Video: Why is there Mold on my Windows?

Mark: Hi, it’s Mark Bossert from Top Local Lead Generation. We’re here with Mr. David Fairbairn of Fairbairn Inspections in Vancouver talking about mold. How’re you doing today David?

David: Oh, Mark I’m ready to talk about mold today.

Mark: Great!

David: I hope you’re looking forward to some mold.

Mark: Mold sandwich. So the question you wanted and this is funnily enough, the question I asked you last week, is why is there mold on my windows?

David: Yeah, so we’re going to talk about mold on windows and so this is probably one of the most asked questions and yourself included, I think we were chatting before the hangout and you we’re actually saying, I’ve got some mold on my windows, what’s going on? So I said o.k., let’s do a talk on this and explain what’s actually happening. I’d like to maybe share the screen
Mark, is that o.k.?

Mark: Yes

David: o.k. I just going to pull up some photos, I actually have some photos from various places, so I’m just going to put it up on the full screen here. I don’t know if you can see that. . .

Mark: I can see that.

David: o.k. so we’ve got some mold on this window here. Now this is a photo of probably you’ve seen a lot of houses like this, so what’s going on with this? So this kind of mold can look kind of scary when you first pull back your drapes and you look at your window and you’re going, first of all its black and anybody who’s watched TV or read any articles on home improvement, you’re going to hear toxic black mold so I get asked this a lot. Is this black mold? The first thing I want to get out of the way is black mold is the wrong name for it. They are talking about a certain species of mold called Stachybotrys and it’s not always black, it can come in different colours, it can come in blue so I want to get out of the way, you actually can’t tell what kind of mold you have unless you actually take it to a lab and sample it. So we know what common types of mold we have indoors so we can usually guess it’s between three different species but if ever have any doubts just as a disclaimer, always call a certified mold specialist who can come out and assist you with your problem before you go jumping to any conclusions. So anyways, we’ve got this mold growing on a window here so basically what we have is, if you think about a house you’ve got a window which is going to be probably the coldest spot on your wall. So first of all it’s on your exterior walls, second of all, a lot of heat loss through windows, right? So this one here, we’ve got an aluminum window frame, I believe it’s an aluminum frame window so it’s probably a chilly day and we’ve got a high indoor either temperature and or humidity, right. So mold on windows, I’m going to go ahead right away and say 99% of the mold on windows problems is going to be coming from indoor humidity so you’ve got a lot of areas where humidity and moisture can originate in homes and the number one is going to be your shower, you’re showers can generate a lot of moisture and cooking, if you’re cooking pasta, you’re going to be sending a lot of water and steam and vapour into the air and your moisture floating around the air is going to settle on the coldest spot just like when you take a can of coke out of the fridge and it gets frosty, right so that’s the same concept here; we’re creating condensation and windows are hot spots for condensation because they’re so cold. So were looking at that and basically the first step you can do to prevent moisture on windows is to ventilate your house properly so this is point one, you’re going to ventilate the house properly. So how is the moisture getting out of the house? Is it clinging to the windows or is it being ventilated properly, so let’s look at a few options for ventilating the home.

So the most obvious option here is we’ve got a bathroom fan and unless you live in a kind of an older house that’s never been updated or you’ve never renovated the bathroom, you probably have one of these in your home and basically we’re going to want to make sure that that fan is running not only when you have a shower but in some cases we’re going to want to have it run for quite a while after you have the shower. So if you go to a newer home, I think yours is actually quite new, you’ve got an eight year old home, we’re actually going to want to run that fan for I believe the building code actually requests that it run for eight hours in every twenty-four hour period. So you may actually have a timer on your fan or in some areas we may have the fan hard wired to run twenty-four hours a day. As the houses get newer the draft is reduced, you’ve got a tighter house, you got a more weather resistant house and there’s not as much in the way of fresh air flowing through the house. You’re going to have to mechanically ventilate it and that’s our number one way to do that.

This is a control that you see a lot in our area in Vancouver, this is a humidistat. So what this does, this was used a lot during the 90’s is that it will actually read the relative humidity inside the house and it will click on the bathroom fan to exhaust the air out of the house when it goes over a certain threshold so this one here is actually turned fully on, I don’t think they realized it was all the way on when they took the picture but the recommended setting for these that we usually see is about 40 to 50% relative humidity so you’re going to set it between 40 and 50 and when you shower and when you cook it’s naturally going to turn on the bathroom fan. Now these kind are extinct now in our area in new construction because our requirements are just a little bit higher and we’re actually having to run the fan for a set period of time.

