Solar Heated Roof

The Modified Trickle Down solar heating system makes use of the entire surface area of a roof just like  Harry E. Thompson system. Harry's 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 the one above, and with the help of Richard Heiliger improvements have been made. If you have basic carpentry skills the 2x8 wood frame collector could make an excellent starter project An MTD collector KIT, complete with an MTD construction guide will facilitate the learning experience. 2x12 steel stud slots are also possible but I tell everyone to start with a  simple wood frame 2x8 collector. The practical nature of MTD comes from the low cost of commonly available construction materials, the ease of construction, the simplicity of installation and the manner in which collectors are pressed together to form arrays.

Flush mounting supports as part of the design,  but don't give up if your roof is oriented in the wrong direction. Instead build an MTD sun shed with a 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 requires four 2’x2’x9’ supports screwed into the roofs rafters. Use a level to position the top supports so. 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 sloped MTD solar heating system.


Richard Heiliger and I both believe that energy from sunlight can and should be a practical investment and we 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.

  Keep a sun person off the streets and on the internet.

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

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

Hit Counter