Improving AC Air Flow

Its common knowledge among vigilant and DIY RV'ers that the air conditioning units in RV's are not installed with much care and the ducting is not very efficient.

There is a product from RVAirflow that takes care of these deficiencies in one upgrade.

Like many RV-DIYers I decided to make and install my own. There are many versions of this mod on the Jayco RV forum such as this one: https://www.jaycoowners.com/forums/f64/seneca-a-c-airflow-mods-81502.html printed on a 3D printer.

My Unit, Better Than Most

I have to admit that I was surprised at how well my unit was taped when compared to pictures I had seen of other installs. 

Frankly, we did not think the noise was objectionable and the output at the vents seemed pretty strong. I decided to go for an improvement anyway.

A Different Material Than Most

After reviewing the other approaches to improving this ductwork I decided to use cardboard as the ducting material. Then while walking through Walmart I noticed the foam board and thought why not!

The Approach

I decided to try just cutting transition sheets from the foam board. These would be sections that would direct the air from the main output duct into the side ducts. I would use a combination of foam board and metalized ducting tape.

I decided to leave the stock centerpiece in place as it looked to provide a good seal.

Transitioning to The Side Ducts

I cut pieces of foam board that would fit from the source duct down to each of the ceiling's side plenums. I annotated the cut pieces with dimensions so that if you have the same unit they might keep you from fiddling to get a good fit.

Note that I cut the passenger piece on the wrong side of the material so it's installed with the blue backing outward.

These parts were taped in place with the Al tape insuring that all gaps and transitions were covered. Finish taping these parts fully before going to the next step.

The driver side

The passenger side. I cut this upside down.

Shows temp install .... before the final taping

First Section Taped

The Lower Baffles

Baffles were cut that provided the lower part of the new ducting. The apex of these two pieces fit against the center of the source opening splitting the airflow in 1/2. The dimensions for these pieces are also written on the part.

The passenger side to left

The driver side

Both installed 

Finishing The Install

The lower baffles are taped. Ensure that all the openings are taped shut. I taped the gaps at the edges near the ducts from the board to the frame to complete those transitions.

The Center Baffle

After assembly, I noticed that there was air leakage around the tape where it was applied to the center baffle. The tape does not stick to the stock center baffle material. Therefore I taped from the output side of the air conditioner down and around the center baffle and connected it to the input side which has a metal surface.

Fully Encapsulating the Center Baffle With Tape

Measurement Tool

I used an anemometer I bought from Amazon attached to a piece of 3/4" foam board to get a seal at each vent. 

Conclusions

In regard to using the foam board, I found it easy to cut and form with a sharp utility knife. It is also light, cheap, and readily available. The Al duct tape sticks to it well and it takes up less space.

I measured the airflow from each vent before I started. The airflow varied and it was hard to get a perfectly solid measurement. Later I discovered the AVG function on my meter, that would have been a better way to measure. In any case, I logged the most steady peak value for each vent.

I think there is enough improvement evident in the results below to consider this a worthwhile modification. I do not know if the results for Row 2 & 3 on the passenger side are the result of measurement error or what? In any case, one got a lot better and one did not change.

Enjoy and comment,

Don

Insulating the RV Doghouse

My wife and I insulated the floor of the cab in our 2019-20 Jayco 26Y last summer. We were quite pleased with the results. Much quieter and most importantly got rid of the "hot feet" on the passenger side. She is happy!

Some users reported that their doghouse got hot and even melted candy that was laying on its surface. We did not experience this problem with our RV.

We had plenty of the materials left over (Killomat) and decided to insulate the "doghouse".

This post summarizes that project.

The cab insulation project is here: https://www.jaycoowners.com/forums/f5/yet-another-post-about-sound-and-heat-abatement-2020-greyhawk-86233.html#post957747

Materials:

Killomat 50 mil: https://amzn.to/3iRFiRB. This was used on the cab floor and the leftover used on the doghouse.

Noico RED 150 mil: https://amzn.to/3hYAbPW. Used on the cab floor but not the Doghouse. I felt that the stock material and the Killomat would be enough sound and heat insulation for our needs. I also worried that three layers of material would be to thick and make reinstalling the doghouse difficult.

Tools

• Application Roller: https://amzn.to/3eKHxoq I bought this when we did the cab and found it to be a very useful tool to form and ensure the insulation fully adhered to the substrate
• Philips screwdriver
• Utility knife with a fresh blade
• Scissors
• Beer

Removal of the doghouse

The doghouse was removed by:

Remove the storage compartment that is on the front of the doghouse. I had no idea this compartment was removable. Getting it out of the way made getting the doghouse out from between the two seats much easier.

The compartment is affixed with two keyholes at the top and a clip at the bottom. When the clip is released the unit can be pulled upward and off.

To remove pull upward on the compartment while depressing the clip on the bottom of the assy. It's a bit "fiddly" but the key is to get the bottom clip to release the compartment so it can be lifted off.

Then release the locking arms at the upper and lower left and right of the doghouse and pull toward the rear of the RV and upward.

Notice the front storage compartment is removed

Remove the stock insulation

The stock insulation can be removed by freeing one edge and then systematically pulling the edges out from under the seal on the outer rim of the doghouse. The stock insulation is not glued in place but rather just held in place due to its form and the seal.

The stock insulation can be removed in one piece. Set it aside as we will replace it on top of the Killomat.

Do not remove the seal that is on the perimeter of the doghouse.

Install the Killomat Insulation

Clean the inner surface with alcohol or something that will remove any oils etc. Then systematically install the Killomat inside of the doghouse. You can fit each piece by placing it on the surface, with the backing on, and then press it in place to get it formed. Then cut it to shape. The Killomat cuts easily with a utility knife and scissors. 

Note: I left a 1-2" area at the edge of the seal free of Killomat. I did not want the thickness of the Killomat to inhibit installing the stock insulation back under the seal. This insured that the stock material was its original thickness as it is reinstalled under the seal.

The basic installation process is easy:

• Place the Killomat in its intended location and form it to the surface.
• Cut it to size. 
• Remove the backing. 
• Apply it to the surface. 
• Roll it on with the roller.

Killomat installed up to within 1-2" of the seal

Replace the Stock Insulation

After the Killomat is installed place the stock material over the top and fit the seal around the edges.

I used a Phillips head screwdriver to pull the seal up and over the edge of the stock insulation. Proceed around the perimeter of the doghouse until the entire edge of the stock insulation is under the seal.

The doghouse is now ready to re-install.

Reinstall the Doghouse Into the RV

Re-install the doghouse back into the RV

Reinstall the storage compartment onto the front of the doghouse. 

Enjoy the COOL & QUIET

Testing & Conclusions

I took 2 measurements with the sound meter on my phone. The first is at idle and the second is with the engine at 3000 RPM. The third measurement was previously made after the cab was insulated and running at idle. The apples-apples comparison is between the 1st and 3rd measurements.

The noise level measurement shows an improvement. I am not convinced that these measurements are consistent and accurate enough to make a conclusion about the value of insulating the doghouse. 

I have found that the real test is climbing up Parley's Canyon while the engine is groaning at 4000+ RPM and trying to have a conversation with the wife.

I don't know yet if this addition further reduced sound but it was easy to do and I had plenty of materials leftover from the cab insulation to do it.

I still have more material left. I plan to insulate the interface between the cab and the house. You will notice a step up from the cab to the house. This is a piece of fiberboard that is open to the road. Although I insulated it on the inside I plan to add insulation underneath and on the outside of this area.

Enjoy the Quiet

Don