Hakan, thanks, > >Yup, we';re > >likely doing straw roof insulation, possibly looking into using light > >clay-straw blocks, and lots of them, (depending on r-value comparisons) to > >protect the straw somewhat. > >Do consider a ceiling humidity barrier in combination with well ventilated >attic. Cheap and significant reduction of heat losses.
Moisture control like that is definitely assumed for something like this, though there are right and wrong ways of doing it. > >and assuming that there'll be spotty maintenance on this thing. > >we';re not using concrete anywhere except for concrete piers anchoring for > >the posts for the post-and-beam structure. Bales sit on a separate > >perimeter foundation of railroad ties which sit on a properly drained > >rubble trench foundation, we're using lime plaster (with free lime from a > >local acetylene plant we've already tested out for plaster mixes), concrete > >stucco is a terrible idea in cold wet climates, > >Mostly because the choice of coloring method and/or concrete stucco blend >ratios. Closing the construction with an unsuitable paint is the secure way >of getting the straw to rotten and you can do the same mistake with lime >plaster. Many ancient and traditional houses with straw in the construction >have been destroyed this way. I've definitely read here, too that a lot of old European straw-insulated houses got destroyed after the introduction of concrete stucco- after they were plastered over with what was thought to be a maintenance-free stucco, vapor had no where to go (at least not fast enough) and the straw decomposed, after doing fine for hundreds of years before concrete. Paint will do this as well- it has it's place, that place probably not being on the exterior, but it's more important to note that concrete stucco itself 'breathes' very poorly- a lot of bale homes covered in this stuff (including the house that's already on the community center's property, which is only two years old and has lots of design problems plaguing it) have had problems that could be avoided with traditional plasters. There's a lot of other factors, but many people today who don't know enough about how moisture moves through strawbale walls and through different plasters assume that concrete is the best choice because it';s the one people are most familiar with today for exteriors. In reality it's horrid unless there's a structural point to it- and in our case there isn't. We wouldn't paint the lime. Part of the point of lime is that it is easy to repair small cracks in it (unlike stucco!!!!!!!!!!! and I've wasted a lot of time doing that for concrete stucco). You give it a limewash every year (granted, not everyone will do that in this day and age, but it won';t fall apart if it's done right and it's not annual, either). Concrete won't repair as easily. Since natural building is frequently discussed on this list, I want to bring to people's attention the following book about strawbale building in cold and wet extreme climates. It contains a very, very detailed discussion of the different factors that influence plaster choices and a lot of moisture control issues that we need to be aware of... Serious Straw Bale: a Home Construction Guide For All Climates by Paul Lacinski and Michel Bergeron.(in the US it's available through RealGoods) Since a lot of strawbale owner-builders do much of their research through books, I can't recommend this one enough for a thorough and detailed description of practices and the scientific evidence you should be aware of in making the various choices you may be faced with in strawbale design. In the volunteer builder group I'm talking about, we happen to have reached the same conclusions as the authors of this book, about some of the major design strategies, via experience- but the strawbale world is still experimenting with many designs and there's a dizzying array of choices facing anyone trying to do a small project as an owner-builder. > >it's not needed in this > >design for rigidity, the local soil is composed mostly of excellent clay > >and there is that mountain of free lime nearby (sand is more of an issue) . > >We're not doing heat tubes in the adobe floor because of maintenance > >concerns and our lack of experience combining the two (rammed earth and > >poured adobe for the floor, with the materials for radiant heat tubes). > >Agree, could be a problem and need to be checked. It would be a petty if >you cannot utilize the energy storage capacity. it isn't storage I;'m worried about, it's our lack of familiarity with installing something like this (doing adobe floor work on top of what seems like fragile radiant heating tubes- I do know that lots of people have done this, we ourselves have not) in an area halfway across the country from where we are, where we wouldn't be able to come fix it if something goes wrong. heat storage in an adobe floor like this shouldn't be a problem, though. I'd love to do this for a place where I myself lived, but don't want to experiment too wildly on others' homes. > >Going to have passive solar design of the > >building, > >Passive solar design assumes that you have energy capture and internal mass >for to store it. A straw bale house might have too good insulation to be >fully compatible with most of those principles and benefit probably more >from internal heat sources like lights, people etc.. The trade off between >capture/storage and the lessening of efficiency in insulation/emission >factors for that, might be negative for a straw bale house. This is wrong, unfortunately. Passive solar is completely compatible with superinsulation strategies, with the thick walls and deep window wells of strawbale, and the adobe floor acts as thermal mass. It also has been done wrong plenty of times- see lots of early 1970's experiments here- too much glass, 'ugly' buildings, and either overheating/heat loss in the wrong seasons- but it isn't complicated and we've learned from their mistakes I believe. Modern passive solar buildings look quite 'normal' and the material isn't all that different from non-solar houses, or expensive. You have to size some thermal mass correctly (that's not all that easy), have windows in the south that let in winter sun and proper roof overhangs that'll shade sun from coming in in the summer, and you need decent insulation which of course strawbale provides. Loads of people have done it successfully with strawbale. Passive solar is one of the best and logical building strategies to incorporate into any building design- and it doesn't have to be complicated or involve any futuristic spaceage glass facade or anything (I know that's not what Hakan was suggesting!). It's free energy! forever! I;m not sure what you're saying above about tradeoff between storage and insulation. The strawbale walls are not your heat storage or heat capture medium- the floor (which receives energy from sunlight coming through your 'normal' looking windows), or interior walls made out of adobe, or something like that (there are lots of somethings possible) , are what usually functions as heat storage (or 'cool' storage in summer)... other 'active' solar heating systems (hot air panels combined with heat storage) have been used but there's no need to build them in new construction if you can plan for passive solar instead- they're more tricky in some ways, and not popular. If you are doing a remodel/retrofit and trying to incorporate active solar home heating in some ways, water heating panels that preheat water for some kind of radiant heating system are more common than active air heating systems. Mark [Non-text portions of this message have been removed] Biofuel at Journey to Forever: http://journeytoforever.org/biofuel.html Biofuels list archives: http://archive.nnytech.net/ Please do NOT send Unsubscribe messages to the list address. To unsubscribe, send an email to: [EMAIL PROTECTED] Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