So here’s a way you can avoid moisture problem windows, this mess of lines here, this is a cross section of what’s called a thermally broken window. Now in the old days we didn’t have what’s called a thermally broken window, it would just be you’ve got the glass sitting in a metal frame and there’s metal connected all the way through, underneath the glass and you’re transferring heat underneath the window very effectively outside and you’re cooling off the window. Same thing, you know, you put a spoon in a hot bowl of soup and the spoon gets hot, that’s convection you’re losing heat across the material, so now what we’re doing, we got our thermally broken windows, this is a newer style of window and we’ve actually got this Polyamide Thermal strips that are actually separating the frame and they’re actually broken, breaking the frame in half and they have very little thermal transfer so they are keeping the inside of window warm and the outside cold and you’ve got this break, so you can imagine the condensation would be a little bit lower on this style of window.

Just going to show you, this is a microscopic shot of some mold growing and the type of mold is called Cladosporium. Now Cladosporium is a very, very common indoor mold and when you see mildew and mildew is a type of mold, you know a lot of time you can get mildew and it’s going to be what’s called Cladosporium. Now Cladosporium grows anywhere that you’ve got warm sort of wet conditions, you see it a lot growing on towels, cheese, bread, and things like that, so it’s a common indoor mold and this is actually under a microscope. This is how they identify the type of mold you have.

So one last thing, I’m going to show you with our bathroom fans, if you’re going to install bathroom fans, it’s just a reminder, you don’t want to install too powerful of a bathroom fan because you can actually pull the heat out of your house and if you install a bathroom fan that’s oversize for your bathroom you can increase your heating bills quite a bit so the calculation that we use is take the square footage of the bathroom and multiply it by 1.07 which gives us, it’s usually slightly larger than the square footage of the bathroom. So if you had a 80 square foot bathroom you’re probably going to want to put a 90 CFM which is cubic feet per minute bathroom fan into the bathroom and that’s going to properly ventilate your bathroom so if I was to summarize what’s causing mold on windows, interior moisture conditions are going to account for almost all of it and if you can properly ventilate your home you can prevent that problem and the last thing I’ll leave you with is, if you need to remove any mold from your windows technically you should be calling a mold removal or abatement company but if you want to do it at home the CDC recommends one part bleach to ten parts water mixture and put that into a little spray bottle, spray it along the bottom edge of your window and clean it off and repeat as necessary and that is one way to remove the mold. Now if it returns then you should call somebody so that is what causes mold in windows. If you have a problem please give me a call, I’d be happy to take a look at it, we can do sampling, we can take a swab test, we can test the air in your home, there’s just a myriad of tests that we can actually do to make sure you that have a healthy home.

Mark: Awesome stuff David. So just to clarify, you’re a certified mold specialist as well as doing home inspections, is that right?

David: That’s correct, yes. So we do both residential, commercial inspections for property purchase and then of course the mold division where we do indoor air quality testing, we can do consulting if you have a leak or flood, you need post or pre remediation consulting, we can do that as well, just give us a call, we’d be happy to give you a quote.

Mark: Awesome, so one part bleach to ten parts water for window mold, to clean it up ourselves and get the fans running.

David: There you go Mark, yeah. You got a project for this afternoon I think, eh?

Mark: We’ve been running the fans a lot and it makes a big difference. So that pretty much sums it up. We’re going to explore mold a whole bunch more with David over the next few weeks, so come back and see us and if want to get hold of him, there’s tons of information on his website or give him a call 604-395-2795. Thanks a lot David.

David: Thanks Mark, talk to you soon.

About the Author DavidFairbairn

Author David Fairbairn is a certified, licensed home inspector serving Vancouver and the Lower Mainland. He has been featured in the media and has contributed to "24" Newspaper, and Global TV. He has spent years working with residential and commercial building projects, and holds a Power Engineering License in BC. Why not give him a call for your next Home Inspection? Call 604 395-2795 or email today!

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