 1.1 – 1.2 – two hours of training for the occupants ( 1 pt )
o 1.3 – promote general public awareness about LEED ( 1 pt )
· TOTAL = 70 pts
Price Breakdown of LEED
Category | Price | Payback Time |
Innovation and Design | ||
Green Rater | ($500) | |
Mech. Engineer | ($500) | |
Civil Engineer | ($500) | |
Extra Costs for Architect/Builders | ($1,000) | |
Sustainable Sites | ||
Erosion Control Materials | ($200) | |
Buffalo Grass (seed) | ($235) | < month |
Trees | ($250) | |
Termite Control | ($100) | |
1/7 acre opposed to 1/4 acre | $10,000 | |
Energy and Atmosphere | ||
Insulation + air leakage reduction | ($2,000) | |
Excellent Windows | ($400) | |
Geothermal System | ($14,000) | 10.2 years |
High Efficiency Forced Air System | ($6,000) | |
30% rebate | $4,200 | |
ENERGY STAR advanced lighting package | ($1,000) | 3 years |
ENERGY STAR appliances | ($1,000) | 5 years |
Materials and Resources | ||
House + garage (reduction in lumber) | $5,000 | |
Indoor Environmental Quality | ||
CO monitor | ($25) | |
Exhaust Systems | ($500) | |
Occupancy Sensors | ($75) | |
Air Filters (MERV > 13) | ($50) | |
Perminant walk-off grates | ($500) | |
Preoccupancy Flush | ($500) | |
Tax Credits and Deductions | $1,500 | $1.50 per sq ft |
Total | ($8,635) |
CO2 Footprint Reduction from LEED
(Generated using EPA Household Emissions Calculator - 2 people)
Before LEED
Vehicles - 24886 lbs CO2 per year
Home - 34855 lbs
Waste - 2042 lbs
Total = 62383 lbs
Changes Made
- no natural gas
- 60% reduction in electricity (ENERGY STAR)
- recylcing
- drop the mileage of each car by 40 miles/week
- cut oil consumption in half
- cut propane consumption in half
After LEED
Vehicles - 21238 lbs
Home - 12478 lbs
Waste - 1149 lbs
Total = 34865 lbs
http://www.epa.gov/climatechange/emissions/ind_calculator.html
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