Ken's DIY Solar Air Heating Collector -- Aluminum Soffit Absorber

This is Ken's homemade solar air heating collector.  The collector uses high quality, long life parts in a high efficiency design.

Thanks very much to Ken for sending this in!!




This is my homemade solar hot air collector. If you are looking for a super cheap collector this is not for you. But if you are looking for a lower cost, easy to build, long lasting collector that you will be proud of, this might be what you are looking for.


Features of this collector:

Materials and Cost

 Material list and prices as of 10/10/10:

For a total of around $200.


How it Works

Sun shines on the aluminum soffit absorber material, heating it up.


Cool room air enters the collector inlet, which is near the bottom and on the back of the collector.


A baffle placed just behind the glazing then deflects the incoming air to the sides and prevents the air from impinging directly on the glazing.


The air flows up and through the vented soffit absorber plate striping the heat off the soffit.

The air (now hot) flows up behind the soffit and out the outlet at the top back of the collector and into the room.


Building the Collector

The collector is a sandwich of the glazing, a foam spacer that holds the soffit, and the back insulation held to gather with the stud track.



The picture above is a cutaway of the collector sandwich:

- The glazing (front of the collector) on the left (has the white cover plastic on it)
- The foam spacer with the soffit (inserted ½ “into it) in the center
- The insulation panel on the right
- The stud track holding it all together


This picture shows the aluminum vented soffit material that is used to make the collector absorber.

The half vented soffit is on the right.

A piece of the stud track that is used to make the outer frame for the collector is shown on the left.

If you can find it, its best to use the fully vented soffit, but if you can’t find the full vent soffit you will have to cut the non-vented part of the soffit off with a tin snips.  

   Note: Home Depot can special order fully vented soffit from Amerimax Home Products, as shown in this collector..., but you have to order a full box.


I was not able to get the fully vented soffit, and cut off the non-vented parts off of the half vented sheets.  The half vented soffit with the non-vented part cut off is in the middle of the picture above.

Cut the soffit  to a width 1”narrower then the glazing width  (48”-1”=47”).

Now paint the soffit black on the side that will face the glazing.


Then lay the soffit panels out so that they form a finished absorber panel that is 47” wide by  about 7” less than 8’ tall.  The number of strips of soffit material needed to make the full height will vary depending on the soffit material.  The 8” open area will be at the bottom of the collector so that you can install the air intake. Use three screws per joint to fasten the soffit pieces together to make the absorber panel.

The stud track makes up the frame of the collector. If the track has a extra long legs you will want to put a piece of insulation in the stud rail to make the remainder of leg a little over 1” ( on mine I user ¾ insulation).

Cut the vertical (sides of the collector) stud track the length of the glazing + twice the leg spacer insulation. On mine it was 8’ 1 1/2” long.

The top cap piece of stud track is cut the width of the glazing + twice the leg spacer insulation + twice the height of the stud track leg length and a little to fit over the side pieces. So on mine it is 48” +(3/4x2) 1 ½ “+(2x2) 4”=53 ½”+ ¼ inch.
The bottom inside piece is the same 53 ½” but – ¼  inch.
I hope that not to confusing.

Now cut a slot in the ends of  the cap stud track and the bottom stud track so the end can be folder over. The cuts should be cut from the end on the leg of the track so that when folded over the corner of the stud track will cover the corner of the fold.


Stud track with the cut from the end on the legs next to the corner. The sides have been folded in.




Bending the top down




Inside after bending.



Paint the four pieces of stud track the color of your choosing.   I've heard that if you wash galvanized steel with vinegar before painting the paint will stick better.



Outside of the cap. The top corners over lap the seam.


Now make the the insulation spacer pieces.

The four pieces will be cut to a width so that it will fit snugly inside the stud rail between the glazing and the back insulation. (refer to the second picture).  The 2 side pieces will be the length of the glazing  (96” - 2” = 94 inches).  The top and bottom spacers will be the same width as as the glazing  (48 inches).

Next cut a ½ inch deep groove for the soffit in each spacer.  Cutting this groove with a power saw works well.

At the same time cut the slots for to accept the baffle.  The baffle  slots will be a ½” from the glazing and on the bottom of the side pieces.


The groove for the absorber plate (soffit) will be at a angle going a ½” from the glazing on the top of the collector to the back of the collector near the bottom you will have to measure the absorber panel to get the length from the bottom (about 10”? ) You will want the bottom of the absorber to be tight to the back insulation panel.


Looking from the glazing side with the collector on it’s side.
The absorber (soffit) and baffle have been inserted into the slots in the side insulation.




Looking into the bottom of the collector with the stud track on the side.
From the left you have the glazing, baffle, absorber, and the back insulation.


With all the parts ready you can insert the baffle and the absorber panel into one of the side insulation pieces then put the other side insulation on the other end of the baffle and absorber panel. Put the glazing on front side and the back insulation on the back side and work the side stud rail over the sandwich. Hold together and flip over and work the other side stud rail on. Now you can put the top insulation in place and put the top cap on. Then put the bottom insulation in place and put the bottom stud rail between the side stud rails.
Now you will put 2 screws into each of the 4 corners to hold the collector together.

All you have left to do is mount the collector and cut the holes for the intake the outlet holes.



All done -- looks great!



Kenneth participates in the Yahoo Solar Heat discussion group, so that's a good way to ask questions -- if you post your question on the discussion group, everyone will learn from the question and answer.

If you want to email Kenneth, you can get him at:




Gary January 15, 2011