[Strawbale] Mumblings about Water in the attic.

[Sherwood Botsford]

Shody Ryon wrote:
> --- Sherwood Botsford <sgbotsford at gmail.com> wrote:
>   
>> Water is heavy. To get significant water in the
>> attic space requires a 
>> much more robust roof structure. 
>>     
>
> Laren went through this with someone. He said the
> weight of water is insignificant in a “to code” built
> structure. He said they are designed to hold the
> weight of SUVs parked door to door (the SUVs doors, I
> imagine) and bumper to bumper and backs that claim up
> with numbers, which I will cross post if I can find
> it.
>
>   
Hmm. If true, this is a bit misleading. An SUV has a fairly low density.
If it weighs 6000 lbs and is 6' wide by 15' long (WAGs) it has a density 
of roughly 66 lbs per square foot. This is comparable to the live load 
design for heavy snowfall areas. I do know that roof designers consider 
snow loads in making their design. I don't know what safety margin they 
calculate in. It's also the weight of a 1 foot layer of water, or 
roughly an 18" deep layer of bottles. It's not clear to me how you would 
attach that load to the roof, without compressing your insulation. 
Doubtless there is a clever way.

My attic is not terribly well insulated. It has a wood stove chimney 
running through it which gives a bit of heat. The roof is a medium dark 
blue in color. Despite this, the outdoor air temperature has to get to 
within a few degrees of freezing for the roof to get warm enough to 
produce icicles. Roofs are normally vented to reduce overheating. As I 
write, the temperature in my attic is -15 C. Water bottles would be 
frozen. Sure, on a summer day, the attic space gets 20 C hotter than the 
outside temperature. On a winter day, with the sun a terrifying 15 
degrees about the south horizon at noon I'd guess that it will average 
only a few degrees above the outside temp. I'm not sure how I would set 
up an attic to work as a useful heat trap.

Here's another thought: What happens if you get a significant 
temperature swing during a period of high humidity? It's cold, and the 
water bottles are full of chilled water. Temp goes up, and with it the 
humidity. Now warm humid air meets cold water bottle. Condensation? 
Dripping off the bottles onto your ceiling? An issue? Lots of other 
things in house design are done specifically to address warm humid air 
meeting cold object.

I used 5 gallon buckets of water to temper a small greenhouse. While it 
helped keep the peppers alive further into the fall, there was 
condensation on the buckets. The greenhouse has a wooden floor 
(converted shed) I had mould under the buckets when I shut down the 
greenhouse in the fall. Not a good comparison, as a green house has a 
constant source of humidity, and pretty wide temperature swings.

On water container life:

I expressed doubt because I don't know. The only type of water 
containers that I know won't spring leaks are glass. Remember that the 
life of a house is 50 to 500 years. Polyethelene bread bags are 
permeable to water. That's low density, long chain stuff, and not very 
thick. While PET bottles (a much more noxious plastic than PE for other 
reasons) may be good for storing pop or gatorade for a couple years on 
the shelf, I have no idea how they fare storing stuff for 50 to 100 
years. Remember too that the cap and the washer are two other kinds of 
plastic.

Remember too, that if this is to be useful, there will be significant 
temperature swings. What does this do to the bottles? PE when warm is 
subject to creep. PE pipe is derated drastically as water temperature 
increases. It also has a substantial dimensional change with 
temperature. Some plastics include volitiles that give flexibility. As 
they plastic ages, they leave, and the plastic gets brittle. I'm not 
saying that it's a bad idea. I don't know. I have a 100 year old glass 
whiskey bottle, nicely violet from years of sun. I don't have a century 
old plastic bottle.

Circuit: I wasn't clear. I was thinking of putting a few hundred feet of 
pex tubing in attic space as a heat collector, with the other end of it 
in a water tank in the basement, or buried under the slab. You're right: 
Retrofitting this would be impossible.

Air through crawl spaces:
I've seen posts about this before. Generally considered a bad idea, as 
the craw space has too many visitors. Spiders, mice, flies, bugs. 
Skunks, raccoons, weasels. Unless it has no organic matter at all, the 
addition of water creates a situation where mold can start. Circulating 
mold spores are not great. Hanta virus (carried here by deer mice, and 
present in their crap) is double plus ungood.

