Bale Smell

I built a straw bale house two years ago. I hired a consultant, plastered the walls interior and exterior, and have a large roof overhang. All that said - when it is warm, I can smell straw. I have used a moisture meter in a dozen places and the walls are hovering between 8%-12%. I found one spot that was particularly vulnerable to moisture penetration that was 14%-15% but I have patched it and it is dropping as well. And yet I smell straw. Anybody had this problem or fixed this problem?

Jason Klassen wrote:I built a straw bale house two years ago. I hired a consultant, plastered the walls interior and exterior, and have a large roof overhang. All that said - when it is warm, I can smell straw. I have used a moisture meter in a dozen places and the walls are hovering between 8%-12%. I found one spot that was particularly vulnerable to moisture penetration that was 14%-15% but I have patched it and it is dropping as well. And yet I smell straw. Anybody had this problem or fixed this problem?

I don't have a solution to your problem... but your query opened up a question of my own in this regard. How bad does a more conventional stick built house smell? I am sure that because it is what I grew up in and live in now, I just don't notice the smell.

So I am wondering:
  A) Is it bad for a straw house to smell like straw (assuming no allergy involvement)

  B) what does a healthy house smell like?

I think with a straw house, very dry is important... except that from my experience of drying fruit and even kiln dried wood, there is such a thing as too dry. over dried apples are weak and crumbly and kiln dried wood is not as tough as air dried (ask a boat builder). So straw probably needs at least some moisture to retain it's strength. Straw (and wood) derives it's strength from fiber cells. If those cells are over dried the walls can loose their integrity.

So perhaps someone with a straw allergy should not live in a straw house. Side note: the suits that allow people to work on the outside of the international space station, leak. Bears can smell the food inside a can. Is there any such thing as sealed.

I like the smell of straw. Had to go out and smell a straw bale just to be sure. Use it as a marketing term when you VRBO it or whatever: "Notes of straw indicate a wild maturity unique to this area yet seldom experienced."

Jason, welcome to Permies!  I'm laughing, but I swearing I'm not laughing at you -- I'm laughing at us.  You have just got a big dose of the thing I call the permies.com superpower: the ability to take any question and tear it apart, not always in a way that feels helpful to people who aren't used to it.  I wrote about it in another thread:

In The Fellowship Of The Ring Frodo famously says "Go not to the elves for counsel, for they will say both no and yes." Our local version of this ought to be "go not to permies.com for advice on how to do a thing, for they will tell you at length how to do something else entirely."

I'm afraid it's the permies.com superpower. That hard thing you want to do? People imbued with permaculture thinking are much more likely to have some clever scheme for doing an easier thing instead, or possibly even for doing nothing and calling it "more sustainable". I've been on the receiving end of this enough times to know how infuriating it can be, and yet it really is the permaculture way.

I'm afraid I don't have the foggiest notion whether or for how long your bale house should smell like straw, or what's to be done about that if you don't want the smell.  I promise that, if there is some expertise on those subjects here on the forums, it will land here in your thread eventually, to go along with our shenanigans.  And meanwhile, again, I say welcome!

Having thought about it a bit more. The question I think, is what the concern is. Just the smell or that things might be going bad, rotten or whatever.

If the smell is the only concern, I would suggest more airflow before anything else. Code requires 1 full air exchange per hour but I think that is minimum... lab rats need 8 air exchanges per hour so 1 is just enough to keep law suits from happening not to keep healthy.

If mold or other growth is a concern and the moisture content of the straw itself is high, I would want both large airflow and to remove some of the plaster skin and dry out the straw... I think. A natural render does allow moisture to pass. In any case, it is the moisture of the bales themselves and not the moisture measured outside the render. This site suggests the moisture of the bale itself should be less than 20%:
http://thelaststraw.org/bonus-articles/moisture-and-straw-bale-walls/

As that article points out, moisture inside the home comes from our activities and not the walls. However, the walls can absorb this moisture which again, points to ventilation.

added later as an edit:
the other question I should ask is if you have a concrete foundation. Concrete foundations tend to trap moisture, porous foundations such as gravel tend to be drier. (assuming in both cases that outside drainage is correct) Certainly all is not lost if your foundation is concrete it just means more ventilation would be required by the foundation to keep it dry.

