Installing an ERV in a Monolithic Dome Home

Last summer, we decided we couldn’t put off installing an ERV in our dome house any longer. The process was pretty straightforward. I want to share our results before getting into the “how-to” of it all.

We installed the ERV at the hottest time of year, so we chose to run it at night. We ran it for 6 hours every night, 12 a.m. to 6 a.m. Now that it is winter, we run the ERV during the day. This brings our CO2 level to under 800 ppm (parts per million). The CO2 slowly rises to around 1500 to 1800 ppm by the time we switch it on again. Twelve hundred ppm is considered the maximum for commercial buildings. Outside air is about 500 to 600 ppm. I calculated that 6 hours was enough time to exchange all the air in our 50’ dome home.

In addition to the lower CO2 levels, we discovered a 10% decrease in humidity and a noticeable difference in how we felt in the house. Raising four kids, we stay moving, but we felt like we had more energy after the ERV was installed.

It took me about three hours to install a small, quiet and efficient ERV—a RenewAire EV130 ERV—in the attic of our home. Here’s how I did it. Scroll down for the list of materials and tools used.

How to Install an ERV in your Monolithic Dome

First, drill two holes through the dome, one for incoming fresh air and the other for the exhaust. Holes should be about 2" apart and only to the depth of the concrete, not all the way out of the dome. The Airform is cut out last. I held the 6" sleeve to the concrete and marked a circle around to show me how big to drill the holes. Then I drilled ½’ holes about ½" outside of the line. I wanted to make the concrete hole just a little bigger than the sleeve for easy installation.

Once I had all the perimeter holes drilled, I drilled 2 or 3 in the center of the circle. Then came the fun part: I used my sledgehammer to break out the circle I had drilled. If you find some rebar, use a reciprocating saw to cut it out of the hole.

Now that you have a hole in the concrete, dig out the foam until you expose the Airform but don’t cut the Airform yet. Do that last.

Insert the sleeve into the hole and foam it into place with canned foam. Once I had both holes drilled and the sleeves foamed in, I went on top of the dome. Marking the center of the holes with a screw, I cut a hole into the Airform that was the same size as the sleeves I had foamed into place.

Glue the roof vent covers right onto the Airform. My roof vents were covered with oil, so I used PVC primer to clean the oil off the metal before gluing them to the Airform.

Apply a healthy line of caulking to the underside of the vent, then press the vent onto the Airform on top of the hole. After I glued my vent, I added some self-tapping screws to help hold the vent on the Airform. Screws with wide threads provide the best hold.

Make a stand for the ERV to sit on or hang the ERV from the dome wall. And finally, connect the vent pipes. The ERV has four ports: air to be recycled, air to be exhausted, incoming fresh air, and fresh air let out.

Final Thoughts

Domes are designed a little differently than standard houses in that we condition the air in our attic as well as the air downstairs. So, I decided to take the air from one of the incoming vents in the attic and dump it into the intake of the central unit. This made my job super easy. (Obviously, there are other ways to do this. In another house, we installed vents, much like the central AC vents, to make the intake and output vents.)

I needed to install a timer once I had all our vents hooked up and our ERV mounted. I bought my timer online from Smart Home. Later, I saw it on sale at Home Depot.

If you need help hooking up the electrical, get an electrician. I used the “old construction” box to install the timer switch downstairs. An “old construction” box is one that slides into a hole in the sheetrock and has flanges that fold out and hold the box in place.

Materials Used

• 2 - 6" sleeves (to stick through the dome wall)
• 2 boxes (50’) of insulated 6" ducting
• 1 - 6" vent adapter
• 2 roof vents
• 1 roll of silver duct tape
• 1 tube NP1 Caulking
• 8 self tapping sheet metal screws
• 1 timer switch
• 1 single gang old construction electrical box
• 50’ romex electrical wire
• 1 can of foam in a can

Tools Used

• Bosch ½" SDS Hammer Drill
  • ½" drill bit
  • chisel bit
• Shop Vac
• 18v Cordless Drill
• Knife
• Small Sledge Hammer
• Reciprocating Saw with metal cutting blade