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Log homes - Breathable & Mold Resistant?

 
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I am planning on building my first home. It will be built in Northern Scandinavia, so the climate is pretty cold with lots of snow.

I want to build it completely mold resistant, and also free of VOCs (as much as possible). I know that "breathable walls" is a well-known concept on this website. I was wondering if a traditional log home would be suitable for this, or if you recommend something like Durisol/Faswall instead? I could also get "Hebel blocks".

Wood however is the most common building material in my area, and I would for sure be able to find contractors who could help build with it.
 
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Location: Seymour, MO Zone 6a
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Sooo, the devil is in the details, but the short answer is no, IMO.

Wood gives off plenty of VOCs, some species more irritating to some people than others. Coniferous species tend to be more offensive in my area. Drying and curing the wood helps.

Rot in log walls depends on species, construction, exposure, and location, but generally log walls are prone to mold. In my area, log siding seems to be the worst. So, in short, this isn't a definite no as to rot, but highly problematic for lots of folks and should be given careful consideration.

As for breatheability, if you use a finish that breathes, you do get some. Again, depends on construction, species, and finish, and to some extent location and sun exposure.

One issue with conventional style log cabins is insulation. If your site has moderate seasonal temperature swings, you might get away without insulation, but you say it is cold, and it is my understanding that the r value of a solid uninsulated log wall tends to be pretty low, again species matters, and of course, r value isn't the whole story. If you have unlimited free heat, say from wastewood, you might be ok with this.

Timber frame infilled with something else might be a better option to my way of thinking.
 
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Location: Abkhazia · Cfa (humid subtropical) - temperate · clay soil
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What about AAC?

I have recently rediscovered it while looking for insulation materials that are mold and insect proof, not a mess to install and could be produced locally (lots of limestone here) if I can get my hand on an autoclave.
 
Anders Hedlund
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Luke Townsley wrote:Sooo, the devil is in the details, but the short answer is no, IMO.

Wood gives off plenty of VOCs, some species more irritating to some people than others. Coniferous species tend to be more offensive in my area. Drying and curing the wood helps.

One issue with conventional style log cabins is insulation. If your site has moderate seasonal temperature swings, you might get away without insulation, but you say it is cold, and it is my understanding that the r value of a solid uninsulated log wall tends to be pretty low, again species matters, and of course, r value isn't the whole story. If you have unlimited free heat, say from wastewood, you might be ok with this.



Thanks for your reply. I was thinking that since wood is a natural substance, that it would be healthy for us. After all, we've lived in wooden houses for a very long time, and among wood inside the forests for all of human history.

Sebastian Köln wrote:What about AAC?

I have recently rediscovered it while looking for insulation materials that are mold and insect proof, not a mess to install and could be produced locally (lots of limestone here) if I can get my hand on an autoclave.



Yes, this is the same as "Hebel blocks" (as it's known in America). But in Europe we just call it AAC. I am also curious to hear more about it. I wonder how well it works in cold climates with lots of snow.
 
Sebastian Köln
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I don't know a lot about AAC. Wiki says it was invented in Sweden, so probably appropriate for the climate.

How about combining both? AAC on the outside and wood on the inside? (I want to avoid exposed wood here because insects will destroy it rapidly, but that is probably not an issue for you.)
 
pollinator
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We lived for 10 years in a 150 year old square-log house in Ontario, Canada. We stripped it back to the logs as there were many many layers of other things on top (1970s fake wood panelling, 1930s? pressboard panelling, cereal boxes covering the original horsehair plaster, whitewash on the logs themselves), removed the original chinking, replaced with fiberglas insulation and rechinked. There were no mold problems and in fact we had to add humidity in winter. By the time we finished the renovation, it was one of the most comfortable houses I've ever lived in.

Friends of ours built a new roundwood scribed log house in New Brunswick, Canada, and now have lived in it probably 15 years or so. Again, no mold, extremely comfortable house, easy to heat.

I'm a bit bemused by some of the criticisms that people have of log houses as it is very different from my experience. Both houses I mentioned above were in cold, snowy climates in winter, with lots of rain in summer. I don't know how they are in other climate types.
 
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I lived in log houses for fifty years and while I wouldn't build another one deliberately, I wouldn't hesitate to buy one either, Everything organic can mold, not all molds are detrimental to health and bleach is astoundingly efficient at killing spores.

The biggest cause of rot is unintended buildup of moisture, (leaking toilet flange, dripping sink drains and supplies......and too tightly built structures)!
Of the three the last one is the biggest culprit in modern times, airflow through and past surfaces to carry away moisture is never a design parameter and we pay for it dearly.
Even areas specifically designed to have airflow (bathrooms, laundries) have airtight bubbles built into them, often there is an evacuation fan but no designed cross flow, if your fan changes pitch when you open or close the door you can be sure the fan is effectively useless, when the door is closed, simply burning electricity in a vacuum until the door is opened again. Floor coverings such as linoleum and vinyl plank entrap moisture and hold it to perishable (organic) materiel.
With modern home often putting ventilation fans on separate switches from lighting, fans are frequently not used during showers and wash ups.
Vents into shelving and closets used to be de rigueur, but are not even a consideration any more, transoms and doors cut 2" above floor level were not a careless feature, but a deliberate design to ensure airflow in a time when a single source of heat carried the whole house,
With central heating the new paradigm has been control, control, control with awful consequences, usually not foreseen by the denizens thereof.
Efforts to conserve energy by closing vents and pushing towels under doors,have left pockets of dead air, and any minute source of moisture becomes a wellspring of decay,
Older windows with their sharp temperature differential are a font of condensation, boxes bags and piles of cloth, / clothing hold moisture to walls and give decay a starting point....by simply blocking airflow.
Unvented gas heaters are a horrific source of added moisture.

If I was building new, I would build with non organic materiel, and ensure airflow. Normal fiberglass will not support mold...but the paper backing will. Sheetrock (greenboard) can be bought with antimicrobial additive built in. Steel studding will carry it to its logical conclusion....but steel studs are weak in the case of fire.
VOC's are rarely a consideration...with adequate airflow, cross ventilation is your friend, and passive solar, a savior, solar preheated air reduces heat load, sunlight kills mold, and and a tidy house, minimally stocked, (as in not occupied by a hoarder!) will keep airflow at a maximum.
 
Luke Townsley
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I do know when I first saw AAC/aerated concrete blocks was in Belarus over 25 years ago. They were building with them like crazy and I know they get plenty of cold (around Minsk). I think it has a lot of promise for meeting concerns about mold, breatheability, and VOCs. With any type of construction, the details are important as is maintenance.

There is no perfect building material that automatically meets all needs, regardless of design considerations, and is plentiful and cheap. If there is a material or style you really want, study it, understand the strengths and limitations, design the entire structure it to meet your needs and enjoy it.
 
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With traditional log home construction methods, mold is rarely an issue.  The problem with log construction is getting it tight enough (that's what chinking is for) to stay warm inside.  If you start playing games with siding and extra insulation (inside or out) with a vapor barrier layer, then trapped moisture might start becoming an issue.  

Every log cabin I've ever lived in has been dry as a bone inside.  You use lots of heating to keep the place warm, cold winters tend to be very dry, and so your interior air starts out dry and just keeps getting dryer.  The cabin I grew up in?  We always had a pot of water on the wood stove steaming away, just to avoid dried out sinuses and constant bloody noses.  Mold? Ha.  That place has been uninhabited for years and was this close to falling over last time I went inside, but it was still dry as a bone in there.  

 
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