Just to confirm the utility of straw bale construction, I partially designed and have lived in a straw bale house for the last 25 years. It is a post and beam structure, with infill straw bale walls, and R-50 attic insulation of blown in cellulose. I bought the bales directly from a local farmer, wheat straw, and there are no signs of any problems, inside or outside. It is not perfect. I could have used a less embodied energy stucco on the outside, and the concrete floor is smooth, but not pleasant in the winter, though it is not so cold here as Canada (Shenandoah Valley Virginia, USA). In our state, as in most, state building inspectors are only slowly grasping that alternative building materials might be better, and local building materials best. Straw is not that hard to find, but getting the farmer to make extra tight bales might get tricky. Overall we are happy with the result.
In the past perhaps, but a hemp SIP wall would be much more effective if you compare the two side by side. A straw wall could combust with a strong fire while hemp does not. Shorter grow season for hemp and less fertilizer if any. Great startup industry, would utilize all parts of hemp. Straw better used for agriculture purposes.
Why do you say straw could combust? They are typically very dense and very low fire risk.
Hempcrete is usually much higher carbon impact than straw due to the amount of lime used and lower R-value for the same reason. So it would be interesting to see a like for like comparison across a range of performance metrics.
Researchers tested the fire safety and strength of hemp blocks, a sustainable building material made from hemp, lime, and water.
The study, published in the Journal of Building Engineering, found that Hemp blocks don’t catch fire with open flames but instead smolder slowly, producing very little smoke. In fact, walls made of hemp blocks stayed structurally intact for 2 hours during fire tests.
In terms of heat tolerance, hemp blocks retained most all of their structural strength up to 200°C (392°F). At 300°C (572°F), they still showed controlled burning without collapsing. The study also suggests that plastering hemp block walls can further enhance their fire resistance, making them even more reliable for building projects.
In short, hemp blocks are not only safer in the event of a fire but are also a sustainable building option. The use of hemp, a fast-growing crop, helps reduce the environmental footprint of construction materials and the minimal smoke produced during fire scenarios makes hemp blocks a safer choice for both occupants and first responders.
That said, hemp blocks have a compressive strength of 1.0 MPa, making them suitable for non-load-bearing walls. This means they aren’t intended for primary structural support but are perfect for walls that don’t carry heavy loads.
I'm wondering how straw may be dried, as any moisture, either within the construction or from humidity inside the building, may lead to mold and mycotoxins. So, while the dwelling is warm/cool, it may lead to serious long-term health issues. Alas, it may not be as hazardous as the off-gassing of petrochemicals and microplastics.
Usually it’s dried in the field and straw is just the stalks, not the leafy material that go to make up hay. So there is very little material in straw that can absorb moisture or is susceptible to mould.
Straw bale houses have been around for decades, but I don't know of any subdivisions built using them, and our major problem, right now, is a tremendous lack of housing all over North America. I've built a SIP house, on a wood foundation (never again), with 3" thick second-hand roofing EPS under the basement slab, and bare feet did not sufffer in the winter, but I did, accidentally, stumble on the fact of almost zero R-value at each vertical joint. Am building a new ICF home, delayed by injury, which has never had heat in it, until a few days ago, and even with just a tarp covering the SGWO, and no basement slab, ground heat kept the interior comfortable. I have designed prefabricate engineered walls that might interest you: see https://open.substack.com/pub/wellingtonp/p/a-possible-partial-solution-to-our?r=56dq46&utm_campaign=post&utm_medium=web&showWelcomeOnShare=true
I hope you don't mind me posting the address here.
I had a lot of problems with the guys working with me: in spite of careful discussions about not cutting the bottom plates, two of them started sawing off the extra inches, after the wood foundation walls were built, which meant that I had to get down on my knees and pour the preservative into the cuts, multiple times (poisoning the subsoil), and then the guy who was doing the backfilling, who knew perfectly well that it had to be done in a certain way, sent his understudy son to do the job, and he bent the walls before I caught him out, and it all had to be removed and remedied. What a nightmare.
