We're putting in radiant in our second floor -- since I have chemical sensitivities,  2 inches of portland concrete (no additives) will be poured over plywood subfloor.  Some people say it's not necessary to use a barrier between the concrete and the wood, but I want to prevent any possibility of mold.  Seeking suggestions on on best type of barrier, 6 ml or 10 ml, and wondering if barriers offgas at all when they are heated up with radiant (if so, are there less "stinky" types of barriers for sensitive people)?

I'm looking at Vaporlok 10 ml right now.  Is 10 ml excessive though?

Also - is there a chance that using a barrier actually could do the opposite and cause moisture to get trapped between the concrete and the wood, thus causing possible mold problem?

Barriers are made from petrochemicals.

Mold is unlikely where a radiant floor is heating away.

Your really should contract a designer if you are that sensitive and that concerned. This is a poor place for design by net.

Might want to look at the 1 inch Crete-Heat board

I believe (but do not know) that the only reason to put a barrier between concrete and a wooden subfloor (we have this situation in our concrete floor bathrooms) is to prevent the water in the initial pour from distending or warping the wooden subfloor which would - of course - then cause problems with the concrete as the wood tried to return to its original shape.

Concrete does not off-gas moisture after it is cured, though it is very moisture permeable, I believe, and would dry easily via the exposed surface if it were to get wet underneath, though this depends on the way that the concrete is finished or coated to produce the end-product floor. In fact, in my bathrooms, the barrier used was a simple paper material - obviously not a vapor barrier at all.

Of course, you should ask the person that's pouring the concrete whether or not the barrier is needed. I don't know where you are, but in California, licensed contractors are quite liable for their work product, whether they state so or not.

Jeff

I've tried to find a "designer" for chemical sensitivities and there are none that knew anything about this issue.  If you have heard of one, I'd love to know.  I don't have any other options.  At the very least, this is a good forum for finding out material suggestions for certain applications regardless of the sensitivities.  And even within our crew and the concrete company and our contractor, there is debate whether a vapor barrier is even needed between the concrete and wood, so I'm trying to find out what is considered the most cutting edge that prevents mold issues since that is what I want to avoid foremost.

I have some experience with chemically sensitive construction methods as I have been designing and installing radiant heating systems with sealed combustion, low NOx boiler since the 80s. I also design indoor air quality (IAQ) systems using energy recovery ventilators.

SIP and ICF homes are so tight that IAQ can be a serious problem. Here in Minnesota we have a high incidence of Radon gas, so again, ventilation is a concern.

The reason people don't volunteer for "chemically sensitive" projects is liability.

jabaron & MA have it right- wood subflooring dries quickly through highly vapor-permeable materials like concrete, particularly since it'll be at elevated temperature during the heating season, so there is zero mold potential as long as you don't have a chronic plumbing leak to replenish the moisture into the wood. There will likely need to be a slip surface like rosin-paper or similar between the wood & concrete though.

If/where you need a zero VOC vapor barrier, metal foils are vapor impermeable, and have no outgassing issues. Be careful where/how you place vapor impermeable materials- in practice they cause as many mold problems as they solve, since they prevent assemblies from drying, even when (or particularly when) they're not fully air tight. Moisture gets into walls/ceilings/floors via capillary draw, air-transport, and bulk leaks, but it mostly leaves via vapor diffusion. When it can't leave fast enough, mold conditions can be created.

I wouldn't put a vapour barrier in myself.  Moisture tends to want to move upwards.  As a long time flooring installer, I have come across many situations where moisture from a spill or appliance breakdown or moist basement/crawlspace got under the vinyl many years ago and never disappeared even though there was no other vapour barrier under the vinyl (moisture just doesn't move down very well).  When the vinyl is removed, there is almost always mold.

Neither moisture nor heat move upwards- it moves from wetter to drier, warmer to cooler, via multiple mechanisms. Moisture moves down just fine, as long as the moisture gradient drops in that direction. Water doesn't float on wood- wood floats on water (and wicks water to the drier surfaces.) In a damp basement situation the vapor pressure can be the other direction, and the vinyl blocks it from drying into the first-floor space.

