Does anybody know about insulation? - PeachParts Mercedes-Benz Forum

lowriderdog37 · #1 09-30-2009, 08:03 AM

I just moved into my new house about a month ago here in FL to find that there is almost no insulation in the attic. With the thermostat set at 77 and the temps outside at 90ish, the AC would run ALL DAY! One day the power went out for about an hour and a half, and the temp inside went from 77 to 83 when it was 87 outside.

I decided then that I was going to blast some more insulation in the attic.

This morning, it's finally starting to cool off here, it's 66, but the temp inside the house is still 77...WTF? I opened all the windows to let the house cool off before I go to work. The house is so quick to heat up but won't cool off. The AC seems to be running well, cool air blows out of the vents, and I patched any holes in the ducting in the attic. What would cause this?

raymr · #2 09-30-2009, 08:30 AM

Your house might be capturing and retaining lots of radiant heat. Look into a radiant barrier that attaches to the underside of your roof. Its just aluminum coated sheeting that gets installed with the shiny side up, to reflect heat energy away from your living space.
http://www.energysavers.gov/your_home/insulation_airsealing/index.cfm/mytopic=11680

mpolli · #3 09-30-2009, 04:12 PM

It looks like DOE recommends R-30 to R-60 for attics in FL. Home Depot here has a good deal on Certainteed unfaced R-30 rolls which are about 10" thick. One or two layers of that should solve your problem.

Yak · #4 09-30-2009, 07:40 PM

Quote:

Originally Posted by lowriderdog37

I just moved into my new house about a month ago here in FL to find that there is almost no insulation in the attic. With the thermostat set at 77 and the temps outside at 90ish, the AC would run ALL DAY! One day the power went out for about an hour and a half, and the temp inside went from 77 to 83 when it was 87 outside.

"New" as in "newly constructed" or as in "new to you?" I'm not up on local building codes, but if it's new and doesn't have the requisite insulation then the builder should be responsible. I think Florida also has an "energy code" requirement.

What kind of wall construction? Brick exterior? Windows facing west? It sounds like your house has a lot of thermal mass and heat absorption.

t walgamuth · #5 09-30-2009, 07:51 PM

I recommend Blowing fiberglass...R 40 at least. You will need baffels to keep it off the underside of your sheathing....this is assuming a trussed roof with plywood, shingles and drywall ceiling. Any other construction type would take a different system probably.

75Sv1 · #6 10-01-2009, 07:28 AM

I would also question if this is new construction or old. Is there insullation in the walls? Also, make sure you have proper airflow through the attic. I put some stroyfoam or plastic rafter slats, that keep the insulation from falling into the eves. I also used some cardboard windblocks too. Lowes or Menards should carry them. I haven't tried the aluminum foil barriers. I have heard they are good.
If you don't have proper airflow through the attic, heat gets caught up in there. I have noticed a big difference, after I had my roof reroofed. I had a ridge vent put on. I also did the afore mentioned slats and windblocks. If you don't have insulation in the walls, then you need to take care of that too. Holes can be drilled and the granulated insulation can be 'poured' in.
Tom

dannym · #7 10-01-2009, 08:06 AM

Even though you say the air is blowing good I would go ahead and clean the coils off. I use a pressure washer but if your not careful you can bend the fins. Apply lots of coil cleaner and wait 10 to 15 minutes for it to soak in. REALLY wait, don't get impatient!
Change your air filter every 2 months, every month if you have pets.

You definitely need more insulation in the attic. That and keeping the eves clear for air flow wil help you a lot.
If you really want your electric bill to go down you can install an attic fan with a thermostat to start and stop it.

I have the same problem with my insulation. It's clumped up and even missing in some places. I'm going to level it out and put up some more but not until it cools down a little.
At least my AC shuts off eventually!

Danny

75Sv1 · #8 10-01-2009, 08:10 AM

Another thing to think about is if the A/C unit sits in direct sunlight. If it does, then it will get very hot. Then it can't cool effeicently. I think you want it on the East side of the house. You would need to look into that. Or you could build something over it to shield it from the sun.
Tom

cmac2012 · #9 10-01-2009, 05:28 PM

Quote:

Originally Posted by mpolli

It looks like DOE recommends R-30 to R-60 for attics in FL. Home Depot here has a good deal on Certainteed unfaced R-30 rolls which are about 10" thick. One or two layers of that should solve your problem.

I would go with that ahead of the blown in stuff. Much more effective.

