Maximize Airflow: Installing Slider Windows

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Maximize Airflow:

Installing Slider Windows

Shelly ponders window placement (before breaking down and getting a ladder).

As summer heated up, we quickly realized that we needed better airflow to cool down the van. Our 2011 Mercedes Sprinter crew van came with factory windows on both slider doors and the back doors, but they don't open. We have a wonderful sunroof where the rear A/C used to be (break-up story here), but it alone can't cool the van down on a hot day.

We had a few obvious choices:

  1. Swap out factory windows with CR Laurence T-sliders (ventilate the living room)
  2. Install new windows in the back
  3. Install a ceiling fan
  4. Install a new roof-mounted A/C in the back

We eventually decided to go with 2 and 3. (We'll talk about our fan choices and the install process in a separate post.) The reasons we went with half-slider windows are mainly two fold.  

  1. Cross-breeze. Similar to most vanlifers, our bed is in the back. So is Shelly's roll top workspace. Improving airflow directly where we sleep and work sounds really appealing. 
  2. Security and privacy. When half-slider windows are placed high on the van, it's relatively difficult for someone to poke their head (or hand) inside, even when the windows are fully open. This means we feel comfortable sleeping with the half-sliders cracked open, whereas we wouldn't leave T-windows open at night.

Sourcing the windows

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A quick search left us with two popular half-slider windows. One is the Hehr 10" X 36" panel bed window sold by RB Components (passenger side here; driver side here), the other is a CR Laurence Sprinter SS window (11.25" X 37.25").  

The specs for both windows are similar: the tempered safety glass is factory-tinted and there's a built-in bug screen. The installation process also seemed similar, but we decided to go for the Hehr 10 X36 windows, mainly because we found two great installation write-ups online (written guide here, and video here). Also, the RB Components service team was rumored to be great. Our experience on this project confirmed this.

The windows were $219.99 each + domestic shipping in the U.S. They arrived quickly and very well packaged. We made sure to label each window (passenger vs driver) and saved the cardboard box they came in to make templates for the install.


Here's our workflow at-a-glance, with details below:

  1. Prepare the van wall (expose the van skin sheet metal)
  2. Make a template for the window (used to cut the hole)
  3. Make a spacer ring for the window clamp ring to clamp onto
  4. Cut the metal supports on the van wall
  5. Cut the hole in the van skin, paint / treat all bare metal
  6. Insert window assembly with butyl tape on flange
  7. Clamp window assembly to van wall using the supplied clamp ring
  8. Spray with garden hose to check for leaks

Admire the work!

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1. Preparing the van

We already had various types of insulation and barn wood paneling on the van, so the first step was to pull it all off. It sounds like a lot of work, but it was also a good opportunity for us to switch from rigid foam insulation to Thinsulate (which wasn't available when we were insulating the van), which we've been meaning to do. We'll talk more about that in a separate post.

We treated some scattered rust spots and cleaned off sticky adhesives with Goo Gone for a beautifully clean surface.

2. Make a window template

This is the template that we used to cut the hole in the van, so we took some effort to make it as accurately as possible.

We used cardboard from the shipping box. We placed each window onto the cardboard with the glass side up, and carefully traced the bottom of the window onto the cardboard with a thin sharpie. We tried two ways to cut the template: plain old scissors+box cutter vs a jigsaw. The jigsaw may seem like overkill but the resulting product was much more precise!

We then labeled each side of the cardboard (in and out), as well as top and down. 

3. Make spacer ring

Note: the spacer ring is NOT the trim ring sold at RB Components. Currently you can't buy a spacer ring; you have to make one yourself.

Why a spacer ring? The window is installed by inserting the main assembly into a hole from the outside of the van and clamping it in place using a supplied clamp ring on the inside of the vehicle. The clamp ring needs something thicker than the van's sheet metal to clamp onto – hence the spacer ring. We used some 1/4" plywood that we had lying around. Other materials work too, but they can't be too thick or thin. 1/4" is the sweet spot.

To make the spacer rings, we traced our cardboard window template onto the plywood, then drew another 1" larger ring.

Why 1"? We wanted the window location to be as high up and as far back in the van as it could go. Because the spacer ring butts up against the structural lip on the van's interior wall, the ring essentially decides how far up and back the window can be placed. We also tried 1.5" but that ended up with the window a little too low for our taste.

We treated the spacer rings with 3 coats of polyurethane to protect it from the elements before putting them to use.

4. Dial-in window location & Cut metal supports

We located the window so that the part that opens is situated nicely over Shelly's roll top area. 

After removing Shelly's roll top desk and cutting through the wall supports, Shelly confirms that our spacer ring will fit flush against the wall. In the morning, we will cut through the wall.

After removing Shelly's roll top desk and cutting through the wall supports, Shelly confirms that our spacer ring will fit flush against the wall. In the morning, we will cut through the wall.

