Passive Cooling - soaker hose on roof?

[Cindy Blankenship]

I wasn't sure which forum this fit but I guess closer to building than the others. Has anyone tried snaking a soaker hose on a pitched metal roof for passive cooling? Lots of people do this from what I've read online and Home Depot folks told me but have some questions.

Does the water need to evaporate to cool the roof? In other words if most of the water trickled down to the gutters would it still cool? If so,that would save catchment water. On humid days evaporation wouldn't work as well either.

Also if anyone's done this how did you get the hose up on the roof? We have a pitched one, so I'm guessing hire someone who works on roofs; i.e. knows how to get it up there without falling or damaging the metal roof.

The attic isn't insulated so I'm guessing this form of passive cooling would lower indoor temp significantly. At least that's what I've read. The problem is nothing I find tells the whole story...just bits and pieces from forums.

Thanks!

Cindy

[Noel M2]

Hi Cindy,

It may help a little as evaporation will serve to cool down the surface. I doubt that it will be sufficient to effectively cool the interior. Of course, you can have a mini rainstorm for many hours but you'll be spending electricity to bring the water up there.

Insulating will help keep the heat from your interior space. Fiberglass rolls can be found at Home Depot and HPM. They are a pain to install especially this time of the year but can be done post construction.

Adding an attic fan can help actively expel the heat. There are local companies that install solar attic fans on metal roofs. With the tax incentives, the cost is around $300-400. The best part is that it runs free and when it matters.

Stay cool!

Noel
http://HiloParadise.com

[Cindy Blankenship]

Thank for your ideas Noel. I'm renting though so looking for something less expensive.

I did some more research and found an article that says sprinkling the roof for four minutes four times a day cut his A/C use almost in half! And he only sprinkled 50 percent of the roof! It lowered the temperature (not cooled)in his house significantly. He talks about BTU's and energy savings, but then he may not have a pump like those on wells or us on catchment.

http://www.doctajstutoring.com/webdoc22.htm

Most of the house is livable, but my son the nightowl isn't sleeping much at all because he has to have windows shut and no A/C (because of the noise). He was ok a couple months ago - I thought his room felt like an oven then, but now with summer it's horrible. I'll keep researching this then...

The only other option is to find someone who can work on A/C's who can rig it up so it's not in the room, attach a duct to it, run through the wall and add a thermostat. Someone posted to a DIY site on how he did this.

If there was insulation between attic and ceiling it would be on the attic floor, right? I got up there today on the ladder and didn't see any. So since the attic's cooking and doesn't have insulation, it seems cooling the roof would bring the temp down in the attic and then in the house. The living room is open beam so it gets a lot of heat too from the roof, but I'm not too bothered by it, not with our tradewinds and fans.

I'm just not sure how evaporation works in humidity. Maybe I should experiment by spraying the roof for the four minutes at intervals like the guy in the article has his sprinklers set to and see if it makes a difference. I could manage that from the ladder with a good hose nozzle.

Finding something to put on outside of windows to reflect sunlight would help too. I have outside blinds but the inside curtains in his room are very warm to the touch.

Cindy

[Hotzcatz]

If it is a rental move somewhere that works for you. Is his bedroom on the sunrise side of the house? If it starts out with the afternoon heat already in his room it will be more difficult to cool it.

Wait until the evening air cools down and then open all the windows, turn on some fans and ventilate the room for fifteen minutes to cool it down then shut all the windows.

Open the windows and wear earplugs.

[Carey]

Cindy,
With the hose, be aware that the water direction should be the same as rain .... roofs are water tight as water flows down, water flowing up (as a hose can do) may leak into the attic

That reflectix stuff we gave you last year could help on the windows....
any insulation (even packing rigid foam - caution though, as this is not fire retardant treated...) would help in the attic, but not sure how much you want to spend.... & if you care if it is fire retardant.... also check around the attic for venting... the older homes had plenty, but we have noticed that alot of the homes built from the mid-sixties on had minimal attic venting(usually to meet code or less)...
If it is OK with the homeowners, adding side vents may not be prohibitive $$$ as roof venting, would not even think of doing this on a rental... as not as easy or inexpensive...) Call us if you need....

[Cindy Blankenship]

Here's a copy and paste excerpt from the article I linked in last post
http://www.doctajstutoring.com/webdoc22.htm

"During the 2006, 110 F heat wave, I set my roof sprinklers up to spray at 10 a.m., 12 noon, 1 p.m., 2 p.m., 3 p.m., and 4 p.m. - for four minutes each time. Although the spray only reached about 50% of the roof, I had approximately 8 gallons of total hot water runoff (water from downspouts averaged 140 F). This meant nearly 88 gallons of cool water was warmed and vaporized on my roof. This was the cooling capacity of 880,000 BTUs!! In comparison, an average window-type air conditioner is rated at about 10,000 BTUs.

Further, my attic temp dropped from 135 F (at 2 p.m.) on a day when the roof was NOT cooled, to 117 F (at 2 p.m.) on a day when it was cooled (two days later). On both days the outside air temp was 108 F (as measured at my house patio).

When I use the roof sprayers to keep my home at 82 F, it required only 40% of the air conditioner use as when I didn't use the sprayers. On the days measured, my A/C use dropped from 7 hours to a fraction more than 3 hours. Based on a measured A/C savings of 0.1 kWh/gal, the minimum A/C savings equated to approx. 9 kWh/day (the energy of 90 screw-in fluorescent light bulbs on for 15 hours a day)."

Others use soaker hoses. With our pitched roof and a soaker hose I don't think the water could flow up so that shouldn't be a problem.
The house other than summer day sleeping is perfect for us. Son doesn't want to move. Not an option. We want to try the water on the roof system. If that doesn't work, since neither of is an A/C repair person or electrician, I will print out the DIY for having the A/C outside of the room and thermostat inside the room and see if I can find someone who can rig this up. I can do the duct part, just not the thermostat part. But anyway I think the roof cooling is brilliant. It's mentioned on many green living sites. The reason I post it here is I was wondering if given our humidity if it works here. But then one of the Home Depot clerks who gave me the idea (before I researched it) said she's seen people use it...doesn't mean it works here though.

Carey we have the windows covered with the reflective stuff so thanks again and that keeps the heat from coming through the glass.

And, yes, we cool it off at night (when he's in nightowl mode)and shut windows while it's nice and cool in there. By 8 or 9 a.m. it's an oven again. Yes, attic has ventilation - an open, screened window.

It's coming from the attic or walls or both. Faces south. Is in shade by 11 a.m. Plan on shading the vinyl siding walls too but I think the hot roof is the main problem. I'm going try the hose first as the cheaper of my two plans and then the remote A/C with a duct going into the room. I found some handymen in the phone book - maybe one won't be afraid of heights like we are.

Cindy

[Noel M2]

Cindy - let us know how it goes with the soaker/sprinkler solution. Given the rental situation, you are limited in what you can do but it looks like you have some options (based on your last reply).



Noel
http://HiloParadise.com

[Cindy Blankenship]

Thanks Noel. I'll be sure to post results. It's so hot today even in the breezy office and living room I'm wishing I had it up there now. Right now son is sleeping in his computer room, with A/C on but just doesn't sleep as well due to noise. He goes in cycle with sleeping days and nights and has always had issues with this...except when we rented a house with central air (quiet) in Oregon.

Cindy

[Larry T]

Here the humidity is way to high for evaporation to work. Where it is hot and the humidity is low ( 10% ) it works great, but here the humidity is 65-85% and doesn't work.