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    Attempting to Retrofit a Mobile Home Floor for Passive Solar Heating 
    #1
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    The PDM and PDC stipulate digging a trench around the foundation line of a house and putting in a stone or concrete band of insulation around the periphery of the floor to direct the heat from the earth upward into the house instead of outward. This seems to imply that the house is resting on the bare ground or a concrete slab. Okay, fair enough.

    What do you do, though, with a mobile home sitting off the ground? If you trap air under the home by skirting it with, say, a band of cinder blocks or bricks -- starting from 18" below ground up to the bottom of the mobile home -- will this be effective or a waste of time? Must the home be sitting on concrete or ground or is there another solution?

    Many thanks!
     
     

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    #2
    Senior Member Grasshopper's Avatar
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    Is the home still mobile or permanently anchored?
     
     

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    #3
    Senior Member pebble's Avatar
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    And what's your climate and aspect?
     
     

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    #4
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    Quote Originally Posted by pebble View Post
    Is the home still mobile or permanently anchored? And what's your climate and aspect?
    Temperate, 36-degrees north latitude, relatively flat site in a mountainous area. The home is mobile but need not be moved (though I've thought about rotating it 180 degrees at each equinox to take advantage of the mobility).

    I can't decide whether trapped air under the home would be a disadvantage as long as the perimeter is fully skirted with thermal mass. Radiant energy (in this case from the earth) heats solid bodies and not air, right? (Think of Bill M's anecdote about the kacheloffen in the German Pub if you know it) So, presumably the heat would radiate upward, straight through the air buffer to the floor. Then again, the radiant energy would be more distant from the floor and so might dissipate. Just don't know.
     
     

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    #5
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    Hello gmpm1,
    A stone or concrete band will not act as insulation. Insulation is about slowing heat transfer between objects which is typically done by trapping air between layers. Stones and concrete typically add mass and are useful for storing thermal energy be it warmth or cold. In the PDM Bill talks about using something like 2" styrofoam boards buried along side the foundations to contain within the house the thermal mass of the solid floor and earth below it.

    For your situation, if the home is staying put then you could approach it like any house on stumps where by putting insulation in the top, bottom and sides - effectively wrapping it in a blanket helps it to retain a more stable temperature.

    The Your Home Technical Manual has loads of great information for building design and retrofitting in an environmentally sustainable manner.

    Good luck,
    Dan
    'nobody will sell you what you need - you gotta grow it from a seed'

    Chris Smither (heard at Apollo Bay Music Festival)
     
     

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    #6
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    Yes, you're right -- Bill talks about putting the insulation inside the concrete band. The concrete, on the sunny side at least, is to catch the winter sun's rays and conduct the heat into the earth, if I understand it correctly. The insulation is to hold the heat under the house so it doesn't escape into the surrounding terrain which it is prone to do.

    Wrapping the mobile home is certainly part of my strategy, but I'm trying to use the earth as well, hence my question. Even if wrapped, I fear the home will end up like a Queenslander house on stilts -- being very cold in the winter.

    BTW, to the prior posters, I attempted a response which apparently didn't take, so here it is again: I'm in the temperate zone, 36-degrees northern latitude on a relatively flat site within mountainous terrain. The home is not permanently anchored. I thought about doing that, but also about possibly rotating it 180-degrees at the beginning of winter and summer to take advantage of the home's mobility, facing the more glazed side toward the sun in the winter only.

    Thanks a lot for considering this question!
     
     

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    #7
    Senior Member pebble's Avatar
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    Housetruckers here use strawbales, but obviously only when they're parked up for a while. Travellers use various skirts along the bottom of the vehicle, which is more about reducing cold wind and frost than true insulation.

    But it really does depend on your climate and what you are trying achieve.
     
     

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    Reply: 
    #8
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    We should consult experts to know the possible plan B or Solution to it. If a Mobile Home Floor for Passive Solar Heating can sustain variable changes in temperatures and has capability to hold itself good against all odds we should consider giving it a try. Me and my foundation are researching on more productive and sound ways to have eco-friendly passive house. Any effort to save nature must be thought upon. I'll try to discuss this problem, may be i'll have some concrete solution to it.
     
     

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    #9
    Senior Member sweetpea's Avatar
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    I'll tell you what we did with ours. Its longest side is facing the way the sun travels all day (south above the equator, north below the equator) It's got lots of big windows (that are not the new ones that reflect heat, Low-E are now the code, but not what helps with passive solar.) I had to search around for the old double pane windows. I can stand by the window and feel the heat from the sun. We put a "skirt" around the bottom of Hardy board, concrete siding that fills in that space down to the ground. I don't know how a trench would help with heat. the heat comes from the sun directly, not the sun heating up gravel in cold soil. We have gravel around the house and it never gets hot.

    Anyway, the skirt wall and the house wall, when painted with a very dark, flat paint brings the heat underneath it. We painted the whole thing the darkest shade of military tank green we could find (it's in pine trees, it's a nice combo) . The space underneath gets very hot. We put black shingles on the roof. It's completely insulated up to code from when they built it a few years ago, walls and ceiling, but it heats up just the same, and the insulation keeps the heat in all night.

    It doesn't freeze where we are, but our summers are cold and foggy, but when it's about 10 degrees above freezing, it's probably 20 degrees warmer inside in the morning. After a sunny day it's very warm inside, and stays that way long after going to sleep. When there is a lot of cloud cover it obviously doesn't heat up as much, but it still is getting some heat. I've used this way of heating up our sheds so they don't get moldy and damp inside. I don't mind wearing a warm jacket when inside.
    "Life flows on within you and without you"...George Harrison
    ~~~~~~
    Coastal California, USA, Mediterranean climate - no summer rain, a little frost mid-winter
     
     

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    #10
    Senior Member sweetpea's Avatar
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    And just to be sure I explained it right, there are absolutely no trees on our south wall (north wall below the equator) and west wall, which captures lots of heat as the sun is setting. If the ceiling isn't insulated, it will lose heat about 3 hours after sunset. You'd think insulation would keep the heat out, but it doesn't seem to, especially with the black composite shingles.

    One way to heat with 20 mm gravel is to make a large metal box, 2 meters by 2 meters, insulate the non-sunny sides, placed near the house in full sun, paint it flat black, fill it with the large gravel, have it exposed to the sun all day long. That way the gravel can heat up and hold the heat. Attach an insulated pipe from this box to the house and the heat from the gravel box will go into the house. this works in mild climates, I've seen it done where I am. But gravel can be extremely cold in winter, so not sure it would be the best source if it stays around freezing during the winter.

    Our dark paint and large windows have really surpassed my expectations about how warm we can make our place.
    Last edited by sweetpea; 28-04-2011 at 03:49 AM.
    "Life flows on within you and without you"...George Harrison
    ~~~~~~
    Coastal California, USA, Mediterranean climate - no summer rain, a little frost mid-winter
     
     

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