Balcomb (Patricia Mullen) House

Balcomb House exterior

The Balcomb/Mullen house was designed by the late solar pioneer and artist William Lumpkins. Many of the guidelines used by passive solar designers today were developed and scientifically studied with data from this home by passive solar scientist Dr. J. Douglas Balcomb, who lived in the home in the early 1980's. Built in 1979, the home still performs excellently, is aesthetically beautiful, and has been featured in Life Magazine and numerous scientific publications. The new owner, Patricia Mullen, also recently added a domestic solar hot water system. Patricia also drives an fuel efficient Honda Insight hybrid automobile.


Balcomb House layout
Balcomb House Annual Balance

Note that the greenhouse area is not a living room per se - it is really an integrated sunspace, the temperature of which is allowed to swing significantly (and more than in a living room). This sunspace has been elegantly integrated into the L-shaped floor plan of the remainder (see left). The floors of the structure, and the walls separating the sunspace from the other rooms, provide enormous thermal mass for the building, which is adequate for storing the large heat gain of the greenhouse on winter days. Natural convections loop through internal doorways and windows move heat into the back rooms from the greenhouse area. The home also has a below ground rock bed for additional heat storage, which was found by Doug Balcomb to contribute little to the building's overall performance (see energy balances at left). The present owner has actually found it instead to be effective for additional cooling during summer. A solar hot water system is installed on a shed behind the home, and another passive solar workshop structure is located on the property just to the northeast.

Some of the energy balances determined by Balcomb for this home are shown at left. This data shows that 77% of the energy used by the home was provided by solar, 17% from internal gains (people, appliances, etc), and only 6% from auxiliary heat.

Solar Domestic Hot Water System for the Balcomb/Mullen House

The solar thermal domestic hot water system (installed on a shed behind the home) provides solar heated domestic hot water whenever the sun shines. This system preheats an electric water heater in the house with fluid heated by the sun. During cloudy weather, backup heat is accomplished through a single electric element in the hot water heater. This "closed loop system" provides solar heated hot water to the home throughout the year. Its operation is simple, effective, and reliable. A single high quality 4' x 10' solar collector allows the sun's heat to warm up a black absorber inside the collector. Small tubes within the absorber contain a non-toxic antifreeze/water solution. A small pump, powered by a dedicated PV (solar electric) module, pumps the fluid through the collector and a heat exchanger inside the storage tank. Whenever the sun's light is heating the fluid, it's also powering the pump. Patricia replaced her old water heater with a new efficient unit with an internal heat exchanger to allow for solar heat input.

This system replaces the original domestic hot water system that had been disconnected by previous owners. Positive Energy Inc. of Santa Fe removed the old system and installed the system you see today in November 2001. The total cost of this system, including all equipment, installation materials, labor, and tax, is $5,300. The equivalent system would be less expensive in a typical roof installation for a conventional home.

Currently Positive Energy works only with licensed plumbers in our area to provide solar thermal installation and service, and provides solar thermal system design and equipment sales as an adjunct to its main focus on independent electric power systems using renewable energy.

Additional Comments/Rules of Thumb about Solar Hot Water Systems:

  • Each square foot of collector heats about 2 gallons of water per day in Santa Fe.

    A typical 40 ft2 collector can therefore heat one 80 gallon tank.

  • If an active solar hot water system is used for space heating with little input from passive solar gain, a collector area of roughly 10% of the floor area is needed to heat a well insulated home.

    A 2000 square foot home would therefore require 200 ft2 of collector area, or five 40 ft2 collectors of the type used for domestic hot water by the Mullen's system.

  • Solar Hot water collectors are ideally suited for radiant floor heating.

    The output temperature of the collectors (150-190 degrees) is easily mixed down to the input temperature of a radiant floor (~110 degrees). This allows active solar heating without the need for a very large hot water tank.

There are several different types of solar hot water collectors and systems for utilizing them:

batch collector tank

Flat plate collectors, the type used by the homes on this tour, can be used in either drain-back systems (which are not necessarily closed loop and do not require glycol for antifreeze protection), or in closed loop (glycol) systems (as both homes on this tour have). There are also various types of batch/integral collectors, which have a water tank inside or just behind the collectors. These are usually used to preheat water. A particularly simple version is simply a black painted tank placed in an insulated box placed in a clerestory, in series with the cold water feed to the hot water tank (see photo at right - courtesy of Karlis Viceps, Taos Solar Designer-Builder).


If you are interested in seeing this house, please call NMSEA to request an inquiry for an appointment.