I have to say the heat in North Texas is really getting old. Not since 2015, have we experienced so many 100 degree days strung together. It is a struggle just to keep our house foundation watered.

Not only does the heat affect the Stick and Brick house but it also affects the travel trailers ability to cool down. As I have mentioned in previous posts, the systems in an RV are not very efficient. This is certainly true of the ducted Air Conditioning System you have in your trailer.

Air that pushes down through your AC Unit is not directed to the ducts. The cold air is directed into a box cavity that has duct work connected to it. This results in air not being pushed through and a build up of pressure that makes the AC unit about 50% less effective than it can be. The following rough drawings give you an idea of current and future design.

Original Air Conditioning set up – Noisy and inefficient with poor air flow.

The AC Modification will stream line the air flow directly to the duct work in the RV.

Modification to route air directly to ducts using foam board.

Now there are two routes you can go if you want to increase your air flow inside the duct work.

  1. You can buy a manufactured unit that will fit your AC unit from www.rvairflow.com for about $170.00. These look like very well made units, and many folks are installing them.
  2. You can buy 1″ foam board from a home center and make your own unit for about $8.00 plus the cost of some foil tape. There are many YouTube videos about how to do this modification; just type “RV AC Modification” and you will see a huge number of videos on the subject.

Since I am very cheap and I’m always looking for something to tinker on, I decided to make my own. This can easily be done by one person. As with any modification, you should never undertake a job you feel uncomfortable performing, or one you feel might put you at risk of an injury.

So here’s what you will need to do in order to make your own:

  1. 2’x2′ – 1″ Foam Board
  2. Foil Tape – Also known as AC/Furnace tape.
  3. Preferably a jig saw for cutting the foam board. You can use a razor blade knife but the cuts will not be clean and it will take longer. In addition, you will need to make six 45 degree angle cuts; probably not easy with a razor blade knife.
  4. Tools for removing AC Shroud.

The first thing I did was to do some rough measurements on paper to make sure that a 2’x2′ foam board would be enough to do the job. It was more than enough to do my Brisk II Air Conditioner.

The Rough Drawing of what would need to be cut from the 2′ x 2′ board.

There are essentially 8 steps involved in this modification (AFTER YOU TURN OFF THE POWER TO YOUR AC UNIT).

  1. Remove the AC Shroud
  2. Measure and cut the Divider between the hot and cold sections of the AC
  3. Measure and Cut the upper Diverters
  4. Foil Tape the upper diverters into place
  5. Measure and Cut the Bottom Board
  6. Measure and cut the two Teepee sections.
  7. Tape the two Teepee sections together and attach to bottom board
  8. Insert the bottom section with the Teepees into the AC Box and then foil tape all the sections together.

Every AC Unit will be a little different so there is no standard measurement I can assign to the pieces above. You will need to measure each piece before you cut. As with all projects that involve cutting material, measure twice and cut once. Otherwise you will be running back to the big box store for more foam board.

I want to apologize upfront because I thought I took more pictures of the process than I actually did. So while I don’t have a picture of each step, hopefully you get a sense for the processes involved. There are so many YouTube videos on this modification that you should have no problem completing it, if you feel it is something you want to do.

Step 1 – Remove the AC Shroud. Start by removing your filter covers, then remove the external shroud.

This is the bottom of the AC after shroud was removed and control box disconnected.

Step 2 – There is a divider that separates the cold side from the warm air side of the unit. It is typically made of foam. Unfortunately mine was actually a foam lined metal plate (see above) that I needed to remove from the base pan in order to get this mod to work. It would be replaced by the foam board.

Unfortunately for me, that meant that I had to loosen and remove the bolts that held the AC unit to the roof. I did not anticipate that would be the case, so it added more work to the mod. Then I had to drill out the rivets that held the fold lined plate to the base plate.

Next Measure for the new divider, keeping in mind that the divider needs to be 1″ shorter because the divider will rest on another piece of foam board later. After cutting this piece, test for proper fitment, and then set aside.

Step 2 and 3 in this picture.

Step 3 – Measure and cut the upper foam pieces. The measurement is from the blower hole to the top of the duct on each side. Each piece will need to have 45 degree angles cut on each side. One piece will not fit tightly unless there are notches cut for the two AC Bolts that attach the AC Unit to the roof. Firmly push that piece against the bolts to make an impression so you know where to cut notches. Using your jigsaw create a 1″ Notch for each bolt. In the above picture the upper diverter is only partially taped into place. All the seams between the foam and diverter were later completely taped to prevent air leakage.

Step 4 – Once these upper pieces have been cut, they can be taped into place with the AC Foil Tape.

Step 5 – Measure and cut the bottom board. The measurement is from the inside of the plenum (cold side) to the outside edge of the foam divider that you created in Step 2 above. The bottom piece will not fit tightly unless there are notches cut for the two AC Bolts that attach the AC Unit to the roof. Firmly push that bottom piece against the bolts to make an impression so you know where to cut notches. Using your jigsaw create a 1″ Notch for each bolt. Test fit the completed section, and set aside.

Step 6 – Measure and cut the two foam sections that will make up the bottom diverter which many folks refer to as the Teepee. Remember that since this fits tight against the bottom of the cold/hot divider you must allow an inch for overlap. One piece will be 3″ high, and the second will be 4″ high. Both pieces must have a 45 degree cut on one side only. The 45 degree angle will be the bottom of the teepee against the foam board.

Step 7 – measure the distance from the top of the plenum to the middle of the cold air port. Transfer this measurement onto your foam board. The purpose is to get the teepee centered under that cold air port so the flow of the air is equal on both sides. Center the teepee and secure it with the foil tape.

Step 8 – Squeeze the Bottom board with into the unit, and put divider into place. Tape all foam pieces into place.

This is the completed modification prior to tightening the bottom plate into place. The grey box to the right is the control box.

Now it is simply a matter of reattaching the AC Shroud.

So, here is my honest opinion of the modification. It is absolutely pushing more air through the vents. Tammy sat on our back couch and said she had never felt that kind of airflow in the rear of the trailer before. Also, it is much quieter. It isn’t silent but it probably won’t require us to turn the TV up anymore when the AC runs, but I will let you know when we go on the road in a few weeks.

In the end, had I known that I was going to be required to remove the Bolts that held the AC to the roof, and then disassemble the metal air diverter from the bottom pan; I may have had second thoughts about doing this modification. That being said I do believe that this is a worthwhile modification because of the increased efficiency that you get in airflow.