American Ingenuity 40′ dome on full basement utilizing Heat Recovery Ventilator.
GENERAL OVERALL VIEW ON MOISTURE CONTROL, VENTING, AIR CONDITIONING/HEATING THE AI DOME
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.
ADDING EXHAUST VENTILATION AT THE TOP OF THE DOME & IN KITCHEN (RANGE HOOD, MICROWAVE), BATHROOMS, UTILITY ROOM (CLOTHES DRYER)
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.)
MOISTURE REMOVAL & VENTING
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 a very air tight structure, with some moisture (water vapor) passing thru the dome wall to the outside. However excess moisture remains in the home. Excess moisture can be exhausted with Exhaust Fans or Air Conditioning unit 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, install an extra exhaust fan in the top of the building to pullout the humidity and circulate fresh air to lower the relative humidity. 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. Check with your local HVAC subcontractor for which ventilator is 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.”
INSTALLATION OF DUCTING TO CONNECT EXHAUST FANS TO EXTERIOR VENTS
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.
One end of the ducting will be connected to the exhaust fan installed in the following locations: Second floor framed wall at the highest point of the dome; 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.
BATHROOM EXHAUST FANS: BROAN AUTO-VENT FANS ($250)
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 ($250) 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.”
Warmer air will collect at the top of the dome. This can be easily circulated to the lower level of the dome by installing 4” vent pipe or stackwall. Run the pipe from a high point in the dome to point just above the 1st floor. By installing small exhaust at the lower end you will be able to circulate the warmer air to the lower level. Use a manual switch or thermostat to control the fan.
TO REMOVE MOISTURE FROM DOME,
INSTALL A ROOF VENT & PVC PIPE
WHERE THE FIVE TOP P PANELS INTERSECT
IN TOP CENTER OF THE DOME PRIOR TO CEMENTING TOP CENTER SEAM
Prior to purchasing your 4” Schedule 40 or Schedule 80 PVC pipe or appropriate pipe to meet fire code; choose the height the pipe will extend above the dome. Be certain it fits in the 4” Galvanized Umbrella Roof Vent Cap that is being used. Vent example is Home Depot Model #EX-RCGV04. Internet #202907396.
Do not use PVC Vent Pipe to secure rope for building maintenance. To protect pipe install five stainless or galvanized eye bolts one in each seam about 5” away from the pipe.
After setting the top five panels prior to cementing the top center seam where all the P panels meet, install a 12” – 14” long 4” in diameter Schedule 40 PVC Pipe or if possible install Schedule 80 PVC pipe…the thicker the better or appropriate pipe to meet fire code. If there is not a big enough area void of mesh in this top center, trim some mesh away or bend it back to allow you to insert 4” pipe all the way through to the dome interior. Meaning use a hand saw and cut out EPS and wallboard. Pipe should be as flush as possible to interior wallboard so the exhaust fan with grill can be installed later. Leave the pipe sticking above the panel prefab concrete four inches.
GENERAL INFO ON HEATING, VENTILATING, AIR CONDITIONING THE DOME
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, top of dome exhaust 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:
- The Consumer Guide to Home Energy Savings (Wilson and Morrill), available from the American Council for an Energy Efficient Economy at 510-549-9914
- 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)