What do you think caused this

[Brian_A.MacNeish]

@vmitchinson

OK lets start with the NBC. It calls for a bitumen coating on the inside concrete from the bottom of the wall up to the level of the exterior grade.
NBC also calls for an air space between the framing and insulation and the exterior concrete wall. This is for the moisture to escape up the space and then out side.
Where and in what code did you find the above 2 statements? My NBC does not say that in section 9.25!!

NBC also calls for 6 mil polyethylene on the warn in winter side of the framing.
NBC also calls for weeping tile around the perimeter of the foundation and damp proofing or water proofing of the exterior wall. This is dictated by local conditions.

You say there is tar paper. Sometimes the bitumen comes off the wall in a sheet that looks like tar paper. Did you check it to make sure what it was.
When you refer to sweating do you mean condensation?
He never said there was sweating or condensation!

Mac was close but not right, if it is condensation. At 20 C 40% RH rises to 100% when the temperature drops down to 10-11 C. At 100% you get precipitation or condensation on surfaces that are colder then the dew point. Dew point is 100% RH. Out side it called rain.
Just went to an engineering site: The calculated dew point of 20C, 40% RH air is a little above 6C. Where did you get your figures?

11:12PM…just checked a site with a psych chart: 20C (68F), 40% RH air has an RH of ~77-78% at 10C (50F). The range at which mould growth is encouraged!!

Mould will start growing on Moist organic material within 48 hours.
You do not have to have moist materials for mould to grow… just the right (or wrong) ambient conditions…many moulds will extract water from air with an RH of >65-70% and thrive if ambient air conditions stay above those ranges.

Within two weeks you will see patches of it. A quick field test is to collect a sample on some sticky tape and put a little bit of chlorine bleach on it. If it disappears it is mould if it stays it’s dirt. If it disappears recommend mould testing by an expert.
The problem in the photos looks to me like the bottom of the wall has mould from moisture but the source of the moisture is most likely condensation. Also moisture could be wicking up from under the wall or from the concrete exterior wall.
Water coming through the wall is wet conditions on the other side. Do you have weeping tile in place and what are your local conditions and local practise.
No drainage via the weeping tile could cause water to build up and seep in.
I can not tell you what the problem is because I’m not there. Hope the above helps you figure it out.

So enough water is coming right through the vapour/barrier to wet the drywall…he said it was fairly dry!!!

Understand the conditions that allow/encourage mould to grow!!

[Brian_A.MacNeish]

@mcyr

Not being there, could be a humidity problem from the first problem.

Don’t be talking in circles, Marcel. ;-):twisted::shock:

The first problem was a “humidity problem” so the sentence then reads “could be a humidity problem from a humidity problem”

[Brian_A.MacNeish]

@pmassie

So the best way to do it is with foam bords, between wooden structure and the concrete.

Joe Lstiburek has been promoting this for over a decade now. There is no vapour barrier* on the interior behind the drywall and the drywall has to be the airtight barrier.

Just wait until you try and get this one by the local code officials!!! It’s not in their code books nor their heads yet…the new building science*, like the new math a lot cannot understand!!

** NEW SCIENCE…just read something today that a Canadian 31 year old physics wiz has been working on…being able to measure characteristics of sub-microscopic particles that past physics experts said could not be done as the light photons/other particles used for measurement would actually change the motions of same size/smaller particles that they were trying to measure!!

[Brian_A.MacNeish]

@dandersen

No, it’s # 1.

Your reasoning??

[Brian_A.MacNeish]

@vmitchinson

OK lets start with the NBC. It calls for a bitumen coating on the inside concrete from the bottom of the wall up to the level of the exterior grade.

In terms of “healthy housing”, why would you want to paint TAR on the inside of your home??

[Brian_A.MacNeish]

[quote=“dandersen, post:13, topic:60267”]

Mold spores can’t dig through plastic can they?
Air sealed wall will not have mold if it can’t get in.
Mould spores are everywhere…airsealed wall will have spores sealed in it unless constructed in a “clean room”!!!

With more information, we can now move up to #2. (Thermal Bypass)

(Still don’t have all the info needed however).

A little more info and we can move to #3. (Thermal Bridging)
Bottom plate and framing conducting heat away at the floor and corners.
You’re thinking like an engineer now and not a building scientist with HVAC experience!!

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Yeah but the thermal bridging is in every wall above grade that experiences more “cold” without the mould growth. The lower wall in the basement does not see the Delta T that the above ground wall does…By the above theory, we should be seeing more mould growth in upstairs corners experiencing colder outdoor temps…if all indoors RH’s are similar.

[ccurrins (Christopher Currins, CMI)]

@belliott

You are not making some outrageous claim that the vapor barrier traps moisture and since the outside is dirt prevents the wall moisture from evaporating are you ?
Next you will be telling us the wood framing absorbs moisture off the foundation or some other **rot **like that.

Didn’t we just “cover” this last week. NO vapor barrier below ground.

[belliott (Bob Elliott, 450.0002662)]

@ccurrins

Didn’t we just “cover” this last week. NO vapor barrier below ground.

