Any solar users in SoCal also using a whole house fan?

[TypeRx]

Guys:

In addition to having a 7.1 kW solar system installed, I am also considering installing a whole house fan (probably http://www.centricair.com/whole-hous...entricair-3-1/). This way we won't be so reliant on A/C.

However, I am wondering if I should bother? With the solar system, I'll be generating enough electricity to power A/C when I really need it. But, that is still a bit wasteful considering the environment I live in is well suited for a whole house fan (low humidity, big temperature drop at night, etc.). The fan is $1300 and there are currently no rebates/incentives where I live (Orange County). I'll install myself, so that saves a few bucks but just wondering if others here see value in a whole house fan vs. just using A/C when you are solar powered.

Thanks!

[lkstaack]

Many people look at solar as "free" energy. It's not; you spend a lot of money up front. The more energy you consume, the more expensive your solar system is going to be. So, you want your solar system to be as small as possible while simultaneously meeting your production goals. You can do an analysis to determine if your $1,300 is better spent with a fan or a larger solar system. You'll probably find that the fan is a better value.

[russ]

Many people look at solar as "free" energy. It's not; you spend a lot of money up front. The more energy you consume, the more expensive your solar system is going to be. So, you want your solar system to be as small as possible while simultaneously meeting your production goals. You can do an analysis to determine if your $1,300 is better spent with a fan or a larger solar system. You'll probably find that the fan is a better value.

Excellent post!

[J.P.M.]

Guys:

In addition to having a 7.1 kW solar system installed, I am also considering installing a whole house fan (probably http://www.centricair.com/whole-hous...entricair-3-1/). This way we won't be so reliant on A/C.

However, I am wondering if I should bother? With the solar system, I'll be generating enough electricity to power A/C when I really need it. But, that is still a bit wasteful considering the environment I live in is well suited for a whole house fan (low humidity, big temperature drop at night, etc.). The fan is $1300 and there are currently no rebates/incentives where I live (Orange County). I'll install myself, so that saves a few bucks but just wondering if others here see value in a whole house fan vs. just using A/C when you are solar powered.

Thanks!

It may have been better to install the fan before solar and thus allow a smaller ( less $$) PV system. Now, if your PV is oversized, it won't matter much $$ wise, but may allow lower A/c use and thus allow use of elec.r other uses w/out a $$ penalty.

As for efficacy, Fans for ventilation at times when outside temps are less than inside during cooling season can save money when used in conjunction with other money/energy saving measures like increased thermostat settings.

In spite of being near San Diego, I'm a bit inland and have a rather significant cooling season w/daytime temps commonly in the mid /upper 80's w/lots of sun.

The use of lots of night time ventilation as/when appropriate on a somewhat common sense basis, along with a 78 deg. F. thermostat setting, use of window treatments for some solar heat gain control and a few other things allows by A/C operation, on average, to be limited to about 100 hrs. of HVAC system operation per year for cooling, consuming about 600 kWh/yr. Most of that A/C happens not only when daytime temps get past 90 deg. F, but also when night time temps. do not drop as much, reducing the efficacy of the intentional ventilation.

Side note: If I had better insulation, a tighter envelope and more thermal mass (all working together to producing what is a longer or larger thermal time constant), I could reduce the HVAC load more, but more importantly for this conversation, reduce the rate of temp. gain during the day so that the A/C, which, on hot sunny days fires up at ~ 1400 - 1500 hrs. solar time for me, might be put off until peak power cost time has passed, or at least shifted to later in the day. That idea, with more thermal mass can work on the other end as well - fire up the A/C in mid morning until peak cost time and "precool" the space using cheaper than peak pricing, but that's a bit trickier than putting off afternnon cooling.

[slopoke]

I'm in Northern Ca, Livermore to be exact and I have a whole house fan in my home. It was installed a few years prior to my solar installation so my solar system was sized correctly. My home is 2400 sq ft and I had a 9000 CFM fan installed. Along with that I had to install seven 18" vents into my roof to get adequate venting, they look like the mushroom type of electric roof fan units minus the fan. If you do decide to install one and your installer does not install more venting to your roof or gable vents, run away. You'll end up pressurizing your attic, blowing the hot air from the attic back into your living space and make your fan motor work really hard and decrease it's lifespan. Also be aware of the "quiet fans", they don't move much air and cost quite a bit and won't cool your house like a properly sized fan should.

