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Solar Blankets


Solar Blankets (aka: pool blankets, solar covers, big ugly blue things) are great for keeping the heat in a swimming pool - They're just so dambed awkward to handle! As solar blankets are very important in keeping the costs of operating a swimming pool down, here are a few pointers that will help you get the best use of them.

SolarOntario does not currently sell solar blankets.  If you're interested in other environmentally friendly ways of keeping your pool warm all summer, check out our information about solar pool heating using solar collectors. We can provide a free quotation for a solar system for your home.

Tips for using a Solar Blanket:

1.) There are two main types of blankets available. The bubble type solar blanket which lets about 50% of the sunlight into the pool, and the foam type, what we call "lunar" blanket which lets 0% of the sun into a pool. Both types of blanket work very well at preventing water from evapourating from the pool when they are used (properly).

2.) Every solar blanket should have a roller to wind the blanket off the pool when not in use. It makes the blanket easier to handle (so you will be more inclined to use it) and will prolong the life of the blanket.

3.) Blankets can be awkward to use on other than rectangular pools. Sometimes it works to place the roller across the middle of the pool rather than at the end of the pool. Sometimes it works to cut sections off the blanket so they don't catch on the sides of shaped pools.

4.) Some pool blanket coverage is better than none. If you can't cover all of the surface of the pool with a blanket, cover as much as you can. As a last resort you could try products that claim to disperse a film over the surface of the water to slow down evapouration - We are skeptical of the effectiveness of these products - a blanket WILL do a much better job. (See item 10)

5.) Bubble solar blankets have very little insulating value - they are best at preventing evapourative cooling. The foam "lunar" blankets reduce evapourative losses and actually provide a small amount of insulating value, plus they will also reduce the radiative losses better than bubble blankets.

6.) The drawback to "lunar" blankets is that they block 100% of the sunshine from entering the pool. This can be great if you are leaving your pool for a week (or so) and you want to keep it from overheating and growing a crop of algae, however, if you want to heat your pool, you can't use them during the day. (Hence our term "lunar" blankets). Lunar blankets usually last at least twice as long as bubble blankets. (5-7 years)

7.) Either type of blanket's ability to keep heat in the pool will be significantly compromised if the top of the blanket is covered with water or has puddles of water on it. Water will evapourate from the puddles and pull heat right through the blanket and cool the pool. After it rains, you should roll it up the blanket and drain the water off of it.

8.) One myth about solar blankets is that they cause algae to grow. Algae grows in pools that are warm and don't have enough chemical in them to kill the algae. What often happens, is that pool owners will cover the pool and neglect it for several days at a time. The (bubble) solar blanket covered pool heats up and the sanitizer in the water disappears, providing a perfect breeding ground for algae. Once algae gets this type of foothold, it requires a lot of chemical to get rid of it. Plus, the solar blanket has now has algae growing on it. The blanket must be cleaned or it will re-introduce algae back to the pool when reused! (This problem basically disappears on salt-water-sanitized pools)

9.) A major advantage solar pool heating systems provide over fueled pool heaters, is that you don't need to use your pool blanket in the middle of the season, and your pool will still be warm. The reason for this is that although the pool will lose a couple of degrees overnight, the solar system will recover that heat quickly the next day - for free! If you have to pay to recover that heat, you may be more inclined to keep the pool cover on the pool....

10.) There are a number of products on the market that claim to keep heat in the pool by reducing the evapouration of water from the pool by spreading a thin layer or film of liquid (material unknown) over the surface of the water. While the science of this effect is well known, and used on ponds and canals in arid regions of the US and Canada, it can't work effectively on swimming pools. The reason is swimming pool pumps & filters actively clean the surface of the water with skimmers - effectively removing the film and filtering it out. The only way to see any benefit from these fishy items is to only use the bottom drain or an automatic pool cleaner (Kreepy-Krawly, Barracuda, etc.) all the time to take water from under the surface of the water. Of course, then the leaves and bugs and dust that fall into the pool, accumulate on the water surface of  the pool.

11.) There are now a number of pool blanket "storage" systems which can take a lot of the trouble out of handling and hiding a solar blanket (and potentially make the pool area safer). Some are even motorized, and come with remote controllers! Two significant issues. 1.) They are very difficult to impossible to add to existing swimming pools. 2.) They are expensive. If you are building a new pool and have the cash ($8,000 to $25,000) then this might be an option you should consider.

If you're interested in other environmentally friendly ways of keeping your pool warm all summer, check out our information about solar pool heating using solar collectors. We can provide a free quotation for a solar system for your home.