While putting my life in danger way up on a ladder at 10pm to hang chrismas lights for my in-laws, my father-in-law, (who is a M.D…he knows all) started to talk about radon. He told me that at their last house, they had a radon problem. Before he told me about this, I had no idea companies did this to fix the radon problems…. He told me that in order to fix it, they had to put a positive pressure on the basement to keep the radon out. I said “that may fix the radon, but sounds like you’ll end up with a much worse problem down the road.” He looked at me like I was an idiot. I explained to him that by putting a positive pressure on the house, in the winter you will be pushing heated air to the outside of the envelope. When you push the heated air out you will create condensation inside the cavity which will lead to rot. His response was “no you won’t.” I had enough, I try to explain a lot of things to this guy, but he seems to know it all. So I figured I’d post this online for him to read. You may have things to say about radon and positive pressure, but I have a feeling I’m going to get more responses about how the guy is a jerk….maybe that’s what I’m looking for?
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"they had a radon problem. Before he told me about this, I had no idea companies did this to fix the radon problems.... He told me that in order to fix it, they had to put a positive pressure on the basement to keep the radon out."
In the radon mitigation class I took, we were taught to put negative pressure under the slab, and plumb it outside above the eave. A house "breathes" thru the year, sometimes has positive pressure, other times negative pressure.
You are right. If you put a house under positive pressure you will drive moisture into the walls just like you say, and risk much trouble to your house.
I'm skeptical that positive pressure would be effective against radon. The reason I'm skeptical is that if you pressurize the basement, since there is not much way for air to flow out into the surrounding soil, you will likely pressurize under the slab slightly as well. Then the system will come to equilibrium and then radon will enter by diffusion. It might enter more slowly, and that may be enough to reduce the concentration to a safe level. But, evacuating it from under the slab and exhausting it outdoors is a better solution. It is certainly a proven one. I would not depend on pressurization to be effective without knowing that it has been tested and proven, because in theory, it would not work well.
Ok you guys have to explain this to me....
Cant you just open the windows once in a while, and also if there isnt a floor pour one even if its a rat slab?
Rob you can push your info into his court too, and tell him to call his basement a treatment center.
Its been recently proven that Radon helps alleviate people who suffer from MS.
Its been recently proven that Radon helps alleviate people who suffer from MS.
Hip new "spa" thing is radon "soaking." Some old mine shafts (incredibly convenient to the brand new resort) are now fitted out with fancy chairs, good lighting, mood music--the whole luxury spa "thing." And you go pay to sit in a chair to get 15 oe 20 minutes exposure to low levels of radon. Sounds a bit like rooking the marks to me--but so does most of the spa business <g>
There's some scientific evidence coming out, that low level exposure (to many things) increases a persons immunity. Part of that is that the immune system responds to a work out like muscles do.
This goes against the way environmental regulations are crafted--that the only good exposure to anything is zero or less exposure. Nature does not tend to work that way.
Maybe there's money to be made, undoing all that work in the rust belt "fixing" radon problems. Or not.Occupational hazard of my occupation not being around (sorry Bubba)
I thought I had heard that, but with my memory I could easily start a war here.
I think if people are willing to pay, cool. I have to find an idea like that.
There is a town close by with a lot of radon in the water, maybe I could bottle it!
lol
a lot of radon in the water, maybe I could bottle it
LoL!
My understanding is that radon only outgasses from rock, and does not go into suspension in water. That's only my understanding--which has got me into trouble before <g>.
Saw a thing, somewhere, in the pile of stuff that mentioned preservatives for vaccines. That a compound of mercury (want to remember it as a mercury salt) was used up until very recently to preserve vaccines. That many of the "current" bad reactions to vaccines are about concurrent with that change.
Which could be completely circumstantial. But, "the danger is in the dose." I was allowed to handle quantities of mercury in middle school that would now require a HazMat team and complete decontamination washdown for the entire school.
Hmm, I've been accused of being as mad as a hatter before . . .
A person might argue that sero exposure does not equal zero risk. That's where the hormesis proponents start their arguments. http://www.alamut.com/proj/98/nuclearGarden/bookTexts/Rad_hormesis.htmlOccupational hazard of my occupation not being around (sorry Bubba)
A house I remodeled last winter had radon mitigation techniques in use...basically, PVC pipes were placed underneath the basement slab. Thes pipes projected up vertically through openings that were sealed with urethane sealant (NP-1) to keep the slab air tight. The PVC pipe had a vacume pressure afixed to it and the pipe terminated outside ...much like in the same fashion as 90% efficient furnaces utilize PVC pipe in place of chimneys.