I really like mine. It's a Triangle Engineering fan with low and high speed settings. I turn mine on when the outside temps are just starting to get lower than the inside and depending on the temp differential, I cool down at around 2 or 3 degrees per hour when the difference is slight. I usually turn it on for a few hours in the evening, then in the early morning prior to work and cold soak the house as much as possible, when the outside air is the coolest. If your house has a musty smell or if you burnt toast or what not, it will evacuate the smell and smoke rather quickly. It comes in handy when seasoning a new wok or fry pan.

If memory serves me correctly, I save around 50 to 75 per month in the summer, since the installation of the fan and I paid $2250 (I just looked at my invoice) for the fan and vents, including labor. So with those numbers, it'll take 6 years to recoup my costs. Good luck.

[TypeRx]

I'm in Northern Ca, Livermore to be exact and I have a whole house fan in my home. It was installed a few years prior to my solar installation so my solar system was sized correctly. My home is 2400 sq ft and I had a 9000 CFM fan installed.

Wow, that is moving some serious air. You can probably clear your house of hot air in a couple minutes, huh?

Along with that I had to install seven 18" vents into my roof to get adequate venting, they look like the mushroom type of electric roof fan units minus the fan. If you do decide to install one and your installer does not install more venting to your roof or gable vents, run away.

Great advice..have already looked at venting in my attic and confirmed I am okay but was looking at a fan that moves about half as much air as you.

Thanks again guys -- I don't want to take this too far off topic. My solar system is not yet installed so I will make sure it is sized according to my anticipated demand, with or without whole house fan.

[jd31]

Wow, that is moving some serious air. You can probably clear your house of hot air in a couple minutes, huh?




Great advice..have already looked at venting in my attic and confirmed I am okay but was looking at a fan that moves about half as much air as you.

Thanks again guys -- I don't want to take this too far off topic. My solar system is not yet installed so I will make sure it is sized according to my anticipated demand, with or without whole house fan.

A lot of great advice so far. I'll just add that I have a whole house fan and love it. Aside from the energy savings benefit, it helps cool your home considerably when the outside temp is lower than your inside temp. The comfort alone was worth it for me...and I use my AC a lot less.

[kylechoffman]

I am looking at putting two of these in due to the setup of my attic and spread-out nature of my 2nd floor: http://www.centricair.com/whole-hous...entricair-3-1/

The one you mentioned is cheaper than two of the ones Im considering but adding in the two speed control brings the cost above 1400. The estimate I received was 2K installed. I think they are a good idea to offset the usage in the evenings.

[bcroe]

The fan is $1300 and there are currently no rebates/incentives where I live
(Orange County). I'll install myself, so that saves a few bucks but just wondering if others here
see value in a whole house fan vs. just using A/C when you are solar powered. Thanks!

Solar energy is only "free" when the solar is already paid for. Still at that point, it is nice to
just turn on what you want and see the meter continue to export your surplus. Bruce Roe

[jonathan]

(Revised after a moderator pointed out I shouldn't have a direct link to gear -- oops, my mistake, sorry.)

We have an AirScape fan. It has an ECM motor, so it's efficient, and virtually silent for 5 of the seven 7 speed settings. We love it. We're in the bay area, and have elected to skip A/C since our house is fairly efficient, and there are only a few days over the summer where it's hot enough to consider using it during the day. With the whole house fan, we can pre-cool at night, as well as replace the interior air with fresh air.

[donald]

Whole house fans are wonderful for areas that cool off at night. It's more than just an energy savings choice. It's an air quality choice. Be sure to at least get a timer.

Mine turns off based on temp by reading the upstairs HVAC thermostat. It also turns off when rain approaches.

[sdold]

We love ours. After a hot day, it's like having a cool breeze blowing through every window. Be sure to get a slower-turning quiet one with belt drive vs. a direct drive one with a higher fan speed. Triangle is a good brand.

[Mike90250]

I cut a plywood sheet to fit my ceiling attic hatch, and suspended a 20" box fan (via bungee cords) to exhaust house air into the attic and then let the attic vents disperse the air. Worked quite well, any room with an open window, had a cool breeze coming in.

[Sunking]

Geez is that what they call Attic Fans now. Damn marketers.

[sdold]

I think attic fan refers to the fans that are on the roof or gable and cool the attic by pulling air in through the gable and soffit vents and blowing it out.