insulating the garage attic?

[roadrnnr]

just wondering if this is done in here to reduce heat in the garage?

I have a small courtyard villa

[jrref]

I resisted insulating the attic above the garage for a long time. But after I did it, I find my garage is about 5 -10 degrees cooler than the outside temperature assuming the car was not driven in hot and the door was closed. We had ours done by the Solar Guys. You can take a credit on your income tax for this home improvement.

[CarlR33]

just wondering if this is done in here to reduce heat in the garage?

I have a small courtyard villaMight do a search as there have been many posts regarding reducing garage and attic heat as well as using solar fans, etc. as I had the same questions.

[retiredguy123]

The basic concept of insulation is that you add insulation between a conditioned space and an unconditioned space to slow down the rate of heat transfer between the two spaces. Builders do not insulate the garage ceiling because the garage and the attic are both unconditioned spaces. Heat always flows from a hotter space to a cooler space until both spaces become the same temperature. If you park a hot vehicle in the garage, the garage will actually become hotter until the heat from hot vehicle flows into the attic. So, in that case, an insulated ceiling will actually act to prevent the garage from cooling down. But, regardless of whether or not you insulate the garage ceiling, the insulation will only slow down the normal heat transfer process until a state of equal temperature is achieved. This process usually takes less than about an hour. After that, the insulation does nothing. So, insulating the garage ceiling will not result in a consistenty lower temperature in the garage. Actually, in the evening, when the attic cools down, an insulated garage ceiling will slow down the time it takes to cool down the garage.

[asianthree]

The basic concept of insulation is that you add insulation between a conditioned space and an unconditioned space to slow down the rate of heat transfer between the two spaces. Builders do not insulate the garage ceiling because the garage and the attic are both unconditioned spaces. Heat always flows from a hotter space to a cooler space until both spaces become the same temperature. If you park a hot vehicle in the garage, the garage will actually become hotter until the heat from hot vehicle flows into the attic. So, in that case, an insulated ceiling will actually act to prevent the garage from cooling down. But, regardless of whether or not you insulate the garage ceiling, the insulation will only slow down the normal heat transfer process until a state of equal temperature is achieved. This process usually takes less than about an hour. After that, the insulation does nothing. So, insulating the garage ceiling will not result in a consistenty lower temperature in the garage. Actually, in the evening, when the attic cools down, an insulated garage ceiling will slow down the time it takes to cool down the garage.

Interesting thought process. We had Solar guys insulate our south face doors. Asked about insulation above garage. He said give us a call if you add a mini split, without mini split, blown extra insulation in garage is good for snow, not heat. But if we wanted to add insulation to rafters that would help? Thoughts?

[dewilson58]

We did our garages during construction.

Depending on the day..................10 to 20 degrees cooler.

Very cheap investment.

[retiredguy123]

We did our garages during construction.

Depending on the day..................10 to 20 degrees cooler.

Very cheap investment.
20 degrees cooler than what? My HVAC system doesn't even keep the inside temperature 20 degrees cooler than the outside temperature.

[dewilson58]

20 degrees cooler than what? My HVAC system doesn't even keep the inside temperature 20 degrees cooler than the outside temperature.

Attic temperature.

Thanks for asking............not.

[asianthree]

We did our garages during construction.

Depending on the day..................10 to 20 degrees cooler.

Very cheap investment.

But if you insulated during construction what do you have to compare temperature that it is cooler?

Looking for before and after insulation results. Just with door insulation we found a 12 degree difference from June before door insulation and June after. Keeping temperature for those months was pretty consistent. Other months temperatures were too far apart for accurate comparison.

Our garage is 20° + less early morning (5-7a) than 10pm temp. Above garage is only builder insulation.
We are considering adding insulation in garage roof rafters, but haven’t noticed any newer facts.

[dewilson58]

But if you insulated during construction what do you have to compare temperature that it is cooler?

Looking for before and after insulation results. .

Have wireless temperature sensors in attic, in garage.

