Yesterday I was doing some framing in an unfinished basement on a newer home, about 1 year old. I pulled the batts out of one cavity to install some backer in the corner and found a heavy layer of frost on the OSB.
Out of curiosity I pulled out a couple more pieces, and same thing, frost on the OSB. It looks like everything was done correctly. Heres what there is;
2 x 6 wall, vinyl siding, housewrap, 1/2″ OSB, R-19 batts, and 6 mil. fire retardent poly, caulked around the perimeters.
It was – 10 degrees outside, but it still concerns me to see all that frost inside the wall. I’m sure it will eventually dry out, but i’m just wondering if there might be some musky/mold issues down the road.
Anyone seen this type of frost in the wall before, or know of any remedies?
Replies
Wood4rd,
Remedy: Remove poly and fiberglass. Put in dumpster.
Install rigid foam insulation board or spray polyurethane foam between studs.
Probably fairly common, only you just tripped across it. The frost will evaporate with no significant ill effects when it warms up. Just assure that the vapor barrier is well-sealed.
I've seen this where even in a moisture barrier sealed wall where you'd think that the moisture couldn't get to that ext. sheathing from the interior, it was actually off gasing vapor from the sealed framing, concrete. The visqueen was keeping it from drying to the inside. It gave me cause to start rethinking basement wall insulation.
A Great Place for Information, Comraderie, and a Sucker Punch.
Remodeling Contractor just outside the Glass City.
http://www.quittintime.com/
Calvin, I see your point about the concrete walls, but this is the wood wall above grade. So I would imagine the whole house, and every house in the neighborhood and county, state for that matter would be having the same frost issues. Maybe not that much of a concern, but I wonder if the installation of the sheetrock has any effect on the issue. Also putting foam in the wall wont do much for the rest of the house anyways. I did notice they spray foamed the rim cavity. If sprayfoam or foamboard was the solution, wouldnt foam sheathing on the house rather than OSB prevent the frost issues?
It (foam sheeting) would certainly help in the elimination of the formation of frost. However, it is still a condensing surface if the temp and humidity are right for it. A cooler full of ice will be damp on the outside bottom in the summer. Dry cold concrete garage floor will be moist on top when you open that garage door on the first couple HUMID warm days of spring.
If that cavity was SEALED, fibreglass still allows air to pass through it-moving moist warm air. Now, if all penetrations and openings were really SEALED I would guess the moist air (warmer than the condensing surface) is present inside the cavity. In a yearold house, moisture in all areas certainly is not unheard of. The framing for sure is still drying out, any concrete/block will wick it up from adjoining areas. And the interior visqueen is not allowing it to pass to the inside. Even if the osb is bone dry up to the inside surface...........Tough one to figure out with complete certainty.A Great Place for Information, Comraderie, and a Sucker Punch.
Remodeling Contractor just outside the Glass City.
http://www.quittintime.com/
Calvin, one other thing I forgot to mention. I opened up the wall adjacent to the garage that had the 5/8" firecode rock, rather than OSB sheathing and there was no frost at all. The temperature is probably a little warmer in the garage, or does the sheetrock absorb the moisture?
You're saying that 5/8's sheetrock is the exterior sheathing?A Great Place for Information, Comraderie, and a Sucker Punch.
Remodeling Contractor just outside the Glass City.
http://www.quittintime.com/
The exterior wall that divides the house and garage, or the inside garage wall, if that makes any sense. That exterior house wall inside the garage just has the 5/8" firecode sheetrock for sheathing.
The garage is at least 10 degrees warmer, and there is no wind.
The mark of the immature man is that he wants to die nobly for a cause, while the mark of a mature man is that he wants to live humbly for one. --Wilhelm Stekel
Yeah, this house is in a new development with open fields and empty lots, so the wind is definatley a big part of the problem.
You were working in a basement, but have exterior OSB sheathing?? I'm confused.
The basement is above grade in the back of house.
Edited 12/23/2008 9:57 am by wood4rd
The garage probably has a lower humidity do to the large doors that open.
