Garage Ventilation

[pchilds]

I have thinking about, installing a whole house fan, in my garage, to remove the summer daytime heat. Out comes the July Harbor Frieght flyer and they have
a coupon for a 30" High Velocity fan, for $99.99. I will let you know how it works out, it hit 112F today, the garage is 97F, last night the low was 68F.

 

[mynameisjim]

How will you install this fan in a manner that provides home security? It seems to me that this will leave your garage vulnerable.

 

[tbleakne]

The fan in this picture appears to be the type that just moves air around in a room. I would think you want a fan that will pump air in or out through a vent.

My garage has a small window in which I have mounted a fan designed for window placement. I have it on a timer to start up after sunset, and stop at sunrise. It definitely cools the garage down faster in the evening, and gets it to a lower temperature by morning. During the day I rely on the garage's heat capacity and its insulated garage door to keep the temperature cooler than ambient. Power expended by the fan is modest, and is of no concern because I have a substantial TOU solar credit to use or lose this summer.

Today was very hot for this early in the summer, maximum 96 F. Overnight low about 65 F. Garage temperature trailed ambient by about 10 F all day.

Security is not ideal, but there is nothing in the garage worth stealing other than the car, it is locked, and the door from the garage to the house is locked.

My LEAF managed to get down to 5 T-bars by morning, but quickly went to 6 T-bars when I went out for an errand mid-day. To do better I could add a small A/C unit. I would not run it all night.

 

[DaveEV]

Your typical inexpensive fan can draw 100-300W pretty easily. Not efficient, and these fans are typically fairly noisy. Run that for 10 hours/night and you're looking at 1-3 kWh/day, or probably a substantial amount of energy that you use driving! Super-efficient mini-split HVAC units are capable of delivering substantial amounts of AC cooling for 300W of input power. So put a Kill-A-Watt on that fan if you're using one, you might be surprised!

Panasonic has a "WhisperGreen" line of DC fans which are highly efficient (FV-13VK3, for example) - they have a 130 cfm model which draws no more than 20W (half that if your ducting provides low resistance to airflow).

Now on a 22'x22'x10' garage, you're only getting about 2 air exchanges/hour, but compared to passive venting (unless very well designed) it should do a very good job of reducing temps in the garage with minimal energy input and noise.

 

[pchilds]

The fan draws 160 watts on low, 6500 cfm, 40 cfm per watt, 210 watts on high 9000 cfm, 43 cfm per watt.

130 cfm at 10 watts = 13 cfm per watt, not as green as they would have you believe.

This just reminded me, I have a 3000 cfm, 12 volt dc fan that only uses 30 watts, that is 100 cfm per watt.

BTW the monster fan dropped the temperature 10F in two hours, if I run the fan for 6.5 hours a day, on low, it will cost me 12 cents a day.

 

[pchilds]

How will you install this fan in a manner that provides home security? It seems to me that this will leave your garage vulnerable.

True, I leave the side garage door open when the fan is running. I have security cameras, feeding a DVR.

 

[mirko]

If you need a new water heater you could get one of these Hybrid Water Heaters. It uses a heat pump to take the heat in your garage to heat the water. As a result it helps to cool the garage with cool air.

http://products.geappliances.com/ApplProducts/Dispatcher?REQUEST=SpecPage&Sku=GEH50DNSRSA" onclick="window.open(this.href);return false;

http://www.energystar.gov/index.cfm?fuseaction=find_a_product.showProductGroup&pgw_code=WHH" onclick="window.open(this.href);return false;

 

[TickTock]

I am considering adding a swamp cooler to my garage - there is a window unit at Home Depot that lookis like it could be secured. They work very well in phx due to the dryness but most of us desert rats aren't used to the humidity it creates. However in the garage, I'm guessing the car doesn't care.

 

[Herm]

how much water does the swamp cooler use?.. Is that an issue?

 

[ztanos]

how much water does the swamp cooler use?.. Is that an issue?

Attach it to the AC units condenser lines and you could have a perpetual motion machine. :lol:

 

[TickTock]

how much water does the swamp cooler use?.. Is that an issue?

Prefect opportunity to use lmgtfy but I will resist. The average households unit uses over 50 gallons a day, but a one room window unit should be a small fraction of that.

