Fiddling on the roof!
I have become obsessed with the laws of thermodynamics.

This (w)hole thing got started earlier this summer when I decided the cover to the attic entrance on my back porch was an agent of the energy industry and was conspiring to keep natural renewable cheap free and clean air from blowing upward to cool off the attic.  Then I took some haldol and realized it's just plain old physics, not conspiracy theory.

Incidentally, that's a shelf from an old refrigerator shoved up in the hole to keep birds from getting up there.  They weren't paying their rent and I'm just that kind of an asshole.


Then I got on the roof and saw these piddly-ass little vents.  I had four of these along one side.  They don't do shit.  I call them vents, but really the space they allow air to pass through is narrower than Bush's views on conservation.

I always liked those turbine things because 1) they spin and 2) they're shiny and metal.  Hey, I'm easily amused. 

I ripped the old vent off the roof and used a jigsaw to widen the hole to accommodate the baseplate for the turbine (not pictured).  This really isn't very hard to do.

The heat being ventilated from the hole made a strong enough breeze that all the dust from the jigsaw actually blew upward instead of falling into the attic.


My neighbor Linda put up with no less than three phone calls (Do you have any roofing tacks?  How about a caulk gun?), but I didn't get everything I needed until it was too late to be hammering on my roof without the police coming by for a noise complaint, and I really didn't want to be that guy on the news standing on his roof when the cops arrive.  Those segments never end well.

Anyway, I left it like this overnight which probably cooled the attic off nicely.


Right out of the box, the turbine itself was flawed.  See how the arms bind on the brace when it spins?...

Now it doesn't.

What's different?


They cut the plastic housing around the axle too short, so I added a nut.  That fixed it, but, hello?  Quality control!

Yes, this is exactly why you need to keep a nut around the house.  Dani's very happy with the one who climbs on her roof and does shit like this.

Bottom line: Overall, this isn't that difficult a job to do.  If your ventilation blows (or, rather, doesn't blow), you can probably do this job in an afternoon.  Let me know if you need any tools.


But I didn't stop there.  I'm obsessed with thermodynamics, remember?
Here's a soaker hose.  I ran it down one length of the peak of the roof and back the other.

It cools by two methods: The first is that is conducts the heat away with the water (a substance with a huge specific heat value compared to any building material).  Second, whatever water remains is evaporated which, of course, removes additional heat energy.


The result is water trickles down and waters the lawn (score one for recycling!).  It looks like a cool sprinkle, but you could make hot cocoa with that stuff.  It's coming off at nearly scalding temperatures.*  The grass didn't seem to mind though.

*I tested the temperature with a couple thermometers on 7/25/06 ~6:15pm.  It had been overcast most of the day, yet the water coming off the roof was 96.7 degrees.

*Again tested 7/26/06 ~12:45pm, and the thermometer stopped climbing at 109.0 degrees when it went off the scale.  I didn't have a cooking thermometer to try for an accurate reading.

I like that the water dribbles onto the compressor as well since under these conditions it operates as a hybrid swamp cooler (aka evaporative cooler) by cooling the coils that normally rely exclusively on air convection.


Yet another idea.

Actually, this is a variation on a couple of things I've tried before.  These are 10' x 10' white sheets ($3 each at Wal-mart or you can capture and skin your own Klansmen), so I've got 300 square feet of reflectivity.  My roof is already more white than black, so this doesn't make much of a difference, but it's a start.

In the past I tried sheet metal or aluminum foil for closer to the maximum albedo, but those are more susceptible to being blown off by the wind.  The sheets don't.  Also, they capture water, so they maximize the amount of time the roof can be cooled by evaporation of standing moisture from the soaker hose.

Oh, and it doubles as a "don't bomb me" sign to terrorists.


Ideally, I would love to find a material that changes color based on temperature (i.e., darker when cool / lighter when hot so the reflectivity would be proportional to the temperature).  Additionally there are alternative designs for roofs that do similar things via the angle of their tiles (e.g., creating "sun troughs" to absorb light from the low-traveling winter sun and reflecting the high-noon summer sun), but our roof is new, so it would take too long to amortize such an investment.  It's something for us to consider in the future and anyone needing a new roof to consider now.

If you know of any alternative materials/technologies/approaches I've missed out on, especially in DIY applications, then let me know.


UPDATE: The next summer

The next summer, I swapped out the sheets for drop cloths left over from a paint job I helped a friend with.  I also added more bricks and haven't had a problem with edges blowing loose since then.

Since I need the roof to be reflective more often than absorbent (i.e., This is Texas), I decided to ramp up the albedo a bit.  I watered down some of the remaining white paint from when I did the house, and applied it to the roof with spray bottles.  You can see a line revealing the original color of the roof where the hose was laying at the time.

We've had loads of rain since I put the paint on, and it has held up quite well.


Cheapest and most effective method: An attic fan.

Rather than shelling out $100 for an attic fan, I simply hung up an old fan of ours that we never used anymore.  I took the top off the stand and put a few hooks into the supports (you can see one of them) and tied it in place with galvanized wire left over from another project.

I don't have it professionally wired in as yet.  It's on an extension cord that runs down to a plug on the back porch from the hole pictured in the first image on this page.

I've been up on the roof while it was running (i.e., I was painting the roof at the time), and you wouldn't believe how much heat was blowing out of here.  This is far cheaper than letting it seep into my house and then paying for my air conditioner to remove it.


More insulation!  We started off with the blown-in stuff you see in the foreground, but I also added rolls of "the pink stuff" (as everyone calls it) on top of that.  The job was only two-thirds of the way finished when the picture was taken.

I also painted the compressor white.  This is the part of the system where the heat has to be expelled.  If your compressor is a dark color, it's just getting hotter than it needs to be in the hot sun.  Paint it white to reflect away heat and get that component running just a bit more efficiently!

Alexplored 7/19-25/06.  Updated 7/2/07.
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