But the real question is why is it warmer then the conditioned house.... that's a problem.
This is the problem with poly vapor barriers. I never use them, even here in an 8500 HDD climate. A new house contains perhaps 50 gallons of water in the framing and hundreds more in the concrete. It can take a year to dry. Putting well-sealed poly on the interior merely guarantees that the envelope cannot dry to the inside, and OSB is not very vapor permeable so there won't be sufficient drying to the outside.
I'm not at all surprised that you found frost on it. OSB has a perm of 0.75. Unpainted drywall has a perm of 40 and can safely store 1% of its weight in water.
Everyone wants to "solve" moisture problems by using more impermeable materials (plastic foam). If you could build with oven-dry lumber, keep the rain off it, and have perfect air and vapor sealing everywhere, perhaps impermeable layers would do the trick.
But since every thermal envelope will start out wet and get wet at some time in its life, it makes far more sense to build with moisture-tolerant, vapor-permeable materials that also have a reasonable safe moisture-storage capacity. That creates a thermal envelope that can handle real-world conditions.
In your situation, I would rip out the poly everywhere in the basement. Hopefully, the upper floors have less moisture load and are more moisture tolerant.
Solar & Super-Insulated Healthy Homes
Edited 12/23/2008 9:39 pm ET by Riversong
"In your situation, I would rip out the poly everywhere in the basement."6 mil. poly is required by the building code. How about if I drill bunch of holes through it? You say you never use a poly vapor barrier. What do you use, and isnt it required in your building code?
Edited 12/24/2008 9:23 am by wood4rd
Vapor-retardant latex paint is becoming more accepted as a vapor retarder. It slows the flow of moisture into the wall cavity but allows the cavity to dry to the inside if/when necessary.
http://www.buildingscience.com has info on it. If your AHJ is friendly or knowledgable a printout from that website might be enough to get you through inspections.
> It slows the flow of moisture into the wall cavity but allows the cavity to dry to the inside if/when necessary.It should be pointed out that there's no such thing as a "one way" vapor barrier -- moisture can flow with equal ease/difficulty in either direction through any barrier.
The mark of the immature man is that he wants to die nobly for a cause, while the mark of a mature man is that he wants to live humbly for one. --Wilhelm Stekel
It should be pointed out that there's no such thing as a "one way" vapor barrier -- moisture can flow with equal ease/difficulty in either direction through any barrier.
He didn't claim it was. The point is that vapor-retardant paint (about 1 perm) is just that: a retarder not a barrier like 6 mil poly (about 0.03 perm). Thus, while it restricts the diffusion of water vapor into the cavity, it also allows an equal flow rate out.
What determines the actual volume of moisture moving in or out is the perm of materials and the partial pressure of water in the air ("HG). Thus if the vapor pressure is higher inside the cavity due to water infitration from the outside, the semi-impermeable paint film will allow drying to the interior. Poly won't.
Riversong HouseWright
Design * * Build * * Renovate * * ConsultSolar & Super-Insulated Healthy Homes
6 mil. poly is required by the building code. How about if I drill bunch of holes through it? Are you sure that your code doesn't simply require a vapor barrier? I would be surprised if it specified what material to use. The codes are well behind current building science in this regard. It's been established for a long time that almost all moisture in the thermal envelope that comes from the indoor environment is due to air movement and not vapor diffusion.
You say you never use a poly vapor barrier. What do you use, and isnt it required in your building code?
I use the air-tight drywall system and a vapor barrier primer. Benjamin Moore makes Moorcraft Super SpecĂ‚¯ Latex Vapor Barrier Primer Sealer 260. There are several others as well.
I would prefer, however, to not use any vapor barrier on my wall system, as drying to both the interior and exterior (depending on season) is critical for optimum performance and long-term durability. And I have 12" of cellulose in the walls which has a high moisture tolerance and moisture-buffering capacity.