This post reminded me of living in a traditional Japanese home while living abroad. I thought I would love the new tatami mat floors in two rooms of my home. I thought the stucco on an interior wall of my bedroom was weird. After 2 years and all possible weather situations it was the opposite,  the walls I loved the straw mat floors I absolutely hated.

You might want to see if overseas military people are posting stuff on facebook on how to deal with your straw smell problem or research deodorizing traditional Japanese flooring solutions.

Best of luck, or... you'll either get used to the smell or it will just drive you slowly crazy over the next few years.

EDIT: This is a question to Jason:

How thick is the inside plaster? 5 cm (2") of clay plaster should keep the smell in the wall.

Sebastian, not sure if that question was directed at me. If so, I honestly have no idea. The reason I liked the room with the Stucco walls is that it ended up being the warmest room in the house during the winter. Our home was heated with portable kerosene heaters. Even properly vented, that was just a migraine waiting to happen. The warmth was a combination of things, not just the walls. You learn to economize space when 4 months out of the year your house is basically downsize to 1 room for a whole family. That downsizing let's you see how little you have to spend to enjoy the true things that make your space a home. Currently on my 30th move. I think I've taken downsizing to an extreme, this move my whole house was less than 2000 pounds move weight.

Mary, sorry I didn't specify that the question was meant for Jason. For a movable house I can totally understand that one wants as little additional weight as possible.

Jason I think it's a VERY VALID question not to be scoffed at.   I intuited that your concern might be a potential for mold.   Hopefully more people who have actually built and lived with a strawbale house can answer your question.   Welcome to Permies - where personalities and ideas and knowledge are huge and diverse and we always try to be nice :)

I just googled the question and found this article.   It seems that 20% moisture would sustain mold,  but 12% is acceptable and normal so it sounds like you're okay.

https://www.strawbale.com/assessing-moisture-in-a-straw-bale-wall/

Jason Klassen wrote:I built a straw bale house two years ago. I hired a consultant, plastered the walls interior and exterior, and have a large roof overhang. All that said - when it is warm, I can smell straw. I have used a moisture meter in a dozen places and the walls are hovering between 8%-12%. I found one spot that was particularly vulnerable to moisture penetration that was 14%-15% but I have patched it and it is dropping as well. And yet I smell straw. Anybody had this problem or fixed this problem?

8 to 12% moisture seems a bit high to me for a two year old Bale house, I would expect it to be more in the 5 to 8% range.

So now I am wondering, is this a moldy type straw smell or a fresh, baled straw smell? How many coats of plaster are on the exterior? is this plaster cracking at the junction of the roof joists? are the eaves wide enough to prevent moisture infiltration?

The "project" bale house here has a three layer plaster on the exterior and a two layer on the interior and the plaster up at the joist junction was repointed this spring because it had separated at that point.
This house was built during a workshop teaching school.

If you can't find anything obvious that could be allowing the odor to "leach" into the home, you might want to get in touch with the folks at Strawbale.com to ask what might be causing this or whether or not it is normal.

Redhawk

But . . .  Straw smells nice.  Is it possible that it's psychological?

I asked Catherine Wanek, the author of several books about strawbale houses, about your problem with the enduring smell and she wrote:

"Smelling straw is not the same as smelling rotting straw.  The moisture level readings he took are all reasonably good, within very acceptable tolerances.  Smelling straw indicates to me that there are gaps in the plaster somewhere, probably at the bottom or top of the wall.  Somewhere it's open and allowing the smell to escape, which is not necessarily mean the bales are wet.  I'd also recommend that he takes more moisture readings, specifically at the bottom of the walls, north, south, east and west. If there is condensation or excessive moisture, that is where it often concentrates.  If there are moisture readings above 20% relative humidity, that could be a problem.  It might mean there is capillary wicking from the ground, or condensation. If he finds gaps in the plaster, best to close those gaps. Hope this is helpful..."

Hmmm.... that's a head scratcher. The best I can think of right now is maybe local odor control by having a little baking soda lying around.

First, I echo what Catherine Wanek said: your moisture levels listed are within safe levels, so your straw is not likely to be moldering.

Second, smelling the straw means air from inside the wall is getting to your nose,  which means there are openings somewhere in the plaster.  The most likely culprits for air leakage are the open joints where the walls meet the ceiling and floor, and around where windows and doors meet the interior plaster. Spend some time sealing those up and see it it does the trick.