Introduction
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  >> Efficiency

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Mission Statement
  Earth (Sheltering)
  Sun (Passive Solar)
  Water (Geothermal)    >> Efficiency test
Design Process
  Timeline
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  Final Design
  Download Plan
Energy Mgmt.
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Final Design.

It was a long road, but the house is complete, and we've been living here for two years. 
Check out the latest interior and exterior photos.
In the end, I'm very happy with the compromises that were made during the journey from design-goals to design-reality.

Last year's temperature and power-monitoring data has also enabled me to simplify my heating system and get even more efficiency from the W-W Ground Source Heat Pump. It's working well this winter.

Here are the features that DID get into the final design: 

  • Predominantly single level, but with small "high" area retreat.
  • Combined Living room and Kitchen area.
  • Passive solar configuration with South facing windows, wide overhanging eaves and Solar Slab.
  • Significant Earth Sheltering.
  • Geothermal Heating and Cooling. 
  • Balanced Ventilation with Energy Recovery (ERV).
  • Radiant hydronic (water tubes) heating in slab

Here are some things that did NOT get into the final design.

  • Green "Earth" roof. (not my goal in the first place)
  • Chilled water dehumidification
  • Radiant cooling
But, even though the radiant cooling and chilled water dehumidification aren't officially part of the current design/build, there is nothing to prevent them from being added later.  Specifically, the Geothermal water-water heat pump being used to generate hot water for the slab is also capable of generating chilled water.  This chilled water could be used to cool the slab, or feed a secondary water feature. 

Basic Stats.  

Here are some basic numbers for my final design: (Download Plan in PDF form)

  • The lower level of the house encloses 2000 ft2 (190 m2) of living space and 500 ft2t  (47 m2) of garage, utility and storage space.
  • The upper level encloses 250 ft2 (24 m2) of space. 92 ft2 (9 m2) of this is open to the lower level. (Click the floor plan above).
  • The lower level has 106 ft (32 m) of walls which are below grade and 104 ft (31 m) of exposed wall.  The upper level has 64 ft (20 m) of exposed walls.
  • The floor for the lower level is a 6" (18 cm) concrete slab (thermal slab) with a total mass of 175,000 lbs (79,500 Kg)


Earth Sheltered.  

A key aspect of my design is that it still strongly Earth Sheltered.  This means that a large portion of the surfaces that are normally exposed to the elements are actually protected by the earth.  Rather than providing extra insulation, earth sheltering actually provides a moderate temperature buffer between the house and the environment.  In a predominantly cold climate like Deep Creek, this means that even if the outside temperate is minus 10 degrees F, the earth sheltered walls are only exposed to a mild 50 Deg F.  The reduced temperature differential in these conditions effectively cuts the heat loss by a factor of 4.  My design uses a combination of earth penetration, and earth berming to achieve a high degree of earth sheltering.  The diagram on the right shows how this works.  The house footprint is essentially cut into the side on the hill, and the excavated soil is used to back-fill both side walls.  The blue lines show the rainwater runoff before and after the construction.

Passive Solar.  

OK, so lets see how well the passive solar will work.  The basic principal is that in Summer the eaves shade the windows from the high sun, and in Winter the low sun enters the house unrestricted.  To test this theory, I setup my CAD program to generate a series of sun positions during a mid-summer day, and a mid-winter day. I then took the images that it created, and turned them into two animations.  To say the least, the results were fantastic. Take a look.  Remember that the windows face South, so the sun starts at the right of the image and moves over the top to the left.  The shadows show up as lighter sections of green exterior.
Hit refresh to synchronize the summer and winter cycles.

Summer shade sequence showing minimal solar gain.SUMMER:
Here we see a sequence of images starting at 8:00am and jumping in one hour steps to 6:00pm.
The right wall starts off being illuminated, but very quickly, the sun rises so that all the windows are shaded. The windows stay fully shaded for the bulk of the day, with only a small amount of oblique light entering in the late afternoon.  The Summer solar gain for this configuration is VERY LOW.

Winter shade sequence showing high solar gain.WINTER:
Here, the same time sequence (less sunlight hours) causes the opposite shadow effect.  Since the sun rises much further South in Winter, the front of the house is almost immediately illuminated.  As the day proceeds, the sun never rises high enough to cause any shade to reach the windows.  Early morning and late afternoon sun can be seen to be reaching well into the living space.  The Winter solar gain for this configuration is VERY HIGH.


From these two simulations, we can see that proper orientation and shading can drastically reduce Summer cooling loads, and Winter heating loads. The 6" concrete slab floor acts as a thermal storage device during the day (slowly rising in temperature), and gives off the heat at night. 60,000 BTU of solar gain is predicted on a sunny winter day.

Geothermal Heating and cooling.  

In addition to using the earth to shelter the house, the earth is also used as a constant temperature source/sink for a Geothermal Exchange HVAC system.  An extensive ground water loop is used to feed two Ground Source Heat Pumps.  One heat pump generates hot water for Domestic use (showers etc) and to heat the radiant slab.  The other heat pump is used to heat or cool ducted air.  In addition to this efficient heating/cooling system, a passive heat exchanger is used on a continuous flow ventilation system to reclaim energy from exhaust air.  The system is diagrammed below.

For pictures of the actual installation, visit the Equipment Room page.

© 2000-2012, Phil and Lisa's relaxed lifestyle home.
An exercise in Energy Smart, Not So Big living.
www.OurCoolHouse.com - Ideas@OurCoolHouse.com

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This site is all about building a cool, energy efficient house, that makes maximum use of earth sheltered design, passive solar heating and cooling, geothermal exchange energy management, and right sizing of the house for it's designated use. The home's placement is on a south-facing hillside in Deep Creek Lake, Maryland. This site describes the design process, the technologies used and the expected results. We also have a comprehensive Links Page for anyone who is also interested in designing a similar project.