All in all, it just took too much time, and too many headaches. My focus now is to make possible the rapid construction of many, many affordable homes, by prefabbing outer walls to allow a house shell to be built in 2 days, single/double storey, with a roof. Almost zero waste, factory or onsite.
Nobody that I know of still jams rebar into bales. It's a condensing point. Boring for concrete is an even worse idea.
Also, I share the concern for the frame wrapping SIPS to conduct energy.
The technique that uses straw walls with outside stiffeners both interior and exterior that are tied together with strong twine poked through the bales to form a kind of site-made SIP is a great solution. Bamboo makes a great stiffener in this regard. Adding fiber mesh increases strength.
I enjoyed building my home studio out of straw bale about 20 years ago. I had to shoo a few mice out before I got the lime render on and carefully work around a nesting Robin, but it was all part of the charm. It would be fascinating & encouraging to watch such an industry develop form out of today's circumstances.
I love the concept of straw houses—primarily for the R-value and wide windowsills that lends themselves to plenty of houseplants lining them—but I do have a couple questions for you Lloyd:
1. Does it make sense to build with pre-fabricated SIPs when each section abutting another has far lower insulative capabilities? I've always understood the contiguous insulation aspect as being the most important part of any structure's thermal comfort and efficiency.
2. Is OSB/plywood always used for either the interior or exterior for structural support? And if not (but instead, relying on wall studs) is strength dependent on tightly compacted bales? Are there problems of longevity with straw houses compared to other building materials?
No, you can use different combinations of structural support. Load bearing walls. Mortared load bearing walls. Bale in-fill or bale wrap that’s inserted between columns of structural framework. Hybrid that uses combination of those. Many builders also reinforce the straw bales with rebar while assembling the walls. In seismic areas, holes can be augured into the bales and filled with reinforced concrete as part of the bond beam. It is best though to start with the most tight, dense, and compacted bales you can find.
Researchers tested the fire safety and strength of hemp blocks, a sustainable building material made from hemp, lime, and water.
The study, published in the Journal of Building Engineering, found that Hemp blocks don’t catch fire with open flames but instead smolder slowly, producing very little smoke. In fact, walls made of hemp blocks stayed structurally intact for 2 hours during fire tests.
In terms of heat tolerance, hemp blocks retained most all of their structural strength up to 200°C (392°F). At 300°C (572°F), they still showed controlled burning without collapsing. The study also suggests that plastering hemp block walls can further enhance their fire resistance, making them even more reliable for building projects.
In short, hemp blocks are not only safer in the event of a fire but are also a sustainable building option. The use of hemp, a fast-growing crop, helps reduce the environmental footprint of construction materials and the minimal smoke produced during fire scenarios makes hemp blocks a safer choice for both occupants and first responders.
That said, hemp blocks have a compressive strength of 1.0 MPa, making them suitable for non-load-bearing walls. This means they aren’t intended for primary structural support but are perfect for walls that don’t carry heavy loads.
Thanks for the mention, Lloyd. Credit to Jonathan Holmes at VIA architecture for crunching the carbon numbers that I used for the analysis and report for Hiberna.
It is critical to protect bales from direct exposure to moisture (while constructing and maintaining). The most vulnerable parts of the straw bales are top and bottom. Very important to have eaves and to have a good foundation with moisture barrier between bottom of bales and footing. Clean straw has very little mold or allergy potential.
I have seen video programs both streamed and on broadcast that show straw bales used as the core for adobe walls in the American Southwest as well. I don't recall whether this was a modern technique or a revival of far older practice in the region.
I am in the early stages of planning a stacked fourplex for my family. 2x 2 bedroom, 2x 3 bedroom stacked units with single stair. I want to build with straw SIPs but there are none available in Ontario. The best option I have found is https://www.croft.haus/ in Maine. I reached out and they will ship to Canada but it is frustrating that none exist here.
Just to confirm the utility of straw bale construction, I partially designed and have lived in a straw bale house for the last 25 years. It is a post and beam structure, with infill straw bale walls, and R-50 attic insulation of blown in cellulose. I bought the bales directly from a local farmer, wheat straw, and there are no signs of any problems, inside or outside. It is not perfect. I could have used a less embodied energy stucco on the outside, and the concrete floor is smooth, but not pleasant in the winter, though it is not so cold here as Canada (Shenandoah Valley Virginia, USA). In our state, as in most, state building inspectors are only slowly grasping that alternative building materials might be better, and local building materials best. Straw is not that hard to find, but getting the farmer to make extra tight bales might get tricky. Overall we are happy with the result.