We then drew a few short lines from the spacer ring onto the van wall, so that we can simply line them up when gluing the spacer ring and it'll go right back to where it's supposed to. Because the interior van wall has two metal supports, it prevents the spacer ring from laying flat against the sheet metal. Those need to go, so we also marked where to cut the metal supports. We used painter's tape to mask off the cut line to protect the paint around it.

Nick very carefully cut the top and bottom of the supports with a Dremel and metal-cutting wheel. Cut too deep and the Dremel would go right through the van skin, so this step took plenty of time, patience and steady hands. We also used a magnetic strip to catch metal shavings, making clean up easier.

The supports are glued to the van skin, so after the cuts we used a metal putty knife and box cutter to gently slice through the adhesive. 

With a flathead screwdriver, we then carefully removed some of the adhesive still stuck on the van skin to completely clear the area where the spacer ring will go. We then cleaned everything with Goo Gone, filed rough metal edges and painted two coats of paint + two clear coats on the exposed metal to protect it.

5. Cut the hole & paint

The most exciting/terrifying part!

We returned the spacer ring to its original location using the drawn lines and used it to guide the location of the cardboard template, taking care that it wasn't tilted. (We don't want a slanted window!) We then drilled four very small pilot holes to locate the template on the outside of the van.

We then held the template onto the outside of the van, lined it up with the pilot holes and used four Q-tips to skewer the template to the van. After tracing the edge of the template with a marker, we masked the surrounding areas with tape to protect the paint from the forthcoming jigsaw.

Nothing like making irreversible modifications to your vehicle.

Next came the cutting.

We expanded one of the pilot holes using a step drill until it was big enough to fit the blade of our jigsaw, and Nick carefully cut out the entire window area. It was surreal to see a giant elliptical hole where sheet metal used to be.

We test-fit the window in the hole, but it didn't quite go in. So we expanded the hole slightly, and re-fit the window until it did not resist.

Note that there are three to four plastic clips on the outside of the window assembly that easily pop off while test-fitting. After several frustrating attempts, we called RB Components to ask if they are necessary. They're not! (Huzzah!) Apparently they're intended to add tension around the circumference of the window, to keep it from bouncing around in the hole, but if the fit is already tight enough they don't help much. And yes, the customer service at RB Components was excellent!

Shelly faces the reality. We made another giant hole in our van.

We then filed down the cut edge, using a magnetic strip to catch the metal shavings, and painted three layers of paint on the exposed surface.

We made one little mistake here: the weather gods suddenly decided to dump a thunderstorm's worth of rain on us. While we were scampering to cover up the giant hole in our van wall, some of the rain rinsed down the wet paint and left a *very* subtle streak on the side of the van. It's hard to see unless someone points it out, but it's annoying to us. We've tried isopropyl alcohol, WD-40, nail polish remover to scrub it off, but nothing worked. Any tips?

6. Insert the window

While the paint was drying (and after the rain) we stuck some butyl tape under the sun to soften it. We then carefully applied it to the window flange, making sure not to over-stretch the tape. 

Before inserting the window, we cleaned the van wall with alcohol, misted both the butyl and the van skin with water (which helps the two bond), and pushed the window in. There was enough butyl that we saw extra squeeze out on all sides, which we trimmed off with a plastic putty knife.

7. Clamp it tight

Back to the inside. We used silicone caulk to stick the spacer ring to the van wall, then immediately slipped on the window clamp ring and started applying pressure. Working from the top-down, we loosely screwed in the supplied screws until all screws were in. Then, with Shelly pushing from the outside, we tightened the screws one-by-one. 

Most of the time we could either see or feel the clamp tighten onto the van. (It felt SO satisfying.) Once the screws were all completely screwed in, the window felt very solidly mounted on the van wall.

Interior view, showing window clamp ring on our 1/4" plywood spacer. That sucker is on tight. After trimming excess silicone and testing for leaks, we'll cover the area with Thinsulate and reinstall our interior wall.

Interior view, showing window clamp ring on our 1/4" plywood spacer. That sucker is on tight. After trimming excess silicone and testing for leaks, we'll cover the area with Thinsulate and reinstall our interior wall.

8. Garden hose test

Finally, after a few days we blasted the window from all sides with water using a garden hose. Zero signs of leakage!

A few days later we repeated the install process on the driver's side, realizing our dream of symmetrical rear windows for cross ventilation.

Eventually, our plan is to cover the window's surrounding area with Thinsulate and a foil-based insulator, make a wall out of bead board and use barn wood to trim the window and walls. So far we've started keeping the slider window open while working in the van, and the fresh air already made a HUGE difference!

Next up: ceiling fan!


What are your experiences installing vehicle windows? Any questions with our install process? Leave a comment below!


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