Hatterasguy · #10 10-01-2009, 07:12 PM

Get it blown in, it works better than the batt stuff.

Don't get Cellulose either, it settles and can cause fires.

We get fiberglass blown into all our new houses.

Larry Delor · #11 10-02-2009, 01:26 AM

If FPL is your power company, you should check out their website. They have energy surveys, and other offers (usually). They came out to my house a few years ago, and "inflated" it to see where I had leaks.
Double paned insulating windows help. Having the A/C on the northern side helps me.
Danny mentioned coils ...I think he meant the condenser coils - I would also examine the evaporator coils (I just cleaned mine today).
Does your roof have vents?
When was your home built?

lowriderdog37 · #12 10-02-2009, 06:57 AM

It's a new to me house, built in 2000. For those of you in the know, it was built to the 2002 code. It has brick frame with a stucco exterior. It does appear to be a trussed roof with shingles, plywood, and drywall ceiling. The few inches of insulation up there now is cellulose.

I did clean off the coils, I used a few cans of the stuff form Lowes. I also used the cleaner on the benz, and it's some good stuff. I would suggest it to anybody. The rood does have slats, I also keep the attic access (in the garage) cracked, and try to keep the garage open in the evening to get some air moving through there.

The AC unit is on the east side. It doesn't have anything over it to block the sun though. That is also on the plan. I think I am going to put an orange tree or something next to it.

The front faces west, with no big windows and the rear faces east with a very large slider set. I put in blinds into the rest of the windows, it was really only the slider and above the front door.

After a few more days, I have noticed that the house ONLY cools off by the AC. I had the windows open for a while last night with the outside temp at 70, and it still stayed at 77 in the house. I turn the air on when I am about to go to bed, and it cools to 75 in about 20 min. I am baffled about this. I am going to blow the insulation in next weekend though.

For those of you who don't know, there is a 30% tax rebate (up to $1500) for energy improvements to your house.

rs899 · #13 10-02-2009, 07:43 AM

If the house is only 10 years old, it's probably too soon to need a new roof , but that's the place to start thinking for the future.

We replaced our dark grey shingle roof with a very light colored steel roof about three months ago and our power consumption seems to be down about 15-20%. We used to walk out into the garage in summer (the attic vented into it) and it was unbearable. Now , it's not. The A/C kicks on much less frequently. Of course, if you live in a development you may not have much choice about how you can live your life.

Rick

mpolli · #14 10-02-2009, 12:39 PM

Brick and stucco have a lot of thermal mass so they will store heat. I used to live in a brick apartment building, think brick oven. It would be 80 degrees at 2 AM when it was 67 outside. Big shade trees are about the only answer for that. Or paint it white. Shade trees actually lower the surrounding air temperature also by evaporative cooling.

t walgamuth · #15 10-02-2009, 08:24 PM

Quote:

Originally Posted by lowriderdog37

It's a new to me house, built in 2000. For those of you in the know, it was built to the 2002 code. It has brick frame with a stucco exterior. It does appear to be a trussed roof with shingles, plywood, and drywall ceiling. The few inches of insulation up there now is cellulose.

I did clean off the coils, I used a few cans of the stuff form Lowes. I also used the cleaner on the benz, and it's some good stuff. I would suggest it to anybody. The rood does have slats, I also keep the attic access (in the garage) cracked, and try to keep the garage open in the evening to get some air moving through there.

The AC unit is on the east side. It doesn't have anything over it to block the sun though. That is also on the plan. I think I am going to put an orange tree or something next to it.

The front faces west, with no big windows and the rear faces east with a very large slider set. I put in blinds into the rest of the windows, it was really only the slider and above the front door.

After a few more days, I have noticed that the house ONLY cools off by the AC. I had the windows open for a while last night with the outside temp at 70, and it still stayed at 77 in the house. I turn the air on when I am about to go to bed, and it cools to 75 in about 20 min. I am baffled about this. I am going to blow the insulation in next weekend though.

For those of you who don't know, there is a 30% tax rebate (up to $1500) for energy improvements to your house.

I bet its on a slab too. The brick walls and a slab floor will store a huge amount of heat once they get hot and will give it off til they equalize with the air in the house....that could take all night.

Brick or concrete accepts heat or rejects it at a rate of about one inch per hour. Insulate the ceiling by all means but keep the ac on all the time, don't let it get too hot because it just takes too long to cool off all that mass.