Posted By Dana1 on 08 Aug 2013 11:23 AM
Clark: Maintaining 40% RH throughout a N-IL winter can create moisture accumulation in the walls with potential springtime mold-spore issues in many stick-built homes. It depends on the stackup & air tightness toward the interior of the wall assemblies. Bumping the ventilation to keep it between 30-35% RH in mid-winter is probably prudent, and still comfortable, and within the healthy range recommended by respiratory health professionals.

My walls are ICF.  Half inch gypsum board over 2-1/2" EPS, 5-1/2" poured concrete, another 2-1/2" of EPS, and finally Hardi-board siding.   My understanding is that if the dew point occurs inside the ICF wall structure, condensation is not an issue.   Not true?

I also understood you to say that with my particular ceiling stackup and with near zero air infiltration into the ceiling joist cavity, that condensation, if any, will be so slight as not to present a problem even at 40% indoor RH, particularly when indoor RH is maintained below 50% the rest of the year for quick drying of any moisture to the inside.  Did I misunderstand?

Posted By Clark on 17 Aug 2013 08:32 PM

Posted By Dana1 on 08 Aug 2013 11:23 AM
Clark: Maintaining 40% RH throughout a N-IL winter can create moisture accumulation in the walls with potential springtime mold-spore issues in many stick-built homes.

My walls are ICF.  Half inch gypsum board over 2-1/2" EPS, 5-1/2" poured concrete, another 2-1/2" of EPS, and finally Hardi-board siding.   My understanding is that if the dew point occurs inside the ICF wall structure, condensation is not an issue.   Not true?

I believe what Dana stated applies to wood frame homes only, not ICF/concrete.

I had a similar question like yours in regards to ICF walls but instead of Hardi-board siding, an EIFS waterproof synthetic stucco application. I am assuming that 2.5" of exterior EPS is considered a "vapor barrier."

Right- that's what's meant by " ...in many stick-built homes." With ICFs the mold risks are inherently lower, but not completely absent.

At 2.5" Type-II EPS is between 1.5-2 perms, which is a fairly stiff class-III vapor retarder (less permeable than #15 felt), but if you put a low-permeance finish onl moisture within the concrete can only move upward or inward. Both concrete and EPS are highly tolerant of moisture, but paper facers on gypsum wallboard are not. If going with an EIFS approach, the vapor permeance of the EIFS matters, since you'd ideally have the moisture in the concrete moving toward the exterior, not the interior. With fiber cement that's not issue.

Anywhere wood meets concrete in an ICF structure there needs to a capillary break, and a means for the wood to dry (in one direction or the other.)

Posted By Dana1 on 19 Aug 2013 02:17 PM

At 2.5" Type-II EPS is between 1.5-2 perms, which is a fairly stiff class-III vapor retarder (less permeable than #15 felt), but if you put a low-permeance finish onl moisture within the concrete can only move upward or inward. Both concrete and EPS are highly tolerant of moisture, but paper facers on gypsum wallboard are not. If going with an EIFS approach, the vapor permeance of the EIFS matters, since you'd ideally have the moisture in the concrete moving toward the exterior, not the interior. With fiber cement that's not issue.

StuccoMax was tested and it achieved a 10 MNs/g.

According to the Method of Assessment and Testing: MOAT No 33: 1986
The water vapour transmission rate (WVTR) was determined on samples of “StuccoMax” coatings. The Assessment of Masonry Coatings “the system is considered to be a vapor barrier if its resistance exceeds 15 MNs/g”. If the water vapor resistance is higher than 15 MNs/g the coatings will be too impermeable and interstitial condensation will occur. The “StuccoMax” coating will not present the risk of condensation on the “cold” sides of walls coated with it.

I could only find that quote in a document relative to code approvals in South Africa, which is a far more temperate, warmer & drier climate than Staten Island.

http://gigacrete.com/wp-content/uploads/2013/06/Durability-Report.pdf

The July-July midwinter mean temp in Pretoria ZA is about 55F, which is 20F warmer than Staten Island's January-February mean.

MOAT 33 is a British test for resistance to algae growth in paint, which isn't exactly the same issue.

It may or may not be sufficiently permeable for use in a much colder wetter climate, and use over an OSB clad SIP in any climate is a very different hygric problem than over ICF, given the radically different tolerances for moisture of concrete vs. OSB.

When it passes muster for use in Vancouver B.C. I'll be comfortable using on Staten Island- the hurdle for South Africa is more like a stripe on the floor than an actual hurdle. ;-)

Posted By Dana1 on 20 Aug 2013 11:48 AM
I could only find that quote in a document relative to code approvals in South Africa, which is a far more temperate, warmer & drier climate than Staten Island.

http://gigacrete.com/wp-content/uploads/2013/06/Durability-Report.pdf

The July-July midwinter mean temp in Pretoria ZA is about 55F, which is 20F warmer than Staten Island's January-February mean.