In the past perhaps, but a hemp SIP wall would be much more effective if you compare the two side by side. A straw wall could combust with a strong fire while hemp does not. Shorter grow season for hemp and less fertilizer if any. Great startup industry, would utilize all parts of hemp. Straw better used for agriculture purposes.
I will look into that. Is anyone doing it?
https://thetyee.ca/WhatWorks/2025/02/03/High-Hopes-Hempcrete/?utm_source=weekly&utm_medium=email&utm_term=builder
https://justbiofiber.com
hempcrete.ca
https://www.hempbuildmag.com/home/new-hemp-building-directory-2024
Why do you say straw could combust? They are typically very dense and very low fire risk.
Hempcrete is usually much higher carbon impact than straw due to the amount of lime used and lower R-value for the same reason. So it would be interesting to see a like for like comparison across a range of performance metrics.
neil degrasse tyson ·
Dave Hanson · January 25 at 5:50 AM ·
Researchers tested the fire safety and strength of hemp blocks, a sustainable building material made from hemp, lime, and water.
The study, published in the Journal of Building Engineering, found that Hemp blocks don’t catch fire with open flames but instead smolder slowly, producing very little smoke. In fact, walls made of hemp blocks stayed structurally intact for 2 hours during fire tests.
In terms of heat tolerance, hemp blocks retained most all of their structural strength up to 200°C (392°F). At 300°C (572°F), they still showed controlled burning without collapsing. The study also suggests that plastering hemp block walls can further enhance their fire resistance, making them even more reliable for building projects.
In short, hemp blocks are not only safer in the event of a fire but are also a sustainable building option. The use of hemp, a fast-growing crop, helps reduce the environmental footprint of construction materials and the minimal smoke produced during fire scenarios makes hemp blocks a safer choice for both occupants and first responders.
That said, hemp blocks have a compressive strength of 1.0 MPa, making them suitable for non-load-bearing walls. This means they aren’t intended for primary structural support but are perfect for walls that don’t carry heavy loads.
Sure, I wasn’t questioning the assertion regarding hempcrete’s fire performance, but that doesn’t tell us anything about straw.
I'm wondering how straw may be dried, as any moisture, either within the construction or from humidity inside the building, may lead to mold and mycotoxins. So, while the dwelling is warm/cool, it may lead to serious long-term health issues. Alas, it may not be as hazardous as the off-gassing of petrochemicals and microplastics.
Usually it’s dried in the field and straw is just the stalks, not the leafy material that go to make up hay. So there is very little material in straw that can absorb moisture or is susceptible to mould.
Straw bale houses have been around for decades, but I don't know of any subdivisions built using them, and our major problem, right now, is a tremendous lack of housing all over North America. I've built a SIP house, on a wood foundation (never again), with 3" thick second-hand roofing EPS under the basement slab, and bare feet did not sufffer in the winter, but I did, accidentally, stumble on the fact of almost zero R-value at each vertical joint. Am building a new ICF home, delayed by injury, which has never had heat in it, until a few days ago, and even with just a tarp covering the SGWO, and no basement slab, ground heat kept the interior comfortable. I have designed prefabricate engineered walls that might interest you: see https://open.substack.com/pub/wellingtonp/p/a-possible-partial-solution-to-our?r=56dq46&utm_campaign=post&utm_medium=web&showWelcomeOnShare=true
I hope you don't mind me posting the address here.
I don’t mind but would love to hear why you don’t like your wood foundations. I have thought we should do more of them.
I had a lot of problems with the guys working with me: in spite of careful discussions about not cutting the bottom plates, two of them started sawing off the extra inches, after the wood foundation walls were built, which meant that I had to get down on my knees and pour the preservative into the cuts, multiple times (poisoning the subsoil), and then the guy who was doing the backfilling, who knew perfectly well that it had to be done in a certain way, sent his understudy son to do the job, and he bent the walls before I caught him out, and it all had to be removed and remedied. What a nightmare.