Riversong HouseWright
Design * * Build * * Renovate * * ConsultSolar & Super-Insulated Healthy Homes
Thanks for the replies, everyone. I'm not going to try to change whats already been done on this job. The basement is already 60% finished and I'm just adding a bathroom and office/room. rjw- I agree that alot of the moisture is in the block wall and slab. I also think they should have used one more course of block on the foundation. Right now the wood wall and windows are only about 4" above grade. So right now the snow is right up to the bottom of the windows.I always thought the code was block 6" above grade. It seems like the codes are more lenient for the new homes than remodeling. MikeM- Thanks for the link, I will definatley look into that. Riversong- I am not familiar with the air-tight drywall system, so I am not sure if it is accepted in the code. Could you describe it? The codes seem to vary from one city or inspector to another. I do know that some want the poly air-tight and caulked around the electrical outlets, windows, and perimeter of the walls. On the other hand, some accept faced batts stapled between the studs, so it all seems pretty confusing to me.
"The codes seem to vary from one city or inspector to another."They should not. At least not that much.I don't know what kind of codes that you have there. A common state code, individual codes, or common state code with local modifications.In any case, with a few exception, they are based on model codes and the local modifiications are usually minor.I suspect that what happens is one inspector will get fixed on one method and think that is the code, even if there are many of there alternates allowed in the code, or if that method was taken out of the code 3 issues ago.And that if one go and check the actual code you will find that there is not that much difference, if any, between those cities..
William the Geezer, the sequel to Billy the Kid - Shoe
I am not familiar with the air-tight drywall system, so I am not sure if it is accepted in the code. Could you describe it?
http://www.southface.org/web/resources&services/publications/factsheets/24ada_drywal.pdf
The codes seem to vary from one city or inspector to another. I do know that some want the poly air-tight and caulked around the electrical outlets, windows, and perimeter of the walls.
This is often the worst thing you can do for vapor control as it guarantees that the wall system cannot dry to the interior.
Riversong HouseWright
Design * * Build * * Renovate * * ConsultSolar & Super-Insulated Healthy Homes
Thats interesting, thanks. It says that it doesnt really provide a vapor barrier though, and advise either paint or poly for that.
Thats interesting, thanks. It says that it doesnt really provide a vapor barrier though, and advise either paint or poly for that.
It's not supposed to provide a vapor barrier. It's supposed to provide an air barrier which is 99 times more important (see attachment below).
Vapor diffusion is not the problem, moist air movement is. Unfortunately, building codes are way behind building science in this regard, though educated building inspectors would know better.
Using a vapor-impermeable barrier, like poly, only guarantees that a wall assembly can't dry out when it - inevitably - gets wet (most walls start out wet).
Where codes require, use latex vapor-retardant primer (about 1 perm), which is vapor-semi-impermeable but will still allow some drying to the interior.
There is also evidence that plastic film in the wall creates a static charge which can draw negative ions out of the living space. Negative ions are what makes us feel so good at the ocean beach or a waterfall - they promote health and people will spend hundreds of $ on negative ion generators for their homes or install indoor fountains (good Feng Shui) to counteract the effect of their poly.
Don't forget that our homes should be like a third skin. Our primary skin has to breathe moisture (but not air) or we die. Our secondary skin - our clothing - is very uncomfortable if it cannot breathe moisture, which is why we spend $ on GoreTex instead of plastic raincoats. Our third skin - the envelope of our home - also has to breathe to maintain a healthy indoor environment.
It makes no sense to live inside a plastic bag, whether that's poly or plastic foam.
Riversong HouseWright
Design * * Build * * Renovate * * ConsultSolar & Super-Insulated Healthy Homes
Edited 12/27/2008 10:58 am ET by Riversong
I'll hijack here for a moment if I may with a call for your opinion for a related question?
My current project is a small 2-story studio, 700sf, perimeter-insulated slab, 8' 2x6 walls, 1/2" ply sheeting, tyvek, Hardiplank below, Smooth T-111 panel siding above with battens. New constr. Up is a scissor (like) truss with a shallow vault.
Elect and plumbing rough-ins are done, building is drying out right now, bare studs inside. All openings are closed but the ridge vent, and the moisture meter is telling me things are indeed drying out. I have to provide the owner and the city with a statemet saying that things are @ 19% or less moist. content of dry...