Nice idea to use the ac drain as a feed, but I already have that going to some landscaping plants.

 

[tbleakne]

If you need a new water heater you could get one of these Hybrid Water Heaters. It uses a heat pump to take the heat in your garage to heat the water. As a result it helps to cool the garage with cool air.

http://products.geappliances.com/ApplProducts/Dispatcher?REQUEST=SpecPage&Sku=GEH50DNSRSA" onclick="window.open(this.href);return false;

http://www.energystar.gov/index.cfm?fuseaction=find_a_product.showProductGroup&pgw_code=WHH" onclick="window.open(this.href);return false;

I like your thinking. However, in my case I don't think I use enough hot water to generate much garage cooling.

Electrical efficiency of a fan is not very important to me, because I operate it in the evening at off-peak TOU rates, and I had a TOU surplus last year that was zeroed out in the 13th month.

Electrical efficiency of a swamp cooler or A/C that operated in the heat of the day would be more important, because this usage would subtract from my peak-rate solar production.

 

[garygid]

Exhaust the garage air through the fan (in a just-fit circular opening)
into the attic, blowing the hot attic air out the attic-to-outside vents?

If so, be sure that the attic has enough vents to avoid too much pressure buildup.

 

[KJD]

The fan draws 160 watts on low, 6500 cfm, 40 cfm per watt, 210 watts on high 9000 cfm, 43 cfm per watt.

130 cfm at 10 watts = 13 cfm per watt, not as green as they would have you believe.

This just reminded me, I have a 3000 cfm, 12 volt dc fan that only uses 30 watts, that is 100 cfm per watt.

BTW the monster fan dropped the temperature 10F in two hours, if I run the fan for 6.5 hours a day, on low, it will cost me 12 cents a day.

How is the fan experiment working out ?

12 cents a day is cheap insurance if that battery pack will last longer than it would without the fan.

 

[DaveinOlyWA]

late to this but i installed 2 attic ventilation fans in my house i built which where i think you need to go. mine is thermostatically controlled to kick on at a certain temp and it exhausts hot air out of both eave ends.

do this and provide an attic access to the garage. this should allow air to circulate from the garage to the attic and out the gable ends

now, i live in moderate climates but i did this because it was supposed to add about 5-10 years to roof life in moderate climates. in the scorching heat you have, i doubt this will do anything for your roof (guessing you dont have many comp roofs anyway)

now this maintains security and probably would recommend you open garage door a few inches to help direct the air flow a bit.

now i did mine in the early 90's and they were square fans. for new construction they have the round ones mounted at the roof apex which works much better. now since i installed these as new construction, have no guideline as to how effective they were and as far as noise. if the house was quiet i could hear them turn on but the sound faded into the background quick enough. outside the house you could hear them run since they were mounted on the side of the gable ends

 

[Nubo]

late to this but i installed 2 attic ventilation fans in my house i built which where i think you need to go. mine is thermostatically controlled to kick on at a certain temp and it exhausts hot air out of both eave ends.

do this and provide an attic access to the garage. this should allow air to circulate from the garage to the attic and out the gable ends...

As I understand it, an attached garage should be firewalled from all other areas of the house. That means properly-rated drywall and door, and no other openings into other areas of the house.

 

[pchilds]

The last couple days have been 105F plus. Have ran the fan for 12 hours. Yesterday, I got the temperature down from 98F at 6:00pm to 70F at 6:00am. I have been opening the door, from house to the garage, to cool the house, so I am getting warmer air, than if it was outside air only.

 

[DaveinOlyWA]

The last couple days have been 105F plus. Have ran the fan for 12 hours. Yesterday, I got the temperature down from 98F at 6:00pm to 70F at 6:00am. I have been opening the door, from house to the garage, to cool the house, so I am getting warmer air, than if it was outside air only.

sounds like the results you want!

 

[pchilds]

Battery temperature this morning, 5 bars, air temperture 69.0F.

 

[Herm]

I still think a swamp cooler window unit in the garage is a low cost way to keep the temperatures down. Has to be a lot less water usage than keeping a lawn green. Electric cost will be nil since its only a fan to move the air around.

http://www.amazon.com/Symphony-SHiCool-Portable-Swamp-Cooler/dp/B000R37378" onclick="window.open(this.href);return false;