Vapor barriers are to be avoided if the stackups can be designed to be resilient to annual swings in temperature & humidity. Like impermeable wall coverings, impermeable flooring tends to create rather than solve moisture issues. I can't imagine that a vapor barrier is really called for here. VOCs are much larger molecules than H2O.

Posted By Dana1 on 05 Oct 2010 02:51 PM
Neither moisture nor heat move upwards- it moves from wetter to drier, warmer to cooler, via multiple mechanisms. Moisture moves down just fine, as long as the moisture gradient drops in that direction. Water doesn't float on wood- wood floats on water (and wicks water to the drier surfaces.)

Dana, that makes total sense to me and would seem like common sense.  But I know that I have witnessed (several times) situations where water made it's way under vinyl and stayed there for years, even though the floor underneath had no undue amount of moisture.  Maybe it was the amount of wood that it needed to travel through that delayed the migration of moisture.  I don't know.  All I know is that when removing the vinyl (a moisture barrier), it was very wet (often moldy).  This was not a one time occurance.  Maybe, if given enough time, the moisture would travel down.  But, given the fact that the moisture seemed to be trapped long enough to create mold and keep the area under the vinyl wet for years, I would be hesitant to install any moisture barriers.  Of course all this is a moot point if there is no significant moisture under the moisture barrier.

We put a barrier ( plastic sheeting). It was so that the concrete would not adhere to the wood. I did lots of research and it was to minimize cracking because we did a stained concrete floor.

One thing to be aware of, is that the concrete will give off moisture for up to a year and the first winter you will need to run a dehumidifier or have an excellent air exchanger. I also agree that radiant floor and mold should not be a problem. The key will be removing all the moisture from that comes off the floor in that first year or you will have moisture problems on windows etc. Jill

Posted By Reiner on 06 Oct 2010 02:08 AM

Posted By Dana1 on 05 Oct 2010 02:51 PM
Neither moisture nor heat move upwards- it moves from wetter to drier, warmer to cooler, via multiple mechanisms. Moisture moves down just fine, as long as the moisture gradient drops in that direction. Water doesn't float on wood- wood floats on water (and wicks water to the drier surfaces.)

Dana, that makes total sense to me and would seem like common sense.  But I know that I have witnessed (several times) situations where water made it's way under vinyl and stayed there for years, even though the floor underneath had no undue amount of moisture.  Maybe it was the amount of wood that it needed to travel through that delayed the migration of moisture.  I don't know.  All I know is that when removing the vinyl (a moisture barrier), it was very wet (often moldy).  This was not a one time occurance.  Maybe, if given enough time, the moisture would travel down.  But, given the fact that the moisture seemed to be trapped long enough to create mold and keep the area under the vinyl wet for years, I would be hesitant to install any moisture barriers.  Of course all this is a moot point if there is no significant moisture under the moisture barrier.

Plywood subflooring has about the same vapor permeance  as an inch of XPS, which could introduce a weeks-long delay in drying from a wetting incident, but not a years worth.

I believe you that you'll often find moisture under vinyl flooring but the mechanism by which it's getting there may not always be clear.  If it's not getting out via wicking vapor diffusion to the bottom, there's something else going on (constant rewetting, high humidity in the basement, etc.)  Water vapor responds to vapor pressure far more than gravity. Wicking of liquid water works in any direction, but can be somewhat slower through plywood or OSB than through planking.

We have concrete for radiant on the second floor with sleepers and cherry hardwood flooring on top of it.  The concrete lies on top of 1.5" decking which is on top of exposed beams.  There is 6-mil poly between the concrete and decking because the decking (first floor ceiling) was stained before installation and we didn't want the moisture from the concrete to stain that ceiling.  It has been in place for a decade without problems.  Understanding how moisture condenses, vapor barriers work, and what temps radiant works at are crucial to eliminate the issue of mold.  Some points to consider:

The poly acts as a release just as one would use builders paper between any sub-floor and flooring.  Keeps the squeaking down to a minimum, but is also a vapor barrier, as are vinyl, concrete sealer, paint, and some sheathings to some degree.  Sealed and painted drywall is just like poly.  Sealed concrete, to keep it from flaking, is just like poly.  They all stop the migration of moisture unless they have holes in them, and that is another problem if you count on them to be vapor barriers.  (And rule number one is that vapor barriers are NEVER perfect, nor is anything else in building construction.  Like Mother Nature, builders (some more than others) strive to give the illusion of perfection, the home buyer insists on thinking that perfection exists, and some of them argue it out in court instead of seeking counseling for fantasizing that perfection is attainable.  LOL)