MOAT 33 is a British test for resistance to algae growth in paint, which isn't exactly the same issue.

It may or may not be sufficiently permeable for use in a much colder wetter climate, and use over an OSB clad SIP in any climate is a very different hygric problem than over ICF, given the radically different tolerances for moisture of concrete vs. OSB.

When it passes muster for use in Vancouver B.C. I'll be comfortable using on Staten Island- the hurdle for South Africa is more like a stripe on the floor than an actual hurdle. ;-)

I assume StuccoMax is similar in its vapor transmittance as other EIFS coatings? It's no better or worse than most EIFS coatings.

In your opinion would a product like StuccoMax be good to use in a Zone 4 climate like Prescott, Arizona with an ICF wall?

Can a wall dry towards the interior with 2.5" EPS, drywall and latex paint or does the the latex paint prevent it?

I haven't chased the specs on EIFS coatings- can't really compare Stucco max to the others (haven't seen any ASTM E96 spec on a specimen of coating + EPS to make the comparison.) I know that many have a very poor track record in rainy foggy-dew Vancouver on a number of building types.

Prescott is a much nicer moisture environment for building materials by any measure, and wouldn't sweat the vapor permeance details in that climate (other than to avoid true vapor barriers like polyethylene sheeting or foil wallpaper, etc.). That said, standard latex paint typically runs 3-5 perms, making it a somewhat weaker vapor retarder than 2.5" of EPS. Gypsum is VERY vapor permeable, so I's hazard that with 3-perm paint and 2.5" of EPS you'd still be over 1.5 perms between the concrete & interior. It's not super-permeable, but moisture won't be trapped in the walls by any means. (At 0.3 perms, & lower, maybe.)

Posted By Dana1 on 20 Aug 2013 06:13 PM

Prescott is a much nicer moisture environment for building materials by any measure, and wouldn't sweat the vapor permeance details in that climate (other than to avoid true vapor barriers like polyethylene sheeting or foil wallpaper, etc.).

Now with a 26 gauge steel SIP roof with a 12" EPS core foam, that would be classified as a 100% vapor barrier, correct? Would one have to do anything special on such a roof assembly in a Zone 4 climate like Prescott, AZ?

Yup, sheet steel is a vapor barrier, no doubt about it!

And a steel SIP is pretty much impervious to climate issues in any US climate zone- nothing special required beyond following the manufacturer's instructions.

The details for reliably air-sealing a steel SIP to the top of an ICF wall is something I've never looked into, but it's probably not too complicated. Thermal flexing and elongation/contraction of a steel SIP may differ somewhat from an OSB SIP or timber construction, but as long as there's some mechanical compliance to the sealing methods you should be able to get there.

I used the forum in 2007 to 2010 when I was constructing my first ICF home and found the information and exchange of ideas to be priceless. I am having a common issue with overly tight build homes and that is humidity and lots of water on my window sills. We moved into our 3300 Square foot ranch type ICF (11 inch) (buildblock) home in February 2011. At that time we observed the condensation and or sweating of the windows. The issue produced significant amounts of water on the sills that required daily clean up. Mold growing on the sills was also a constant battle we dealt with. During Spring, Summer and early Fall of 2011 we had no issues with condensation or sweating windows. Mid Fall and Winter 2011 into winter 2012 same cycle with mold and lots of water on the sills. Yes, clearly I should have taken some action at that point. Fall 2013 into Winter 2014 same issues. Again, no issues in spring, summer and early fall. As of today 01/10/2014 the humidity in upstairs is 59% and downstairs is 62%. Typically the numbers are in the mid 60 range. Some Background: The house has a Econar Geothermal Forced air heating and cooling system - two stage compressor with variable speed fan. Half of the Walkout Basement is finished and there is return and supply ductwork to the basement. I have another water to water Econar unit for the radiant heat in the basement floor and garage floor that I have not yet hooked up. I have a Fan Tech SHR 3005R (Heat recovery Ventilator) hanging in the basement, but it is not yet hooked up or operational. Energy Wise Structures provided the parameters for the sizing of my Geo units as well as all of the ductwork. The Seal plates at the top of the ICF walls were personally sealed by me around the entire perimeter inside and out. My brother and I sprayed 3 inches of closed cell spray foam down onto the attic floor (against the drywall and between the bottom truss cords) and then I blew in 12 inches of cellulose over top that. There is no HVAC equipment in the attic space. I don't recall my blower door test results, but we are tight. I have high volume Panasonic fans in every bathroom and a high volume fan for the kitchen stove and they all get used heavily. All windows are wooden HURD double pane, Argon filled Casement type windows with Extruded aluminum on the exterior. Form-a-drain was incorporated into the concrete footer and dimple membrane was used on the below grade ICF's on the entire perimeter. I backfilled to grade level with 2B stone. Basement is dry. So before the window or sills are ruined or we get sick from the mold issue I need to take care of business. I sent an E-mail to Aprilaire providing them with the above information. I indicated I was planning on purchasing there Aprilaire 1770A Dehumidifier to correct my issue, but after reading there Question and Answer topic on de-humidifying in the Winter I was unsure if that was going to correct my issue. They responded back and informed me I needed to install an ERV not a HRV and explained why. I then went back and re-educated myself on the differences between an HRV and an ERV. (When I purchased the HRV back in 2010, I based my decision to obtain the HRV over an ERV off the charts that FAN TECH provides, which is dependent on your geographical location. I know now that I was wrong in going with the HRV.) Aprilaire did not suggest I install a whole house de-humidifier for my issue. I sent the same question to Fan-Tech, but have not heard back from them as of today. I have read the explanations on line on how temperatures outside in conjunction with window temperatures in conjunction with indoor temperatures and dew points all determine condensation build up on the windows. I get the idea of what they are saying, but how do I quantify and implement the proper solution to nix my issue. My hope is that someone on this forum will be able to assist me. I am ready to throw some green at my issue. Do I: 1) Remove the HRV and install an ERV? 2) Keep the HRV and install a Energy Star whole house de-humidifier? 3) Install an ERV and a Energy Star whole house dehumidifier? Any thought, suggestions or opinions would be greatly welcome. Thank you again, Kelly Lentz South Central Pennsylvania

