Erdrick - I don't know about straw bale housing, there's a lot of disadvantages there. You've got to treat the stuff to keep mice and fires out, and replace the bales every so often. No idea how insurance might treat you on this, I know if I was an insurance agent I'd view a straw bale house as a fire waiting to happen.
An alternative for you might be to look at dry stack block building. I've been researching different building processes to find a cheap, sustainable way to build, and really like what I see with this. You can build it yourself, the walls act as thermal mass, and will be damn near tornado-proof. Another thing to look into, the solar heating shed. Collect sunlight to heat about 1000 - 2000 gallons of distilled water/antifreeze stored in a heavily insulated tank, then pump that water/antifreeze solution through the house to keep it warm inside. Use a heat exchanger to use the same system to keep the house hot water hot too. I figure the shed would make a great utility point, you can keep a full electrical system (think off-grid PV setup) inside the same shed as the water heating system, so long as you have a way to keep the electrical side heat isolated in the summer. In the winter, residual heat would keep the batteries at the optimal temp to provide power to the house. And, I plan to use a wood fired boiler for emergency heating. There's probably a week, maybe two, in my area cold enough that I might have to run it. I have more thoughts on this if interested, and tons of links put back, if interested. |
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Regarding foam insulation that Telco mentioned, there are many manufacturers now. I was considering a brand called Airkrete, which is supposed to be more environmentally friendly than the urethane foam insulations like Icynene. Any foam insulation saves 40% - 50% more energy than fiberglass or cellulose because it eliminates air infiltration, the major cause of heat or cooling losses. |
Telco: I appreciate the links. I will be sure to look into those two building techniques. A word on straw bales though. According to the sources that I have gathered information from, straw bales, if properly packed at the source, and dried, are more flame retardant than your average building materials. I don't remember the specifics, but they definitely outperformed conventional building materials when subjected to a fire test. There is also no nutrition in them, thus deterring any rodents (and especially bugs) from taking residence in them. Again, it is key that the bales are very compressed, so that there are no air pockets in them, and there is no moisture left in them. As for longevity... if they are properly sealed, so that no moisture can get into them after installation, then they can last for a reallllly long time. There are historic homes from back in the 1700s and 1800s that were built with straw bales... and they are still standing.
So, I would suggest taking another look at straw bales for use in home building. I think that if done right, that they can be an excellent alternative to conventional building materials. |
Oh... links! :thumbup:
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If you can afford it, concrete walls, then a continuous XPS inner layer - maybe 4" thick (but it is a case of declining returns so choose whats best for your climate and pocketbook), then internal wood framing for the inner walls and floor joists (you could still use rock wool batts for interior or exterior stud walls for sound deadening and also some internal zoning if needed or firebreaks - the XPS already is serving as the vapour barrier). XPS under the slab or in the middle of a slab sandwich and then a roof with minimal thermal breaks. The walls will be pretty thick.
If you can eliminate thermal bridging and build it tight enough (that you'll need a HRV/ERV), you're heatloss will be extremely low. Best thing is to keep the house small so that the internal gains can be best used. If 6 cattle will keep a barn's foundation from freezing in the great white north imagine a superinsulated sub-1000 sf home with a couple of big slobbering Newfoundland dogs using renewable energy in the form of dog food doing about half the heating! ;-) |
2ton - Blueboard is nice, spray in is better, especially with new construction. I'd not hesitate to use the blueboard if I were putting new siding on a house, but new construction may as well go whole hog.
My own plan also counts on no insulation on the interior walls. Concrete is a pretty good soundproofer on its own, and the thermal mass should contribute to a warmer house in winter. Should be able to manage about 2000 sq ft with no monthly heating expense, too. At least, this is the goal. There was one company building huge houses, 3000 - 5000 ft, that used timber for the thermal mass, these huge houses are heated and cooled for about 25 bucks a month in Colorado. No idea what the name of the company was anymore, but they had some impressive looking hunting-lodge looking places. Insulating the interior walls would defeat this. |
Telco, spray is better for many applications, especially using stud cavities but spraying an even coating on the bare concrete walls and then having to clean everything up for the studding afterwards... *trembles*
Thermal mass is your friend and your foe... the in floor radiant crowd loves it on the inside of the insulation envelope. It takes a while to get it up to temp and then after that forget setting it back unless you'll be away for weeks. Just watch out for solar gain. My preference is to have the mass on the outside - hugely beneficial in flattening out the daily outdoor temperature variations although it would do much more for a home at altitude in NM than here, but still. As for the interior, I like low mass. Combine that with TRV's panel rads sized for low water temps and you have a house that is responsive to changes in internal gains and losses whether or not they are intentional. How is the house being heated for free? Solar? |
2ton, I'll have to give that some thought. Everything I've read about mass says that it's useless if you insulate the inside and not the outside, and I can see the point. The mass would be cold in the winter and hot in the summer, and would fight with the inside. Insulation is not a true heat block, it resists the movement of heat, so having a thermal mass against the insulation on the outisde would either be a heat source or a heat sink accelerating the movement of heat through the insulation. Having the mass on the inside means the mass will be less affected by the outside, so should emit or draw more from the room and less from the outside. This would mean a more regulated interior temp. Yes, it would be harder to change the interior temp, but this is what you want. Once the temp is set to a comfortable level, it should work to maintain that level with small inputs.
Yep, solar is free. Since you have to pay for whatever method is used, that part is pretty much a wash. Maintenance is also required on all systems, so that is out. I'm basing that off the monthly operational charges. The only time the system would not be free is if I had to burn wood during deep winter, or had to run a backup generator. Check out the solar shed idea for how I plan to gather and use solar heat for the house. That fellow was able to keep his house warm a lot further north than I am using only the sun. |
Yes, the golden rule of heat transfer is that heat energy will transfer to anything with less heat energy and all insulation can do is slow it down.
That solar shed is nice although I'd be tempted to add sliding doors of some form to limit gain. Solar can be very tough to control and by the time you have enough for the winter you have to have a great strategy for limiting it in the sunnier warmer periods and also have a good way to dump all those excess BTUs if you get caught off guard. I'm fond of geothermal... in essence it is already stored solar energy. Howver if truth be told, if I could get peak consumption low enough like 1 or 2 BTUs per SF per heating degree day, I'd probably just use an electric boiler off the grid and try to ensure it uses offpeak power. Right now I use a condensing gas boiler and I'm around 5 BTUs per HDD per SF which still is good, considering the fact I can't do much about my walls, although they are insulated. Probably far cheaper and simpler for control and materials required than going solar. I'd still try and have some form of solar preheat for the water heater. Have you seen the newer evacuated tubes that are becoming more common in Europe? |
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