ventilation | AiDomes


Exterior stone front w wood deck2

American Ingenuity 40′ dome on full basement utilizing Heat Recovery Ventilator.


To read about the Ai dome and heat recovery ventilators, click on HRV.   To read Ai’s most common asked energy questions and answers, click on Energy FAQ.  To read about the Ai dome and geothermal pipes, click on Geo Thermal.


Dome Exterior Waterproofing is separate from but very much tied to your Indoor Waterproofing. For Indoor Waterproofing, see HVAC/Vent Section for requirements to remove humidity/moisture/water vapor issues created every day by cooking, showering, laundry, equipment using propane or gas and other daily activities. If this moisture is not removed it will cause bubbles/blisters under your exterior paint. Vapor passes thru the dome wall and will get trapped under the paint and condense to water. This bubble water will leak back into your dome with you thinking you have a leak….when it is a water vapor issue that you have not addressed. This results in a secondary issue: the bubbles in your exterior paint have to be repaired. Ai cannot over emphasize the importance of how the installation of Broan bathroom exhaust fans & other items described in the HVAC/Vent Section will save you time and money in the long term on your exterior shell waterproofing issues.

Range Hoods, Microwaves, Clothes Dryer, and Bathrooms need to vent outside. (In some cases insulated metal ducting may be required. Check local code.)


Anytime we cook or shower in a residential structure a significant amount of moisture collects inside the structure. This moisture becomes visible in the form of condensation (sweat) or frost on cold surfaces, such as windows. (Less so on well insulated windows.)

The American Ingenuity Dome is an air tight structure, with some moisture (water vapor) passing thru the dome wall to the outside. However some excess moisture can remain in the home. Excess moisture can be exhausted with Exhaust Fans or Air Conditioning unit or dehumidifiers and for southern climates an Energy Recovery (ERV) Ventilator or in northern climates a Heat Recovery Ventilator (HRV).

What happens when moisture is not exhausted or vented out of the dome?
1. It raises the relative humidity (RH) above our comfort level of about 55 to 60 percent RH, making us perceive the inside as “muggy” and supports the mold growth if not removed.
2. Bubbles can show up under your exterior paint. Moisture will escape thru the dome walls and get trapped under any paint that is not marginally breathable. The sun heats up the moisture/water vapor and it condenses as water. Prick the bubble and water will come out. If bubbles of water are left to sit on the dome, the water will pass back into the interior looking like there is a dome leak…when there is not. The issue is that moisture is not being ventilated or exhausted out of the air tight dome.

A very simple way to remove moisture is to open some windows, turn on the bathroom and stove exhaust fans. However, in some geographical areas of high outside humidity this will not work so well. Resulting in the need to install an Energy Recovery Ventilator or a Heat Recovery Ventilator or dehumidifiers. Check with your local HVAC subcontractor for methods are best for your area.

Excess humidity can also be removed by the cooling coil of the air conditioning unit. This will work well if the weather permits an AC to be run. What happens when an A.C. runs is the water dripping from the A.C. coil is carried outside in a PVC drain line. The air conditioning unit will usually do the job if the unit is not over sized. What will happen if the A.C. unit is over sized, it won’t run long enough to get the moist air dried out giving you that “muggy feeling.” So be certain when installing the A.C. not to go bigger in size but a little smaller so you’re A.C. will run just long enough to remove the moisture. See A.C. Size doc in this section.

The other way to remove moisture is to install a Heat Recovery Ventilator. Although an (HRV) can be effective in the summer months, when it will take heat from incoming fresh air and transfer it to stale air-conditioned exhaust air, it’s most popular in colder climates during the winter. If the temperature falls below about 20° F, however, frost can build up inside the exchange core. To handle this, a damper closes off the cold airstream and routes warm air through the core. After several minutes, a timer opens the fresh-air port and ventilation continues. A typical HRV for residential use might move as much as 200 cfm of air, but the fan speed can be set to suit the air quality in the home. For example, a slow to medium fan speed may be adequate for normal living, while a house full of guests might require the highest setting. Controls are available for intermittent and remote operation. HRVs are ideal for tight, moisture-prone homes because they replace the humid air with dry, fresh air. In climates with excessive outdoor humidity, an energy-recovery ventilator is more suitable. This device is similar to an HRV, but dehumidifies the incoming fresh airstream. See doc in this section named “How a Heat Recovery Ventilator Works.”


After the second floor joists, edge beams are installed and interior walls are framed in but before the wallboard is installed: install flexible, galvanized metal ducting through the inside walls, joist spaces or drop down ceilings to connect exhaust fans to exhaust vents.

Possible Solution: One end of the ducting will be connected to the exhaust fan installed in the following locations:  Framed wall in each bathroom; In wall behind clothes dryer in the utility room; In walls by stove hood & microwave in the kitchen (may require insulated metal ducting. The other end of the ducting will be connected to the exterior vent which will be located in exterior dome panel or in a framed wall under an entryway or dormer.

To install the Vent, a hole can be cut in the exterior dome panel just do not cut within 8” of the center of a seam. Or the vent can be installed in a framed wall under an entryway or dormer.