Don't need "before & after insulation results"..............I have realtime facts.

:loco:

[retiredguy123]

But if you insulated during construction what do you have to compare temperature that it is cooler?

Looking for before and after insulation results. Just with door insulation we found a 12 degree difference from June before door insulation and June after. Keeping temperature for those months was pretty consistent. Other months temperatures were too far apart for accurate comparison.

Our garage is 20° + less early morning (5-7a) than 10pm temp. Above garage is only builder insulation.
We are considering adding insulation in garage roof rafters, but haven’t noticed any newer facts.
Correct. You really need to compare temperatures in the garage before and after installing the ceiling insulation, and at different times during the day. The attic temperature doesn't mean much because hot air rises. The temperature inside my garage almost never exceeds the outside air temperature, and my garage ceiling is not insulated.

Personally, I don't think adding insulation to the rafters will provide much benefit, if at all. It could even keep the attic hotter longer after the sun goes down.

[Tvflguy]

Attic temperature.

Thanks for asking............not.

Yikes. Perhaps change your title to “Mr. Sensitive”….

[Boffin]

just wondering if this is done in here to reduce heat in the garage?

I have a small courtyard villa

Installed radiant heat barrier on rafters.

[dewilson58]

Correct. You really need to compare temperatures in the garage before and after installing the ceiling insulation, and at different times during the day. The attic temperature doesn't mean much because hot air rises. The temperature inside my garage almost never exceeds the outside air temperature, and my garage ceiling is not insulated.

Personally, I don't think adding insulation to the rafters will provide much benefit, if at all. It could even keep the attic hotter longer after the sun goes down.


:what::what:

Insulating the rafters above the house will not provide much benefit either.

:shocked::shocked:

[It's Hot There]

But if you insulated during construction what do you have to compare temperature that it is cooler?

Looking for before and after insulation results. Just with door insulation we found a 12 degree difference from June before door insulation and June after. Keeping temperature for those months was pretty consistent. Other months temperatures were too far apart for accurate comparison.

Our garage is 20° + less early morning (5-7a) than 10pm temp. Above garage is only builder insulation.
We are considering adding insulation in garage roof rafters, but haven’t noticed any newer facts.

Before and after results are pretty much impossible because duplicating conditions is impossible. Duplicating inside/outside temp, rising temp rate, clouds, etc.

[gorillarick]

Before and after results are pretty much impossible because duplicating conditions is impossible. Duplicating inside/outside temp, rising temp rate, clouds, etc.

Yeah, you'd have to study it for a year or two; before and after.

No one mentioned putting a ceiling fan (maybe solar) thru the ceiling of the garage and roof to suck warmer air outa the garage.

[retiredguy123]

Yeah, you'd have to study it for a year or two; before and after.

No one mentioned putting a ceiling fan (maybe solar) thru the ceiling of the garage and roof to suck warmer air outa the garage.
That would work only if the temperature in the garage is higher than the outside air temperature. But, the temperature in my garage is usually about the same as the outside air temperature, so a fan wouldn't do anything. Currently, the outside air temperature is 82 degrees, and the temperature in my garage is 82 degrees. I would suggest that you place a thermometer in your garage and monitor the garage and the outside temperatures. Also, if you do install a fan in the ceiling, it will need to have a fire damper to maintain a fire and smoke separation between the garage and the attic to comply with the building code and prevent a fire from spreading.

[asianthree]

Yeah, you'd have to study it for a year or two; before and after.

No one mentioned putting a ceiling fan (maybe solar) thru the ceiling of the garage and roof to suck warmer air outa the garage.

We actually keep temp monitoring in this garage , have kept since 2/2022. It’s an older graft system mainly used in medical facilities, for temp monitoring. A equipment perk when systems get replaced.
Certain items are removed from the garage once it hit a certain temp. This is the first south facing garage, out of all of our TV homes.

[Boffin]

just wondering if this is done in here to reduce heat in the garage?