Moisture condenses at the "dew point" where moist warm air meets a cold surface or cold air.  A vapor barrier prevents the moisture from getting to that dew point interface which is inside the sandwich of walls or ceiling somewhere (between the lettuce and cheese) depending on your insulation and the temps on the two sides of that wall or ceiling.  (Reiner - the vinyl may be the cold surface, especially true in a second floor bathroom where the rooms are somewhat cooler than the rooms on the floor below, and thus the trapped moisture will always condense on it)

The poly next to the concrete is the same temp as the concrete so the dew point interface is unlikely to be under it.   Also, you will have a sub-floor with a moisture barrier on the ceiling surface under it regardless of whether it is wood, as we have, or painted drywall.  Thus, moisture is more likely to condense on the ceiling surface as the moist air in the room below condenses on the colder ceiling.  Of course if you are keeping the temps in the house relatively the same, there is no cold surface to condense on. 

However, that moisture barrier on the ceiling works both ways, i.e. it will HOLD IN the moisture if the ceiling is painted before any moisture in the floor joist and sub-flooring have dried up.  Just remember that moisture can't leave if two barriers are in place (the reason that moisture is a problem under vinyl flooring and especially in a basement where ground moisture is constantly seeping up from below the floor if there is no vapor barrier under the floor.).  Therefore, if you choose to have poly under the concrete (the dryer the concrete the less need for it), DON'T SEAL your first floor ceiling until you are sure that the moisture is out of the joist and sub-floor.  Insist that the wood be dry, especially if it has rained on that sub-floor during construction.  And if you don't use poly but do seal the ceiling below the joist, it will take longer to dry out the concrete, joist, sub-floor, et al from above.

If you are going to have the concrete as the exposed surface for your second floor, you will seal it at some point.  It is crucial that you NOT seal it until the moisture is completely out of the concrete.  A simple test for moisture content in concrete is to put a piece of poly on top of it like a throw rug.  Leave it for a few days while heating the floor.  If ANY moisture condenses on the bottom of the poly, the concrete is NOT DRY.  (This step is also especially crucial if you plan to cover the floor with wood flooring as we did!  Both concrete and flooring need to be "acclimatized" before you nail the flooring down.  This is the reason that contractors and manufacturers refuse to put hardwood flooring over radiant heat.  It is not that it can't be done.  It can be, but you need A LOT of patience - perhaps waiting months and putting down the flooring in the winter when the air is driest.)

Radiant temps are 80° or you would burn your bare feet (which is my preference when indoors) and thus poly only off-gasses a tiny bit when first unrolled.  It never heats up again to cause off-gassing.  (BTW, I want to take contractors, and especially building codes people, to task at this point.  Dr. John Siegenthaler, the father of Hydronics, says that a hot water heater is perfect for radiant.  Boilers, to work efficiently, require working temps that are too hot for bare feet.  Thus a mixing valve is required to lower the temps for radiant.  IMHO, there is only one reason to use a boiler in an average-sized, well-insulated home [mine is 2100 sq ft. and I have used the same propane 42K btu hot water heater for 12 years in Maine.] and that is to inflate the profit of the installer.  And building codes that require a boiler are just a scam perpetrated by those same manufacturers and contractors upon the average homeowner.  I witnessed how that process works as legislators listened to all the "experts" insist that the codes be "strengthened".  Funny that the "experts" were all contractors and business owners with a vested interest in increasing profits [many of whom hadn't a clue about the science], were there en mass, but not one engineer or scientist.  {Now watch me get flamed!!})

Moisture is always a factor in any home and that is why heat recovery ventilators are necessary in cold climates where the home is tightly built.  (Many states and all of Canada require one in new homes.)  Thus YOU control the humidity and can set it to please your needs.  If you have moisture condensing on walls and ceilings, you will have a mold problem.  Our HRV collected a few gallons in the first year, then minimal amounts thereafter, and now, generally within two days after my wife waters the jungle that we live with. 

