Climate’s Effect on a Straw Bale House

Tree in the fogThere’s no question that a local climate’s effect on your home, whether it be a bale home or a home made of concrete block, is something you need to consider. In fact, the climate is often a driving force in people’s decision to build with bales. I’m sure you’ve heard people talk about how hot their climate is or how cold it is and how if they only had a more efficient home, they could better stand the extremes. Unfortunately, some people decide to build a straw bale home before they consider the potential affects that their climate could have on it until its too late. It’s important to know what might happen to your home before you build it because there may be steps you can take to minimize those affects if you plan ahead.

Below are some of the affects that climate has on a bale home. Some of these may seem obvious while others may not. I’m sure I’ve missed some, so feel free to add your own in he comments section.

  1. Rain can saturate walls if they are not properly protected. You may have heard the saying “Big Hat and Big Boots” referring to a good roof overhang and a large raised foundation. These are two very good ideas if you live in an area with high rain totals. Also consider adding a waterproof membrane above the bales, just below the bale stop or box beam. The challenge is avoiding punctures in this membrane during construction. Make sure it laps over the edge of the bales a couple inches. Too little overlap and water can still make it down into the bales. Too much overlap and your plaster will not adhere to the bales at the top of the wall.
  2. Humidity, unlike rain, cannot be designed out of the equation with a hat and boots because it permeates everywhere and it can cause moisture to build up in the walls if not handled properly.  The best approach to high humidity is two-fold. First, build with quality materials that can help in removing excess moisture from your air/wall interface. Hygroscopic plaster such as lime or earth is a great idea as it will naturally help keep a constant moisture level in the wall. If there is excess moisture in the air, it will absorb it and hold onto it (until it reaches saturation of course). Once the air dries out below the level of what the plaster is holding, the plaster will release the excess moisture back into the air. The second approach is a mechanical one. Install an Energy Recovery Ventilator (ERV) to help keep the air in your home fresh and to remove excess moisture. These are simple to install and work very well. They are also very energy efficient. Don’t rely solely on them as anything mechanical can fail (power loss, broken parts, etc) so be sure to use them as part of the two-fold approach.
  3. Cold weather can have all kinds of impacts. One that is often overlooked is the condensation of moisture in the walls. Because cold climates require us as humans to heat our indoor air space to stay warm, we create uneven climates from one side of a wall to the other that are quite drastic. If the warm and moisture laden air from the inside of the house pushes into the center of a bale wall where everything is cold, the moisture can condense on the straw. The best way to win this battle is to not heat your home and live in the cold. Not very likely option I suppose, so another plan of attack is to make sure you seal any penetrations into the wall and seams between the wall and other surfaces. The most common areas are around electrical and plumbing installations and at the floor to wall and wall to ceiling transitions. Be sure to pay special attention to these areas and you’ll be fine. Use foam gaskets at the electrical and plumbing installations and vapor tape and/or caulking at the wall to ceiling/floor transitions.
  4. Hot climates pose their own set of issues. Of course, hot climates that are associated with high humidity must be approached in accordance with #2 above; however, dry climates have a different set of concerns. One that is often not considered is the life of the plaster. Natural plasters are not built with chemicals designed to help them resist cracking and thus must be installed carefully. Be sure to plaster the house when it is protected and ONLY then. Hang tarps from the eaves so that you can plaster in the shade and out of the wind. These two aspects of a hot and dry climate can ruin a plaster job. Keep in mind that your plaster is not only the “look” of your house, but also its protection. If it is compromised, so too is the substrate, in this case, your bales.

Like I said at the beginning of the post, this list is in no way complete. There are many other climates that should and will be considered and many other affects of each of those climates. This is a list to do one thing: get you thinking. I hope it does just that. As always, I welcome your comments and input.

If you’re interested in really learning how to build with bales and you want to have perhaps one of the best weeks of your life in the process, then come to one of our workshops. We ALWAYS have a good time and you will gain the confidence to build your own house too. CLICK HERE to see what workshop locations and dates we have available this year!

