solar shed is too hot, recommend efficient attic fan??

I put the solar control system in a tiny, uninsulated metal building ... the kind you see for sale at the big box home improvement stores. Temps were getting in the 90's and I installed a box fan in one window (blowing out) and opened the other window for air intake. Even so, temps in the building were recording up to 110 degrees F. Definitely bad news territory.
I went in and insulated the south wall (R13), west wall (R13) and ceiling (R19). North wall and east wall are sheltered and don't receive direct sun. Now, with the forced box-fan ventilation, internal building temps are pretty much equal to ambient temps. The negatives are that I have to open the windows in the morning and set the box fan in place and reverse the process at night.
Long story short, got to thinking about an thermostatically-controlled attic vent for exhaust and a return-air floor grate for air intake (animal/insect proofed). I found one efficient attic gable fan that claims it draws 30 watts AC for around $300 (QuietCool AFG ES-1500). Found another attic gable fan that comes with it's own solar panel and this one looks pretty interesting for about $400 (Natural Light Energy Systems 36W). Anyone had any experience with these two gable fans? Are there others that are better?
Sure could use your input.
I went in and insulated the south wall (R13), west wall (R13) and ceiling (R19). North wall and east wall are sheltered and don't receive direct sun. Now, with the forced box-fan ventilation, internal building temps are pretty much equal to ambient temps. The negatives are that I have to open the windows in the morning and set the box fan in place and reverse the process at night.
Long story short, got to thinking about an thermostatically-controlled attic vent for exhaust and a return-air floor grate for air intake (animal/insect proofed). I found one efficient attic gable fan that claims it draws 30 watts AC for around $300 (QuietCool AFG ES-1500). Found another attic gable fan that comes with it's own solar panel and this one looks pretty interesting for about $400 (Natural Light Energy Systems 36W). Anyone had any experience with these two gable fans? Are there others that are better?
Sure could use your input.
Comments
Solar hybrid gasoline generator, 7kw gas, 180 watts of solar, Morningstar 15 amp MPPT, group 31 AGM, 900 watt kisae inverter.
Solar roof top GMC suburban, a normal 3/4 ton suburban with 180 watts of panels on the roof and 10 amp genasun MPPT, 2000w samlex pure sine wave inverter, 12v gast and ARB air compressors.
A computer fan would most likely move more air than the $ 400 solar powered fan would.
Maybe use oil pan 4 idea and when the temperatures are still rising then have a thermostat turn on the computer fan. Or get a small solar panel and hook your computer fan up to that and every time when the sun is shining the fan will come on.
I sure like the energy cost of passive cooling. Have you tried this approach or seen this approach used?
This Natural Convection cooling is quite common for Passively cooling attics, and commercial metal buildings, etc.
Works well. Vic
Solar powered roof fans do not move much air (one poster here years ago found a couple of solar fans had failed, and the attic was still as cool as when the fans where running--Additional venting was enough to keep the place cool(er).
-Bill
Yes houses all around the country use this to cool the attic space. It can cool the attic space 30 to 50'F.
Solar hybrid gasoline generator, 7kw gas, 180 watts of solar, Morningstar 15 amp MPPT, group 31 AGM, 900 watt kisae inverter.
Solar roof top GMC suburban, a normal 3/4 ton suburban with 180 watts of panels on the roof and 10 amp genasun MPPT, 2000w samlex pure sine wave inverter, 12v gast and ARB air compressors.
The walls of the solar shed are white sheet metal. The roof is a "mill" finish silver (like galvalume).
After insulation, I'm guessing the only coating that would help would be some kind of ceramic coating. In central Florida, they built houses out of forty foot shipping containers ..... and sprayed these containers with an expensive ceramic coating that repelled just about all radiant energy. This was very expensive stuff a few years back, I wonder what it costs today?
A computer fan might just be the ticket as part of the solution.
2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric, 460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.
AFAIK, ceramic paints are a scam in terms of blocking heat (ie, don't expect any better than white paint).
I am available for custom hardware/firmware development
- With the afternoon sun on the West wall of the metal building, the outside metal skin temperature was 130 - 136 oF
- The surface of the Styrofoam inside the building was ~97 oF the same West wall
- The equipment inside the building was ~94 oF
- The SMA Sunny Boy max surface temperature was 115 oF
- The ambient temperature was slightly above 90 oF
- The bottom surface of the PV panels was 125 oF (mounted on the roof of the metal building).
- The areas above the ceiling panels were approx. 120 oF.
I found several areas that need the foam installed behind the metal skin. I definitely need to install the ventilator above the ceiling panels to move more hot air out of the building.
The walls of the solar shed are white sheet metal. The roof is a "mill" finish silver (like galvalume).
After insulation, I'm guessing the only coating that would help would be some kind of ceramic coating. In central Florida, they built houses out of forty foot shipping containers ..... and sprayed these containers with an expensive ceramic coating that repelled just about all radiant energy. This was very expensive stuff a few years back, I wonder what it costs today?
A computer fan might just be the ticket as part of the solution.
After much research, I started looking at greenhouse louvered-ventilation fans. I found an ok model (1 amp motor w/decent airflow) from a reputable vendor and placed the order. Also ordered a fan speed control, thermostat and sheet-metal, rain-proof canopy. I'll use standard central air conditioning return air grills for the input air source (20x20's).
I'll post some data after a meaningful time.