None of this is rocket science, but there are definite scientific principles at work.  If you understand the principles and work within those parameters, you will have the same joy that I have with our radiant floors.  Good luck with your project.

Gomer- some clarifications & corrections of fact:

Sealed & painted drywall has 50x the drying capacity of poly, unless it's been painted with a special vapor retardent paint, in which case it has only 10x the drying capacity of poly. It is in no way "...just like poly", quite the contrary- it's vapor semi-permeable.

Same story with masonry/concrete sealers, except for those specifically designed to be vapor retardent as well. The vast majority of masonry sealers do a good job of retarding capillary wicking of liquid water, but do practically NOTHING for slowing down water vapor. Stopping the movement liquid water out is important to inhibit water-transported mineral from leaching from the concrete. But sealing the concrete doesn't slow down it's drying by an order of magnitude or anything like it. Poly is about 2 orders of magnitude (100x) more vapor retardent than sealed concrete.

The dew points of the air masses on either side of a sheet of poly can have radically different dew points, resulting in condensation on one side, but not the other. It's common in cooling dominated climates with ventilated crawlspaces to end up with condensation/mold issues under the sub floor when exterior dew points are in the 70s F. Vapor retardent flooring in those situations make the problem much worse. Only if the vapor retarder is over conditioned space maintained at a similar temp & humidity are vapor-barrier floors risk-free.

Radiant under hardwood is common, and not very problematic at all, although radiant-SLAB under hardwood requires sufficient curing/drying time on the concrete/gypcrete, as well as the wood.

Tank type water heaters work fine for running low-temp radiant as long as the burner is big enough to handle the actual heat load, and they typically deliver 75-78% efficiency. Condensing tanks will break well over 80% in a radiant application but not into the 90s with most of them. Whether it's "worth it" to run it off a condensing boiler depends on the cost of fuel and the required water temps, but with slab-radiation it's pretty easy to break 95% efficiency and cut your fuel use by ~20-25%. If you're burning 1000gallons/year of propane an NPV financial analysis on projected fuel cost savings vs. the installed cost of a mod-con starts looking pretty good, but if you're only burning 300/year, not so much. Per BTU retail natural gas in New England is roughly half that of propane, which pushes out the break-even point.

So they ended up putting 10 or 15 ml Vaporlok (Raven Industries - NFI) in between the concrete and the plywood.  Because of what you wrote, now I am wondering about a few more possible upcoming issues:

1) They were planning to put a vapor barrier in the ceiling.  Should we not now?  One of the reasons for this was to prevent fumes from the insulation into the living space, since I'm so chemically sensitive

2) They want to wrap the wood studs (for the walls) with the same Vaporlok, on three sides, and then put those plates on top of the concrete floor.  This is instead of using treated wood apparently.  I'm concerned about this as I've never seen it done.  I thought I might actually be ok with ACQ treated wood, but didn't test it yet.  Will the vapor barrier (about a foot under each plate, glued to the bottom of the plate, wrapped then stapled up to the stud) be a problem over the concrete simply because there is already another vapor barrier beneath the concrete or since it is in pieces and not across the whole floor, will it not create a sandwich? 

3) We had planned to use an engineered wood (Ecotimber or Kentwood, NFI) over the concrete floor.  The crew said they can't wait longer than a month to install it but I've read just what you wrote - that we'll need to let it cure for a long time.  It's a 2 inch slab (this is the main floor), we're in Colorado mountains and it's getting cold...how long do you think we're talking about before a floor can go on?

Thanks

Gomer -
I read your response too fast and when I just reread it, realized you meant to take care if applying a vapor barrier under the subfloor/first floor ceiling.  I wasn't intending on doing that, although they mentioned using foil backed insulation which would be somewhat of a vapor, or a reflective barrier, which I'm also leaning against doing.  Still figuring which insulation to use under the subfloor...

In terms of using a hot water heater, I read a bit about that and asked our radiant guy why we needed a boiler.  He said "hot waters are meant for heating water and boilers are meant to heat your home.  They will last longer for this type of application." Please let me know what to say to him or info to send  - if it's worth it - to see if we can just use a hot water heater.  Our radiant is hydronic and the rest of our house is all electric.  No gas.  Not sure if that matters.  We have radiant on both floors - 1450sf on each floor.

