Building climate responsive homes in Lesotho, Africa by Javed Sultan

This is our response to the judge’s comments. First we would like to thank the judge’s for their time and feedback.  Our response is as follows:

1. Q. How do people living view the comfort levels…

(Answer) People have now spent two seasons, winter and summer, in the home. From what the sisters at the Roman catholic Charity, where the home is located, tell us they find these homes very comfortable.  In summer the house is cool most of the time. The location where our prototype is situated rarely experiences summer temperatures exceeding 90 degrees Fahrenheit. Cold water (CW) based cooling, although available, has not been needed and to the best of our information has not been utilized. The site is also, most of the time, not uncomfortably humid. However in other locations of Lesotho summer does get very hot and CW circulation could further cool the house in extreme hot weather. Our cooling and heating system, the location experiences bitterly cold winters below freezing temperatures, is based on using water as the exchange medium in a heat exchanger.

There are two closed water based loop that circulate either cold or hot water depending on the season. Water loop system (WLS) “A”  warms or cools the water in a heat exchanger “C”. WLS “B”, a second hydronic loop, transfers that heat via radiant floor system. See diagram and section below. Loop “A” cools or warms the house, depending on the season, as it travels in an exposed copper pipe adjacent to the internal concrete wall. WLS “A” is able to transfer the heat to concrete wall, via perimeter piping similar to a perimeter baseboard system, as concrete has thermal mass and can store heat or cold and dissipate that slowly. The water in loop “A” is gravity fed from a tank located on the roof, and then it is pumped up to the tank using a 12 volt water pump.

The third critical system, a thermal storage system,  ( System “C”) is a water based heat exchanger (a tank full of water). So water in WLS “A” heats or cools the water in System “C”, which in turn heats or cools water in  WLS “B”. The water in System “B” transfers the heat, or cooling, through a radiant flooring system that runs under the floor slab. Since the floor is a concrete floor, it has thermal mass, and it gets cooled or heated in turn and keeps the room warm or cool as required. The water in system “C”  is circulated by a 12 volt water pump. System “C” is a water based system and in  future we anticipate using liquids which have a higher thermal mass capacity, such as mineral oils,  thereby we can store more heat during a 24 hour cycle.  

This circulating pump for either “A” or “B” is turned on or off by a timer, with a manual over-ride, to run for 15 minutes at intervals of every 6 to 8 hours.  The water in the tank has a capacity of over 30 gallons.

The water in system “A” comes from a solar hot water (SHW) on the roof – and that water is piped municipal water from a utility. The water in system “A” also has a direct line to shower and sink. Also a cold water line connects to WLS “A” and there is a manual toggle valve that either feeds system “A” with cold water(CW) for summer or HW for winter. A separate CW line feeds the sink and shower for CW.

In 2006 and 2007 we had built several earthquake resistant structures for the poor in Kashmir. Later our trained workers were able to build high end homes, sustainable, well insulated, energy efficient homes for the rich. The technique is very similar to our Lesotho prototype, but instead of using "Lunch Boxes" we used off the shelf expanded polystyrene (EPS - 4" thick), and some waste insulation, in the high end homes. The insulation is sandwiched between two layers of thin concrete walls. The poor workers got uninterrupted regular employment for more than a year and earned significant sum of money. Some of them went back and either invested in new business or improved their home.

Please note a small error in the comparison chart for masonry vs prototype. Column "F" should say net volume of concrete and not cement. It is estimated that 1 bag of cement produces 6 cu.ft of concrete for a concrete matrix mix of 1:2:4. Thanks.