BLACK SOLAR CURTAINS FOR 30% SAVINGS OF WINTER HEAT by J.E. Ante
Approximately 75% of all sunlight that shines through east, west, and south facing windows and doors is wasted as light energy in cooler winter months. This 75% solar gain “loss” can amount to 30% or more of your total heating bills in the typical home or business. All windows and doors that the sun shines through can produce either heat or light but not both from this sunshine. But since approximately 95% of all curtains have only white backing to reflect the suns rays most all of this potential solar heat gain in winter from windows and doors is lost or never used in most homes and businesses.
For example I have two doors and 10 full window sets in our house that face either east, west, or south that get the sunshine. I have a choice to either let light into these 12 windows and doors or I can make heat by installing flat black or dark colored reversible curtains. If I choose to let only the sunlight into the windows and doors then I get light in 100% of these areas or rooms but almost no heat gain. But if I use the black backed curtains I can save 30% or more of my total heating bills per year. Each black solar curtain does not keep out all of the sunlight and it is a simple matter to open a curtain in a room which I am working to get additional light to work. And since I can be in only one room of the house at a time it makes sense to me to make heat in the other 11 unused room windows and doorways instead of the light which is 100% wasted. Most people do not realize that they have this choice to produce either heat or light from sunshine that shine into their home or business.
In order to gain this 30% winter heat savings you need two things. One, seal the windows and doors with Duct or other Roll-On Clear Window film for about $1.00 per window. And two, cover you windows and doors with a dark, black, or better flat black colored material or curtains to start making heat rather than light with this sunshine. The black materials will absorb the sun’s rays and create a heat draft which will draw cooler air upward from the floor and from the cold spots in the center of a room.
The best solution to make solar curtains is to sew on a reversible black liner material into your existing curtains or possibly dye some curtains black. If you have venetian blinds you can spray paint one side flat black for winters and use the existing white side for summers. And you can make a very good temporary window solar panel simply by taping 10 centt black trash bags over the windows or draping black sheets or other dark material. But let a space of 2 inches at the top and bottom for air to circulate upward and at least 2 to 4 inches away from the window.
Thermal back curtains that cost about $30 per window that reach all the way to the floor are the best option because they make a natural chimney which raises cooler air from the floor upward. If the black material is too close to the window and/or can not circulate then you end up heating mostly the window panes and loosing much heat from convection of the cooler glass window panes. So keep the black materials or curtains at least 2 to 4 inches from the window pane. The thermal curtains are the best option because they also conserve heat loss during the night and also whenever the sun is not shining during the daytime and so the extra expense is well worth it. But simple black faced curtains or curtain liners with no thermal layer work fine.
The Duct or other Roll-On Window kits can be purchased at the end of winter season at 75% off and/or simply buy a $3.00 additional roll of double sided tape and save and reuse the clear plastic next year. These clear roll on kits take only about 5 minutes to install per window and are advertized to save $190/year on a five window kit or $38.00 per window or door.
The 30% solar savings can be greatly increased by reflective surfaces outside of the house that reflect sunlight into your windows and doors from the outside. I like 3/8 inch foam with silver backing on one side for this purpose. For instance my south facing door entry is lined with this foam board vertically on each side wall which is little noticeable to anyone. These two reflective surfaces on either side of the door entry doubles the square footage of usable solar gain and sunlight coming into my door’s passive solar panel. My south facing door is covered black and I simply open the door as far as possible with the door chain lock still fastened during the day when the sun shines to gain this free solar heating.
Other outside reflective surfaces for windows should be roughly set at 45 degrees so that they reflect sunlight into the window solar curtains. The 3/8 inch 2ft by 4ft reflect foam boards cost about $1.00 each when purchased in packs of 12 at the hardware store such as Menards. And these same 2 ft by 4 ft foam boards can be used to make rigid thermal covers for the inside of windows for nighttime. And they can be used to make additional passive solar panels that hang down the outside of a window for additional solar collector space and heat. They can also be used to make a very good solar oven or stove.
Professional passive solar panels are expensive and not highly promoted for home heating but designs are so simple that anyone can make their own for additional solar window heating panels that hang out the window. Mother Earth Magazine sells several designs and how to articles to do this. I am very suprised that the larger plastic companies like rubbermaid have not come out with an inexpensive $30 window solar panel made of plastic. These could easily be mass produced and sold at a profit. And the additional heat gain in winters from these passive solar collectors along with solar window curtains could easily provide 65% of most home’s heating needs in US homes. And reversible thermal curtains will provide additional savings year round for cooling in warmer months.
The biggest drawback to thermal solar curtains today is that they are not widely available yet and so most people will have to make their own by sewing or attaching with velcro strips a black material to their existing curtains. But local schools or community groups might start programs to do this for their community for a minimal cost or donation to raise money. This dark solar curtain program is definitely a green program that pays for itself in 2 to 3 months time the very first year and saves you money every year thereafter and reduces you environmental footprint for homes, apartments, schools, churches, and businesses. And these solar window curtains and solar window panels are portable and can be taken with you to your new home or apartment.
So decide what you want from sunlight –90% light or 90% heat in EACH of your rooms in your home, apartment, or business. I choose 90% heat during winter months and save 30% or more on my home heating bills.
All of my 100 plus articles can be reposted anywhere without permission.– J.E. Ante