My question is about insulating the walls:
My code requires R-21 in the walls and the original plan was for conventional/quick/inexpensive FG batts. Temps rarely get below freezing here in winter in our PNW rainy climate.
I've had to stick to basic details due to cost and time but I'm thinking about doing something better than FG batts in the walls, only, for the client without breaking the bank. Can't afford foams, foam board...
What I was contemplating is blowing cellulose in the walls from inside, thru insul-mesh as outlined extensively here in the 'mooney wall' but I want to know if there would really be a significant benefit there if I do not increase the depth of the wall and go right to the studs with the mesh--thermal bridging? And can I get the R-21 in 5.5" of Cellulose--and prove it to my inspector?
The pluses i know of would be--better air sealing, better moisture transfer, better sound attenuation...
Cost wise it looks like it wouldn't be appreciably more. Locally Home depot has "green fiber" cellulose in 22.55lb bricks, and the blower for free w/purchase. I'd need to spend a couple hundred bucks for mesh...add a day of labor.
What's your opinion? Glad to have you back!
Pat
What I was contemplating is blowing cellulose in the walls from inside, thru insul-mesh... but I want to know if there would really be a significant benefit there if I do not increase the depth of the wall and go right to the studs with the mesh--thermal bridging? And can I get the R-21 in 5.5" of Cellulose--and prove it to my inspector?
If you can get a minimum of 3 lbs/cf of cellulose in the walls, that will give you a real R-20.9 (3.8/inch). But remember that typically-installed R-21 "high-performance" fiberglass has been tested to be as little as R-13.3 in place.
With 16" oc framing, your as-built clear wall R-value would be 20.59 with cellulose, and taking into account the typical 23% framing the whole wall R-value would be 17.3. But that's still going to be a lot better than the equivalent depth of fiberglass.
The pluses i know of would be--better air sealing, better moisture transfer, better sound attenuation...
Absolutely, as well as better fire-resistance, and insect and rodent resistance.
Cost wise it looks like it wouldn't be appreciably more. Locally Home depot has "green fiber" cellulose in 22.55lb bricks, and the blower for free w/purchase. I'd need to spend a couple hundred bucks for mesh...add a day of labor.
I suspect the cost would be roughly the same if you blow it yourself. Just make sure that you have a decent machine and can guarantee a minimum density of 3 pcf.
Riversong HouseWright
Design * * Build * * Renovate * * ConsultSolar & Super-Insulated Healthy Homes
Thank you!
FWIW, moisture levels are pretty high in new houses for quite a while. Esp basements, as the slab dries out.
"Ask not what the world needs. Ask what makes you come alive... then go do it. Because what the world needs is people who have come alive."
Howard Thurman
Edited 12/24/2008 9:45 am ET by rjw
Frost is solidified moisture.
Fibreglass is porous and can contain moisture.
Do you have poly on the concrete wall? Concrete also wicks.
The poly on the inside of the concrete wall should be only up to grade level not to the top of the wall.
Often a recent build home is not completely dried out. Concrete basementfloors give off a lot of moisture, did the framing material get wet (heavy rain)?
I would take the insulation out and get a good heater in the room(s, dry everything out and either re-install the fibreglass insulation or go rigid. Seal vaporbarrier on bottom and right into the floorjoist exterior trimboard (insulate joistspace)
There is no poly on the concrete wall. There is a 3.5' blockwall, with rigid foilface foamboard on it. Above that is a 4.5' 2X6 wall with housewrap, 1/2" OSB sheathing, fiberglass batts, and 6 mil. fire retardent poly caulked around the perimeter, and taped at the seams. The rim space is spray foamed. The basement walls were already insulated by the original builder and passed the insulation inspection when the house was built, before I got involved in the job. The frost was on the inside of the OSB, the insulation seemed to be dry. I wasn't around when the house was built, so I have no idea of the condition of the lumber at the time, but it appears to be pretty dry right now, I think the -20 degree temps and high winds had alot to do with it. I have the radio tuned into a home show, and there have already been a couple calls about frost issues. I don't think this was the only house with froston the sheathing, just one of the few that was opened up to reveal it.