Well, I was just composing a reply when your next post came in. I'm curious as to why you are putting in insulation in the first floor ceiling under the second floor concrete? It seems like an added expense and unnecessary. Your living space is contained within the confines of the exterior walls and the bottom floor and attic. Think of your living space as inside a plastic foam beer cooler - everything inside (moisture, fumes, heat) tends to stay inside because you are surrounded by insulation and a vapor barrier. Since the second floor joists, concrete, and second flooring are inside this perimeter, they are just another part of the mass within, like clothing, furniture, etc. All of those things hold heat and give off heat, but that heat stays within the confines of your insulated perimeter. If some of the heat from the 2nd radiant floor is "lost" to the first floor area, so what? Some of the heat from the 1st floor area will be "lost" to the second floor through the natural convection of the air in your rooms. We have 3 floors, but only radiant on two of them. The highest floor has no heat, yet is 65° even in the dead of winter, which is fine for the bedroom, and not bad for my office if I wear a sweater. Enough heat is "lost" from the other two floors to heat this 3rd floor. Of course, we have exposed beam ceilings on the first and second floors, so there is no way we could fill between the beams (joist) with insulation. Again, so what? It is all warm. You would only need insulation in a floor if there is an UN-insulated space under it, like a crawl space. Interior floors have heated spaces on both sides therefore no insulation is needed. Am I making sense? Put all your insulation into exterior walls (R-24 or more), and attic (R-50 or more) and good quality windows. (And windows with gas are a waste of money as the gas will seep out in a decade or less because no seal will hold perfectly).

BTW, that tightness is the reason it is necessary to have an HRV. The air needs to be changed or it runs out of oxygen. Old houses leaked and the air changed constantly and because of that, the heat was lost. New houses are very tight and there are few changes of air. Sometimes so tight that wood fires can't burn well. An HRV helps to preserve the heat while changing stale air for fresh because it takes heat from the stale air and warms the incoming air. Moisture condenses out of the stale air in the process.

As for your water heater, wetheads (an affectionate term for plumbers) in general haven't read Dr. Seigenthaler's "Modern Hydronic Heating for Residential and Light Commercial Buildings (Heating Ventilation/Air Conditioning)" because it costs $240 new, they tend not to read, and probably don't need a library card because they already know it all. In the chapter on heat sources, he has one little paragraph about using a hot water heater which he says works fine. Water is water, and hot water is simply water that is heated whether with a match, an electric element, or a gas or oil flame. Your choice of equipment should be determined by price and efficiency and available fuel source. Where I live propane is the only reasonable fuel as electricity is more expensive per BTU. (Lots of people have those outdoor wood boilers, but I'm sick of burning cord after cord of wood each winter, not to mention cutting and splitting it.) Of course, if you have a south facing roof, solar hot water panels are the best because it is free heat. I have 4-4'x8' panels on the south face of our roof. Now that I have an equipment shed, I would like to get 3 or 4 more as I have to supplement those 4 panels with propane during Dec. Jan, and Feb, but then I have free hot water 7 months out of the year.

My house requires 45K BTU to heat it. My 50-gal, thru-the-wall-vented propane gas water heater is sized to heat the house. There are probably more efficient ones now available compared to what was available in 1998. Check with ACEEE.org for their listings of efficient equipment. (you might have to buy their yearly book.) It cost $850 then, vs $1800 for a boiler. Since I built my home without a mortgage, I went for the 10 year warrantied water heater. (Wetheads flamed me and said I could never heat a 2200 sq ft house with one) I have been using it all these years. Boilers are expensive, overkill, and generally heat the water hotter than is needed for radiant. 80° is the right temp for radiant if your house is well insulated and tight.