All in all, it just took too much time, and too many headaches. My focus now is to make possible the rapid construction of many, many affordable homes, by prefabbing outer walls to allow a house shell to be built in 2 days, single/double storey, with a roof. Almost zero waste, factory or onsite.
Nobody that I know of still jams rebar into bales. It's a condensing point. Boring for concrete is an even worse idea.
Also, I share the concern for the frame wrapping SIPS to conduct energy.
The technique that uses straw walls with outside stiffeners both interior and exterior that are tied together with strong twine poked through the bales to form a kind of site-made SIP is a great solution. Bamboo makes a great stiffener in this regard. Adding fiber mesh increases strength.
I enjoyed building my home studio out of straw bale about 20 years ago. I had to shoo a few mice out before I got the lime render on and carefully work around a nesting Robin, but it was all part of the charm. It would be fascinating & encouraging to watch such an industry develop form out of today's circumstances.
I love the concept of straw houses—primarily for the R-value and wide windowsills that lends themselves to plenty of houseplants lining them—but I do have a couple questions for you Lloyd:
1. Does it make sense to build with pre-fabricated SIPs when each section abutting another has far lower insulative capabilities? I've always understood the contiguous insulation aspect as being the most important part of any structure's thermal comfort and efficiency.
2. Is OSB/plywood always used for either the interior or exterior for structural support? And if not (but instead, relying on wall studs) is strength dependent on tightly compacted bales? Are there problems of longevity with straw houses compared to other building materials?
No, you can use different combinations of structural support. Load bearing walls. Mortared load bearing walls. Bale in-fill or bale wrap that’s inserted between columns of structural framework. Hybrid that uses combination of those. Many builders also reinforce the straw bales with rebar while assembling the walls. In seismic areas, holes can be augured into the bales and filled with reinforced concrete as part of the bond beam. It is best though to start with the most tight, dense, and compacted bales you can find.
neil degrasse tyson ·
Dave Hanson · January 25 at 5:50 AM ·
Researchers tested the fire safety and strength of hemp blocks, a sustainable building material made from hemp, lime, and water.
The study, published in the Journal of Building Engineering, found that Hemp blocks don’t catch fire with open flames but instead smolder slowly, producing very little smoke. In fact, walls made of hemp blocks stayed structurally intact for 2 hours during fire tests.
In terms of heat tolerance, hemp blocks retained most all of their structural strength up to 200°C (392°F). At 300°C (572°F), they still showed controlled burning without collapsing. The study also suggests that plastering hemp block walls can further enhance their fire resistance, making them even more reliable for building projects.
In short, hemp blocks are not only safer in the event of a fire but are also a sustainable building option. The use of hemp, a fast-growing crop, helps reduce the environmental footprint of construction materials and the minimal smoke produced during fire scenarios makes hemp blocks a safer choice for both occupants and first responders.
That said, hemp blocks have a compressive strength of 1.0 MPa, making them suitable for non-load-bearing walls. This means they aren’t intended for primary structural support but are perfect for walls that don’t carry heavy loads.
Thanks for the mention, Lloyd. Credit to Jonathan Holmes at VIA architecture for crunching the carbon numbers that I used for the analysis and report for Hiberna.
I will!
Are there concerns about increased risks of molds w this type of construction?
It is critical to protect bales from direct exposure to moisture (while constructing and maintaining). The most vulnerable parts of the straw bales are top and bottom. Very important to have eaves and to have a good foundation with moisture barrier between bottom of bales and footing. Clean straw has very little mold or allergy potential.
I have seen video programs both streamed and on broadcast that show straw bales used as the core for adobe walls in the American Southwest as well. I don't recall whether this was a modern technique or a revival of far older practice in the region.
I am in the early stages of planning a stacked fourplex for my family. 2x 2 bedroom, 2x 3 bedroom stacked units with single stair. I want to build with straw SIPs but there are none available in Ontario. The best option I have found is https://www.croft.haus/ in Maine. I reached out and they will ship to Canada but it is frustrating that none exist here.