Radon removal via HRV

[Lee Batchelor]

Hi everyone! I'm new here. I built a house in 1982. It has the following details:



• 2,000 sq ft ranch style
• Double stud walls - outside perimeter structure 2x6 fully insulated and air barrier sealed. Inner 2x4 wall offset to the exterior wall insulated (no air barrier), which carries electrical and other minor stuff
• Floor trusses - full web trusses, 34 foot span
• Floor truss pockets recently spray foamed
• Attic R60 insulation

I heat the house with a gas furnace. As you can see I need an HRV. I installed a Venmar EV05-500. It works very well. Problem: I have a radon level of 200 to 300 Bq/m3. The HRV can drop that level down to below 100 Bq/m3, but the house humidity drops below 40 percent, which is really rough on the skin and nostrils!

Questions:

• There doesn't seem to be a reliable agreement about what's considered a safe level of radon. The WHO says less than 100 Bq/m3, whereas the Canadian government says less that 200 Bq/m3. I believe the U.S. folks say less than 148 Bq/m3. Who the heck do we believe??
• What is my best way to keep these levels down without drying my house out like a leaf? I've heard about these suction fans you can install under your cement slab. They create negative pressure, which sucks the radon out.
• Can my HRV be used in another way to exhaust the radon? At the moment, the freshened air is fed into the cold air return in the basement. Can I put an additional pipe in that runs outside so I can choose whether or not to keep the freshened air or get rid of it? I draw stale air strictly from the basement at the moment.

Many thanks!

- Lee

[Admin]

I don't much about Radon gas or its dangers.  In new construction they dig below the foundation and use a fan system to suck out the Radon gas before it enters the home.

You should hire a Radon mitigation specialist to give you options.

Are far as HVAC equipment goes, the HEPA systems or UV bulbs don't stop Radon gas.  Using the HRV is really the only option I know of.  When you balance the HRV try to create a positive pressure inside the home and seal any cracks on the foundation floor.  This may help prevent Radon gas from entering.

[Lee Batchelor]

Thanks ! I wondered about the cracks too. Unfortunately, roughly one half of the area is carpeted and would need to be pulled up to access the floor cracks. I'm pretty good with my hands, so the thoughts of installing a sub-slab suction fan to outdoor air, doesn't frighten me in the least. I'll check to see if there any radon specialists in my area first. Thanks again!

- Lee

[bster352]

Not sure where you are but check these guys out... https://www.mr-radon.ca/ .

[Lee Batchelor]

Thanks bster352. I sent them an email and have already heard back. Most "Contact us" buttons result in nothing. These guys are different. I'll keep you posted. Best...

- Lee

[Lee Batchelor]

I received a quote from Mr. Radon. Very professional people and quick to respond!

Meanwhile, I'm looking at two of the same fans by RadonAway. One is the RP145 Pro Series (SKU 28461) and the other is the RP145 (SKU 23030). The latter is available on the Canadian Amazon site for a very good price. In comparing the two, the Pro Series one is good for indoor or outdoor installs, is waterproof, and made from non-fading white plastic. We're allowed to do indoor installs in Canada. Any reason I can't go for the cheaper RP145? I believe it moves the same amount of air.

[Lee Batchelor]

Hi team,

I just wanted to follow up on my radon problem. In Canada, we're allowed to install the fan in the basement. I purchased the RadonAway RP-145C fan. It took me two days to install. Schedule 20 PVC pipe was used. The hole in the floor was drilled about 6 inches in diameter, and then 8 gallons of ¾ crushed stone was vacuumed out with an industrial vacuum. The pipe extends into the floor about 4 inches (the thickness of my slab). My exit pipe extends about 3 feet outside my foundation through the rim joist. There is a 90 degree elbow attached, and then a critter screen. The pipe is located under a 5 foot high deck, which has a skirt around it, so the pipe is neither in the way of foot traffic, nor visible.

Before installation, my readings were from 200 Bq/m3 to 350 Bq/m3. Using my HRV, it would take about 3 days to get the levels below 100 Bq/m3. After running the radon fan for 18 hours, my levels went from 189 Bq/m3 to 39 Bq/m3!! The fan is dead quiet, although I can hear it upstairs a wee bit because the fan is right beside one of my hot air vents where we have a chair. I had no choice but to install the fan there, however, the sound presents itself as a slight whirring sound – nothing we can't get used to. I may try wrapping the heat duct pipe adjacent to the fan, with some Safe and Sound insulation.

I installed the fan with an Off/On switch. It seems that was a good move because I may only need to run the fan three quarters of the time. The basement has large windows, so that in the nicer weather the fan can be switched off while the windows are opened.

My thanks goes out to those who read and contributed to my post. Also, to Mr. Radon. Their price was approximately $3,000, which consisted of $1,000 for an assessment (air flow, fan sizing, and system design) and $2,000 supply and installation. My total cost was around $275. To be fair to Mr. Radon, they were my backup plan in case my plan failed. I would have gladly paid the $3,000 to drastically reduce my odds of lung cancer. I still highly recommend them if you haven't the time or ability to handle this issue.

One more interesting note: I noticed a smell of fresh air in one of our upstairs bathrooms after the radon fan was engaged. The pull from the radon fan actually pulls a wee bit of outside air past the bathroom fan outside vent flap, which is mounted on our roof. The house is very tight, so I guess the air has to come from somewhere. It just goes to show you how many leaks the slab has! I also installed the manometer. A YouTube video indicates that ½ inch to 1 inch of pull is really good. My reading is 1 inch.

Anyone interested in posting questions, please feel free to do so. Thanks again for the input everyone!

- Lee

[flash21]

I'm not a professional or an expert on Radon, but I just wanted to add my experience with Radon

I started to monitor Radon in my house and I noticed that level are way higher in heating months and since I don't have HRV my suspicion was that during heating months my house is under negative pressure (bathroom and kitchen fans) and this is what pulls the radon to the house.

I more or less sure this is the problem because I tried to open a window in the basement for several days couple of times. The window is too small to actually remove radon , but I think it allows me to avoid negative pressure and it drops the radon levels. If I open most of the windows in the house for a while to vent the house radon drops significantly and stays low as long as my small basement windows stays open. As soon as I close it radon level starts to increase
   
I'm hopping to solve my problem by installing ERV that will first of all introduce fresh air and vent some of the radon from the house, but will also help me to avoid this negative pressure

[Admin]

If the ERV is balanced properly the exhaust and intake should be within 10 CFM.  You could balance it so the intake is around 10 CFM higher than the exhaust to ensure there's no negative pressure.