Buying the solar hot water panels was an after thought when I read about "Solar One" a house in Vermont that was built during the fuel crisis in the '70s. Check it out at http://www.radiantsolar.com/index.php and read the Magazine pdf. I asked Radiantec if they still had any of those solar packages left (no one bought them so they switched to radiant heat systems) and they had one in the warehouse, so I bought it on impulse. I amortized it based on 1998 propane prices and it would take 17 years to pay off a system guaranteed for 25. It seemed worth it, but then the price of fuel went up and it was all paid for in 8.5 years. Of course, I did my own plumbing/installing, so I didn't have to listen to a HVAC guy tell me I was stupid while I paid him enough to make it not worth doing. The panels preheat my 50° well water to 65° min. to 180°+ depending on how much I use for domestic purposes. One year of propane was $1160 - that's for all cooking, heating, and my propane standby generator which was on 48 hours due to stormy power outages on the grid. I've averaged $1500 during the past few high oil price years. Considering all the new products you have available, you should do even better. Now there are new on-demand Polaris water heaters for less than $3K that were not available to me then. They work well with solar panels, whereas boilers do not, so if you are thinking of solar panels talk to the guys at Radiantec first before you buy a fancy boiler.

Make sure that you know how many thousand BTUs you will need per hour to heat your house in the worst months. That is the size heater or boiler you will need. If my water heater lasts 15 years and the next one does too, that's 30 years at a cost of about $2K What does his cost? Ask your radiant guy how long the warranty is good for on his boiler. Compare that to the equipment on ACEEE. Also, does Colorado allow you to use domestic hot water in your radiant system? Some states do and some don't. If not, then you will need two heaters. His boiler is oil probably not electric so gas is just an alternative form of oil. Whether a boiler lasts as long as he thinks is conjecture, and besides, in 15 years, the energy efficiency ratings might have gotten better and you will have an older boiler that is still good for another 10-15 years, when you could have a second but new hot water heater. Lots of things to think about and investigate, and in the end, you either do the numbers or you have to trust your contractor. Read this http://www.aceee.org/consumer/how-choose-contractor

As for your sensitivity, you need to do a smell test yourself. Everything that goes into your house comes in bundles. If you go to a lumber yard and stand next to a bundle of OSB sheathing, you can smell the chemicals. The same with insulation. Did you say what kind of insulation you are using in your exterior walls and attic? We used blown-in cellulose (4 atmosphere pressure). I did the work myself, and I have a very sensitive nose and have never been aware of any fumes from it. It was dusty, but no smell. I was not aware that any of the other common insulations (fiberglass, rock wool), except sprayed foam have any smell/fumes, but I admit my ignorance, as my experience is limited to those I just mentioned. Probably the smartest test you could do is actually go and smell a container/package of the insulations or whatever else you will be using (like the manufactured flooring) before you choose them. Contact a contractor who is installing something in a building and go there and smell it, and touch it. Then you will have the knowledge to make the choice. Better to do that now beforehand.

As for "wrapping the studs in the walls on 3 sides and then put those plates on top of the concrete floor" I'm confused about that. Why wrapping studs? Also, are you having a solid 2 in concrete floor on the second floor? My floor has 2x sleepers 10" O.C. glued and nailed to the subfloor with cutouts where the radiant tubing lays. None of the wood is treated, just standard kiln-dried spruce studs for the sleepers. The poly was then laid over it all, then the radiant tubes were laid in the cutouts and concrete poured into the remaining spaces. The poly is not used as a vapor barrier, but rather to keep the water in the concrete from streaking finished beams and ceiling underneath. Remember, concrete and wood was allowed to dry before laying the flooring. Then the hardwood flooring was nailed to the sleepers. Using an engineered wood rather than plain hardwood is a whole different ballgame, and the manufacturer will have the specs on how to do that (different for each product). If you want that floor's warranty to be valid, you will have to follow those specs.

"how long do you think we're talking about before a floor can go on?" There is no way to know this except by using the poly "carpet" I mentioned. Drying has so many variables (moisture of wood, concrete, humidity, temperature of radiant heating) that the time is totally unpredictable. Also using engineered wood may make it more or less crucial. These are things only the manufacturer can tell you.

Well, it's long past my bedtime, and I hope this is not too rambling and confused. Be well.

Thanks Dana for your facts and corrections.  I do believe that woksawi was speaking of a second floor meaning that it was over a conditioned space when I referred to their being no dew point issue.