  • To route the ducting, do not ever cut a 6” hole in 8” joist. See your local code. Code may allow a hole to be cut in one or two joists but not in 3-2×10” joists to get to a framed wall. Never cut a hole in an edge beam or trimmer. Go up and over an edge beam or trimmer. If there is no knee wall on the second floor, install a box cavity over the ducting.
  • The following 6” Round Wall Vent from Home Depot has been used by some dome owners. Master Flow 6 in. Round Wall Vent – WVA6. For use as the outside sidewall termination of kitchen and bath fans, range hoods, microwave venting, dryer exhaust systems. All-aluminum construction. Free flow damper flap moves with airflow. Seal exterior flashing to help limit leakage.


Dome owner quote: “I have seen no moisture problems yet and I think one key is I put in the relatively expensive Broan auto-vent fans  that automatically come on when moisture is high in the bathrooms.”

BROAN Sensaire® technology is a hands-free solution to fighting excess humidity and possible mold problems. It detects rapid increases in moisture levels at the ceiling, where steam and humidity naturally rise, and automatically turns the fan on. With a fan this quiet, we included automatic shutoff to save worry, and money. BROAN Sensaire® technology is a perfect solution for high traffic bathrooms, the kids’ bathroom, or for anyone who leaves the house before humidity is properly vented.

Install high cfm fans in all bathrooms and kitchen vent fans as well. One or our dome owners had this advice: “I tied my bathroom vents to the HRV which has a humidistat that kicks it into high gear when the bath humidity hits it.”


The Geodesic Dome by American Ingenuity, Inc. due to its insulation not being separated by wood, 30% less surface area and R28 insulation, produces a super-insulated home that is air tight.

One dome owner in South Carolina, had his dome tested for energy efficiency by an independent testing company who submitted the results to EPA (Environmental Protection Agency) EPA designated the structure to be ENERGY STAR and certified the dome using 61 percent less energy than a comparable conventional built home.

Small 22’ & 27’ Aidomes can be heated with a relatively small Kerosene heater, wood stove or fire place and cooled with small window type air conditioning units. Building Code has changed in some states (CA. & Fl.) where an AC is not required but a permanent heat source is required. Which means a wood stove or fireplace is not acceptable. Code will accept baseboard heaters as permanent heat source.

It is recommended to combine these locally installed heating/cooling units with exhaust fans connected to exterior vent,  heat recovery ventilator and a central ceiling fan at the highest point of the open space in the dome for even temperature distribution in the dome. Aidomes 36’ or larger require Central air conditioning/heating for even distribution of cooling and heating.

To remove hot air, stale air and moisture off the second floor, install an upper air intake ducting behind 2nd floor knee wall with grill and filter in the knee wall. See HVAC diagram in this section.

Conventional Insulated Flexible Galvanized Ducting installed in between joists is used as air ducting in combination with standard, adjustable outlet registers.

Mini Split Air Conditioning Systems can be installed in the dome which have the compressor and fans outside. These units are very energy efficient with “registers” in each room so temps can be set separately and work automatically. See separate doc in this section about Mini-splits.

The following came from the EPA’s Energy Star web site:

The air within homes can become stale from moisture, odors, and pollutants that penetrate the home or are generated internally by human activity and out gassing from building materials and furnishings.  A constant supply of fresh, outdoor air can provide greater assurance of good indoor air quality and improved comfort.

In most homes, ventilation is provided accidentally when air leaks through the building envelope.  Accidental ventilation is unreliable because it is dependent on a pressure difference between indoor and outdoor spaces caused by temperature or wind variations.  Too much fresh air often enters a house during cold weather, causing uncomfortable drafts and high heating bills.  Not enough fresh air may enter during mild weather which can lead to poor indoor air quality.

Air leakage through the building envelope accounts for between 25 percent and 40 percent of the energy used for heating and cooling in a typical residence.  Many new homes are being air sealed to reduce this energy use.  Where tighter construction reduces air leakage and accidental ventilation, active ventilation systems may be needed to provide fresh air.

Figure 1 shows how a balanced ventilation system works in a small home.  Fresh air enters the home through a single intake and is then distributed through ducts to the living and sleeping areas.  Stale air is removed from the home through a separate exhaust duct with inlets typically located in the bathrooms.  The kitchen has a separate, manually operated exhaust fan located in the range hood.  These systems can operate continuously or only when home are occupied.  The supply and exhaust fans are equal in capacity to maintain indoor pressure balance.

In severe climates, balanced ventilation systems can be equipped with a heat exchanger that recovers most of the heating and cooling energy from the exhaust air.  There are two types of heat exchangers: sensible and total.  Sensible heat exchangers recover dry heat.  They are well suited for cold climates and are becoming common in many parts of Canada and the northern United States.

Total heat exchangers transfer heat and moisture for additional humidity control.  They work well in both cold and moderately humid climates, and can help prevent moisture-related problems.  Balanced ventilation systems can be used safely with all types of heating and cooling equipment, but are more expensive than other ventilation systems (exhaust and supply ventilation).

