Sunday, September 22, 2013

A Unique, Passively Cooled Home in the Tropics

Kotaro Nishiki built a passively cooled home in Leyte Philippines at 11 degs north latitude that incorporates a number of unique cooling features that allow the home to be cooled passively and without electricity.  Definitely worth a look if you live in a hot, low latitude climate.

In this area, most homes are constructed of concrete, and the concrete structures tend to absorb solar heat during the daytime, and then retain that heat through the night making the homes uncomfortable. Kotaro's design is centered on eliminating these daytime solar gains.

Leyte is quite warm summer and winter, so solar heat gains is to be avoided all year long.  At 11 degrees north latitude, the  winter sun shines on the south side of the house, and the mid summer sun actually swings into the north and shines on the north side of the house.  He keeps the whole house shaded using these techniques:

  • The south facing single slope roof has on overhang on the south that keeps the south wall in shade most of the day.
  • The north side of the house is shaded by an roof extension sloped down to the north that shades the north side of the house most of the day.
  • The roof is double layered with airflow between the well spaced layers.  This greatly reduces solar heat gain through the roof.
  • The east and west walls of the house are double wall construction with a couple feet between the walls.  The shading that the outer wall offers plus airflow between the double walls keep the wall temperatures low.
  • In addition, he has worked out ways to take advantage of the night temperature drop and to use thermal mass on the basement to provide some cooling.

I think that even homes that are mechanically cooled could utilize some of the Kotaro's techniques to reduce heat gain and AC energy use.

Kotaro's website provides more detail, diagrams and pictures of the house ...


Monday, September 9, 2013

Update and Thoughts on Treated Lumber PV Array Mounts

Back in 2009 I built a ground mounted PV array for my house. The mounting system used treated 4 by 4 treated lumber for the mounts.

There was some concern expressed that the treated lumber would not have a good life. So, I've put up a page that covers:

  • How things are going so far with the treated lumber mounts
  • Results of a little research on various types of treated lumber.
  • Ongoing maintenance.
  • A design detail change for better timber decay resistance.

The treated lumber PV array supports

One of the posts after 4 years.
The new page gives some detail on types of treatment you want to use, ongoing maintenance,  better design details, ...

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