Fresh Air and ERVs
How do you bring fresh, breathable air inside your home, school or church without losing the dome’s energy efficiency?
Carbon dioxide gas (CO₂) has many sources. We produce CO₂ when we breathe and plants give off CO₂ when the sun is not shining. (They give off oxygen when the sun is shining.) Combustion also produces CO₂, as do coal-fired energy plants, cars, trucks, forest fires, etc.
High levels of CO₂ in a home may indicate poor overall air quality. For instance, one can assume that if CO₂ levels are high, so are other pollutant levels such as outgassing from carpets, furniture and pet dander.
Monitoring brings surprises
Since June of 2002, the Monolithic Dome Institute (MDI) has been monitoring CO₂ in many homes – both domes and conventional. They all have too much CO₂ most of the time. If windows are opened, CO₂ levels drop to 450 parts per million (ppm) – the same as outside. But modern houses are airtight, and Monolithic Domes are the tightest of them all. Consequently, CO₂ levels can rise drastically over short periods of time—generally from the breathing of the occupants. Obviously more people – more CO₂.
For commercial buildings, 1200 ppm is considered the trigger point upper limit for fresh air intake. So we are assuming that 1200 ppm is the maximum we should have in our houses. (Some say most we should allow is 1500 ppm.)
It was a surprise to us to discover (in both conventional and Monolithic Dome homes) how often we found CO₂ levels above 1200 ppm. We were shocked to find that, at times, the CO₂ in some homes reached 4000 ppm. In fact, we found that most homes are always above the 1200 ppm number. (OSHA fines facilities with readings above 4000 ppm.) I have carried a portable monitor into many buildings and places. It is amazing how few buildings with people inside stay below 1200 ppm. As I analyze this, I think it is because unless we measure we have to guess and most guesses are wrong.
We believe we have found an answer to the CO₂ issue. It comes in the form of an ERV (Energy Recovery Ventilator or HRV Heat Recovery Ventilator). These machines bring outside “fresh” air into the home and exhaust an equal amount of the home’s stale air. And, as if by magic, ERVs also recapture most of the heat from the respective air streams. This is done in the box by an air-to-air heat exchanger. ERVs are an absolute must in our modern buildings. They are great additions to any building. By recovering the heat, we spend less to heat or cool the exchanged air, thus saving huge amounts of energy while getting the fresh air we need.
In Canada, most new homes must install an ERV. Studies have led us to conclude that we should follow suit. After extensive research, MDI has found several ERV units that work well.
On my home (Charca Casa) we installed a demonstrator ERV called RecoupAerator. It’s a permanent model, but we installed it in a window so we could monitor it closely and show it to visitors.
As many of you know, my house consists of two, 40-foot-diameter Monolithic Domes with a central connector. Each of the domes has a 1.5 ton AC unit with internal ducting. Surprisingly, we found serious air mixing from each dome. The single unit in the living room does well for the entire house.
When we complete our experiments, we will install an ERV permanently in the furnace space. Our experiments have shown it will work perfectly there.
My home is now always under the 1200 ppm level – even with lots of company. We only run the ERV for a few hours each day. All homeowners should have their homes checked for CO2 levels. Not very long ago a CO2 meter was in the $800 range. Now they can be bought, in many cases, under $125. It is an extremely good idea for everyone to check the CO2 levels in his or her house and in schools, churches – wherever.
As an option, the RecoupAerator can have a CO₂ monitor self-sensing switch for automatic on or off. A second option allows manual control, that can by-pass the exchanger and heat or cool the house, to actually pull in outside air at appropriate times.
We have recently installed an ERV in a church facility Monolithic Dome that is working very well. It has cut the air conditioning need in half. This means we can bring in fresh air through the ERV and save the heat loss we would have if we brought the fresh air through an open duct, as is done in most schools, churches and commercial buildings. We are now incorporating ERVs into most of our new commercial projects.
In my opinion, every home and commercial structures should have an ERV. I often travel with a CO2 meter. I find that airplanes have it down pat.They have a lot of people inside. CO2 levels would sky rocket if it were not for the fact that they are taking fresh air into the airplane at a rate that holds the CO2 level down to the range it is supposed to be. I find that airplanes will take off and the CO2 level will stay absolutely the same throughout the entire flight.
I installed an ERV that’s small, quiet and efficient in the attic of our home in about three hours.
Chew On This:
Keep in mind that there are many days when we could heat or cool a dome using just fresh air.
Example: This morning it was 57 degrees outside and my air conditioner was running. It was cooling the shell a bit from yesterday’s temps in the upper 80s. If we had a good way to bring in lots of air at those times, we could use it to charge the dome’s thermal battery. On the other hand, we do not want outside air during an ozone alert, or when it’s very humid – even if the temperature is optimum.
At present, I’m searching for a furnace that pulls fresh air from the outside, on command, either full-flow or through an ERV. It will be controlled by a simple computer/thermostat system that can be programmed for a full range of possibilities. Properly equipped and programmed, this system could keep the air fresh while heating and cooling the Monolithic Dome as needed, using virtually no energy, for much of the year.
Updated November 2012