I have a small courtyard villa

My complete list:
Radiant barrier on garage doors
Two vents (one high one low) on garage doors
Radiant barrier on rafters
Ceiling fan in garage

Garage temperature is within 5 degrees of exterior ambient air temperature.

[jrref]

The other thing everyone is missing is when the attic in the garage and for that matter the attic over the Lanai, both areas not insulated when the home is built, superheats, the sheetrock in the ceiling expands excessively. This extreeme expansion and contraction causes the sheetrock to crack. Only insulating these areas will minimize or prevent this from happening.

[daniel200]

Have wireless temperature sensors in attic, in garage.

Don't need "before & after insulation results"..............I have realtime facts.

:loco:

I do not have insulation over the garage. And my garage is always 10 to 15° cooler than the attic in the summer.


Right now my garage is 87 and my attic is 98°. I do have very good insulation over the rest of the house and my garage is on the south side.

To really know if your insulation was effective you need data without the insulation in place. My data indicates you did not gain anything

[dewilson58]

I do not have insulation over the garage. And my garage is always 10 to 15° cooler than the attic in the summer.


Right now my garage is 87 and my attic is 98°. I do have very good insulation over the rest of the house and my garage is on the south side.

To really know if your insulation was effective you need data without the insulation in place. My data indicates you did not gain anything

You're funny.

Based on your numbers, you wasted money by insulating your house if insulation does not "gain anything" as you state.

I have plenty of neighbors who did not insulate the garage......their garages are a lot warmer than mine.

Thanks for the laugh.

[crash]

That would work only if the temperature in the garage is higher than the outside air temperature. But, the temperature in my garage is usually about the same as the outside air temperature, so a fan wouldn't do anything. Currently, the outside air temperature is 82 degrees, and the temperature in my garage is 82 degrees. I would suggest that you place a thermometer in your garage and monitor the garage and the outside temperatures. Also, if you do install a fan in the ceiling, it will need to have a fire damper to maintain a fire and smoke separation between the garage and the attic to comply with the building code and prevent a fire from spreading.
The temperature in the attic can reach 140F doubt your garage ever gets that hot.

[sdeikenberry]

just wondering if this is done in here to reduce heat in the garage?

I have a small courtyard villa
We own a courtyard villa. First thing I did after moving in was increase my attic insulation and put it over garage also. Makes a big difference in heat gain.

[SaucyJim]

I spared myself the stress of all this by having a full-body suit made of insulation. Garage attic. Garage itself. Lanai. Bedroom. They all feel the same temperature to me now.

[MandoMan]

just wondering if this is done in here to reduce heat in the garage?

I have a small courtyard villa

I live in a courtyard villa. If your garage door is hit by sunlight, insulating the garage door helps a lot. (I have two layers on mine—styrofoam panels and reflective foam and bubbles. I did it myself last winter. It was a lot of work, as the hurricane bracing has to be removed to install the insulation.

Yes, insulating your attic over the garage will help a lot, too. I had SolarGuys install an attic fan. They did a great job, but it didn’t help much, it uses a lot of electricity, and it’s pretty expensive. The problem is that if it’s 90° in the shade and humid, that fan is pulling 90° humid air into your garage, and it won’t feel cool, even if it is getting rid of air that is even hotter than that.

Once you’ve insulated your attic and garage door, what is next. Well, if you take your car out somewhere in the daytime, when you drive it back into your garage, it is going to radiate heat like a hot iron or a wood stove. So, instead of parking in the garage, park it in the driveway, then pull it into your garage an hour after sunset. That will help a lot.

The temp here at night at this time of year drops down to the mid to low 70s. If your garage door is open all night, your hot concrete slab in the garage and the car and Sheetrock and everything will cool down. Then close the door at dawn, and it will be a lot cooler all day than it would have been otherwise. But I definitely do not recommend that. For a year I used a sliding screen on my garage door and left the main door open. That kept things cooler at all times. Then an expensive bicycle was stolen in the night. No more screen door.

