Monday, May 20, 2013

Energy Savings

HERS Rating: 57% Improvement over Code  (What is a HERS rating?)

Projection: 80% Improvement over Code
  • load calculations from HVAC engineer of the highly efficient geo-thermal system together with infrequent usage of the system due to the Owner's preference for the designed natural ventilation
  • ceiling fans
  • CFL Energy Star and low-wattage LED fixture
  • all Energy Star appliances
  • ERV (what is an ERV?)
  • Rainwater collection pumps
  • Photovoltaic production contributing to Net Usage

Actual: 85% Improvement 
  • One year of energy bills logged and added up

Rainshine's actual energy consumption for 2010, the first full year of occupied operation, is remarkable.
The 2008 HERS (Home Energy Rating System) rating projected only a 57% improvement over code for RainShine.  Not pleased with the HERS rating we chose to conduct our own calculations and projected usage averaging $71.22 per month, an 80% improvement over a code compliant house.

We were confident in our numbers and knew HERS did not consider a variety of factors contributing to energy consumption. Among them:
1. The microclimate of the house
2. The extensive passive solar feature such the overhanging eaves, light shelves and east/west windows located to reduce solar gain through screening from existing trees.
3. The critical factor of the willingness of the clients to live a sustainable life in a sustainable house.

To prove our calculations we tracked the house's actual occupied energy consumption and photovoltaic production for 2010. Average gross utility cost per month was $48.57, an 85% improvement over code. A few more photovoltaic panels and the house would be net zero. 

The most disappointing result from our survey was photovoltaic production. Our calculations were based on a site specific calculation provided by the manufacturer who estimated (conservatively according to them) generation of 7,500 kWh/yr. Only 3,155 kWh were generated in 2010, less than half of the projection and a shortfall of $740 for the year and an average of $60 per month. If the PVs had performed up to snuff the house would easily be net zero. 

Conclusion: energy projections can be, as we all know, misleading and every house should be tracked to determine actual energy consumption. In general we were delighted with Rainshine's real-life performance. Rainshine proves how energy efficient thoughtfully combining site features, orientation, passive solar design concepts with active systems can be (even when incorporating major areas of glass). Kudos to the owner and design team!

Throwing features and systems at house designs in order to improve energy performance is, as I suspect HERS is necessarily dumbed down to do, wasteful and counterproductive. As in Rainshine an energy efficient house should look like an energy efficient house, not a neo-eclectic mishmash with energy features screwed in/tacked on a sideways compromising manner.

Monday, May 13, 2013

Goal 6 - Shady Screen Porch

  • Goal 6 - Shady screened porch for summer use
  • Preserve trees and locate on shadiest portion of site

Monday, May 6, 2013

Goal 5 - Sunny Back Porch

  • Goal 5 - Shade in summer, sunlight in winter for an open south facing backyard porch

Monday, April 29, 2013

Goal 4 - Photovoltaics

  • Goal 4 - Design the house to incorporate photovoltaic modules
  •  Roof design maximizes exposure to sunlight for photovoltaics

Monday, April 22, 2013

Goal 3 - Rainwater Collection

  • Goal 3 - Collect rainwater for household use
  • Roof design simplifies collection of rainwater
  • LEED credit for impermeable site
    • SS4.1 Permeable Lot
      • RainShine House built site characteristics:
      • SA   Site area                                          15,747.0 sq.ft.
      • ISS   Impermeable site surfaces               397.5 sq. ft.      (exclusive of areas under roof)
      • VL   Vegetative landscape                  15,369.5 sq. ft.      (vegetative landscape)
      •  97.6%  Is collected or Permeable
      • 2.4% Is impermeable, 100% of all RainShine House impermeable site surfaces (Iss) are designed to direct all runoff toward permanent infiltration features (see site plan).

Monday, April 15, 2013

Goal 2 - Natural Ventilation

  • Goal 2 - Extend the times of the year when the house can use natural ventilation instead of heating and cooling
  • Stack effect with operable clerestory windows
  • Thru house ventilation
  • LEED Innovation Credit : 
    • EA 1.2 Innovation in Architecture - Natural Ventaiation and Cooling
      • Documentation and Verification: In the primary living areas natural ventilation is achieved as follows:
      • Over 12% in operable window area/conditioned floor area in the Master Bedroom in addition to a pair of screened French doors to a covered deck.
      • Over 12% operable area/conditioned floor area in the remaining primary living areas (Living Room, Dining Room, Kitchen, Bed Rooms).  Operable area achieved through inclusion of one door to the Living Area to the Screened Porch.
      • At least two windows in each room, on opposite or adjacent walls.
      • Insect screens installed on all operable windows.
      • Ceiling fans in all primary living areas.

Monday, April 8, 2013

Goal 1 - Sunlight

  • Goal 1 - Bring as much winter sunlight as possible into the house to counter the owner’s Seasonal Affective Disorder
  • Excellent southern exposure
  • A neighborhood of mature trees