Tuesday, November 6, 2018

Passive Solar Home Using Below Floor Soil Heat Storage

Josh built this very unique passive solar home in Missouri. The house incorporates the usual south glazing to gather solar heat and good insulation to reduce heating requirements.  But, it also has a unique heat storage capability using the soil under the main floor.  And, a unique cooling system that makes use of the same soil heat store.

Passive solar home with under floor heat storage
 The home has a 2 foot deep earth heat storage bank under the slab floor of the house.  During sunny periods, solar heated air from the main floor is circulated through ducts embedded in the heat store in order to store heat for use during the evening.  This has the added benefit of reducing the chance of overheating the main floor as sometimes happens on passive solar homes.

To provide cooling in the summer, cool well water will be circulated through pex tubes embedded in the under floor heat store.

Solar heated air is circulated through these under floor ducts to add heat to the heat store.
All the details on this unique design here...

Thanks very much to Josh for providing information on this unique design.

Tuesday, February 27, 2018

Rain Harvest Calculator

Darrel sent in a note on the Rain Harvest Calculator that he has developed and made available free of charge on his website.  Its a dandy.

Its a very good Rain Harvest tool that provides a lot of flexibility -- you have control over all of the following:

  • Location -- specify your location and the calculator looks up the average monthly rainfall.
  • Collection area
  • Collection efficiency
  • Water usage by month
  • Water storage available
  • Supplementary water available by month
  • Specify years with less or more than average rainfall

The calculator provides very nice graphic output that makes it very clear what your rain harvest and water supply situation is and makes it very easy to do what if studies on collection area, storage, usage, ...

Well worth having if you are planning a rain water harvesting system.

Thanks Darrel!


Saturday, January 13, 2018

David's DIY drainback solar water heating system

David has designed and built a very nice solar water heating system for his energy efficient home. It is a drainback system that uses an EPDM lined, non-pressurized wood tank for heat storage.

Some of the highlights of Dave's system...
  • Tank design suitable for limited height crawlspaces.
  • Nice tank frame design using half lap joints for the corners
  • Used new old-stock commercial collectors at a very good price
  • Efficient heat exchanger installation
  • Using used and recycled materials kept the cost of the system down
David with his three drainback collectors
David's system consists of three collectors mounted vertically on the south wall of his house. The heat storage tank for the system is in the crawl space under the collectors. Its a drainback system, so for freeze protection, the water in the collectors drains back to the heat storage tank when the pump turns off.

The collectors were obtained on Craig's list as "new old-stock" for a very good price.
The heat storage tank is a non-presurized, wood framed, insulated with polyiso rigid foam, and then lined with an EPDM liner - this is a design that has been used on quite a few Build It Solar projects, and works well.

David with heat storage tank in his 29 inch deep crawl space.
The heat exchanger uses a 300 ft coil of pex pipe that has been used successfully on several Build-It-Solar projects. The scheme that Dave used to support the pipe coil and space the coils out is very nicely done and likely provides a worthwhile gain in heat transfer efficiency. One nice thing about this style of heat exchanger is that it stores several gallons of fully preheated water right in the coil.

PEX coil heat exchanger with nice coil separation and support scheme.

See all the details here...

January 13, 2018

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