Radon with added heat recovery unit

[BayPointArchitect]

A home owner is required to install a retrofit radon mitigation system and they asked if they could exhaust out the side of their home (it would be easier) rather than carve through the structure to reach the attic.They would also like to incorporate a heat recovery unit so that they can make use of the exhaust temperature to pre-condition a little fresh air supply.Makes perfect sense to me but would this be acceptable?Registered ArchitectICC Certified Building Plans Examiner

View attachment 1503

RadonFreshAir.pdf

RadonFreshAir.pdf

 

[jar546]

I have seen air exchangers used for this purpose but not the setup that you are showing. 98% of the time a sub-slab depressurization system is all that is needed but it needs to be discharged above the roof and the fan has to be in the attic or outside. It (fan) cannot be inside the home. Is there a reason why they want to spend all that money on an air exchange system?

 

[BayPointArchitect]

The home owner has just made it clear that he does not intend to install under the slab.

http://www.fileden.com/files/2007/3/25/925948//RadonFreshAir.bmp

 

[jar546]

Go here, some states such as PA have written standards too.

http://www.epa.gov/radon/pubs/mitstds.html

 

[mn joe]

Who is requiring the radon mitigation retrofit? If it is a permitting authority, is there a code or standard that has been adopted? Retrofit can be problematic in existing homes, but i don't think a system will work that doesn't use sub-slab depressurization. JAR is right, the discharge point should be above the roof. If a fan is used it should be above the living space. If you design a heat recovery setup you should be very careful that the system is well sealed to prevent cross contamination of incoming air.

joe

 

[Dr. J]

The second posted sketch is not a radon mitigation system. It is not preventing radon from entering the occupied space - it just exhausts a fraction of the air that is already in the basement. So, from a code standpoint, it is just an environmental exhaust duct - as seen by the "Thats Better" guy, the air being exhausted is simply human-occupied-space air. So there are no cross contamination issues.

In the first sketch, which IS a radon mitigation system, there is minimal cfm actually being discharged, and therefore minimal heat to be recovered. Besides, the exhaust is coming from under the slab, which is NOT conditioned, and the minimal air that actually gets into the duct is percolating through the soil and therefore did not come from the building anyway - they would just be exchanging outside air with outside air. I would think this is just a waste of money. But if they insist - the heat exchange unit should be fail safe - exhaust side negative, supply side positive pressure.