This pressurization was very slight... just enough suction on the line to evacuate any potential gas build-up underneath the slab. Would this or did this particular system invite or invoke rot?...Absolutely Not! Detected no signs of rot, mold, or mildew. Worked there all last winter.
Was the pressure positive?.. I dunno...is vacume positive or negative? I always thought vacume was negative pressure...if so, then the radon mitigation process used in this house was negative...I think.
Davo
Yes, the system you saw is the traditional method, and it uses negative pressure to evacuate radon from below the slab. Quite simple, really. The original poster's system was different, and he had a very good point.
AndyAndy Engel
Senior editor, Fine Woodworking magazine
Other people can talk about how to expand the destiny of mankind. I just want to talk about how to fix a motorcycle. I think that what I have to say has more lasting value. --Robert M. Pirsig
Andy / RobDo either of you know where to get info on such "positive pressure" radon mitigation systems?
I don't know about yours, but my church isn't a hotel for the holy, it's a hospital for sinners
Sojourners: Christians for Justice and Peace
I don't. This is the first description of such a system that I've seen. One benefit I can imagine is a slight turbocharging of any combustion appliance <G>
AndyAndy Engel
Senior editor, Fine Woodworking magazine
Other people can talk about how to expand the destiny of mankind. I just want to talk about how to fix a motorcycle. I think that what I have to say has more lasting value. --Robert M. Pirsig
The radon systems I have seen around here involve sucking air from under the basement slab and blowing it out a PVC vent pipe. They sometimes have a manometer on the vertical pipe so one can check that the pressure is indeed negative.
How do you put a permanent positive pressure on a house? With the usual leaks, chimneys, appliance vents and opening and closing of doors it would seem difficult. At least your furnance wouldn't back-draft! It seems like it would also be wasteful to blow all that conditioned air out of the house all the time. That would be my main concern.
If the house had a proper vapor barrier, I don't think that much moisture would be forced into the wall cavities. The air would follow a less-resisting path.
Here, I will avoid any jokes about whether his house blows or sucks.
Al Mollitor, Sharon MA
It is my understanding that all houses have positive pressure in their upper half, from the simple fact the hot air rises, just as the lower half has negative pressure from the same simple fact. (Poorly sealed return ducts can also contribute to neg pressure in the furnace area.)
It is also my understanding that the neg pressure in the lower part of the house can contribute (cause?) radon problems by sucking gases up through cracks etc in the foundation and floor.
In my area, slightly high radon levels (slightly above 4 pCi/L) can be fixed merely by putting a sealed cover on the sump crock.
The next step is the type of mitigation system which sucks from under the slab.
I haven't seen any positive pressure systems.
NB: The Ohio EPA warns against increased negative pressures in basements from mitigation systems potentially causing draft problems with furnaces and water heaters.
I haven't done draft testing in many homes with mitigation systems so I can't generalize, but the few I have done haven't had draft problems. (I have had some houses where running bath and/or kitchen fans can mess up the draft from combustion appliances. I don't know how the sucking power of mitigation systems compares.)
And I would be concerned about combustion effects from radon mitigation through pressurizing the basement/combustion zone, especially for any naturally drafting appliances, but also for any fan assisted ("80+") furnaces.
For naturally drafting furnaces and boilers, I'd be concerned about possible air curtain effects in the draft hood/ bonnet, with the pressurized air "rushing" into the flue through the bonnet and possibly blocking the flow of flue gases. (Not likely, I know, but I have tested a couple of appliances where there was a air curtain effect causing major CO problems.)
For fan assisted, I'd be concerned with the additional pressure forcing additional air through the heat exchanger and resulting combustion inefficiencies and possible CO problems.
I don't know about yours, but my church isn't a hotel for the holy, it's a hospital for sinners
Sojourners: Christians for Justice and Peace
Rob,
My guess is that your FIL doesn't know what he's talking about, and the system at his home is a negative pressure radon drain just like the others. Maybe he heard "active system" or "positive displacement" and got it altered in his head. If he did, your characterization of him suggests he would never retreat from his statement even if he realized the error. Too much arrogance.
Bill
I agree that he probably has a negative pressure subfloor system, and he doesn't quite know what he's talking about.
I believe hereabouts on retrofits they run PVC from the interior basement up through the roof. If that doesn't provide sufficient venting for the radon, they add a small blower on it.
On new contruction you can do all the fancy under-the-slab stuff, with the little channels off the sides for radon and water and such... with a drain on one end and a vent on the other.
I understand these system that you are all talking about. I am in the process of building my own house right now and am using pvc under the slab, with an upright hidden in the wall cavity going up through the roof. Cheap and easy.