Resources for this article:

    1. The Consumer Guide to Home Energy Savings (Wilson and Morrill), available from the American Council for an Energy Efficient Economy at 510-549-9914
    2. Moisture Control in Homes fact sheet available from the Energy Efficiency and Renewable Energy Clearinghouse (EREC), POBox 3048, Merrifield, VA 22116, (1-800-363-3732)


Kaufman garage house 1536

Kaufman 45′ dome home linked to 34′ garage dome in Forest Ranch California

Utilizes Heat Recovery Ventilator & Geothermal Energy for Heating & Cooling

The following article was taken from the Summer 2009 Butte Environmental Council’s (BEC) News.   The geodesic dome home featured was built from American Ingenuity dome building kits.  BEC is a not-for-profit public benefit corporation.  Founded in 1975, BEC protects the land, air, and water of Butte County California through advocacy, environmental education, and information and referral services.

ChicoEco Highlights a Geodesic

By Nani Teves

Hidden among the trees in the mountain community of Forest Ranch is the most amazing example of living more responsibly by combining conservation and cutting edge.  Ron Kaufman and Marti Leicester spent four years planning and 14 months building their geothermally heated and cooled, concrete geodesic dome home, which, when all was said and done was approximately the same cost as building a traditional house of the same size.

A geodesic dome looks like the top half of a soccer ball, and theirs is two domes connected by a 12 ft length.  They used concrete as a building material because it is low maintenance, highly insulated, insect resistant, and most importantly for their area – fire resistant.  They built to optimize passive solar potential usinged double pane windows.

Throughout the house, renewable and reused building materials were used including the floor, which is made from Marmoleum, a durable linoleum made from linseed oil, jute and rosin.  For carpeted areas, 1ft by 2ft squares were used, making it possible to replace only damage areas.  Framing studs were reused to build the loft, the kitchen cabinets are bamboo and the stairs, window seats and baseboards are all make from a material called Evergrain, which consists of 50% HDPE (typically recycled milk bottles) and 50% wood fibers (typically old pallets).

One of the most fascinating things about this house is that it uses geothermal energy for heating and cooling.  The system was expensive but they wanted to push the technology forward by experimenting.  How the system works is heat is collected from the dome interior and then pumped into the ground during cooling, and reversed during heating.  They hired an out of state company (no one was available locally or even in California) to drill four 180ft deep holes.  Crystal Air in Weaverville installed the system by placing tubing surrounded by Bentonite in the holes.  A two-way pump is run using energy from PG&E and a back-up generator, and the extra heat from this system is used to preheat the water for their on-demand tankless water heater.

Another unique feature they included in the design is a Heat Recovery Ventilator (HRV) System.  The HRV brings in fresh air and exhausts stale air, while transferring a significant portion of the heat in the stale air to the incoming fresh air.  It also maintains a slightly positive air pressure in the dome so that pollen and dust are not drawn in through open doors and windows.

From the jars reused to hold screws, to the dome itself, this house is an example of how fun it can be to research, experiment and live outside the box.


Ai is sometimes asked – Which is more efficient a Heat Recovery Ventilator or Dehumidifiers to control moisture inside the dome?

One of American Ingenuity’s Missouri Dome Owners, Mr. Nicks, sent us the following email. “I was having trouble with winter humidity in my dome until this February 2006 when I purchased and installed a Heat Recovery Ventilator (HRV). Air quality is noticeable fresher and relative humidity is under control. The HRV has eliminated the need to run dehumidifiers during the winter for me. Additionally, small dehumidifiers are electricity hogs (costing more to operate than central air in the summer).


My home does have high cfm fans in all bathrooms and kitchen vent fans as well. I tied my bathroom vents to the HRV which has a humidistat that kicks it into high gear when the bath humidity hits it.


My dome is still a work in progress, but I love being the first and only one around here to “think outside the rectangle” in home design. The spaces in a dome have amazing character….anyway just wanted to share an idea that has helped me defeat the humidity in my dome.”


Ai asked him where and how did he install is Heat Recovery Ventilator?

He replied, “I installed the HRV in my utility room with an insulated intake duct through a joist space. The unit I installed was manufactured by Lifebreath (model 200 max). Depending on which standard is used it may be slightly undersized, but works fine. Three of my bathroom vent fans had previously come together in the utility room to exit through a single 6” vent (I had a box with dampers to prevent backflow). I connected the HRV to those three bath vents which allowed me to pull air from three different floors of my dome.


The HRV I installed has a humidistat in its exhaust air stream (household intake). When someone is taking a shower that humidity causes the HRV humidistat to switch the fan to high speed. I have mine set on low speed continuous as a default.”

Are electric vents necessary at the peak of the dome as well as in the bathrooms to prevent moisture buildup?

A: Yes. The electric exhaust vents are installed in a vertical wall near the top of the dome, in top center of the dome, in bathrooms and above stove/microwave to exhaust water vapor (from laundry, cooking, showering, etc.)  In interior walls, use galvanized metal ducting that extends down the interior wall, through the floor joist and vents out under an entryway.  And in some areas install a heat recovery ventilator or energy recovery ventilator to remove moisture.