Archive for the ‘SIPs’ Category

Trailer Trash Adventures

July 3, 2010

Proto-Mobile-Home, minus a hundred years -- OK, it's an RV, but I love the photo. Thanks to CollectivePic.com

What is it about mobile homes, anyway? They get trashed in the movies, the press and in tornadoes, and the people who live in them are “trailer trash.”

We who live in these little boxes do so for the most part, not because we prefer them, but because we can afford them.

If we “trailer trash” could afford airtight, green-weenie, artsy-fartsy, “net zero energy,” computer-controlled living spaces, lighted with creepy, AlGore curly-bulbs, heated and cooled with sunlight and geothermal, roofed with photovoltaic arrays and sprouting wind farms – or, at least, wind gardens — out back, with the power company sending us monthly checks for the electricity we produce in excess of what we use… most of us would have them.

We here on Danley Road can’t afford to build such a house, so we are doing our best to modify our existing mobile to make it more comfortable, affordable, and – forgive me for borrowing a PC term – sustainable. That’s why I put in a wood stove last winter.

When the electricity goes off in the wintertime, I don’t want to be frozen out of my own home and evacuated to some Red Cross shelter in a nearby town, while my rescued dogs and cats fend for themselves, and the opportunists among us rifle my belongings for things to take to the pawn shop and turn into meth money. I want to be home, managing my own heat, keeping my pets fed and watered, and protecting my own property with my 12-gauge. That’s what I mean by “sustainable.”

Of course, even if we could afford it, we wouldn’t buy some politically-correct, Department of Energy and Sierra Club-blessed box in some crowded, little “sustainable community,” because we don’t want one. We want to live where we want, not in the Obama-era descendant of the Stalin-era concrete wedding cake apartment monolith.

We want to provide our own heat, to the extent possible, grow (and catch) our own food, to a similar extent, and we absolutely don’t want the Secretary of Energy able to turn off any of our electrical outlets by remote control in a bow to the colossal fraud and power grab that is Carbon Dioxide-driven Global Warming. Barry can stick his “Smart Grid” where the solar cells definitely will not work.

We understand that the Stalinists in our government and around the world want us all lumped together in collective housing — not because they give a damn about the environment — but because we will be easier to spy on and control in those settings. It only takes one party stooge to keep track of several families of Kulaks, that way. Very efficient and sustainable, comrades!

Just as we recoil at handing our medical care over to faceless, government bureaucrats, we find the thought of leaving our rural homestead to live in a government-controlled, UN-approved “sustainable community” repugnant.

So, where does that leave us? It leaves us trying our best to make our rickety mobile home into a sound, efficient, comfortable structure, while confined to a tight budget and a desire to maintain a low profile with the various regulatory bodies that would love to be looking over our shoulders and calling every shot.

Where do we start? Logically, we start with the roof. The sheet metal “lid” (I hate to dignify it with a term like, “roof”) over this place reminds me of baking a turkey in the oven. When I was a kid, Mom put the turkey in the oven with a “tent” of aluminum foil (Reynolds Wrap!) over it to recapture the heat and moisture that would otherwise be lost in the oven.

TrailerTrashTurkeyTent

My own turkey tent. As lovely as it is effective!

With record summer heat in progress as I write this, we are finding out what it was like for the turkey. The galvanized sheet metal is thin enough to be subject to damage by any object that hits the roof in a storm, and walking on it is out of the question. It must be about 29 gauge, if that thick, which is about like the metal on the roof of a car. In theory, there’s insulation between it and the flat ceilings in the rooms at both ends of the trailer, but in the middle, we get “cathedral ceilings,” which means there is next to nothing in the way of insulation between us and the Tennessee sky.

The insulation above the flat ceilings can’t amount to much, because there isn’t enough space between the ceiling and roof for more than a couple of inches of any kind of insulation, and that’s right in the middle, under the ridge.