However, I brought this up with my father last night (not father in law) and he heard the same thing from somebody that worked for the EPA. He was sitting in a seminar, and the speaker mentioned putting a positive pressure on the house. He raised his hand and said the same thing I said. Believe it or not it, is an actual system they use or used. Foolish. If will take care of the radon problem, but down the road, someone will need mold remediation.
RA
http://healthandenergy.com/suggested_indoor_air_pressure.htm
http://healthandenergy.com/radon_mitigation.htmI did a google on positive pressure radon and got lots of hits. These are the first 2 and they mention the EPA positive pressure system.But it does not appear to be the "best" method in general.
Bill, thx for finding that“Plan the HVAC systems so that the building interior in all ground contact rooms is slightly pressurized (about 1 Pascal or 0.004 inches of water column) relative to subslab and outdoor pressure).”FWIW, 0.004 wc" is an incredibly small amount of pressure.The draft gauge I use only measures down to 0.01 wc" on the scale, and to get it to read 0.01, I would blow across the end with the amount of "blow" I'd use to just barely blow out a single birthday candle from a couple of inches.I don't know about yours, but my church isn't a hotel for the holy, it's a hospital for sinners
Sojourners: Christians for Justice and Peace
I should have kepot reading ...Further down in the article:Moisture Condensation due to Excessive Air Pressure Differentials1. Moisture condensation and damage can occur below the roofs and within outer walls of air-conditioned buildings if indoor air pressure is significantly less than outdoor air pressure. When the temperature of materials in the wall and ceiling cavities is below the dew point temperature of moist air leaking in, moisture will condense, enabling growth of fungi that damage materials and produce noxious gasses.2. Moisture condensation and damage can occur below the roofs and within outer walls of heated buildings if indoor air pressure is significantly greater than outdoor air pressure. When the temperature of materials in the wall and ceiling cavities is below the dew point temperature of of moist air leaking out, moisture will condense, enabling growth of fungi that damage materials and produce noxious gasses. Preventing Mold Growth in Building CavitiesExcessive positive or negative pressures can move large quantities of moisture-laden air through holes in a building's shell, leading to condensation and mold growth within building cavities. Moist insulation is less efficient. Building experts have observed pressure-derived moisture problems at only ± 1 Pascal (enough to raise a column of water .004 inches) during severe humidity conditions."
— John Krigger, Residential Energy (3rd Edition), page 75.I don't know about yours, but my church isn't a hotel for the holy, it's a hospital for sinners
Sojourners: Christians for Justice and Peace
We just met with a state moisture expert and learned that there is air in the gravel/sand under the slab, and that by poking a 4" hole in the slab and using pvc pipe and a small fan, you can exhaust the moist air out of the house. the floor needs to be sealed where it meets the foundation wall, and where the pipe and anything else penetrates the basement floor. then you don't impact the pressure IN the house, but suck the moist air, including radon, out of the ground. tests show that 30' away in the ground outside the building, suction can be measured. This guy estimated that 50% of the moisture that enters your house is from below the slab.
The theory is that rather than buying a heat exhanger to take out the moisture, keep the moisture from entering the building.
Dan
>> then you don't impact the pressure IN the house,I don't know if he is right. First, if you have an unsealed sump crock and pump you might pull air from the house, and second, the way radon gets into the house is from negative pressure in the basement/crawlspace/lower plane of the house and cracks and gaps in the slab and foundation.If air/radon can get pulled in from negative pressure inside the house, it seems to me are could get pulled out by negative pressure under the slab.But this is theory - I don't know if there are real life examples, although I note again that the Ohio EPA warns against possible depressurization of basement spaces resulting from mitigation systems.I don't know about yours, but my church isn't a hotel for the holy, it's a hospital for sinners
Sojourners: Christians for Justice and Peace
Bob,
thats why i noted to seal ALL penetrations in the floor, including the sump basket. then you won't affect the pressure in the house, just the soil around it. it works.
>>thats why i noted to seal ALL penetrations in the floor, including the sump basket. then you won't affect the pressure in the house, just the soil around it. it works.
How about hairline cracks?One of the sources linked shoews that sealing isn't completely effective.I don't know about yours, but my church isn't a hotel for the holy, it's a hospital for sinners
Sojourners: Christians for Justice and Peace
it might not be COMPLETELY effective, but it helps, and it works.
I only skimmed over those and a few of the other links that I found with that search term.But it seemed like where they where talking about using positive pressure was in schools.So I am assuming a large singe level structure on a slab.Much different dynamics (and construction) than a 1 to 2 story house over a basement.
I think the MD should suit up with scuba gear.
and with a very short supply of air in the tank
Have I ever heard of a vapor barrier?
Your in-law isn't young enough to know everything..
Have you ever heard of Vapor barrier?