Essentially, having a cooler garage is like having a cooler house if you don’t have air conditioning. In much of the country, people open their windows at night and use a whole house fan in the attic to expel the warm air and suck in the cooler air. Then at dawn they close all the windows and curtains and blinds to keep things cooler. That works, to some extent, but around here, that air that gets sucked in is very humid, and again, I really don’t recommend leaving your garage door open at night.

[dewilson58]

Once you’ve insulated your attic and garage door, what is next. Well, if you take your car out somewhere in the daytime, when you drive it back into your garage, it is going to radiate heat like a hot iron or a wood stove. So, instead of parking in the garage, park it in the driveway, then pull it into your garage an hour after sunset. That will help a lot.



:BigApplause:

[Captainpd]

We did our garages during construction.

Depending on the day..................10 to 20 degrees cooler.

Very cheap investment.

Absolutely noway your garage is 20° cooler

[HJBeck]

Same here, they did a real good job. They also blew in insulation above my enclosed lanai.

[TomSpasm]

At a previous house in Sarasota, my wife complained that the garage was too hot and insisted we insulate it. I thought it was a complete waste of money, but compromised and insulated it. I was surprised at how much difference it made. When we bought a courtyard villa here in 2012, one of our first projects was to insulate the garage and the lanai, and we believe both are more comfortable areas as a result. Highly recommend doing both, in spite of not having any hard data to present.

[jrref]

Do you know that you can take 30% of the total amount of the insulation job off your income tax as a CREDIT? That's right off the top.

Considering this, the cost will be a lot cheaper and you will save some money on your electric bill, your garage will be cooler how much will depend on your individual home and you will stop the cracking of your garage and lanai ceilings over time. I used the Solar guys to add insulation and they do a great clean and thorough job.

[roadrnnr]

Who's does this that some one has experiance with?

some one suggested Munns

[JRcorvette]

I wish that they installed Factory insulated garage doors.

[G.R.I.T.S.]

just wondering if this is done in here to reduce heat in the garage?

I have a small courtyard villa

We did ours and lowered the temperature in the kitchen.

[Birdrm]

It really does not matter to me, I am only in the garage for less than a minute to drive out my car or golf cart.

[Lizlo]

I had my attic above garage done in a concrete house in Naples and it resulted in the garage being hotter! It held the heat in there making the space super hot all the time. I totally regretted doing it. Here in central Florida, my stick built house has blown in insulation and it's not too bad, probably because the garage door isn't insulated. The door in Naples was.

[daniel200]

You're funny.

Based on your numbers, you wasted money by insulating your house if insulation does not "gain anything" as you state.

I have plenty of neighbors who did not insulate the garage......their garages are a lot warmer than mine.

Thanks for the laugh.

Your logic on your insulation is flawed. Correlation ≠ Causation

I do not doubt your temperature readings but it appears you do not like my temperature data … but it is factual. And it just demonstrates you are mistaking a correlation and that other factors are important

[dewilson58]

Your logic on your insulation is flawed. Correlation ≠ Causation

I do not doubt your temperature readings but it appears you do not like my temperature data … but it is factual. And it just demonstrates you are mistaking a correlation and that other factors are important

You call me a liar.
Now my logic is wrong.

You have no information on my garage, the attic temps, the garage temps, but you call me a liar and question my intelligence.

For the factual record, the difference between temps has exceeded 20 degrees on hot days............but I just conservatively stated up to 20.

I don't care about your reading, never debated your readings..............they might be true, I just know my reading are true.

You are without facts, so you make me laugh, despite.

[It's Hot There]

You call me a liar.
Now my logic is wrong.

You have no information on my garage, the attic temps, the garage temps, but you call me a liar and question my intelligence.

For the factual record, the difference between temps has exceeded 20 degrees on hot days............but I just conservatively stated up to 20.

I don't care about your reading, never debated your readings..............they might be true, I just know my reading are true.

