My attic is running 135Fahrenheit (55 Celsius) and more right now. And that's before it even gets to the hottest part of the day! The A/C guy said the A/C's are working perfectly. But he tested the ceiling, and it is a completely different temperature than what comes out of the A/C vents! So I'm boiling in my new home, even at night!

The A/C guy verified that it is terribly insulated in my attic. I have a radiant barrier, (whatever that is), but there is not sufficient insulation to prevent the heat transfer to the rest of my house. The second story is definitely the hottest, but even the first story is too hot. Because of this my electric bill is insane which I also cannot afford because the A/C can never work hard enough to do the job I want it to do.

It's been suggested to me to lay down rolls of insulation across the floor of the attic. After attempting to read on-line how to do this and what kind of insulation to buy I am overwhelmed at all the information given as well as the references to blowers, joists, and many other words that are completely new to me.

Because of recent personal problems I am on a really tight budget. Can somebody offer me some guidance on how to insulate my attic?

  • 1
    Is my post too long for people? This is my first time here.
    – LuxeGypsie
    Aug 7, 2012 at 6:47
  • 5
    Hi - I am terribly sorry to hear about your personal problems. It is clear that it has led you to some DIY hell and you are desperate to sort things out. This Q&A is a friendlily community and we love helping people out with DIY problems. We do try and follow some rules in asking and answering questions to keep things on topic and clear and obvious for other users. It is in the interest of some members to edit and maintain this quality.I have edited your question. Hopefully answers will follow
    – Piotr Kula
    Aug 7, 2012 at 9:38
  • Could you uplaod some pictures of the attic? We can then try and see what to do. Generally a few cm of fibre glass filling works well with insulation.. but styrafoam is also pretty excelellent. Also some pics of the A/C the intakes and vents. Possbily something is not done correctly
    – WillyWonka
    Aug 7, 2012 at 9:46
  • Related - diy.stackexchange.com/questions/4481/…
    – Freiheit
    Aug 7, 2012 at 16:38
  • Is your A/C unit installed in the attic?
    – RSMoser
    Aug 8, 2012 at 17:31

6 Answers 6


The most direct answer to your insulation question is fairly simple. Your goal should be to have insulation equaling an "R" value of 40 or above on top of the ceiling of the second floor.

The cheapest method for a DIYer is to roll out unfaced fiberglass insulation over any existing insulation. We don't know what you have now, "R" value or type. That would be a helpful factor in determining how much more you should add.

But with that said, here are some general guidelines:

  • Standard fiberglass blanket insulation adds between 3.2 to 3.4 "R" per inch. Example: 3 1/2" insulation = R-11, 5 1/2" = R-19, etc.
  • This comes in rolls either 15 1/2" or 23" wide.

It is fairly easy to install, but precautions must be taken not to breath in any fiberglass dust or expose skin. Dust mask and light weight full clothing is good.

Also be careful moving around in your attic. You must keep your weight on the ceiling joists, never step on the actual ceiling or you may find yourself in the room below. A few boards strategically located across a few joists can make a walkway and can be moved as you work.

If you are completely inexperienced, perhaps you can get the help of a friend with a little DIY experience to help you out. Added insulation is always a good investment and will give you a fast payback on your A/C energy costs.

If any of my fellow SE guru's have any good video tutorial links, please add them.

Good Luck.

  • 2
    +1 Also fiberglss blankets can be stacked, usually at right angles, to achieve the R levels shirlock suggests. Even more necessary to be careful when moving about once a first layer has been installed.
    – bib
    Aug 7, 2012 at 17:13
  • Adding a powered roof vent may be less expensive and do a better job in the summer. There are solar powered vents that when the sun is out and hot really move the air and may reduce the attic temp by more than 20 degrees.
    – Ed Beal
    Feb 20, 2019 at 15:09

Some states subsidize professionally-installed insulation as well as other energy-efficiency improvements. If that is the case in your state, you will likely be able to hire a pro for less than what you would pay for the materials if you were to do it yourself. Massachusetts covers 75%, so I paid only $300 to insulate the attic, including two roof vents and some caulking along the foundation. Ask your gas and electricity companies to find out about such programs in your state.