35 Responses to Climate’s Effect on a Straw Bale House

  1. Jamie McKay, P.Eng. Wed, November 9, 2011 at 9:22 am #

    Thanks Andrew – this is a big issue and difficult to summarize into a short post. I, as an envelope consultant and owner of a post/beam strawbale infil, am constantly asked if straw makes sense for clients.

    I agree with the “big hat, good boots” philosophy and the air leakage control (especially as people push the boundaries of design and the climates of use). I think that people must understand one big point, which is that of “breathable wall design”, which means vapour movement, not air. Vapour movement means that there is no vapour barrier and vapour diffusion can move from inside to out or vise versa. Strawbale walls typically act on a “storage and release” basis, meaning that the materials will store an amount of moisture wihtin the materials, and then release them when conditions change. This works, as long as the storage is sufficient and the release is timely. As for air leakage, no amount is good, but some amount is tolerable (storage and release basis again). So, Owners/builders please make sure that you review the edges of your exterior walls and use fans in Kitchens and bathrooms to keep the source moisture down.

    Cheers,

    Jamie.

  2. Andrew Morrison Thu, November 10, 2011 at 8:14 am #

    Absolutely Jamie. All good points, clearly made. Thanks for that.

  3. Kallee Fri, November 11, 2011 at 5:03 am #

    Hi Andrew, great website! I live in Nova Scotia, Canada. We have long wet, snowing winters, long rainy springs and moderate summers. Would a straw bale house survive our climate or am I dreaming?

  4. .Ellen Ronis Fri, November 11, 2011 at 5:06 pm #

    I live in the Northeast upstate NY where all those climates are not only possible but likely. It sounds like there are solutions to all the issues but does it make sense to build with straw Bale if you have to keep putting out fires, so to speak?

  5. Andrew Morrison Mon, November 14, 2011 at 1:57 pm #

    Definitely, especially where you are. The moisture (humidity) that you speak of is not a big problem. I’m referring to places like Georgia and Florida when I mention high humidity. There are lots of straw bale houses in Eastern New York. I have done three workshops there as well (NY State). In Hurley, Bainbridge, and Cuyler. Perfect locations as far as I could tell.

  6. Andrew Morrison Mon, November 14, 2011 at 1:57 pm #

    Indeed. In fact a friend of mine just build one there. It will take some detailing, but can work.

  7. Amy @ Six Flower Mom Thu, December 1, 2011 at 5:45 am #

    My family and I are planning to build a house, it has always been my husbands desire to build straw bale. We live in Southern, Central Kentucky and I am concerned about our wet, humid, every changing climate here … do you feel that this is a good location for straw bale or not? I am reading the challenges above and feel like we would have to deal with all of them, I am very nervous about this. Just seeking advice!

  8. Andrew Morrison Sun, December 4, 2011 at 8:22 am #

    Hi Amy. We have built homes with success in Tennessee, Florida, Georgia, and other wet climates. You will definitely need to pay attention to the details and add some mechanical dehumidifying details to the design. Check out this link and talk to the folks there as it may be helpful for you to talk to people in Kentucky who have actually built.

  9. Susan Wed, December 7, 2011 at 8:29 am #

    Hi… I have always dreamed of building strawbale someday, and I thought this would happen in the Texas Hill Country…but…life happens and we have found ourselves in Florida instead! Must I give up my strawbale dreams? Can I still build my forever home here with strawbale? Please advise!

  10. Andrew Morrison Wed, December 7, 2011 at 2:59 pm #

    Hi Susan. It is not as easy in high humidity areas, but it can still be done. You’ll need some extra detailing to handle the humidity, but keep smiling!

  11. Gail Thu, December 29, 2011 at 3:04 pm #

    Hi, My neighbor owns (vacant) rental property next door and has his poor dog outside in a piece of crap dog house, that’s surrounded by mud and water. I started feeding it/playing with it. Now, it’s whimpering during the nice in the 14 degree weather. I can’t afford a insulated dog house. I’m in Pittsburgh, Pa. Can I build a cob house in 40 degree weather?

