Mold caused by wood stove heating?

[RoxyL]

Hi! Though I've thoroughly enjoyed lurking here, I'm brand spanking new to any kind of wood stove. We are building a two story 2400sqft home with a wood stove in the 1400sqft downstairs. We live in the damp Pacific Northwest.

We have friends who heated their similar two story home (built around 2000) exclusively with wood. The upstairs would get pretty cold, but they'd just hurry downstairs in the mornings to warm up. Here's the problem and/or question. They are moving and during the inspection it was found that they have a huge mold problem in the attic. It was built to the standard of all the neighboring homes which have no problems. The only difference I can see is the heating. In our damp climate, is there any way that heating with wood could be the cause of this kind of mold problem? I'm thinking, a tight house with heat differentials between the top and bottom floors and condensation buildup or something (really I have no idea what I'm talking about

Anyway, it's got me rethinking our idea of trying to heat mainly with wood like our friends (we will have central heat to supplement if needed). Any reassurance or advice you could offer?
Thanks!

 

[daryl]

HI Welcome to the forum
On your question about causing mold.If there is a big temputure swing between upstairs and down. I could see that the difference in temp and high humity migrating to the upper floors might condence and keep things damp enough to promote mold growth. I would put a wood furnace add on to your forced air system if thats what your putting in your house.That way you have a balenced system.heating all the areas the same not just the basement.

 

[quads]

From my experience, wood heat seems to be drier and/or causes the air to be drier than other types of heat. I keep a tea kettle on the stove to help ADD moisture to the air.

 

[DAKSY]

I'd say the mold is caused by an improperly ventilated attic.
There are formulae to calculate the amount of air flow required.
That's what I'd check first.
Do they ridge or gable vents along with soffit vents?
If so, are the soffit vents blocked by overzealous insulators?
JMHO...

 

[EatenByLimestone]

I've seen where I've over humidified my house and after the warm air hit the cooler air in other rooms moisture precipitated out. The mildew tended to gather on window sills and in corners.

For attic mold I'd first look to see if the bathroom vents empty straight into the attic. I've seen it more than once...

Do your friends have an attic mounted AC unit. The AC was mounted up there in my house in TX. If the drains became clogged I could see where it would spill the precipitate out into the attic. I'd think a wet spot would form on the ceiling, but it might not have shown up.

Attic venting and even leaks in the roof that let water down around a chimney or vent pipe could also introduce enough water for mold to grow.

Matt

 

[BrotherBart]

Yep. Everything points to inadequate attic ventilation. Had it happen here. Two different builders built our house and the closest one down the hill about the same time. The folks down the hill not only had mold problems but had to replace their shingles after only seven years because the original ones literally got cooked because of poor ventilation. As to does wood heat cause it? I have to say no based on experience because we live in a very humid part of the country too, have heated with wood for 25 years and I was up in the attic three weeks ago and I can smell mold from three hundred yards and didn't smell or see any up there. But we have adequate soffit vents and a power attic ventilator that comes on any time the attic reaches 95 degrees.

 

[jdinspector]

Hi! Though I've thoroughly enjoyed lurking here, I'm brand spanking new to any kind of wood stove. We are building a two story 2400sqft home with a wood stove in the 1400sqft downstairs. We live in the damp Pacific Northwest.

We have friends who heated their similar two story home (built around 2000) exclusively with wood. The upstairs would get pretty cold, but they'd just hurry downstairs in the mornings to warm up. Here's the problem and/or question. They are moving and during the inspection it was found that they have a huge mold problem in the attic. It was built to the standard of all the neighboring homes which have no problems. The only difference I can see is the heating. In our damp climate, is there any way that heating with wood could be the cause of this kind of mold problem? I'm thinking, a tight house with heat differentials between the top and bottom floors and condensation buildup or something (really I have no idea what I'm talking about

Anyway, it's got me rethinking our idea of trying to heat mainly with wood like our friends (we will have central heat to supplement if needed). Any reassurance or advice you could offer?
Thanks!

I agree with others about inadequate ventilation. I also doubt that heating with wood would actually add moisture. On the contrary, it usually causes the home to be too dry. However, if your neightbor's home is similar construction to neighboring houses, I think that there is more to the problem than first meets the eye. Frequently, moisture can migrate up from lower levels into the attic. I would guess that there is some soft of moisture source in the home that created excessive moisture to collect/condense in the attic. Some thoughts...
Do they have a large number of people living in the home (normal breathing and perspiration can add a great deal of moisture into the home)
Did they store firewood in the house? This can add a great deal of moisture, as I'm sure molst of the others on the forum will agree with.
Do they dry clothes in the house by hanging them on a drying rack or clothes line?
Do they fail to use the bathroom exhaust fans or kitchen exhaust fan?
Fish Tanks? Hot tub in the house? Room Humidifier in a baby's room?

