20th Century Passive Solar

Our house was originally built with a passive solar design by the civil engineer, James Kachadorian, author of  "The Passive Solar House." After the renovations of 2001–2002 the passive solar feature was severely compromised to accommodate the new additions. While the passive solar system cut our energy costs by about 40% and maintained an indoor temperature minimum of 45°F with all active heat turned off even on the coldest days, the renovated house is much tighter, and with the all-new windows and new insulation it is very energy efficient.

Here are some recent blog posts by Kachadorian at Chelsea Green Publishing. He has a Facebook page.


Sunrise Over the Passive Solar House

Posted on Tuesday, November 24th, 2009 at 2:11 pm by James Kachadorian.

This will be the 29th November I have lived in my passive solar home.

frosty tree
The picture was taken at 8:00 am, November 19, 2009. The outside temperature was 24 degrees and the expected high for the day is predicted to be in the mid forties. You can see from the picture that we had a hard frost the night before. Since my solar home faces true south, the sun is almost rising at the position it will be in on the shortest day of the year – Dec 21.

There will be no need to start my woodstove today as the low angle of the winter sun will quickly heat my home and provide excess solar energy to be stored in the Solar-Slab for evening use after the sun goes down. Solar-Slab is a name I coined for my formally patented method of storing heat in the base of a solar home. The Solar-Slab consists of an array of concrete blocks positioned to allow air to pass through them. The blocks are then capped with concrete to make a ventilated concrete heat storage unit. The Solar-Slab then acts like a battery that takes on a charge and then gives the electricity “back” when needed. In the case of the Solar-Slab heat is stored instead of electricity. How this all works is described in my book The Passive Solar House (Chelsea Green Publishing, 1997).

The response from my book has been very pleasing to me. It has done exactly what I hoped. It has enabled people from all over the country to realize the dream of owning and living in a solar home. There are now hundreds of solar home owners that will have the same gratifying morning experience I had today.

James Kachadorian is a civil engineer with degrees from the Massachusetts Institute of Technology (M.I.T) and Worcester Polytechnic Institute. He is the founder of Green Mountain Homes, a company which gained national recognition as the first provider of innovative, manufactured solar homes. He has built more than 300 passive solar homes. Kachadorian resides in Woodstock, Vermont.


Winter Has Arrived

Posted on Thursday, December 2nd, 2010 at 9:28 am by James Kachadorian

It all happens so quickly each year that my Passive Solar Home “automatically” switches itself from summer/fall cooling mode to winter heating mode. See how the macro environment helps make this happen.

summer
Summer
Deciduous trees shade the south elevation.
winter
Winter Mode
The winter solstice approaches. The sun is almost at its lowest angle in the south sky. The next picture shows how far the sun will penetrate into a south-faced solar home on December 21st.
winter solstice
Winter Solstice

All you need do for your solar home to heat itself is, first, properly site it, and second, take advantage of deciduous trees. If they don’t exist on your site, plant them. You’ll be surprised how fast a sugar maple grows in the Northeast.

Fifty per cent of the heat for the solar home pictured is free, supplied from the sun. There are no rooftop collectors and the east, south and west windows and patio doors serve as the only solar collectors. At north-latitude forty degrees, a vertical south-faced window on December 21st collects almost three times more solar heat than on June 21st due to the difference between the low angle of the sun in winter verses the high angle in summer. Thus, south-faced glass “automatically” collects more solar heat in winter than summer. Strategic use of deciduous trees enhances summer cooling.

Another key element to the functioning of a passive solar home is the use of mass to store heat – we’ll talk about that in a future discussion.


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