> I don't think this was the only house with frost on the sheathing, just one of the few that was opened up to reveal it. Right. It's normally not seen and causes no damage. No need for any corrective action.
The mark of the immature man is that he wants to die nobly for a cause, while the mark of a mature man is that he wants to live humbly for one. --Wilhelm Stekel
Had a malfunction there, but what I was going to say is, I agree.
It's normally not seen and causes no damage. No need for any corrective action.
"Not seen" and "causes no damage" don't necessarily equate. Most in-wall mold and rot problems are not seen until the damage becomes problematic.
Small amounts of condensation are not problematic as long as the wall system can dry itself out. OSB is relatively impermeable to moisture and poly is completely impermeable. This doesn't allow drying. If moisture continues to accumulate, then there will be problems.
Riversong HouseWright
Design * * Build * * Renovate * * ConsultSolar & Super-Insulated Healthy Homes
But this form of construction is common, and the specific instance cited didn't appear to be defective in any way. If it caused problems there would be lots more complaints than you're hearing.The frost in this case is of no consequence -- it will (if undisturbed) sublimate back into vapor with no significant effect on the OSB.
The mark of the immature man is that he wants to die nobly for a cause, while the mark of a mature man is that he wants to live humbly for one. --Wilhelm Stekel
The frost in this case is of no consequence -- it will (if undisturbed) sublimate back into vapor with no significant effect on the OSB.
And how will that vapor be removed from the thermal envelope?
Riversong HouseWright
Design * * Build * * Renovate * * ConsultSolar & Super-Insulated Healthy Homes
Why does it have to be removed?
The mark of the immature man is that he wants to die nobly for a cause, while the mark of a mature man is that he wants to live humbly for one. --Wilhelm Stekel
Why does it have to be removed?
Very odd question, since water is the primary enemy of wood and we go to great lengths to keep moisture out of thermal envelopes to prevent accumulation and eventual mold and rot. We, however, do a very poor job of allowing moisture to get out once it's in.
From our friend Lstiburek:
Joe's Ten Building Science Principles<!----><!----><!---->
<!----> <!---->
All of these principles are at least indirectly related to moisture. Even in hot-dry climates, moisture events related to occupant activities, leaks, and singular climate events can bedevil the performance and durability of today's homes.
<!----> <!---->
Our efforts to save energy and reduce the flow of heat through building assemblies have reduced drying potentials and, therefore, increased the importance of controlling moisture flow through building assemblies. <!---->
Ideally, building assemblies should be designed to dry to both the interior and exterior. In heating climates, the primary drying potential is to the exterior (but not necessarily exclusively so); in cooling climates, the primary drying potential is to the interior (but not necessarily exclusively so); and in climates with both heating and cooling, some drying potential in both directions is typically a good idea (but not necessarily exclusively so). <!---->
Building materials last longer when their faces are exposed to similar or equal temperature and humidity. This is why the ventilation of claddings, particularly those that store moisture (reservoir claddings), can be important. <!---->
Drainage planes, air barriers, and thermal barriers must be continuous to be truly effective. Being able to trace each of these on a full elevation drawing without lifting your finger (or pencil or pointer) from the elevation is a good test of continuity. <!---->
In moisture control, the priority is liquid water first, particularly when it comes in the forms of rain and groundwater. In these forms it is referred to as "bulk" water. Following are air-transported vapor and then diffusive vapor, all other things being equal. It's always a question of quantities and rates, of wetting and drying, and the tolerance of materials (individually and in combination) for each and all of the above. <!---->
Three things destroy materials in general and wood in particular: water, heat, and ultraviolet radiation. Of these three, water is the most important by an order of magnitude. <!---->
When the rate of wetting exceeds the rate of drying, accumulation occurs. <!---->
When the quantity of accumulated moisture exceeds the storage capacity of the material or assembly, problems occur. <!---->
The storage capacity of a material or assembly depends on time, temperature, and the material itself. <!---->
The drying potential of an assembly decreases with the level of insulation and increases with the rate of air flow (except in the case of air flow in severe cold climates during cold periods where interior moisture levels are high).
