Trickle Down Solar Heating


In the 1950’s, Harry E. Thompson, a North Carolina engineer, had a dream about a low cost solar heating system that used of the entire surface area of a south facing roof. His invention became known as the ‘Trickle Down Solar Thermal Roof”. It involved a corrugated metal roof covered with glass. Cold water from a large insulated tank in the basement was pumped to the top of a specially prepared roof where it was allowed to "trickle down”. Solar heated water from the roof was than collected in a gutter and returned to the basement storage tank. This innovative solar heating system is still functioning in numerous households along the US/Canadian border, but there is now a  new improved, more cost effective, more efficient, more DIY friendly modification of Thompson's invention called: Modified Trickle Down Solar Heating.  Upon close examination of the Thompson thermal roof we notice that water flows over the steel corrugations. The underside of the corrugated steel is  insulated to prevent heat loss, but a lot of heat is still lost through the cold outer glazing surface.  



      Harry Thompson’s “Trickle Down” dream became a reality but it was never fully realized until now with the invention of the “Modified Trickle Down” solar heating system. TD and MTD are alike in that they are both open loop systems that pump water to the tops of collectors but there are significant differences between them.


              Trickle Down                                                            Modified Trickle Down          

Open loop

Open loop

Trickles water on absorber

Trickle water through absorber

Glazed in glass

Glazed in polycarbonate

Unit construction

Modular construction

Corrugated steel absorber

Polyester felt absorber

Not portable

portable array

Has no inner film

Has inner film


 My first MTD collector looked something like this, but the screen has been replaced with polyester felt along with numerous other modifications to make MTD more cost effective and more reliable than oil heating systems. I have experimented with dozens of collector designs over the last three years and I am now only promoting my best design. If you have basic handy man skills the MTD kit will greatly simplify the construction of your first MTD collector. The true magic of the  MTD has a lot to do with the way they are mounted  to form arrays. Here is a simple small system.

Three 2x12 MTD collectors pressed together.






MTD collectors have been designed for flush mounting on a house roof, but don't give up if your roof is oriented in the wrong direction. Build an MTD sun shed and use a multi multi drum heat storage system right inside the shed.  


The top and bottom 2”x2” mounting supports provide an ideal platform for flush mounting MTD collectors. An eight collector system would require four 2’x2’x9’ supports screwed into the roofs rafters. Use a level to position the top supports so that the mid section. This will help to channel the gutter water into a central drain connected with a 2” rubber T boot. Water will never cause a freeze problem inside a properly installed MTD solar heating and DHW system.


Richard Heiliger and I both believe that energy from sunlight can and should be a practical investment and we both encourage the reader to gain hands on experience through experimentation and discovery. There is only so much to be learned from reading. Dreams are given wings not only by our thoughts and understanding but also by the actions we take to turn them into reality. The MTD construction starter kit along with the MTD construction guide and video CD will help clarify the construction experience of this innovative solar thermal application..  Energy independence is possible but it will only become a reality if we make it so.  


Richard Heiliger's MTD solar heated home in Northern Utah


Bob Gering's MTD solar heated year round greenhouse in Canada  


John Canivan's MTD sun shed used for manufacturing Differential Controllers

STARTER KIT...The starter kit is designed to give the reader some hands on experience with a Low cost MTD collector. The kit contains a construction guide book, TDM materials (2'x8' polyester felt, two 30"x8' sheets of polypropylene, five Berger Bros Bibs), a Trickle Down Distributor, a gutter end cap, a gutter compression support and a 3/4" L connector. The kits  comes with an instruction booklet for a wood frame  MTD collectors and a CD with an MTD steel stud slot instruction video and a Solar Plumbing multi media shown. This CD runs on standard PC computers. You really need a kit to get started.

  MTD Collector Starter Kit  with construction guide and CD video      USA shipping only                 $75



Sunshine Books
MTD Solar Collector Kits
Differential Controller
Temperature Probes
Collector Efficiency
MTD Solar Heating

MTD Solar Home 
MTD Data

Energy Alternatives 

Green Collar Work

Solar Heat in December

Solar Heating in January
Multi Tank Heat Storage