How can I determine if I need more attic insulation to keep cool in summer?

I live in the desert of southern California so it can get pretty hot in the summer (110+ is not uncommon). I would like to lower my electric bill but more to the point I would just like to ensure that our house is comfortable without the air conditioning going all the time.

I feel if I asks a company that does insulation I know they will say we need more but I don't know who else to ask or how to determine this.

The electrical company does not offer an energy usage assessment at this time (they used to).

5 Answers 5


What kind of insulation do you currently have in your attic? (Note: head on up there and check it out.) If it's batt insulation -- large units of fiberglass -- then that information will be printed on either the paper facing or the insulation itself. If it's loose fill insulation, which is far more common in attics, then you can usually figure out what the product is (pink, yellow, or white and very itchy = fiberglass, dirty grey = greenfiber, white and not very itchy = cellulose) and find it's value per inch on this handy table of R values.

For best performance, I'd go up to R-60. In a home built by your average builder in the past decade, R-30 meets code. Adding blown-in insulation, which you can do over fiberglass batts, is extremely cheap if you DIY ... although it's not a pleasant job to do. Rental of the machine from Home Depot or Lowe's is usually free with the purchase of a certain number of bales of insulation, and greenfiber especially is cheap. To bring my 1600 sq. ft. ranch up to R-60 would only cost me a couple hundred dollars in materials.

Do check at all ends of your attic. You might find that the areas close to the attic access are R-30 to meet code, but areas farther away might have less. I've known a few builders to be stingy with the insulation. One home I helped a friend with here in Houston had less than four inches of insulation in most of the attic.

One caution point is to make sure that in the process of adding insulation that any attic ventilation that you may have at the soffits is not blocked off. Soffit air is essential to the ventilation of your attic, if your home is designed that way. I would recommend installing Berger AccuVent baffles over every soffit vent before adding more insulation.

Last but not least, consider coating your roof with a reflective coating. You might need to get a contractor to do this, but it's simple and straightforward work. In the Inland Empire, nothing is more effective than keeping the solar rays from heating your house in the first place. Unfortunately, many find these roof coatings to be unsightly, so you might have to check with your HOA if you have one before applying anything.

  • 4
    20 greenfiber bales at $11 each gets you a free 24 hour blower rental at HD. It's by far the messiest DIY project I've ever done. Make sure you wear a respirator - not just a dust mask. The dust was so thick that I couldn't see much more than 5 feet in front of me at one point. A headlamp would also be a good idea, since you'll need one hand for the hose and the other for balance.
    – Doresoom
    Mar 26, 2012 at 14:01
  • 1
    @Doresoom: Hear ya, been there done that. lol. very messy project and actually difficult for a DIY to get it evenly distributed without some practice. I have gotten the blowers at both HD and Lowes and not really impressed. Maybe the ones I got were tired. My local Rental store has a nice one, more power and much much faster. Mar 26, 2012 at 16:13

Insulation is always good, hot or cold.There are a lot of other considerations to save energy and keep cool. Air leaks, unprotected windows, ventilation are also important factors. Perhaps you can find an energy audit professional that is not in the business of selling you a product, rather just an honest evaluation and recommendations for your specific situation. There are still some Federal energy tax credits available and perhaps some State ones in your area


As a DIY alternative to an energy audit, get a non-contact IR thermometer and walk around your home on a hot or cold day. Point it at walls and the ceiling, around doors, windows, vents, outlets, any other protrusions in the structure, the lowest floor, and corners. Look for places where the measurement varies from the room temperature. Note that glass tends to reflect temperature readings from somewhere else, so measure the window frame, blinds, curtains, or something else close by. This exercise is also helpful for balancing HVAC systems between multiple rooms, so keep track of the readings as you go around your home.

If you find the ceiling beneath that attic is well above room temperature, then it's a good idea to add more insulation there. But you may find your money is better spent insulating outlets and switch plates, adding weather stripping to your doors and windows, or fixing a vent's back flow preventer.

  • I like this idea, but aren't these kind of expensive? I may be thinking of infrared cameras. Is this $12 thing from WalMart sufficient?
    – elrobis
    Nov 8, 2017 at 21:08
  • IR thermometers are what I recommended for a DIY audit. Pay attention to "distance spot ratio" that indicates how large of an area is being measured (a 12:1 ratio measures a 1" circle at a 12" distance, if you are trying to find a draft from across the room, a poor ratio may average away an issue). IR cameras are more expensive but give you a picture of the whole wall rather than checking spots, so they have their place too.
    – BMitch
    Nov 8, 2017 at 21:13
  • Hey thanks for such a quick response considering your original answer was from 2012! Can you provide a link to a make/model you consider a quality device?
    – elrobis
    Nov 8, 2017 at 21:15
  • Product recommendations and links to specific products are frowned upon at SE, too easy to confuse with spam.
    – BMitch
    Nov 8, 2017 at 21:16
  • Hmm gotcha. Ok thanks for the insights though!
    – elrobis
    Nov 8, 2017 at 21:20

I would suggest looking at your area and seeing what R-value has been determined to be applicable. Check your attic for gaps and other problem areas. I found this "how to" article, it may be helpful - I hope you can share it with your readers: http://www.prohome1.com/howtos/how-to-check-attic-insulation.html


I hired a Green Tech Insulation to re-insulate my attic, have about 10 inch of insulation, they will add R-50 blown fiberglass, up to 22 inch high, they promised me it will cool my home during hot summer days. They will also install baffle system, extend the wooden box ( door to come in attic), insulate hatch, and use weather stripping around door. They guarantee me, it will cool my home during summer. I am not doing this to get a rebate from our Ontario Government, I am doing this so I can stay inside my home, without turning on a/c and live well. Investing $ 1,000.00 will be worth it. I also hired another company to re-insulate my exterior walls with 1 1/2 inch R-9 enerfoil insulation with new recap of all windows, caulking and install new siding. All this will keep my home comfortable, and will save me lots of $$$$, in heating costs, and will not need to turn on a/c.

  • 2
    This doesn't really answer the question.
    – Tester101
    Apr 22, 2015 at 10:06

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