March 2010 Archives

Solar attic fans are one of those ideas that just make sense, they are simple, effective, inexpensive and they work exactly when you need them; when the sun is shining and it's hot outside!

I've been down in Texas visiting friends and family for the past month, taking in the different types of architecture here in San Antonio. I've been noticing the large pointed roofs on many of the houses, a feature designed to keep heat away from the ground floor. I've noticed the trees strategically positioned to shade windows and all of the white trucks parked out front... The ceramic tile that extends from bathrooms and showers to cover the entire house floor because cold tiles feel nice against bare feet on hot summer days.

There a few really simple techniques you can use when designing a house to keep it cool. Have a ridge vent installed in addition to intake vents along the eves. This type of setup pulls in cold (or at least relatively cool air) from the sides of the house and drafts it up through the hotter internal spaces out through the top. You can use spray-on heat deflecting materials or attic foil such as Radiant Barrier (highly recommended by construction workers in these parts) designed to reduce radiant heat. But both of these options are easier to do when you're already replacing a roof or starting from scratch but will probably become more and more favorable as the price of electricity rises.

This is exactly where solar attic fans. These devices come in all shapes and sizes, some lower quality than others, but they all follow the same basic concept: get air circulating through your attic space to keep it cooler and thus, keep your living rooms below the roof and attic cooler as well, all while conserving energy by leveraging solar power.

It sounds simple but there is really more to consider here. First, you want to make sure you aren't sucking cool air away from your living spaces. This can be avoided by checking the seals on inset light fixtures (Home Depot sells sealed ones) as well as light switch and plug outlets (you can get foam pads that fit behind the plastic covers and block the holes and cracks). You really want to make sure you have some eve vents on your house so there is a place, other than the rooms below, for air to travel up into the attic from. It's a real bummer when you realize all of the AC you're generating is being sucked up into your attic! Eve vents (also called soffit vents) and good sealing techniques will solve this.

Installation of a solar electric attic vent is something you want to execute very carefully or hire a professional to do. Most installers recommend positioning one or two of them at opposite ends of the house. And don't get thrown immediately if one of these contractors tells you otherwise about a solar attic fan. I heard one gentleman say "the hottest your house will be is after dark in August," implying that the solar powered device would be shut off (no sun after dark), but he was missing one important point. Even if it were true that the hottest part of the day in a house was after the sun had gone down, it would certainly be less hot after a day full of venting than one with no venting at all.

The best solution for one house is probably different from another and might combine all of the passive cooling techniques described here. A solar powered attic fan is certainly not going to hurt you if it's installed correctly and fit into your venting design with a bit of intelligence. Consider plugging those air leaks, utilize a ridge vent or at least the eve vents as well as a fan approach and good luck with those hot summer days!

Recently I visited San Antonio Texas where half the population lives on farms and ranches outside city limits. People raise cattle and other livestock which requires good fencing, to keep the animals from wandering off. In addition to barbed wire, electric fences and chicken wire people build stronger metal fences near the entryway and driveway leading up to their houses. This is a popular ritual, even people who don't have animals usually have a gate across their driveways to provide security and privacy.

Anyone who's visited a ranch knows about these long metal swinging gates. They work pretty well (unless kids have been riding on them) and are effective property markers. I've seen them in use in the mountains of Colorado, ranches in Texas and just about anywhere else that people are living on two or more acres. They are useful and economical, the only downside is that they've traditionally required a lot of effort to use.

Imagine getting out of your truck or car each time you arrive "home" finally after a long day in town or hauling loads across the countryside or mountains. You're back, but you're not really there yet. You have to stop your car, get out and unlock the gate or just loosen the chain. Swing the gate open and maybe tie it up, then you get back into your car, drive through and park again. Get out and close the gate. That's five steps total and that's a waste of gas (whether your car is idling or using extra energy to stop and start twice). It's no wonder that electric gate openers are in widespread use across the country. Much like a garage door, these devices usually rely on a car battery to prop the gate open and then close it 30 seconds later. They are secure, reliable, and they save a lot of energy.

These gates use car batteries in most cases because they are cheap, convenient and much easier to place than wires running from the main house. The jump from stand alone batteries to trickle charged batteries operating off of a small panel took less than a nanosecond. Trickle charging is one of the best ways to charge batteries, adding to their lives, and the panels don't have to be too large to make it all work. Just like the panels you might see on roadside emergency phones, lights and even trashcans, these work great for solar powered driveway gates.

Just below are several images and descriptions of these solar powered gate systems. First up is a complete shot of the light poll with the solar panel attached, the electronics box and the gate with the electric motor.

Next is the back side of the mini solar panel (this one was made by UNI-SOLAR) used to charge the car battery inside the electronics box which opens the gate and controls the remote control activator.

Just below is an inside shot of the car battery and electronics printed circuit board (PCB) that controls the gate and sets the security code. This particular unit was made by Apollo Gate company and is from 2001. Not much to it really, the battery connects to the control unit and there is a radio receiver for the remote (works just like a garage door opener) and a few pins that control the opening code. There is also a turn key and button on the exterior of the box which can be disabled. Apollo sells swing gate and slide gate systems depending on your taste as well as barrier arms (think railroad tracks only smaller) and there are keycode boxes that can be mounted on the driveway if the remote control isn't your style. Using the small solar panel and trickle charge setup the battery will last years and the entire system can run $500 or less if you've already got fencing in place and it will save you a lot of  hassle, gas and frustration (especially if it's raining).