I can think of many other scenarios in which excess moisture is put into the home's air. Any of these can add EXCESSIVE moisture into the home. Ventilating the attic (and the rest of the home) would help to prevent mold growth, but cutting down on the amount of moisture being introduced into the house is where I'd start looking.

Don't worry about heating your house with wood. Try it, you'll like it!

 

[begreen]

Doesn't sound like it's wood heating related. Overkill can be as bad as underkill when it comes to moisture. This reminds me of a very large wooden boat built locally. It hit the waters and in a few years had serious issues with rot. The owners had spared no expense in building the boat. But an over-anxious and under-informed builder, trying to appease the new owner's concerns about corrosion, had gone way overboard in trying to protect the hull. By overprotecting the boat with a large amount of zinc tied to the grounding plane system, they actually created a battery. The hull destroyed itself by applying the unintentional salt water battery voltage to every nail in the hull.

It sounds like your friends had at least a couple bad decisions made by either them or the contractor building the house. It happens. The issue with the cold upstairs is obvious, design the house so that wood heat the house well and thoroughly. We have a 1924 2000 sq. ft. farmhouse that heats relatively evenly in the same climate. Why?, open floorplan, no cathedral ceilings and it has a well placed, central woodstove. The second issue is ventilation. At some point someone made a bone-headed decision and left off ventilation. When it's 35 outside and 70 inside, with a lot of moisture on both sides of the barrier, wood needs to breathe. Just like a glass full of ice, the moisture is going to condense where the cold meets the warm. This is the area that needs ventilation. Typically this is in the attic.

Getting a good contractor that understands ventilating and how a building deals with moisture (from rain or from human showering) is important. Visit www.buildingscience.com for some good research and guidance in how to mitigate moisture issues.

 

[madrone]

What everyone else said. I found one of my bathroom fans was venting into the ceiling soon after I bought my house. Not pretty. Sometimes it's as simple as a loose duct for the bath fan, or as mentioned above, plugged soffit vents. I'd expect mold and condensation on interior surfaces rather than the attic if it were an over-humidified, warm/cool zone problem. Woodstoves tend to dry the living space out.

 

[coolidge]

Thats what i would look for first( bathroom fans vented to attic). I too have seen that many times. Also look for the size of pipe coming from the fans. You should go from the 4" outlet to a six" smooth bore pipe immediatley. Not doing this will cut your cfm in half.

 

[jdinspector]

Getting a good contractor that understands ventilating and how a building deals with moisture (from rain or from human showering) is important. Visit www.buildingscience.com for some good research and guidance in how to mitigate moisture issues.

I agree, buildingscience.com is a great website to start with. The author, Dr. Joe Lstiburek (sp?) is world renowned for his views on how buildings work. I've seen him speak several times and he knows his stuff.

In the case of RoxyL and the neighbor, I'd bet it's a simple fix. Get rid of the moisture source and the mold will stop. Unfortunately, they still have an existing mold problem to deal with. That won't be a simple problem to fix. Speaking from experience, I'll bet the inspector has made it a big issue and the potential buyer of the home is looking for the seller to fix it. In the current market place, the seller doesn't have too many options. Further, there are some scammers out there who will turn the whole mold issue into a big (and expensive) deal. I feel kind of bad for the neighbor.

 

[firefighterjake]

Hi! Though I've thoroughly enjoyed lurking here, I'm brand spanking new to any kind of wood stove. We are building a two story 2400sqft home with a wood stove in the 1400sqft downstairs. We live in the damp Pacific Northwest.

We have friends who heated their similar two story home (built around 2000) exclusively with wood. The upstairs would get pretty cold, but they'd just hurry downstairs in the mornings to warm up. Here's the problem and/or question. They are moving and during the inspection it was found that they have a huge mold problem in the attic. It was built to the standard of all the neighboring homes which have no problems. The only difference I can see is the heating. In our damp climate, is there any way that heating with wood could be the cause of this kind of mold problem? I'm thinking, a tight house with heat differentials between the top and bottom floors and condensation buildup or something (really I have no idea what I'm talking about

Anyway, it's got me rethinking our idea of trying to heat mainly with wood like our friends (we will have central heat to supplement if needed). Any reassurance or advice you could offer?
Thanks!

Just echoing here . . . I don't think a woodstove would create mold . . . as others have said, woodstoves tend to dry things out if anything which is why many folks use steamers, tea pots, etc. to add some moisture to the air. Like others . . . I think the issue is with the ventilation in the attic.

 

[Highbeam]

I also live in the northwet and heat entirely with wood. In the winter when you heat the cold air it becomes very dry. My interior humidity is in the teens whether it is raining or not.

In our part of the country it is very common to find kitchen vents and bathroom vents just venting into the "ventilated" attic. These moisture feeds can condense on the inside of the roof and cause mold. That's your most likely cause.

Wood heat can only help dry the home out.