[Cob] New, climate questions

[Bernhard Masterson]

Hi Jamie,

I teach natural building and have built a couple of cob and straw bale hybrid houses and plenty of other cob structures in the Pacific Northwest.  I lived very happily in a 450 sq.ft. cob-bale hybrid I built with my wife for several years.  Here are some general comments.

Uninsulated cob is really only suitable for very temperate climates (central California, South West U.S. etc.) and maybe areas where there is consistent enough winter sun to be able to generate excess passive solar heat (Colorado, Utah, Northern climates have such short winter days passive solar gain is limited).  I believe that in almost all climates some sort of insulation will be worth your while, especially on the north side.  I don't recommend perlite or vermiculite as insulation since they have high embodied energy.  Straw-bale, Light-Straw-Clay, and Chip-Slip are much more environmentally friendly options and will provide better insulation than adding an insulating aggregate to the cob.  Where will you be building?

How big a crew and how much time do you have to build?  How will you be mixing?  Have you taken a workshop?  If not I highly recommend it.  You can calculate how many hours you will be cobbing by figuring the total volume of the walls and estimating on one hour to mix and apply 3 cubic feet of cob (tarp mixing by experienced fit individuals).  Cob is the most labor intensive of natural building techniques.  One of the reason straw-bale is such a great match with cob is that it is far less labor intensive and pairs beautifully with the thermal mass of cob.

You say you want to heat the home to 65 to 75 deg?  If so, sub-floor and perimeter foundation 
insulation will be beneficial since your winter soil temperature is 50 deg.  You will only gain 
heat in the house from the earth when the temp inside drops below soil 
temp.  Heat energy moves from hot to cold.  Any colder mass or surface 
will "take" heat from warmer masses and surfaces.

Keep researching and dreaming, Cob and natural building can create truly wonderful homes that surpass expectations,


- Bernhard 



Get under a sustainable lifestyle umbrella, the carbon is going to hit the fan.

____________________________________http://bernhardmasterson.com

Natural building instruction and consultation

Message: 4
Date: Thu, 23 Jun 2011 10:39:02 -0700 (PDT)
From: Jamie Carr <kfmaille at yahoo.com>
Subject: Re: [Cob] New, climate questions
To: coblist at deatech.com, Ron Becker <ron45 at tularosa.net>
Message-ID: <866595.73850.qm at web65918.mail.ac4.yahoo.com>
Content-Type: text/plain; charset=iso-8859-1
 
So...how excessive is 1250sq ft for 4 people? As a cob house I know that's huge (small for most of the country though) but we do have a family, and I cook a lot and we eat together so spacious kitchen and a dining room is a must. I would close those off at night and try to only heat the LR and BRs, 680sqft.
 
As far as passive solar goes, I'm already planning the most and largest windows for the southern side and a good roof overhang to block some summer sun. In my current home I close my heavy cotton curtains on summer days and winter nights. The bubble wrap idea is neat, one could even hide it inside normal curtains. Not letting the children pop it might be a challenge...and resisting the urge myself lol. I was unfamiliar with glazing so I looked it up and found some info on using higher heat gain windows on the south side to let in more winter heat, lower elsewhere. I have to wonder even with roof overhang if that might sacrifice summer comfort if I can add heat but can't cool this house. I don't really want an in-floor heating system, too much cost I'm sure.
 
Anyway, I expect I want 24" walls, I need many of them straight for the look I want so I can't skimp on the thickness. I might need buttressing in places too. 14" sounds very minimal even just structurally, I assume yours is a small house with lots of curves in the walls? I want an earthen floor and a cob couch and woodstove surround. The thermal mass of this place will be excellent so once we have a good temperature it sure will stay there. Not sure if the subfloor should be insulated or just have lots of gravel and sand for drainage, the deep earth here is like 50F so that's good to let through, right?
 
Self sufficient resources are high on your priorities list I see. I think I'm going with solar power, propane range and fridge, woodburning stove for heat. The pellet ones I'm told are more efficient but I'll have my own little forest so maintaining it will provide lots of firewood. If the fuel prices soared I could switch to a wood cookstove and small electric fridge or just a root cellar at some point, and outdoor cob oven. A greenhouse, chickens and sheep are in the longterm plans (a few years after I build the house) but for now and near future it'll be perennial fruit bushes and trees, cultivated mushrooms, and direct seeded garden (beans, peas, lettuce, greens, squash, carrots, herbs) plus whatever I can start in my nice deep windowsills. Been growing a few veggies here in my little yard in the city so far, enough to feed us through the summer mostly.
 
Thanks,
Jamie