As I understand, it’s glass fiber, which is only good for about R-3 per inch, and then, only if it is maintained in its ideal “state of loft,” or fluffiness. Since it is between a vapor-permeable drywall ceiling and a metal roof, it has undoubtedly gotten damp long ago from moisture penetration from below, and can’t even remember what its ideal “state of loft” was like. As nesting material for mice, it’s great, but for insulation, it’s mostly an empty gesture.

Over about the middle third of the trailer, the cathedral ceiling consists mostly of textured drywall under the sheet metal, which is visually pleasant, but of no insulating value to speak of.

A couple of businesses serve the middle Tennessee area with systematized, fast and effective “roofovers.” (One I have had some correspondence with is Southern Builders, which sells the “PermaRoof” product line . These places will bring a kit of materials and a crew to your mobile, apply a support framework, and slap on a foam-insulated roof – a real roof – over your sheet metal turkey tent. I have no doubt that any of the reputable dealers I have seen would do a creditable job, and greatly improve the quality of life in the mobile, as well as making a quantifiable improvement in the heating and cooling of same.

What I wonder is, where is the outfit that will do the same for my mobile’s walls, doors and windows?

I’ve been reading  lately about the newest craze (actually, the idea is decades old, but the building industry is slow to adopt new ideas) in the building industry: SIPs. Structural Insulated Panels, according to the Structural Insulated Panel Association,  are a sandwich of sheath and insulation, bonded permanently into a panel that is not only a barrier to heat loss and air movement, but also strong enough (the significance of the “Structural” part of the term) to serve as a load-bearing section of wall without framing.

Recently, the market for SIPs has become more competitive, and the manufacturing processes have been streamlined, reducing the cost to a point where it is a realistic alternative. When the “supply” and “demand” curves both rise, wonderful things happen. Someone please explain this to the simple-minded, “Capitalism is EEE-VILL” crowd.

SIPs are now available using OSB plywood sheaths and a couple of types of insulation in the middle. They are also made with sheet metal as the sheath material, which makes them lighter for the same structural strength and insulation value.

SIP panels resist bending, twisting or crushing better than the same size “stick built” wall, when properly installed. Perhaps more importantly, they also provide much higher levels of insulation and sealing against air movement (infiltration) than studs and sheath.

Part of the reason for this superior weather-tightness is the use of plastic foam, most versions of which offer much more insulation for a given thickness than either glass fiber or cellulose fiber. Of course, the fiber insulation is overrated anyway, since its ratings are based on an ideal set of conditions that is as rare in the real world as a cold day in Tennessee in this month of June.

The insulating value of glass fiber and cellulose are based on laboratory-controlled measurements under ideal conditions, including 70 degrees F and no air movement. Moisture, settling and nesting by insects and animals all furnish the less-than-ideal, but far from uncommon conditions in the real world that lower the actual insulating power of fiber batts.

In the real world, the fibers are stuffed into a wall panel – a space with a lot more room in the vertical, than in the horizontal axis. The pull of gravity is relentless and patient, and the result is inevitable – insulation piled in the bottom of a cavity, with heat leaking like mad across the upper, uninsulated space.

Heat loss in this scenario is due to three mechanisms, in no particular order:

Convection (air movement, AKA infiltration), happens because the fiber is no longer dividing the wall space into lots of smaller spaces. Warmer air rises and comes into contact with cooler air or cooler surfaces, gives up its heat to them, regains its density and drops. Rinse and repeat.

Conduction is the way heat gets from a burner on the stove, through the handle of a skillet and into your hand, and that’s how warm air loses its heat. Every point at which a stud or rafter makes contact between the inner and outer surfaces of a wall, and there are many, since typical stud spacing is 16 inches center to center, is a bridge from hot to cold. Heat is conducted across this “thermal bridge” with the ease with which illegal aliens cross our southern border, and with similarly negative results. The R-value of the best insulation in the world does absolutely nothing to prevent a thermal bridge.

