There are three main ways to lower your energy usage due to air conditioning in the summer:
- Insulate your home so cool air doesn't leak out
- Program your thermostat so the AC doesn't have to come on as much or stay on as long
- Keep solar heat out in the first place!
I've been thinking a lot about the last one lately since the front of my home faces due South and receives sunlight almost all day. In order to prevent my house from heating up like an oven, I somehow have to find a way to limit the solar radiation that enters the home. There are several methods to do this including:
- Solar Screens
- Window Tint
I was stumped last month when my uncle asked:
What are the pros and cons of Solar window screens vs solar film? What are the best products? What is more cost efficient?
Quite frankly I had no clue! And I could understand his confusion after I did some searching on Google and couldn't find a comparison. Most of the sites are selling product, not giving objective analysis.
An example of a Solar Screen can be seen in the images by the company Insolroll and their energy-efficient SilverScreen. Insolroll states that their SilverScreen solar screen "gives the best view retention, glare control, and heat reduction". Insolroll's solar screens install from the inside, but from what I can tell, solar screens are most affective when they are mounted outside the windows (like in the image at the top of the post). This way any heat the screen absorbs is given off outside the home, and not in the home's interior. I like what the eHow on "How to Save Money with Solar Screens" says about mounting interior vs. exterior:
Decide whether you want your screens on the inside or outside of your windows. While screens may be installed on the inside of the window, the most efficient solar screens install on the exterior of your home. With the screens on the exterior, the heat that is not immediately deflected will be absorbed by the screen while a major portion is dissipated into the surrounding atmosphere. Solar screens on the exterior also eliminate the need for covering windows in the winter time as the insulating techniques work year round. The installed screens help to hold the heat that is generated in the interior of your home.
Based on some preliminary research, it seems that solar screens are extremely popular in Texas. This fact was re-itereated by the energy audit recommendations from the City of Austin, TX, which has a requirement that many homes have energy audits (my uncle who asked the solar screen vs. film question and my father -in-law who informed me about the Austin energy audit both live in TX). Statesman.com reports the following findings from the first year of the Austin energy audit city ordinance:
In the first year of a new city ordinance, energy audits were completed for 4,862 homes. Here are the most common issues uncovered during that year:
58 percent needed window shading (solar screens on windows).
Nearly 80 percent needed more attic insulation (another 10 inches, on average).
About 68 percent needed duct repair work in attics. (On average, 22 percent of the air conditioning in older homes leaks into the attic, Austin Energy says.)
78 percent needed weatherstripping, sealing or caulking around windows, doors and other openings
If you don't mind the aesthetics of them, solar screens seem like a great solution. And if you really don't mind the aesthetics of them (an off-grid cabin maybe?) check out project 16 of the Home Energy Projects Guide, which shows you how to build your own solar shade screen!
I'm still looking to see how they perform vs. window tint. Does anyone have any experience out there? We'll look closer at window tint and other solutions in later posts in our Keep out the Heat series.