OK ,OK,so you just proved you were paying attention.Big Deal…

Now riddle me this.
In the present situation when you are not sure…who do you call? (what type of contractor)?

[Brian_A.MacNeish]

@belliott

OK ,OK,so you just proved you were paying attention.Big Deal…

Now riddle me this.
In the present situation when you are not sure…who do you call? (what type of contractor)?

You call someone like a certified energy auditor with** lots of field** (not book) **experience **in house retrofit, IAQ, HVAC.

[mbeauchemin (Marc-Andre Beauchemin, MAB,(CMI), (CPI), interNACHI, interNACHI Quebec,A)]

Bonjour Patrick, (and all)

In an ideal situation I would prefer foam insulation as it sticks to cement and seals.
But since it is not a perfect situation, Grading & French drains I would investigate and of course, I would also try to determine weather the heating baseboard is actually being used or if is it only used as a decoration!

Marc-Andre
BMAinspection.com

[Brian_A.MacNeish]

@pmassie

Hi Folks

Basement walls, mold on surface, material moisture content 19%.

One section of the wall was opened :
1-Vapor barrier, there (hot side of course),
2-Bat insulation
3-Framing is right against the foundation wall, no gap between them
4-Framing is not wet, but also have 19% humidity
5-Foundation is not wet (no water)

do you think number 3 could be the cause of the mould?

Any concensus developing yet??

[mcyr (Marcel Cyr, CMI)]

Well, since we are just giving opinions on what the problem may be after all the information supplied, why don’t you the GodFather of all HI’s tell us exactly what caused the problem, then we will all know.
I think you are the one talking circles here.
I have seen exactly what happens in the field when a vapor barrier is installed on the inside. I have taken some apart due to the same problem.
Extruded foam is the answer when the foundation walls don’t leak.
And do we all know if that is the case here.
No, Might it be humidity, maybe.
In anycase, we are all speculating except you of course.

[rcooke (Roy D. Cooke, Sr)]

Marcel is the greatest He saw through Brian M instantly .
Thanks Marcel … Roy

[Brian_A.MacNeish]

@mcyr

Well, since we are just giving opinions on what the problem may be after all the information supplied, why don’t you the GodFather of all HI’s tell us exactly what caused the problem, then we will all know.
I think you are the one talking circles here.

I gave the reasons in post #3 but everyone else tried to make it a much larger problem than it appears to be!

I have seen exactly what happens in the field when a vapor barrier is installed on the inside. I have taken some apart due to the same problem.

Yes, the earlier ways of insulating a basement walls with batts and wood studs was a “hit and miss” affair with a lot of failures due to lack of building science knowledge of airsealing, code required humidities for wood framing, proper drainage, etc. But I have seen quite a few basements that have been in place for 15-20-25+ years with older technioques and no apparent problems. Just because the VB was on the inside directly behind the drywall did not gaurantee failure just as it did not gaurantee success.

(1) The wall system that Patrick showed had no visible mould or active mould odour (or he probably would’ve mentioned the odour) inside when opened.

(2) The studs showed 19% moisture…I have seen 17-18 to 21-22% in essentially “dry” (no leaks) basement wall systems, so the 19% is alright to myself. Much framing goes in at moisture contents above the code required 19% here…hard to find a contractor or carpenter with a moisture meter…they and the building inspectors don’t care!! So when I find studding in this location that has dried to 17-22% since installation, I think it’s a win!!

(3) The drywall apparently showed no deterioration through its thickness from the back paper to the finished inside layer or else this would have been mentioned (I assume).

(4) so we have an interior surface “on the paint” phenomenon, essentially surface mould…caused by ambient high RH’s caused by dead air, no heat being on or on at very low levels to save energy. Without heat being created to cause sufficient air movement (or a forced air heating system), corners become microclimates with essentially dead air pockets that become cooler. A shown last night, 40%, 20C (68F) air when cooled to 10C (50F) now has an RH of 77-78%. When you read/consult about ambient RH’s, 50-55% or lower is always recommended to prevent surface mildew/mould growth.

Another other possible problem is a piece of furniture in the corner blocking heat/air movement from getting behind it…leads to the cool/cold microclimate that supports/encourages mould growth.

In 34 years hanging around this part of the industry, have seen these things many times!

Extruded foam is the answer when the foundation walls don’t leak.
Definitely a better system with a much higher chance of not having problems… assuming a leak does not occur after the system is installed ). With code only foundations, this is never a guarantee (unless you don’t finish it for 3-4+ years and know there are no leaks…even then not 100% foolproof)!! There are techniques that lessen chances of problems with small leaks after finishing the walls.

And do we all know if that is the case here.
No, Might it be humidity, maybe.
Mould is always a humidity problem!!

In anycase, we are all speculating except you of course.

So do we have a leaking concrete wall, blocked drainage tiles, poor grading at the exterior, lack of air space behind the batts and the foundation wall causing this? From the info supplied so far, I don’t think so!

