What's causing this?

[gtblum]

A row of townhomes built in 94. The staining is over the top of bedroom windows that face west, without any treeline obstruction to sunlight.

Any ideas?

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[Marc]

Past event with no evidence remaining other than the 'stains'.

Just a wild guess.

Marc

[gtblum]

I forgot to include, it's the same on the homes to either side.

[Tom Raymond]

Cheap ass windows, no insulation at the headers, no insulation in the RO. It's the same ghosting phenomenon that happens on the inside at missing insulation and thermal bridges.

[Chad Fabry]

Exactly what Tom said- I've seen it a few times in cheap ass developments.

[Les]

CAW. Really common in the cornfield palaces around Michigan.

[Garry Sorrells]

2nd fl window.

Window in bathroom? Bathroom vented?

Is there a heating register below window?

Would also question insulation at header.

Side of house also looks like staining.

Might look to sump pump location as a cause.

Or HVAC duct work location as cause. Then insulation again.

[David Meiland]

Air leakage out/around the window.

[Marc]

I don't quite understand the mechanism that results in the staining.

Is it moisture escaping?

Marc

[Tom Raymond]

Conditioned air. It carries water vapor out that then condenses on the cold siding, dust and dirt stick to that before it freezes.

It is directly above the windows because the leak is at the RO or between the sash and head jamb, or both.

[kurt]

I'm behind on acronyms. What's RO?

Them's some cheap ass wood boxes with big holes masquerading as windows.

[Tom Raymond]

Rough Opening.

[Jim Katen]

Never seen it in my climate.

Why only on the west sides?

Why would trees obstructing the sun prevent this from happening?

[Tom Raymond]

It's just like ghosting that occurs on the inside of the building. It can vary based on any one of hundreds of variables.

I would think that all the openings have some degree of this. I'd have to see it first hand, and possibly open it up, to see why it's worse on the west side.

[gtblum]

Never seen it in my climate.

Why only on the west sides?

Why would trees obstructing the sun prevent this from happening?

Jim, Not preventing it, promoting what looks like the fungal growth typically seen on the north side of a wall, due to the lack of sunlight.

Why only on the west side of all of these places is what I'd like to know, too?

Because of exposure to the afternoon Sun?

[Les]

Building orientation on site. Residual heat from sun for west side. Most weather in my area and that area is from south and west. I can sit in the street and watch hoary frost move around these houses.

We also see the stain as green on occasion and really black when the building is in wide open fields that have lots of palaces and no trees.

The same ghosting is common for us on nearly all vinyl siding. Especially that siding that is directly on foam and no tyvek.

[kurt]

Rough Opening.

Proof I've lost it.....

[John Kogel]

Tom says it is ghosting which is soot.

Les says it is black or sometimes green, that is algae growth.

Which is it? I can't tell from here. We need a swab sample. []

I've noticed black soot ghosting where there is a busy road close by. Carbon from diesel engines. and maybe dust from brake pads.

Algae stains, we have plenty of that here. But like Jim, I've not seen it concentrated above windows like that.

[David Meiland]

Why only on the west sides?

I bet it has more to do with those being bedrooms than it does with the windows facing west. Bedrooms are often small, heavily occupied rooms. It could also be the case that those rooms have supply registers but no returns, leading them to be slightly pressurized when the doors are closed and the heat's on, causing exfiltration.

[Jim Katen]

. . . It could also be the case that those rooms have supply registers but no returns, leading them to be slightly pressurized when the doors are closed and the heat's on, causing exfiltration.

Good thought.

Still, never seen anything like it. Maybe its just not cold enough here.

[Les]

Why only on the west sides?

I bet it has more to do with those being bedrooms than it does with the windows facing west. Bedrooms are often small, heavily occupied rooms. It could also be the case that those rooms have supply registers but no returns, leading them to be slightly pressurized when the doors are closed and the heat's on, causing exfiltration.

That is a good thought.

The color really is only an indicator or what is contained in the air; soot, lead from exhaust, rubber fines, algae, etc. Likely there is mold and the entire neighborhood should be warned and evacuated.

I am sure it is air, warm air or at least conditioned air.

Thanks David for the new info and thinking.

*info means information (for Kurt)

[kurt]

Yeah, info. The new stuff has squeezed out the old stuff. I find it shoved into corners in my house. I'm toast.

Astute observations. I especially like the BR supply/no return theory. West may be, and probably is, a coincidence, and nothing more.

[Marc]

Folks sleeping in bedrooms with the door closed makes those bedrooms sources of humidity. Compounded with no sunlight at night time to warm the siding and leaky window installations and you have is a 'perfect storm' for that sort of result.

Marc