A passive radon mitigation system installed in new construction.
One thing I am seeing more and more in new construction is the installation of a passive radon mitigation system which would only need a fan should a house test positive for radon.
Not all the builders do this.
But when I see it I point it out to the buyers.
This area of Northern Virginia has a medium radon potential. But there are some spots that are more prone to radon than others.
However, any house can test with a "high" radon result*, and the only way to know is to do a test.
With a passive system, when a house is built a tube is placed through the slab, extending to the dirt below.
Doing this when a house is being built makes it dramatically cheaper to install a radon system in the future, which would have to create a new hole through the slab, and run new PVC tubing that extends from the basement to the outdoors.
Tubing like what you see here makes its way through the house from the basement to exit through the roof.
In the photo on the right the builder actually put a small access location into the roof space where the tubing passes through the roof sheathing.
A receptacle was also placed there to accommodate the electrical needs for an eventual vent fan.
If the house tests positive for radon only a fan 
would need to be installed, likely in this attic space, and plugged into the receptacle provided. This would make the installation of a remediation system much cheaper for the homeowner.
Outside the house you can see how the vent tubing passes through the roof to ventilate outdoors.
The system is complete, sans fan.
This buyer would need to wait until he occupies the house, so he can control the opening and closing of windows and doors, and then have a radon test conducted.
And proceed from there.
My recommendation: if you live in an area of the country prone to underground radon and want to build a new house, ask the builder if they install a passive system. If so the aftermath of a positive radon test is much easier to deal with.
* This post is not to comment on the controversy of what a "high" radon result is, or whether a high test result is in fact dangerous.
Jay Markanich Real Estate Inspections, LLC 
Based in Bristow, serving all of Northern Virginia.
Office (703) 330-6388 Cell (703) 585-7560
Interesting. I have not run into passive radon systems, but definitely have run into high radon results which require a brand new system to be put in place.
We have Radon everywhere throughout southeastern Wisconsin ...and this is a very wise addition to new construction...had we known 20 years ago.....but we know now !
Thank you for the information. I will share this with others
Good morning Jay. Seems like a really good thing to have in a new home.
This is an excellent solution for this problem when building a new home
Radon is pretty common in my area so we're seeing an increasing number of mitigation kits installed. What's interesting to me is that the one you show is vented through the roof. It's a heavy gas, so I've only seen them vented out walls at a much lower elevation. Does it matter, Jay Markanich ?
Good morning Jay. Radon is a bigger issue than people think. This is forward thinking most would not consider! Enjoy your day!
Now here is a home builder who is using his brain. I love to see proactive actions to eliminate future problems.
Pretty conscientious builder... kudos to him!
Kat - around here a new system costs $800-1200 or so. This system in place first saves the buyer a lot of money.
S&D - I have been suggesting this for a long time. Nobody heard me...
Thanks for stopping by, Gita.
Sheila - it cannot hurt. Worst case, there is no radon, but a tube is in place should a future buyer be hinky about radon. In that case this becomes a sales feature.
Harry - I see it now and then. And why not do it now?
Nathan - no, it doesn't matter. It is a very fragile ion, so it dissipates immediately no matter where it is blown.
Only a couple of builders do around here, Wayne. This practice probably will catch on.
S&N - this is a national builder, and I typically have fewer problems with their homes.
Fred - the house is in a particular area with a lot of positive radon test results. So they are thinking ahead.
Nothing like planning ahead. I'm scratching my head trying to get LAN wiring from the basement to the attic. Can't imagine trying to get a 3" PVC through the roof!
Thanks for the information. In Oklahoma City we can hardly measure radon and we don't do basements.
That's usually the only way to go Stephen. But it's not always easy to anticipate when!
Joe - some areas have radon and some don't!