  12. Andrew Morrison Mon, January 2, 2012 at 2:55 pm #

    Hi Gail. The dog would be better off with a straw bale house as cob does not insulate, it is thermal mass. Meaning that if it´s cold outside the cob house it will be cold inside the house unless there is a heat source. A bale structure will provide insulation and the dog´s body heat (assuming you include a door) will be enough to warm the space. Good luck.

  13. david snow Mon, August 19, 2013 at 9:17 am #

    Thank you for the update.

  14. Church Thu, November 13, 2014 at 4:49 pm #

    Hi A,
    We R presently building a passivise solar straw bale house in Halifax area of Nova Scotia. I have been viewing your videos on U tube and have found them to B helpful Thank U

    ” C “

  15. Marcus Thu, December 3, 2015 at 9:14 am #

    So reading what I have it seems it would be an unintelligent idea to build with this material in a place that has average daily humidity of say 75%. I think I read somewhere else that StrawBale walls should find its saturation equilibrium below 20% Is this correct?

  16. Andrew Morrison
    Andrew Morrison Wed, December 9, 2015 at 10:35 am #

    Not necessarily Marcus. The 20% number is related to moisture content by volume in the bales. That is different than relative humidity. There are bale houses in Georgia, Tennessee, West Virginia, Washington State, and other areas that would seem “too wet”” and yet they are doing really well. Incorporate some type of mechanical system to help with the moisture control such as an Energy Recovery Ventilator and use proper design, and you can be fine, even in wet environments. I would need more details to be able to say for certain that your area would work, but you may be surprised to know how well they CAN work in wet climates.

  17. Kit Wed, March 9, 2016 at 8:03 am #

    I’m looking to build a single level, straw bale home in tge Sarasota, Florida area. Besides the humidity issues, we have very high winds, hurricane force, from time to time. I’ll need to have it engineered to conform to the 2014 codes, but the building dept. hasn’t said no yet. Straw bale construction has never been done in this county. So aside from being a test case, my question is this. We have high humidity. Fero cement was used before, with success, in other parts of the country. Not sure that this breaths at all. What can you tell me about
    Humidity, moisture absorbtion in the walls in tjis case. I’ll look at your videos too. Thanks.

  18. Andrew Morrison
    Andrew Morrison Wed, March 23, 2016 at 8:51 am #

    Hi Kit. I would strongly recommend that you use lime plaster. It is very strong and allows for moisture control that cement will not. It is the best of both worlds. Good luck!!!

  19. jm young Wed, May 11, 2016 at 7:25 pm #

    hi im living in Australia near the beach ,ocean, one side of the road has a tree line of protection what would the sea air do to my hay bale house re condensation etc ??? we do get sea mist winter and summer and in winter it is like walking into an ice wall two houses away you can feel it the cold air

  20. Andrew Morrison
    Andrew Morrison Wed, May 18, 2016 at 8:47 am #

    As long as the plaster is done properly and the home is well baled, you should not have a problem with the sea air. If you are concerned and want an extra layer of protection, you could do a special wall on that side that has cladding/siding over an air gap over a plastered bale wall. This will give you lots of protection against the mist.

  21. Carol Sat, January 14, 2017 at 6:55 am #

    Hi Andrew! I live in Central Oregon and own a straw bale home. We recently have had record breaking snow fall. I have 5ft drifts up against my house. Should I have it pushed away from the house or is it ok. I am concerned there could be potential leakage through the walls??

    Thank you,
    Carol

  22. Lani Thu, February 16, 2017 at 7:47 pm #

    Thanks for this great Web site! I once helped insulate a new house with straw bales (loved it) so am wondering if we could insulate the perimeter of our manufactured home CRAWLSPACE, or even the area in the crawlspace where there is no plumbing or electrical. We are in winter-wet SW Oregon and want to avoid mice, rat and opossum intrusion. Our new roof is vinyl so there is no overhang, but gutters (we were new to the area and rains are much more than expected). What materials would best work on the exterior for skirting to protect the coated straw bales? Many thanks!!!

