When I walk into a large multi-family building, I see more than just a complex footprint… I see a puzzle. With multiple units touching the ground and mixed-use spaces like offices tucked between residential wings, these buildings are notorious for being difficult when it comes to commercial radon mitigation and finding ways to reduce radon costs.
A few years ago, at the 2021 International Radon Symposium, I shared a case study that perfectly illustrates a trap many in our industry fall into: the “more power is better” fallacy. I want to break down why my findings changed the way system design should be viewed and, more importantly, how it can save building owners hundreds of dollars.
case study: radon mitigation for a 6-story, multi-family unit
The building in question was a six-story slab-on-grade structure, roughly 75’ x 75’. The residential units were getting high-pressure fans installed on a “per unit” basis, but there was a stubborn office area that simply wouldn’t respond to the depressurization.
The initial approach was simple (and common):
- Install high-pressure fans for individual units.
- Assume high airflow would eventually reach the office.
The Result? I had high airflow, but zero “Pressure Field Extension” (PFE) reaching the office. Air was moving, but the systems weren’t moving the radon.
Before we look at the fix, let’s look at the “hidden tax” of that initial design. Each high-pressure fan was pulling about 100 watts. At an average energy cost of $0.11 per kWh, one fan costs about $600 to run over a 10-year period.
If you have a building with 13 ground-contact units and you slap a high-flow fan on every single one, you’re looking at $13,000 in energy costs over a decade. And in this case, the office was still testing high for radon.
Instead of just adding more fans, we switched to a diagnostic-first mindset. We stopped guessing and started measuring. We looked at the radius of the pressure field-testing how far that “suction” actually traveled under the slab (15’, 20’, or 30’).
The realization was clear: Soil resistance is a powerful thing. Increasing suction pressure by 25% rarely helps in tight soils. In other words, you don’t need a bigger hammer…you need a better angle.
The Solution: Less is More
By using diagnostics to match the fan type to the actual soil resistance, we completely redesigned the system.
We saved the owner $4,000 over ten years on just this one section, while finally making the building safe.
Case Study: The Minneapolis Example
I saw this again in a new build in Minneapolis. The builder skipped Radon Ready New Construction (RRNC) and was forced by the city to install active systems after the fact. The initial design called for four systems with high-flow fans.
Our diagnostics showed the actual airflow needs were only between 19–47 CFM. A high-flow fan is a waste of money in those conditions. It costs three times as much to operate, but provides zero extra performance benefit.
If you are a building owner or an HOA member, you are the one who eventually pays the electrical bill and the maintenance costs for these fans… Meaning, an inefficient system is a long-term liability.
For my fellow pros, the takeaway is simple: Don’t just get lucky.
- Validate performance with diagnostics.
- Match the fan to the soil, not the building size.
- Document everything so the owner knows exactly what their long-term costs look like.
In the world of radon, the right fan matters much more than more fans. By designing for performance rather than assumptions, we protect people’s lungs and their wallets at the same time.
Is Your Radon System Costing You Thousands in Hidden Fees?
If your building uses high-flow fans without validated diagnostics, you could be overpaying on energy and maintenance by up to 300%. Let us optimize your system for peak performance and lower long-term liability.
Reach out today!