<!----> <!---->
Riversong HouseWright
Design * * Build * * Renovate * * ConsultSolar & Super-Insulated Healthy Homes
Edited 12/27/2008 3:55 pm ET by Riversong
Edited 12/27/2008 3:56 pm ET by Riversong
You didn't answer my question. The amount of moisture involved here is quite small, and it will be reabsorbed into the air and building materials once the temperature warms up. Eventually it will make its way out, if it's in excess of equilibrium amounts.If the structure is built to modern standards very little additional moisture is entering, and there's no chance of a buildup of moisture."Drying to the inside" is only necessary in exceedingly wet environments where there is limited "drive" to the outside.
The mark of the immature man is that he wants to die nobly for a cause, while the mark of a mature man is that he wants to live humbly for one. --Wilhelm Stekel
You didn't answer my question.
Actually, I answered it back in post #34:
"Not seen" and "causes no damage" don't necessarily equate. Most in-wall mold and rot problems are not seen until the damage becomes problematic.<!----><!----><!---->
<!----> <!---->
Small amounts of condensation are not problematic as long as the wall system can dry itself out. OSB is relatively impermeable to moisture and poly is completely impermeable. This doesn't allow drying. If moisture continues to accumulate, then there will be problems.<!----><!---->
And I offered a further elaboration by posting Joe's Top Ten Rules, including:
Ideally, building assemblies should be designed to dry to both the interior and exterior. When the rate of wetting exceeds the rate of drying, accumulation occurs. <!----> When the quantity of accumulated moisture exceeds the storage capacity of the material or assembly, problems occur.
The amount of moisture involved here is quite small, and it will be reabsorbed into the air and building materials once the temperature warms up. Eventually it will make its way out, if it's in excess of equilibrium amounts.
You're making an assumption which is likely incorrect. The OP found "a heavy layer of frost on the OSB" everywhere he looked. Reabosorbed into what air? The wall space is sealed from the inside environment by poly caulked at the edges, and from the outside environment by OSB which has a perm of 0.75. "Eventually it will make it's way out, I'm afraid, is wishful thinking.
If the structure is built to modern standards very little additional moisture is entering, and there's no chance of a buildup of moisture.
"Modern standards" includes a very broad spectrum of quality. Is the WRB taped and lapped properly? Are all the flashings installed correctly? Are there proper flashings and sill pans at windows and doors? Are the roofing details done correctly? Adequate overhangs? Good grading and ground clearance?............................................
One thing only is certain about all building envelopes: they start out wet and will get wet at some point in their lives (probably many points).
We've speculated that because it is a "newer" home, that the moisture might be construction moisture, possibly from the foundation, possibly from the framing. But there's no way to know wether the moisture passed into the wall assembly and whether it's going to continue to do so.
In any case, there are plenty of chances of moisture accumulating sufficiently to bring the wood sheathing and framing up to 16% MC, which is the surface mold threshold. Since the moisture is in the form of frost, it's either going to stay as is or continue to accumulate until the weather warms. At that point, there may be sufficient frost to melt into sufficient water to cause mold growth when the temperature rises to 50°.
"Drying to the inside" is only necessary in exceedingly wet environments where there is limited "drive" to the outside.
While the moisture drive in a heating climate is predominantly to the outside, it will reverse itself in the summer and even in the winter when the sun is pounding on the facade. Temperature gradient from solar radiation can easily overpower vapor pressure gradient. And driving rain can increase the outside air and vapor pressure sufficiently to push moisture inside.
More from Joe Lstiburek: "Moisture accumulates in the building envelope when the rate of moisture entry into an assembly exceeds the rate of moisture removal. When moisture accumulation exceeds the ability of the assembly materials to store the moisture without significantly degrading performance or long-term service life, moisture problems result. The moisture storage capacity of a material depends on time, temperature, and material properties."