  23. Andrew Morrison
    Andrew Morrison Mon, March 6, 2017 at 8:54 am #

    Hi Lani. I think the bales in that application would be sacrificial as they would not likely last more than a season in good condition. You could place them up off the ground and then protect them from direct rain with plastic backed plywood, but even that would not likely be perfect.

  24. Andrew Morrison
    Andrew Morrison Mon, March 6, 2017 at 9:08 am #

    Hi Carol. that depends on how tight the bale walls are. If they are built well, there will not be heat loss through the walls and any melting of the snow will take place from the exterior face in TOWARDS the house, meaning that the coldest, driest part of the the snow drift will always be the portion against the house. If there are leaks in the bale envelope that allow interior heat to escape through the walls, then you could experience melting against the walls. This would have to be significant to cause problems, so you are likely fine either way. Just have to share the potential risks so you know what to consider.

  25. Jaime Cuppen Sun, January 21, 2018 at 6:50 pm #

    Hi Andrew, looking for some advice. We bought a straw bale/cob home from someone else and moved in 3 months ago just before summer (in New Zealand). We were looking forward to the house staying nice and cool over summer, but it doesn’t! It gets quite warm and humid inside and takes a long time to cool down at night after the outside temp has fallen and we’ve opened all the windows.
    Any ideas what the problem may be? It’s difficult because we had no part in the build and don’t know the wall structure exactly.
    The outside temps are moderately hot (30’C) and a little humid.

    Thanks!
    Jaime

  26. Andrew Morrison
    Andrew Morrison Mon, January 22, 2018 at 8:55 am #

    Hi Jaime. That must be very disappointing. I’ve had similar reports in the past and it’s always been one of two things, so I hope the same is true for you.

    First, check that there is insulation at the perimeter of the foundation. If the concrete is directly exposed to the exterior climate and not insulated to the inside of the house, the concrete (especially if it’s a slab floor) will draw in all kinds of heat that the walls can’t affect. Simply adding a wrap of 3″ rigid insulation (and a metal cap to hide the ugly insulation) can solve the problem. One thing to consider here is termites and the potential path this may create for them behind the insulation. I recommend you speak with an expert in the area if you have termites to see what options exist.

    The second place is in standard insulation locations: ceilings, roof, any conventionally framed walls. If there is a lack of quality insulation anywhere else (usually the attic) that can have a huge impact. After all, the walls may be great but if the roof is terribly insulated they won’t have a chance to fight off that point of access for heat.

    Hope that helps. I can share that when folks in the past have found this to be the solution, they were elated. I wish the same easy solution for you as well.

  27. Renee Hastie Wed, February 28, 2018 at 10:33 am #

    Hi Andrew,
    Thank you for all of your information. My family has recently purchased land in NE Minnesota( NE like 1 hour from Canadian Border). We know that the climate there is cold and snowy during the winter months and our summers are low to no humidity. I am looking at some alternative ways to build our homes. Cob would not work as there is no insulation, so straw bale is the next best thing. I saw where you said that there are some issues with heating during the winter causing moisture in the bales as our inside heat flows through the wall and hits the cold in the bales. The heat source we will be using is wood burning stoves. How big of an issues is this exactly, something that would cause us to have serious mold issues within the bales? I guess what I am asking is would a straw bale home work for the area we will be living?

    Thank you
    Renee

  28. Andrew Morrison
    Andrew Morrison Mon, March 5, 2018 at 10:08 am #

    Hi Renee. You would be a PERFECT candidate for a bale house. It will be amazing in that climate. The biggest issue with the dew point in the wall (what you’re describing) is when there is cold steel in the wall (rebar pins, for example). If you design and build the house properly (keeping all steel out of the center of the bales and using a welded wire mesh on the surface instead, you will be fine and THRILLED to have built a bale home. Warm and cozy!!!

