straw bale insulation in existing house
DgH
| Posted in Energy, Heating & Insulation on
Has anyone ever used straw bales to insulate an existing wood framed house?
Mostly academic because I am about to use cellulose. However, I started reading about straw.
The house is 2 1/2 stories. Balloon framed. Brick over 1″ tongue and groove boards and wooden laths with plaster on the inside. I have the attic torn apart. All the laths and plaster gone.
It occured to me that it would be possible to build a straw bale wall behind the “kneewall” area. Of course there are air sealing details to take care of. Any bales in that area would of course be treated with lime plaster or cement inside and out.
I am in Owen Sound, Ontario. (7500 heating degree Fahrenheit days).
Mainly just curious.
If my house wasn’t a 100 years old… there would go a really fine hobby.
Replies
A stawblae house must be an integral design. There are unique structural, moist-proffing, and vermin problems to deal with.
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Not exactly a BALE house, but I just finished working on a house built in the 20's that had loose straw insulation over a layer of sawdust in the ceiling. By the catalog pages stuffed in holes, the sawdust was original and the straw was from the '30s when the winters were cold and the times were hard.
Also loose foam over that and r20 batts over that, so it clearly wasn't too warm.
Jeff
One of my brothers built a strawbale guest house. The walls are over 16" thick and I believe such thickness, in addition to being the width of a common bale, has a lot to do with the insulating value of the straw.
My suspicion is, (and I don't know this for a fact), is that a traditionally framed wall, balloon or platform or whatever, would provide a wall cavity too shallow for straw to be an effective insulation medium.
In addition, it would be pretty time-consuming and a PITA to evenly fill the stud cavities with straw. It's packed fairly tight in a bale, but to break the bale to pack your walls and then to achieve any kind of density would be an interesting challenge.
If I was going to do it. This is how it would work.1. Fill up the cavities between the floor joists and air seal.This would be with a mixture of lime plaster and straw. Or clay and straw. Either one would work in basically the same way.2. Build a wall of straw bales behind the existing framing for the kneewall. Plenty of room. I even figured out how I was going to get in there to apply the 1" thick coats of plaster on all the "outside" surfaces of the bale wall (that is outside relative to the bales).The way that straw bale houses deal with moisture is by the plaster coatings being extremely hydrophilic and the very large surface area of the cellulose fibres.Any moisture that gets in spreads out over a huge surface area. When things dry out the plaster sucks moisture out of the bales and lets it dry.I agree that the design of a straw building needs to be right on to work. I have even seen indications that straw bale houses don't use straw in the roof insulation in high heating climates. Just curious about it really.If my house wasn't a 100 years old... there would go a really fine hobby.