No Sweat: Managing Humidity in your Monolithic Dome Home

It’s hard to put into words how comfortable and peaceful living in a Monolithic Dome home feels. You know you’re safe, and the steady temperature inside makes daily life more relaxed. It gets hot in Texas, but my family’s dome home stays cool even when outside temps rise.

One summer, our AC went out during a 100-degree week, and my wife and I didn’t even notice. We keep the thermostat at 72, and one day I saw it had crept up to 74. That’s when we realized the AC was broken and hadn’t been running for at least a day or more. Even without it, we were perfectly comfortable.

Monolithic Domes are super-insulated, airtight structures that save money on heating and cooling. A byproduct of this excellent insulation and closed system can be a rise in CO₂ and humidity. Luckily, these are problems easily fixed with the right design and air handling system tailored to fit the space.

Every dome needs to have an Energy Recovery Ventilator (ERV) to bring in fresh air without losing heat from or adding heat to the system. There are times when household needs change, like when my wife and I have all our kids at home. The CO₂ levels increase, and we have to run our ERV more often.

One of the best things about an ERV is that it removes humidity from fresh air before it reaches the HVAC system. We live in the South, so like every other home in Texas, we need a dehumidification plan. Our ERV maintains the air quality inside our dome by removing stale air and replacing it with dehumidified, fresh air, while maintaining a constant temperature.

Before there were all these modern systems, my dad came up with some great ideas to keep the air fresh inside. One of his methods involved rigging a timer switch on the HVAC system that would simultaneously activate both the heater and the AC for a limited period. It’s not the most energy-efficient way to dry moist air, but it works.

Another strategy we swear by is to ensure that the HVAC unit installed for your dome home is precisely the right size to cool the space, and no bigger. With the AC and fan running more hours a day, there’s natural dehumidification of the air.

Warm air can hold more moisture than cool air. When the AC is on, air passes over the cold AC coil, condenses, and is drained away. The longer the AC runs, the more moisture it removes from the air. You can see the same effect when a cold soda can sits out on a hot day: the humidity in the warm air condenses on the cold surface and forms droplets.

At my house, I made the mistake of installing a larger AC system—a three-ton system—because it was the same price as a one-and-a-half-ton system. I thought it was a smart bargain, but after it got installed, I had a humidity problem and had to install a dehumidifier to dry the air. The dehumidifier runs for a couple of hours a day. It’s a hands-off system, and once it was installed, I never had to think about it again.

My sister’s dome house of a similar size does not have a whole-house dehumidifier because she installed an HVAC system designed for a much smaller conventional home. Her system has no problem keeping her Monolithic Dome cool, even in the hottest part of our Texas summers, and she doesn’t have a humidity problem.

Actually, she does have an isolated humidity issue in the main bathroom with a shower that sees heavy use. An exhaust fan was never installed to vent moist air from hot showers outside. That would be a problem in any home. She manages it with a small dehumidifier they flip on after showers. The lesson here is to install proper exhaust fans in full baths. She’ll get around to it.

My mother also had her methods for managing humidity, specifically in tight spaces. When she and Dad built Charca Casa in the late 1990s, she insisted on HVAC vents in every closet, pantry, and den—even the smallest ones—unless the closet doors were vented. She had her reasons…

In 1979, my parents moved into Cliffdome in Menan, Idaho—one of the first Monolithic Dome homes ever built. Not realizing how airtight the new home would be, my mom planted a large indoor garden, which created excessive humidity. They installed a dehumidifier, but since there was no central AC (no one had it in Idaho back then), there weren’t any vents to the closets or small rooms on the first floor near the garden. Sometimes mildew would pop up. She would install a small fan in any “hot spots,” and that took care of the problem.

Modern HVAC systems can include integrated ERVs and dehumidifiers, but ensuring your home has vents in every room and exhaust fans in every bathroom will always be important, even if the new all-in-one HVAC systems eliminate the guesswork of keeping your air fresh and dehumidified.

Another consideration related to the energy efficiency of Monolithic Domes is that leaving the footing exposed to the elements creates a temperature differential, resulting in condensation at the base of the dome wall. In Texas, we can cover the footing with dirt. In colder areas, it’s essential to ensure that the footings are insulated.

When it’s well-designed, there’s no place more comfortable than a Monolithic Dome home. The needle on the thermometer rarely moves. Most of the time, we can’t even hear the sounds of tornado season, let alone feel a change in ambient temperatures inside due to soaring (or diving) temperatures outside.