As with everything else, the decision to get Radiant Barrier depends on a few factors.
Work with a contractor you trust. If you don't have someone in mind, get multiple quotes. There are a lot of variables that can affect the cost. Some attics are very tight and require crawling on hands and knees, others are very tall and require moving ladders all day.
The time of year you get the installation also plays a role. The labor expense will be higher in the summer time since the installation crew will have to take many more breaks so they do not over heat. In the winter the team can work much longer and not worry about heat exhaustion.
There are two different materials to choose from:
- Foil - The best material is a thick, laminated Radiant Barrier foil. Radiant Barrier foil blocks 97% of the radiant heat. It does not wear out. Dust does not affect it appreciably. Radiant Barrier foil does not affect TV antenna signals or cell phone reception. It does require more time to install than the other type: paint. Radiant Barrier Foil qualifies for the 25C(g) Tax Credit of 10% of material cost up to $500.00. Labor is not eligible.
- Paint - The paint that is advertised as radiant barrier does not meet the US Department of Energy's definition for radiant barrier, which is to block at least 90% of radiant heat and have emittance of less than 10%. The top rated paint claims to only reflect 80.5% of the radiant heat, and that is with a perfect installation. If the paint is not applied evenly the effectiveness suffers greatly. The main reason it is still used is ease of installation. A crew can usually finish two houses in one day of spraying, where a crew installing foil can take multiple days to complete one house. The paint does not qualify for any tax credit.
In San Antonio, the foil used should be perforated. The perforations allow moisture to pass through. The foil should be stapled to the roof rafters and not the floor of the attic.
Different contractors claim to use the best foil or have a proprietary foil. In our testing, all of the foils available from US manufacturers performed as specified by the manufacturer. There was not a discernible difference in quality or reflectivity. There are many US manufacturers of Radiant Barrier, so make sure to ask for it.
The foil we install is Radiant Guard. The woven scrim held up a little better and the foil was a little thicker, which made it easier to install.
A great time to evaluate getting radiant barrier is when you are replacing an air conditioner. The radiant barrier does lower the heat load of the house. In some cases, the drop can allow a smaller air conditioner to be used. You could be saving money on the cost of the air conditioner, as well as the energy savings from the Radiant Barrier. Ask your HVAC professional to run a load calculation with and without Radiant Barrier. If there are other energy saving items you are considering, ask them to run all of the scenarios.
Don't worry, changing a few values doesn't take long at all. If they can't (or don't know how to) run Manual J Load Calculations, there are red flags with this contractor.
Measure your ROI ( Return on Investment). If the savings do not exceed the expense of installation over the life of the product, then it doesn't make any financial sense. Of course, it may make emotional sense since you would be doing what you could to limit your energy consumption. Oak Ridge National Laboratory estimates homes in our climate zone, with duct work in the attic, would on average save between $150.00 - $200.00 per year. The US Department of Energy pegs the savings between 5% and 10% of cooling costs in warm, sunny climates.
Radiant Barrier foil is something handy homeowners can install themselves. Most of the cost of installing Radiant Barrier is labor, so significant savings can be realized by doing it yourself. If you do decide it is a project you want to tackle, there are plenty of instructional videos on the internet. If you are doing it in the summer make sure to take very frequent breaks and drink plenty of water.
A reason that should not be used for deciding to get Radiant Barrier is, "My air conditioner is not keeping up." If the air conditioner was sized properly when installed, there should not be any problems with the air conditioner "keeping up". There may be other problems that can be much less expensive to correct than radiant barrier.
- In the average home, 20% of the conditioned air escapes into unconditioned space through duct leakage. If you see holes in your duct or notice areas deteriorating, you may just need duct sealing.
- Duct work may be undersized in some areas, or the duct may be damaged. People working in the attic may have crushed a duct or knocked it loose.
- Rodents can cause serious damage to duct work. If rats, mice, racoons, or possums may have had access to your attic, make sure to get it checked by a professional.
- Your air conditioner may have a refrigerant leak. As refrigerant leaks out, the cooling ( and heating if its a heat pump) capacity diminishes. The air conditioner will have to work harder to maintain the temperature.
All of these issues can be corrected by a licensed air conditioning contractor.
More interesting articles on heating and air conditioning here.