My half-baked idea to cool my roof

I own a one-story rambler in Maryland, where it is 98F today and has been near that for a couple weeks. Given that we are setting temperature records here annually (like virtually everywhere else in the country), I am trying to do what I can to (a) cheaply keep my house cool in the face of a changing climate and (b) reduce my part of the fossil fuel usage which is contributing to the problem in the first place.

In the 18 months I've lived in the home, I've noticed that while one end of the house (shaded by tall firs and with a ventilated attic) stays pleasantly cool even on days like today without the A/C on, the other end (unshaded, with a low-sloping, black EPDM roof) is a veritable sauna. If you close the door between the two areas, the temperature differential is pretty impressive.

Since the area with the flat(-ish) roof seems to have little room for insulation between the ceiling and the roof on top, my focus has been on finding a way to stop the sun from pounding the black surface, which in turn heats the interior. I spent some time researching these elastomeric roof coatings, but in the end learned that for EPDM it would have to be a 3-stage process (cleaning solution, then primer and final white coat), and I'd need to buy or rent a special sprayer (heavy-duty enough to handle the viscous material, I guess). Given the cost ($200 plus the sprayer), the effort, the fact that I'd need to luck into a weekend (and soon, please) with a dry and mild two-day forecast so the roof wouldn't be 120F+ (bit of a Catch-22), and the mixed message I've gotten from local roofing supply places about which product(s) will actually adhere well to my roof, I've... well you get the picture. What started out as a no-brainer ("paint the darn thing white", she said) has become convoluted to the point where I want to drop back and punt.

Which brings me to Plan B. It's also occured to me that, while summer A/C costs predominate over winter heating costs, there is still some benefit to having a black roof in the colder months (assuming we ever have another winter here). So... what about a "convertible"? White in the summer, black the rest of the time. So far I've come up with two methods for bringing this about:

1) Rolling waterproof (but breathable) white TyVek Home Wrap onto the roof for the summer months, then roll it back up and store it away in September. One concern is that the manufacturer only recommends it be exposed to the elements for 90 days. Not sure what that means - maybe it loses its water repellancy over time.

2) This one is the current frontrunner. For about $90 I can cover the entire 550 sf expanse with bats of 1" styrofoam insulation. It has roughly the reflectivity of snow (.8), and the insulating value (while most sane people put the material on the *inside* of the roof) ought to be a bonus.

The obvious questions, for both options, are:

- how to secure the material to the roof to withstand wind, rain, and everything else mail carriers deal with. I'm thinking light-colored bricks at the moment.

- do I need to worry about mold, fungus, etc growing under the material and harming the synthetic rubber, even if it's up there just 4 months of the year?

- how well would the material hold up over time, and would it withstand spray-washing with a garden hose to keep it white?

I'm sure there are others I haven't thought of. The roof is about 8 feet off the ground, so easy access is not an issue. The slope is about 1-to-12. Only one of the neighbors would have to look at what I put on the roof, and they seem like easygoing folks. My girlfriend has promised not to leave me, based on this one deed alone at least.

Thoughts, suggestions? Recommendations for a shrink? Please do me a favor and nip this idea in the bud if it's truly and unredeemingly nuts.

 

The sun will break down the foam insulation. I had some extra white polystyrene I placed against the foundation over winter for temp. insulation and by summer it was quite yellow and starting to deteriorate.

 

Thanks for the reply Schiejr.

I was hoping to hear that it would take longer than that to deteriorate. I may go ahead and try this, if only as a relatively painless way to test how much cooler that end of the house can be when the sun's energy is mostly reflected. I'll post a followup, in case anyone's interested (and I'll check back here periodically, if anyone has any other tips/opinions).

 

Is actually going ot let you put that on your house ??

Seriously try going with a radiant barrier that staples to the underside of the rafters or increasing ventilation in the attic.

Don't ruin the looks of your house by covering the roof with stuff

 

Actually, it's a (nearly) flat roof on a 1970s addition wing with no attic/space that I can access (and very thin, so little room to install anything if I could get in it).

My girlfriend was actually quite delighted a couple of days this week when she came home after days in the 90s, and that end of the house was as cool as the other end (which is shaded by trees).

So far I have to consider it a tentative success. I had a false start the very first day, when 3 of the 16 panels blew off while I was at work. But I went up the next morning and did a better job weighting them down with bricks (the brightest white I could find). In the 2 or 3 days since then they've stayed in place. It hasn't been tested with a real serious windstorm, so I still have to find a more secure system to hold them (someone has suggested lacing clothesline across the 24x24 foot expanse.

As for appearances, you have to go way out to the edge of the yard to glimpse the "layer of snow" up there. It's not that bad.

 

That explains a lot, can you imagine how it would look on a normal pitched roof ?? LOL