Radiation is the third path from hot to cold, and the one you feel on bare skin when you are out in bright sunshine on a cool day. Radiation is an important form of heat gain on a roof in the summer, and two ways to head off radiation-born heat are shade, as in shade trees, and reflection, which bounces the radiant heat back into space, where it belongs. Reflective foil on the surface of a batt or board of insulation under a wood or metal roof has the effect of bouncing the heat back before it can get deep enough to be dealt with as hot air in the structural cavity.

If you want to be as wonky as a physics major, all three methods of heat exchange – convection, conduction and radiation – are just special cases of radiation. When heat passes up the handle of the frying pan, it’s really just radiating from one atom of iron to the next, because the space between atoms is, on their relative scale, as vast as the space between the earth and the sun. Electromagnetic radiation, in the form of heat, travels through the space between atoms with the same ease with which it travels from the sun to the seat of your car. Convection is just a case of heat energy passing from one air molecule to another, and making the cooler molecules denser, causing them to settle and displace the warmer ones, squeezing them up to the top of the wall cavity.

As the physics wonks will say, heat, and all forms of energy in the universe, goes from where there is more of it, to where there is less of it. The same process lets heat into the house in summer, and squeezes it out in the winter. It’s just the way of things. If this process is allowed to complete, the universe will wind up as a cold, dark lump. Just don’t mark your calendar for it, because it will be a while.

A SIP is another story. The insulating quality of the foam is unbroken edge to edge across the surface of the panel, and the standard means of attachment of the panel to the building doesn’t provide any of those pesky thermal bridges. Individual panels are joined by various methods, according to the manufacturer. Some use dovetail joints formed into the edges of the panels, and others are connected via a wood timber called a spline that the crew drives screws into from the inside and outside. Each panel is joined to the building by being fitted at the top and bottom into tracks or channels that are attached firmly to the framework of the building. The result is a strong, weather-tight wall.

Of course, this practice makes retrofitting to a trailer nearly impossible, because there are so few suitable places more substantial than a cardboard box to anchor the channels that hold the panels top and bottom. That’s ironic, since I wanted to USE SIPs to add some structural integrity to this otherwise low-hanging-fruit for a toy tornado.

I began to suspect SIPs and the DIY/retrofit market was not a good marriage early, while searching for other people’s experience with them. There is none. Yes, my privacy-respecting search engine, Ixquick, did return a few hits with search terms like, “SIPS and retrofit,” and “SIPS and mobile homes,” but they never resulted in finding me one, single instance of somebody using SIPs to make a mobile home a little less mobile in a high wind. In fact, I was hard-pressed to find SIPs used in any retrofit situations, even in conventional houses.

This could be attributed by an optimist in my position to the newness of the products, and the lack of “generic SIPs” at places like Lowes and Home Depot. Most of the SIPs projects I saw were shipped to the site in kit form, complete with cuts for windows and doors, although the marketing people are always quick to say that any such openings can be cut on site, as needed. After all, one of the appeals of SIPs is the relative lack of waste, as one sees filling the Dumpster at the typical home construction site. Since ideally, every piece you need for every foot of outside wall is pre-cut and stacked on the truck, I can see why that would be.

So, anyway, I scaled back my aspirations of applying this technology to tightening up and fortifying my mobile. My earliest impulse for tightening up this trailer and making it safer was getting a “real” roof put on, and then, maybe, adding insulation and siding to the outside walls, and, finally, windows and doors that are worth a damn.

The roof turns out to have been much less of a chore than I expected. I found what I believe to be the best deal from Southern Builders, referenced earlier, and they had a crew close by between two other jobs in the region. They showed up WHEN THEY SAID THEY WOULD (Contractors, take note; you should try this!) and we went from ratty old roof to snazzy new, sturdy, well-insulated roof in a little over four hours. I recorded the whole process on camera, complete with before and after shots, and will be posting the whole, exciting tale shortly.

Sneak-peek at the new roof -- painful detail to follow

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