I have a basement slab which has lots of clear stone under it and I have very deep sump.
When it rains this system stores lots of water under slab I only run sump once a week.

So, I suspect that you have water under the slab.

goinggreen
kelly, do you have curtains on the windows and doors that sweat?
do you have condensation in areas other than the windows/doors?
try hanging a heavy blanket/curtain over the wettest window, after drying it first, and see if it still sweats.
peter
insuldeckflorida at aol dot com

Posted By goinggreen on 10 Jan 2014 01:32 PM
I have a Fan Tech SHR 3005R (Heat recovery Ventilator) hanging in the basement, but it is not yet hooked up or operational.

Why not? Has it been hanging there since you built the house? The whole idea of a ventilator is to exchange indoor air for outdoor air. If you're in a climate where the RH of the winter outdoor air is lower than the indoor air then using the ventilator to exchange the air is the first step to reducing the humidity in the house. How can you even know if you should have used an ERV instead of the HRV if the HRV isn't functional? Get the HRV up and running and then tell us how much of a problem remains.

Sorry to be so blunt, by my God man, after all the research you did before building how could you even think about not having a functioning HRV from day one?

I am having a common issue with overly tight build homes

I don't think there is any such thing as an overly tight home, is there?

The real problem, as dmaceld points out, is most likely that you have no ventilation.

going green

A couple of suggestions.

If your basement floor is just concrete ie no floor covering, take a piece (about 6 feet by 6 feet) of poly and lay it on the floor. Tape the edges. If condensate forms under the poly, the floor is allowing moisture to wick and could be part of the problem. If not, you can eliminate the slab as the problem.

Get a standard portable dehumidifier and get the rh down to 35 to 45 and maintain it there for a month or two. (maybe rent a couple from you neighbourhood rental shop to really hit it up front.)

You need to determine if all the moisture is out of the ICF. It seems to me that it should be but maybe your summers have been moist as well. Without any hrv running you are relying on open doors and windows to let in the air the exhaust fans are moving out. You may not have had enough through circulation to remove the moisture from the walls. In any case, it is clear that the house is saturated at a relatively high rh. You need to get that down and a few portables is the easiest way to do that quickly. After that you can see it the rh goes up again.

HOOK UP THE HRV

Posted By FBBP on 10 Jan 2014 10:17 PM
going green

A couple of suggestions.

If your basement floor is just concrete ie no floor covering, take a piece (about 6 feet by 6 feet) of poly and lay it on the floor. Tape the edges. If condensate forms under the poly, the floor is allowing moisture to wick and could be part of the problem. If not, you can eliminate the slab as the problem.

I guess this method works beter if it is done on the corner or on top of a crack.

You are right that moisture usually shows up at a crack or wall joint, it is usually self evident at these locations. That is why we test for moisture out in the middle if we don't see it at those locations.

In a PA climate with an HRV, dialing back the ventilation rate in the summer and using a standalone dehumidifier to manage the latent loads is a cheaper solution than swapping out the HRV.

In winter you can purge humidity cheaply by bumping UP the ventilation rate on the HRV.

Whole house dehumidifiers are almost never the right solution, unless you have 25 fish tanks and take 40 minute showers daily. For most homes it would be like swatting flies with a sledgehammer.