The budget might not permit it, but the first thing I did that worked immediately was to install a solar attic fan (1000cfm) to dump the hot air (pre-fan 170F, post fan 120F). It got me an extra 3 years on the roofing material (35 year old organic, well past its sell by date) while I saved up for a total reroof job. The reinsulation came after the roofing for obvious reasons.

  • 1
    +1 Fans can help a lot, but thermostatically controlled ones are pricey to buy and install. not your typical DIY project. Aug 7, 2012 at 21:39
  • 3
    It's why I went with Solar, self-contained, no messing with mains power. Aug 8, 2012 at 2:28

I just happened upon your question when I was looking for some advice on ceiling insulation for a house we will build next year.

My opinion about your attic is that the first thing you have to do is air seal the attic. Not necessarily expensive, but certainly a pain, especially when the air temp in the attic is so high. I worked on the attic in my rental house when it was 140F up there and it will make you sick. You can only work for a little while before getting down and drinking fluids.

The main thing you do is get some (probably many) cans of foam and seal where you see gaps.

Links for airsealing: "A Do-It-Yourself Guide to Sealing and Isulating with Energy Star http://www.energystar.gov/index.cfm?c=diy.diy_getting_started

from BuildingScience.com Attic Air Sealing Guide and Details http://www.buildingscience.com/documents/guides-and-manuals/gm-attic-air-sealing-guide/view

from GreenBuildingAdvisor.com How to Air-Seal an Attic: Introduction (you can google it)

I think "Fine Homebuilding" has the same series of videos on air sealing the attic.

I would not recommend a Solar powered attic fan especially with air leaks. It sucks the cooler conditioned air out of the house and into the attic. Your attic will be cooler, but the AC will have to work more. See energyvanguard.com article on Don't Let Your Attic Suck - Power Attic Ventilators Are a Bad Idea.

Then insulate. You can do your own insulation. It is not difficult, but again it is a PAIN and itchy (no matter what form of insulation you use) when it is that hot.

I hope that helps.

  • Powered vents in the attic is the first thing I do to my homes after starting doing this back in the 80's I have seen my power bill drop by half because the air in the attic was 140f after the vent install it did not get above 115f. The first one I installed was line powered the last 2 have been solar. If you have proper attic vents this dose nothing to the conditioned air space in the house but remove the heat load from the ceiling.
    – Ed Beal
    Feb 20, 2019 at 15:15

The attic is likely so hot because it has a lack of proper ventilation. I would first check if there are any vents that allow hot air to leave the attic. Often, people throw insulation into the attic which blocks the vents to the outside air, turning the attic into a greenhouse. Current thinking is that you should have a combination of soffit vents and ridge vents. The required amount of ventilation is a "net free ventilation area" (NFVA) of 1/150 of the square footage of the attic. So, if your attic is 300 ft2, then you should have 2 ft2 of ventilation.

The second thing to do is to ensure that any hole between the house and the attic is sealed. Are there holes for wires in the attic? Fill them up with expanding foam. Be careful around lamps. Keep insulation away from them. Hot insulation can catch on fire.

The third thing to do, if money is available, is to buy the cheapest (per R value) insulation that you can. You may be able to find used insulation from Craigslist or your local paper. I'd start insulating with one layer of "faced with kraft paper" insulation batts that are unrolled between the joists. Have the paper touching the drywall which is the ceiling of the top floor. Then, spread as much loose-fill insulation as you can afford, or lay some batts of insulation perpendicular to the already installed batts. At a minimum, I'd ensure that you have at least a R value of 20, about six inches of fiberglass or cellulose. Do not install multiple layer of insulation with paper stuck to it (faced-batts). Having multiple layers of kraft paper can trap in moisture, causing mold. You may want to buy some special baffles that keep insulation from blocking soffit vents.


your "barrier" insulation is most likely the foil. it is good to have for a start but only R1 insulation factor. the best and cheapest way to cool a house that heats up due to direct sun exposure is to paint the external walls and tiles either white or close to it. it stops the electromagnetic radiation turning to heat in the first place. if you are not prone to falling off or into roofs, i suggest get it done for you. you can save heaps though when done yourself. i'm putting in double glazed windows and ripping off plaster to install the barrier and batts. takes a lot of money even though doing all myself. meanwhile our gas and electricity rates shot up by lots again, and got massive gas bill. spent more money replacing old hot water system.

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