Installing an ERV in my Home
by Michael South
January 18, 2007
I moved my beautiful wife, Tessa, into a dome the first night we were married, and in the last 7 years we have learned a lot about life in a dome. One of the biggest improvements we have ever made to our home is installing an ERV (Energy Recovery Ventilator).
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Holes drilled, ready to be broken or chiseled out |
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Concrete removed. Rebar needs be cut out with saw |
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Sleve is foamed into place, ready for vent cap on roof. |
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Vent cap glued and screwed onto the Airform. |
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NP1 Single part Urethane caulking used to glue down flange and water proof. |
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Looking up from inside after roof vent cover is installed. |
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Flange ready to connect to ERV |
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The ERV Unit itself is hooked up. |
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CO2 levels before and after ERV installation. Covers 4 Days. |
The ERV that I installed is the RenewAire EV130. It is small, quiet, and it works great. I installed it in our attic on a Saturday and it took me about 3 hours. Here are lists of materials and tools that I used:
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 role of silver duct tape
- 1 tube NP1 Caulking (bought from Monolithic)
- 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 1/2" SDS Hammer Drill
- 1/2" drill bit
- chisel bit
- Shop Vac
- 18v Cordless Drill
- Knife
- Small Sledge Hammer
- Reciprocating Saw with metal cutting blade
You will need two holes through your dome -- the further apart they are, the better. One of those holes will be for incoming fresh air and the other will be the exhaust.
I began by drilling the holes in my dome. Drilling holes in a concrete dome is a harder project to think about then it is to actually do. I used my Bosch 1/2" SDS Hammer Drill. You can rent similar drills at any tool rental location.
I held the 6" sleeve to the concrete and marked a circle around it so that I would know how big to drill the holes. Then I drilled 1/2 holes about 1/2" outside of the line. (I wanted to make the concrete hole just a little bigger than the sleeve for easy installation). These holes were about 2 inches apart and only the depth of the concrete. Do not drill the holes all the way out of the dome. The Airform is cut out last.
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 sledge hammer to break out the circle I had drilled.
If you are like me, you may find some rebar. So you will need the reciprocating saw to cut out the rebar that is in the hole.
Now that you have a hole in the concrete, you can dig out the foam until you expose the Airform. Don't cut the Airform out yet. I like to do that last.
Insert the sleeve into the hole and use the foam in a can to foam it into place. 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 went on top and cut a hole into the Airform that was the same size as the sleeves I had foamed into place.
The roof vent covers then glue right onto the Airform. The roof vents that I bought were covered with oil, so I used some PVC primer to clean the oil off the metal, before I glued them to the Airform.
I applied a healthy line of caulking to the underside of the vent, then pressed the vent onto the Airform on top of the hole. After the vent was glued on, I added some self-tapping screws to help hold the vent on the Airform. If you use the right screws, with really wide threads, they will provide a lot of hold.
Once the roof part is done and the sleeves are in place, it's time for the easy part.
I made a stand for the ERV to sit on, but some people hang theirs or attach them to walls when that is an option.
I started to hook up the vent pipes. The ERV has four ports: air to be recycled, air to be exhausted, incoming fresh air, and fresh air let out.
Domes are designed a little differently than normal 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.)
Once I had all our vents hooked up and our ERV mounted, I needed to install a timer. 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.
We had been measuring our CO2 levels in our house for a few weeks before. Our chart shows 4 days of readings.
We installed the ERV in the summer and ran it for 6 hours every night, 12 a.m. to 6 a.m. We ran it at night because we wanted the coolest air possible. Now that it is winter, we run the ERV during the day. This brings our CO2 level to about 800 ppm (parts per million) and then up to around 1500 to 1800 ppm. Twelve hundred ppm is considered maximum for commercial buildings (see Fresh Air and ERVs). 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.
The other advantages that we discovered included a 10% decrease in humidity and a really noticeable difference in the way we felt when we were in the house. Raising four kids we stay moving, but we felt like we had more energy after the ERV was installed.
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