I think we both agree that having a good analysis of the heat load of the house is important, and then one is able to compare the latest equipment to find out which is "best" if there is such a thing.  Ultimately, the idea is to not have to use much fuel regardless of its type (only oil, propane, wood and electric where I live) and that can only happen by a well constructed building.  The less fuel one uses, the less price differential there is between a 80% and 90% efficient appliance.  One of my reasons for using a water heater was that there was not much available in 1998 that was high efficiency. and my hope was that when the water heater needed replacing that there would be better equipment available.  Hopefully, by the time this heater goes bad, that will be true.

Gomer
I'm still up - trying to get answers for the guys who need an answer by tomorrow.  I can't believe we actually are paying a contractor sometimes...I'm his guinea pig for building a "healthy home" for someone with sensitivities.  Fun.

Thanks for all that info.  I, too, wondered about why we had to insulate below the main floor when no one else had mentioned it until the plumber (same guy who said we can't use a hot water heater).  I'm trying to figure out how to tell him nicely everything you just wrote so that we can make this happen. 

Anyway, with the insulation, what he claimed is that we will lose the radiant to the downstairs.  But now there is a Vaporblok barrier between the already poured 2 inches of concrete and it's plywood (exterior grade, no OSB!) subfloor, so I imagine that might stop some of the heat anyway.  He also said that it would help sound issues between the floors. 

But - our house is made from 12 inch AAC blocks (autoclaved aerated concrete), so tons of thermal mass, passive solar (no panels, ran out of money a while back and are just trying to get this done now - we don't get the rebates from our utility company unfortunately).  I did blocks in part to avoid using nasty insulation in the walls.  I like the breathable/thermal mass system idea, especially for someone sensitive.

We were going to do R60 blown in cellulose or possibly certainteed fiberglass in the ceiling, but I don't think my body liked the flame retardant in the cellulose.  Tonight I sleep with/test Certainteed. 

I am in the process of picking out an HRV (another post on this board) and like the Venmars but still don't know which to go for.  Not sure if I want the hepa or not, sometimes they can actually be more icky than not, again with sensitivities.   Lifebreath is used by many with EI, but Venmar has better efficiency.  What did you use?

The issue with the studs -- I wrote it all wrong (layman me)...it's the sole plates for all the INTERIOR walls - the bottom of the wood walls that will be in contact with the concrete floor.  Per code, there has to be a barrier between them.  So they started already wrapping Vaporblok so that it was under the wood, then stapled up the sides, if that makes sense.  Then those plates would be laid on top of the concrete without a problem, so they say.  I just looked up the MSDS for the Vaporblok though and don't love the hexene, in case of fire.  Tu Tuff is a better product for sensitivities.  But they already started.  Not sure if I should tell them to find a better way because I don't know a better way yet.   Don't like ACQ qood.  Redwood could be better, but still need a vapor barrier.  Ideally would like AAC interior walls, and we have a lot of extra, but that would mean extra money and labor and...as I mentioned, they are waiting on me.  Although it would have been nice to have had a heads up about this issue weeks ago.   I only find things out when I go on site of course.  And when I asked if anyone asked the very picky Boulder County if this was even code, of course no one had.  So...I'm up trying to figure out what to use.  I love the gasket idea, but it has a lot of stuff in it, including rubber, which I think might not work well for me. 

Too much info, I know.  Thanks for your help.  People like you keep me sane.  Now I have to go teach the plumber stuff...

also...
you wrote about gas leaking from the windows...we paid almost $2500 about for that krypton gas and then had to store the windows for a while because I got too sick to keep the project going and it had to be put on hold.  It's all gone - and that was from being stored (oh, by the window manufacturer by the way, who we're arguing with because he won't warranty any of the gas now). 

And to clarify the floor thing...we had a plywood subfloor for the main floor, then put on a vapor barrier, then put the radiant tubing on that (on the wire grid), then poured two inches of concrete over that (yes the main floor was engineered for that.)  No one wanted to do the sleeper system, although I researched it and brought it up.  So we have a ton of concrete in the house.  Very green.  Anyway, it's because they are putting wood walls over that concrete now, before the final floor goes on, that we need some barrier between the wood and the concrete. 

I haven't actually picked a final wood product but was told engineered is best over in floor radiant (in concrete) so might be limited because it's not easy to find eco-engineered flooring that doesn't require glue down. 

I wish there were a good consultant for all this out there.  It's incredibly time consuming.  I never thought I'd learn how things are built...