1. How Radon Pipe Routing Works
Every active radon mitigation system uses the same basic principle. A hole is drilled through the foundation (or a pipe is placed beneath a crawl space membrane), and a PVC pipe connects that suction point to a fan that exhausts radon gas above the roofline. The pipe is the highway that moves radon from under your home to safely above it.
The pipe is typically 3-inch or 4-inch schedule 40 PVC, the same type used in residential plumbing. A radon fan is installed somewhere along the pipe run, usually in the attic, garage, or on the exterior of the home. The fan runs continuously, creating a slight vacuum beneath the foundation that draws radon away from the living space.
The route this pipe takes from the foundation to the roofline is where the interior vs. exterior decision comes in. Both approaches work equally well at reducing radon. The difference is in how the pipe gets from point A to point B, and what trade-offs come with each route.
2. Interior Pipe Routing
Interior routing runs the radon pipe from the suction point up through the inside of the home. The pipe typically goes through closets, utility rooms, or chases (vertical channels between walls) and exits through the roof. The fan is usually installed in the attic.
Advantages
- Better thermal performance since the pipe stays warm inside the home, improving natural draft and fan efficiency
- No visible pipe on the exterior of the home
- Protected from weather, UV exposure, and physical damage
- Fan noise is contained in the attic, away from outdoor living areas
- Pipe and fan are protected from ice and freezing
Disadvantages
- Takes up space inside the home (closet corners, utility areas)
- Requires penetrations through floors and ceilings
- Fan vibration can sometimes transmit noise through the structure
- If a pipe joint fails, radon could leak into the living space (rare with proper installation)
- May be more difficult in homes without convenient vertical chases
Interior routing is often the preferred choice when the home has a convenient path for the pipe, such as a closet that stacks vertically from the lowest level to the attic. It is also preferred in colder climates where keeping the pipe warm improves system performance, though this is less of a concern in Georgia's milder climate.
3. Exterior Pipe Routing
Exterior routing runs the radon pipe from the suction point through the foundation wall or rim joist and up the outside of the home to above the roofline. The pipe is typically attached to the exterior wall with brackets, and the fan may be installed on the exterior pipe run or in the attic.
Advantages
- No interior space used, no closet or utility room impact
- Easier installation in many home layouts
- If a joint fails, any leak is outdoors, not in the living space
- Fan is accessible for maintenance and repair without entering the attic
- Works well for homes without interior vertical chases
Disadvantages
- Visible pipe on the exterior of the home
- Exposed to weather, UV degradation, and potential physical damage
- Fan noise may be audible in outdoor living areas
- Slightly reduced thermal performance (pipe is exposed to outdoor temperatures)
- HOA restrictions may limit exterior pipe placement in some communities
Exterior routing is very common in Georgia because the climate is mild enough that thermal performance is not a major concern. The pipe can be painted to match the home's exterior, which significantly reduces its visual impact. Many homeowners find that after a few weeks, they barely notice the pipe at all.
4. Side-by-Side Comparison
| Factor | Interior Routing | Exterior Routing |
|---|---|---|
| Radon Reduction | Equally effective | Equally effective |
| Visual Impact | Hidden inside the home | Visible on exterior (can be painted) |
| Interior Space | Uses closet/utility space | No interior space used |
| Thermal Performance | Better (pipe stays warm) | Slightly less efficient |
| Weather Protection | Fully protected | Exposed to elements |
| Fan Access | Attic access required | Accessible from outside |
| Cost | Similar ($1,200 to $2,500) | Similar ($1,200 to $2,500) |
The bottom line is that both options work equally well at reducing radon. The choice between them is primarily about aesthetics, convenience, and your home's specific layout. For pricing on either approach, see our mitigation cost guide. A good installer will evaluate your home and recommend the option that makes the most sense for your situation.
5. Factors That Determine Your Best Option
Your installer will consider several factors when recommending interior vs. exterior routing. Here are the main ones.
Home layout and vertical chases
Homes with stacked closets or utility chases that run from the lowest level to the attic are good candidates for interior routing. Homes without convenient vertical paths are better suited for exterior routing.
Foundation type
Slab-on-grade homes often use interior routing because the suction point is inside the home already. Crawl space homes may lend themselves to exterior routing since the suction point can be accessed from outside the foundation wall.
HOA restrictions
Some homeowner associations have rules about exterior modifications, including visible pipes. If your HOA has strict guidelines, interior routing may be the better option. Check with your HOA before installation.
Aesthetic preferences
Some homeowners strongly prefer not to have a visible pipe on the exterior. Others would rather not give up closet space inside the home. Your personal preference matters, and a good installer will work with you to find a solution you are comfortable with.
The Best Route Is the Right Route for Your Home
There is no universally "better" option. The best pipe routing is the one that works effectively for your specific home while meeting your aesthetic and practical preferences. An experienced radon professional will walk through both options with you and explain why they recommend one over the other for your situation. Contact us for professional radon mitigation.
6. What to Expect During Installation
Regardless of the routing option, a radon mitigation system installation typically takes 3 to 5 hours. Here is a general overview of what happens.
The installer first identifies the best suction point location. For slab-on-grade homes, this is usually in the basement or lowest level, often in a utility room, closet, or garage. A 4 to 5 inch hole is drilled through the slab, and material beneath the slab is excavated to create a small pit that improves air flow.
The PVC pipe is connected to the suction point and routed (either interior or exterior) to above the roofline. A radon fan is installed along the pipe run. The fan is wired to a dedicated electrical circuit and runs continuously.
A manometer (a simple U-tube gauge) is installed on the pipe to provide a visual indicator that the system is creating suction. As long as the fluid levels in the manometer are uneven, the system is working. If the levels are even, it means the fan has stopped or there is a blockage.
After installation, a follow-up radon test is recommended within 24 to 30 days to verify that the system has reduced radon levels below 4 pCi/L. Most systems achieve reductions of 90% to 99%. For ongoing care tips, see our radon system maintenance guide.
