On 12/17/2012 9:18 AM, Steve B wrote:
I got my 1200+ sf roof on my shop. It has no peak, just a slope. I was
given a HVAC study here that some organization did that said with foam
sealing, and water flowing over the outside of the roof, a 25F degree
reduction was capable. Has anyone ever used flowing water over the roof of
a building or carport or plain roof to attain cooling?

Would like to hear your stories.

Steve


A reputable/competent HVAC analyst will be able to understand your total
situation and give coordinated advice.
What you'll get here, based on almost zero description of your situation,
is a bunch of random input from people who've never made an actual
measurement in their life.

First question I'd ask is why didn't the people who commissioned the study
implement the recommendation?

Second question is, "do you really care what the roof temperature is?"
You really need to address the thing you care about.

If what you care about is the heat coming thru the ceiling, you might
take a broader approach.

The climate where you live is CRITICAL.
The current roof situation is CRITICAL.

If your inside is 80F and the roof is 160F, that's 80 degrees differential.
lowering that to 55 differential cuts your heat flow to 69% of what it was.
But if the R-value of your roof is 5 and you add 5 more insulation,
you halve the heat flow.
And insulation works in the winter too.
Your starting point matters a LOT.
Take the passive "low hanging fruit" first.

Are you OK with the side effects of water?
Mold/mildew/green slime/leaks/corrosion.
Frozen water system in the winter.

Then, there's the payback period on the investment. Do the math.

Google "white roof". There's a lot of info on the virtues of painting
your roof white. The supporting math will apply to any roof cooling
situation.