"Wood can safely store moisture until the moisture content by weight exceeds 16% (the “surface mold limit for wood”). The equilibrium moisture content of wood exposed to a relative humidity of 80% is 16."
Since framing in walls tends to reach annual equilibrium around 10% MC, it requires only an additional 6% moisture by weight to bring wood to the mold limit.
"Various strategies can be implemented to minimize the risk of moisture damage. The strategies fall into the following three groups:
Control of moisture entry,
Control of moisture accumulation, and
Removal of moisture.
These are best used in combination. Strategies effective in the control of moisture entry, however, often are not effective if building assemblies start out wet. In fact, these strategies can be detrimental."
The fact that there's a well-sealed and completely impermeable inner vapor barrier and a relatively impermeable outer skin suggests that the wall system will not dry out and moisture accumulation and mold and possibly rot are a likely possibility.
Riversong HouseWright
Design * * Build * * Renovate * * ConsultSolar & Super-Insulated Healthy Homes
> But there's no way to know wether the moisture passed into the wall assembly and whether it's going to continue to do so.So you're assuming the worst, rather than taking Occam's suggestion. Where is this moisture going to come from, with a tight vapor barrier, and a halfway decent sill treatment?> Temperature gradient from solar radiation can easily overpower vapor pressure gradient.That's BS.You've hitched your wagon to one "authority", then you interpret his statements in the extreme.
The mark of the immature man is that he wants to die nobly for a cause, while the mark of a mature man is that he wants to live humbly for one. --Wilhelm Stekel
This is why we don't use housewrap. You cannot always control the presence of moisture in an exterior wall and the housewrap will prevent the liquid water generated by the melting of the 'heavy layer of frost' from escaping, as will the poly. The notion of a heavy layer of frost simply evaporating directly and dissapating does not seem to really represent real-world conditions, where a sudden warm up or sun coming out on one side of the residence causes rapid warming, especially on the exterior side of the insulation.
To answer your question - this wall is likely to have rot and mold problems as a result. The culprits are housewrap and interior moisture control.
Jeff
> The notion of a heavy layer of frost simply evaporating directly and dissapating does not seem to really represent real-world conditions, where a sudden warm up or sun coming out on one side of the residence causes rapid warming, especially on the exterior side of the insulation.Of course it doesn't seem to represent real-world New Jersey. Try Minnesota, though. I've SEEN frost evaporate off a wall.
The mark of the immature man is that he wants to die nobly for a cause, while the mark of a mature man is that he wants to live humbly for one. --Wilhelm Stekel
Well then, we won't really be expecting to hear about any problems in Minnesota then, will we?http://www.hobb.org/index.php?Itemid=197&id=1992&option=com_content&task=viewhttp://www.stocorp.com/allwebpr.nsf/5d5efb09f77373618525666a004bca57/d4f316cb97c674368525692d006d00ea?OpenDocument
http://www.insurancejournal.com/news/midwest/2008/12/23/96558.htm?print=1
http://www.health.state.mn.us/divs/eh/indoorair/mold/moldqa.htmJeff
Edited 12/28/2008 9:55 am ET by Jeff_Clarke
Were any of those caused by having a vapor barrier??
The mark of the immature man is that he wants to die nobly for a cause, while the mark of a mature man is that he wants to live humbly for one. --Wilhelm Stekel
So what do you use for a WRB in place of housewrap? Or do you feel that the cons of a WRB outweigh the pros?
Jon Blakemore RappahannockINC.com Fredericksburg, VA
So what do you use for a WRB in place of housewrap?
Paul Fisette, director of Building Techonology at UMass Amherst has done extensive testing on most of the plastic housewraps and he says he still prefers felt.
Well-lapped and shingled 15# felt will serve as a secondary rain barrier and keep most of the wind out, but it will also absorb and release liquid water and is vapor permeable (Perm = 6 dry and 31 wet).
Riversong HouseWright
Design * * Build * * Renovate * * ConsultSolar & Super-Insulated Healthy Homes
Ditto.
Jeff