Energy costs of moving dirt:
Compared to the other costs this is small. E.g. the fuel for the bobcat 
is probably less than the plastic for the water containers.

Consider this as a possibility:

Suppose that you have to dig 5' for your foundation anyway. Dig out the 
interior. Flatten Pour your foundations. Insulate bottom and sides of 
hole. Half fill with dirt. Put in layer of Pex done as several chunks, 
connected to a manifold. Fill with dirt. Build house. Put pex in attic, 
or have solar colletors on south side of house. Heat dirt.

This has the potential to store a lot more heat than the attic system 
does, and since the collection point for the heat is separate from the 
storage point, you can save it until needed. (Attic bottles will cool 
off during the night, and in the morning, when you most need a bit of 
warm, they are least able to give it.)

Houses and cities, in general, are not designed to be maintained. Ships 
and airplanes are. Take a good look at techniques used in the latter. 
Lots of access. Few non-reusable fastening systems. (A screw is 
reusable. A nail is not. Paneling is reusable. Drywall is not.) My one 
objection to radiant slab heating: 30 years from now the ground shifts, 
the slab cracks diagonally. The pipes are cut in 47 places. How do you 
fix it? With a crawl space, you can fix it.

Even with mainstream technologies, we see things that were once done and 
no longer accepted. Example: Aluminum wiring. Scratch coat and embedded 
mesh for tile laying. Alternative technologies don't have the man 
centuries of experience as to what works and what doesn't.
All technologies have unanticipated consequences. This doesn't mean they 
shouldn't be used, but we are wise to try to figure out ways to 
de-couple them from the well understood part of the dwelling.

Ideally there are more than one way to accomplish any task. (In the 
sysadmin world, the goal is to set up your data center so that it is UZI 
proof. A Black Hat can walk in, empty a couple of clips of machine gun 
fire into the hardware, and it will slow down, as it reconfigures around 
the damage. Hard to do, both in data centers and in houses.) You don't 
want to be dependent on a new idea working in order to live in the 
house. Any new idea has to have a backup if it doesn't work.

So, for example, if I wanted to heat water using the sun, I would try to 
make a system that wasn't part of the main structure: Possibilities:
1. Indpendent HW heaters similar to the ones built at rutgers for 
heating their greenhouse.
2. A sunroom/greenhouse on the south side of the house with pipes at the 
peak of the room to pull out heat either as hot air or hot water.
3. A Nick Pine style hot water battery -- a separate building that 
heated a year's supply of hot water over hte course of a summer.

Water is clever. Water is hard working. Put it at the bottom of the hill.
Water is clever. Plumbing is weak. Put your pipes where you can see them.

<rant>
I won't put water in my attic as a heat store. I can see three 
possibilities.
1. The system won't work well enough to matter. I've wasted some time, 
and effort.
2. The system works. Hip Hip,,, Hooray!!!
3. Two years from now the roof collapses because I believed it was 
strong enough to park SUV's on it.
4. 8 years from now I notice soggy spots on my ceiling because the 
washers on the bottles let go. Four outcomes. One is good, two bad. Move 
the water down hill. I can live with a leak that drains into the earth 
instead of my ceiling.

I won't put in a radiant slab. It will break. Maybe not now, maybe not 
in 30 years. What about 100 years? 200? If I pour my soul and sweat into 
a house, I intend it to outlast my grandchildren! I'll put in my crawl 
space because there I can fix it.

I'll consider trying to heat a cone of ground. It may work, it may not. 
But if it doesn't, my house is still livable, and all I've wasted is a 
hole, and a bunch of plumbing. Heating that water in another way isn't 
too hard. If it works, but breaks, I can build a replacement cone of hot 
dirt next to the house.

If I try some really whacky idea, I'll try it with the shop, garage, or 
other outbuilding. A major screwup there will collapse on my car and the 
kid's bike, not on me or the kid.

During the day I work as a computer sysadmin. The only real lesson I've 
learned is, "Avoid doing anything that you can't undo." I don't like 
concrete. It's too hard to change a slab back into sacks of cement, a 
pile of rocks, a pile of sand, and a stack of rebar. I love hanging 
ceilings: One surface of every room has easy access for adding 
electrical circuits, internet wiring, phone, tv, pipes, air ducts....

</rant>