  29. Jaime Tue, April 3, 2018 at 3:07 pm #

    Hi Andrew, thanks for your reply to my earlier question in January.
    I realise I didn’t give much information about our house in that post! I read through your reply and I’m not sure that either of those issues are the cause of the heat build up. Firstly, our house is built on timber stumps, not a concrete base. Our land is gently sloping, so the height of the stumps varies from about 50cm at one end to over a metre at the other end. The underfloor is insulated well above the building regulation R code level, as is the ceiling. The roof is almost flat with a slight 5degree aprox. slant. There is no ceiling cavity apart from the insulation, but it too is well above the building reg.

    There are a couple other factors I wondered if you could comment on? Our house is a combination of straw bale and cob. I’m not sure why it was built this way, but 3 sides of the house are straw bale, with the 4th side – the one that gets most sun on it, is just cob. From what I understand, cob is not insulative? could this be why the house is heating up, from sun hitting this wall (although it doesn’t feel warm to the touch inside the house, so I’m really not sure)
    The other thing is what role may windows play in our problem?
    Our thought is that the windows, which are old recycled and only single pane, are the cause of heat entry. Does this seem probable? We are considering putting in double glazing, but the cost is huge and if it doesn’t solve the problem for us will be very disappointing. We are also looking at installing a ventilation system to remove the humid air build up inside the house – not something we thought would be necessary in a straw bale house.

    Thanks so much for any advice. It is really hard to find help anywhere with these problems – even the ventilation company has no idea how to install a system in our house without a roof cavity nor walls able to be drilled through to put in a wall unit!!

  30. Mary Kniskern Fri, April 6, 2018 at 5:29 pm #

    I have another thought for Jaime re: house too warm in the summer. Think about the heat and humidity you are generating through your daily showers, cooking, running computers, etc. Just as the insulation keeps the heat in during the winter, it will do so during the summer when you don’t appreciate it as much. We do most of our summer cooking on the porch to keep the heat outside, and ceiling fans keep us comfortable. If the summer sun hits your windows, you may want to invest in some awnings to keep it out, or plant a trellis that will shade the west-facing windows.

  31. Andrew Morrison
    Andrew Morrison Fri, May 25, 2018 at 2:16 pm #

    I think you have hit the two main issues on the head. The cob wall is thermal mass so will heat up in the sun for sure. The single pane windows are also a problem as they are just holes in your wall that allow heat in during warm months and cold in during cold months. 🙁

  32. DIA ALLEN Fri, July 20, 2018 at 7:05 am #

    I have been interested in this for many years, but honestly I live where the lowest temp is usually in the teen for maybe 2 weeks out of the year and the rest is hot and dry (north texas), it isn’t unusual to have 90 to 120 straight days of heat over 100 degrees. I want something I can leave to my children but will also work and not need a lot of maintaining in the mean time. Is it better to do one or the other or a combination?

    Thank you

    Dia

  33. Andrew Morrison
    Andrew Morrison Fri, July 20, 2018 at 8:18 am #

    Hi Dia. I’m not sure I fully understand your question: “is it better to do one or the other or a combination”. I think you’re asking if it’s more important to focus on the longevity of the home during construction or on building something that is easy to maintain. The good news is that a well built straw bale home can give you everything you are looking for. It can provide you with a beautiful, energy efficient and healthy home that lasts for generations all while being easy to maintain. They’re amazing homes to be sure. If that’s not the question you were asking, please shoot me a new message with some clarification. Cheers.

  34. Nakinda Sat, September 29, 2018 at 4:35 am #

    Do you think a straw bale house with cob interiors could work in a house built in the Lowcountry of South Carolina? I only recently discovered that these types of homes existed and I want to pursue building my own. If it could be done in an area with high humidity, exposure to hurricanes, heat during the summer, and some rain in the winter…I am very interested! Any suggestions from you?

  35. Andrew Morrison
    Andrew Morrison Sat, September 29, 2018 at 8:04 am #

    Hi Nakinda. Thanks for your interest in straw bale construction. The biggest issue would be humidity. You can design out things like rain and heat, but the humidity can be tough to handle. I have built bale homes in Tennessee, West Virginia, and Arkansas with success, so if your climate is similar to that, I don’t see it being a problem. If you’re closer to Louisiana’s humidity levels, that might be too much. Good luck!

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