[gmathias1 (Greg Mathias, CCHI, CMI)]

I have seen this problem over and over as a carpenter doing reno’s and as an HI. The problem is the tar paper that is put up on the interior of the wall. If a concrete wall cannot breath then when they sweat the moisture has no where to go. The proper way to do this is: 6 mil poly to grade and swept under the interior 2x4 or 2x6 frost wall. If you put it all the way up the vapor from sweating will have no where to go. then you install the insulation and then the vapor barrier. Drywall follows.

[gmathias1 (Greg Mathias, CCHI, CMI)]

@gmathias1

I have seen this problem over and over as a carpenter doing reno’s and as an HI. The problem is the tar paper that is put up on the interior of the wall. If a concrete wall cannot breath then when they sweat the moisture has no where to go. The proper way to do this is: 6 mil poly to grade and swept under the interior 2x4 or 2x6 frost wall. If you put it all the way up the vapor from sweating will have no where to go. then you install the insulation and then the vapor barrier. Drywall follows.

Forgot to mention the required 1" air space so that air can move around behind the wall to help keep it dry.

[Brian_A.MacNeish]

@gmathias1

I have seen this problem over and over as a carpenter doing reno’s and as an HI. The problem is the tar paper that is put up on the interior of the wall. If a concrete wall cannot breath then when they sweat the moisture has no where to go. The proper way to do this is: 6 mil poly to grade and swept under the interior 2x4 or 2x6 frost wall. If you put it all the way up the vapor from sweating will have no where to go. then you install the insulation and then the vapor barrier. Drywall follows.

Greg:

Yes, the tarpaper is the wrong material to place in that wall system but not because it will not “breathe” (I hate that word) but because it is a permeable paper…it will let soil moisture (if poor or deteriorated exterior dampproofing) or leaking water behind it at the concrete to diffuse inward into the insulated wall system…not a good situation.

The 6 mil poly moisture barrier at the concrete as you described is a system that has a chance of working but excellent detailing/airsealing must be carried out. The framing being put into this “plastic bag with an open top” must be dry!!!

From “Keeping the Heat In” from the Canadian Government"
“Use dry lumber for the framing. If not, allow the framing to dry for at least two weeks before adding insulation and covering the wall with the air and vapour barrier. Some temporary bracing may be tacked on to keep the wet studs from twisting as they dry.”

[Brian_A.MacNeish]

@gmathias1

Forgot to mention the required 1" air space so that air can move around behind the wall to help keep it dry.

Don’t shoot your self in the foot anymore!! What document from a recognized agency or expert says there must be an air space?

From “Keeping the Heat In”:

Framing a New Wall
The next step is to install a wood-frame wall in the basement. There are two approaches. You can install the new wall flush to the old wall using 38 mm x 89 mm (2 x 4) lumber. Alternatively, you can use 38 mm x 64 mm or 38 mm x 89 mm (2 x 3 or 2 x 4) lumber built out from the wall by 64 mm (2 1/2 in.). The second method takes up more room, but does provide more insulation, less thermal bridging through the studs and better moisture protection.
**
Insulating
Insulation is installed in two layers (for the thicker spaced-out wall system) . The first is a horizontal layer between the studs and the wall.** It is important that the insulation is tight against the foundation wall.** Next, install a vertical layer and make sure it fits snugly between the studs. There should be no gaps or air spaces where convection currents could help heat to bypass the insulation. Insulation should be wide enough to match the stud spacing and be cut to fill the full height of the wall.

[Brian_A.MacNeish]

@rcooke

Marcel is the greatest He saw through Brian M instantly .
Thanks Marcel … Roy

You wish…

Many couldn’t see the answer when it was right in front of them in post #3.

In post #4, Patrick saw and recognized the correct answer:
“It makes sense, how can we control that?”

but others chimed in and it moved backwards from there!!!

Don’t get too NACHI-fied, Patrick…others from outside have knowledge also!

[gmathias1 (Greg Mathias, CCHI, CMI)]

@Brian_A.MacNeish

Don’t shoot your self in the foot anymore!! What document from a recognized agency or expert says there must be an air space?

From “Keeping the Heat In”:

Framing a New Wall
The next step is to install a wood-frame wall in the basement. There are two approaches. You can install the new wall flush to the old wall using 38 mm x 89 mm (2 x 4) lumber. Alternatively, you can use 38 mm x 64 mm or 38 mm x 89 mm (2 x 3 or 2 x 4) lumber built out from the wall by 64 mm (2 1/2 in.). The second method takes up more room, but does provide more insulation, less thermal bridging through the studs and better moisture protection.

Insulating
Insulation is installed in two layers (for the thicker spaced-out wall system) . The first is a horizontal layer between the studs and the wall.** It is important that the insulation is tight against the foundation wall.** Next, install a vertical layer and make sure it fits snugly between the studs. There should be no gaps or air spaces where convection currents could help heat to bypass the insulation. Insulation should be wide enough to match the stud spacing and be cut to fill the full height of the wall.

did not know I was speaking to the guru of framing. I guess my 24 years as a framer was for nothing. You always leave an air space between the concrete and the wall. If not thermal bridging can occur and the concrete wall will begin to sweat.