Active Dampness Control System Details
Active Dampness Control (ADC) Systems are installed primarily during new construction to reduce moisture and radon. ADC System rough-ins prepare new homes for future moisture and radon reduction. ADC installation principles can be used for partial, passive systems (also known as Radon Resistant New Construction or RRNC), but are not fully effective until they are activated with an ADC fan. HomeAire recommends that ADC Systems be installed by a trained professional.
There are 6 major components in an ADC System. They are built in from the ground up, beginning with HomeAire's unique and innovative ADC-T. If the first 4 steps are followed, your home has a passive or RRNC installation; if steps 4, 5 and 6 have all been included, you have a fully operational ADC System. Either way, we recommend that you test your home for radon if you have not already done so. The U.S. EPA recommends that all homes, new and existing – with or without a moisture and radon control system, be tested for radon.
ADC System components:
The ADC-T prepares for the installation of the ADC System. It provides a stable base for the system and allows water vapor and soil gases to be drawn from all angles. It is staked into the ground and surrounded by aggregate before the slab is poured. A 3-4 foot length of PVC pipe is inserted upright into the ADC-T and capped so that construction debris cannot enter and block it.
Aggregate, usually consisting of crushed rock or gravel, is poured into the foundation area and leveled out to a depth of about 4 inches to provide a base for the concrete slab that will allow air and vapor to be drawn from below the slab. (Where aggregate is not available, choose another acceptable option such as geotextile matting.)
- Vapor Barrier
Also before the slab is poured, a vapor barrier (a special type of 6 mil polyvinyl sheeting that resists the diffusion of moisture) is used to cover and seal the aggregate. Next, concrete is poured over the barrier to form the slab.
- PVC Pipe
After the walls have been framed, additional 3-4 inch PVC pipe is extended up through the framing, terminating at least 12 inches above the surface of the roof.
A u-tube manometer is affixed to the PVC pipe (usually in the basement), providing an easy method for visually monitoring system operation. If the fan (step 6) is operating properly, the fluid levels in the u-tube will be uneven.
- ADC Fan
An Active Dampness Control (ADC) fan will be mounted to the PVC pipe in the attic to draw moisture, radon and other soil gases from beneath the slab and up through the vent pipe, exhausting them safely above the roof of the home.
HomeAire recommends that you check the ADC System’s u-tube monitor periodically to make sure the fan is operating properly and to test the home for radon [link to HA test kits] every 2 years.