You are without facts, so you make me laugh, dispite.


Yes, 200 thinks he knows all and thinks .............. well, I won't say.

[Battlebasset]

I've thought about it. But I don't see the value.

Your garage will not be cooler than the outside air for most of the time. If too hot, open the garage door to let the built up heat out.

If you want your garage to be cooler than the outside air, you need AC. How much time do you plan to spend in your garage? If not that much, why do you care?

[Marathon Man]

I am following this thread with great interest. I am considering buying a hybrid or an EV, and garage temperature is a concern. Batteries do not like heat generally speaking. I have yet to find any information confirming that a hot garage is no good for lithium batteries. Anyway, this may be a reason for investing in garage heat abatement.

[asianthree]

I am following this thread with great interest. I am considering buying a hybrid or an EV, and garage temperature is a concern. Batteries do not like heat generally speaking. I have yet to find any information confirming that a hot garage is no good for lithium batteries. Anyway, this may be a reason for investing in garage heat abatement.

Both boys are in the south, and EV dealers strongly suggested to them to AC the garage for longer and better performance of EV. Since dealers don’t install AC might be worth looking into. Our garage is south facing and roughly 20 to 30° higher than any of our north facing garages that were in TV. Heat can destroy grips, club covers, anything with elastic. We store all our equipment batteries inside. We have insulated the doors, which has helped, but AC is next on the list. At this time we store all of our decorations and extra stuff in climate control unit. Worth the $50. Plus no climbing stairs, easy access. Once we AC garage will probably retain the unit.

[Rocksnap]

just wondering if this is done in here to reduce heat in the garage?

I have a small courtyard villa

One way to figure out if your garage door would benefit from adding insulation? If the sun hits it, touch the inside of the door. Is it hot? If yes, you would benefit from insulation. I like to keep things simple.

[Maker]

If your HVAC equipment is in a closet in the garage, most have a lot of available space where the water tank used to be placed before they started using tankless.
That space is indirectly cooled from the HVAC gear. Usually much cooler than the inside of the garage.
Great place for storing only the things that don't do well in the heat.

[Marathon Man]

If your HVAC equipment is in a closet in the garage, most have a lot of available space where the water tank used to be placed before they started using tankless.
That space is indirectly cooled from the HVAC gear. Usually much cooler than the inside of the garage.
Great place for storing only the things that don't do well in the heat.

That is a great idea. Mine does not have space for a water heater, but it does have a little room.

[dewilson58]

Absolutely noway your garage is 20° cooler

Today's a good example:

Attic 117.6 degrees
Garage 88.3
Outside 93


Knocking on the door of 30 degrees cooler.

:evil6:

[Kenswing]

Today's a good example:

Attic 117.6 degrees
Garage 88.3
Outside 93


Knocking on the door of 30 degrees cooler.

:evil6: Yeah, 20 degrees seems pretty easy. I’m at 30 without any extra insulation.

[retiredguy123]

Yeah, 20 degrees seems pretty easy. I’m at 30 without any extra insulation.
In my case, at 3 PM, outside air temp is 99, garage temp is 95. No ceiling insulation. I don't care what the attic temp is, or the garage temp either. I don't live in the garage or the attic.

[Kenswing]

In my case, at 3 PM, outside air temp is 99, garage temp is 95. No ceiling insulation. I don't care what the attic temp is, or the garage temp either. I don't live in the garage or the attic.

That’s great.

[BigDawgInLakeDenham]

My garage attic and garage stay 72 to 74 degrees all day. Costs about 10k to get it like mine and for us well worth the expense, because of the needed attic storage space....so maybe not worth it for villa attics??? I can't say because I've never been in a villa attic. I can say that the cool garage buffer space keeps the whole house cooler and my main ac will work less. Our house faces west and after noon the garage doors will fry your hand and or a ribeye. Before enacting my upgrades our garage was easily 120 degrees in the afternoon. Cool garages are achievable and less than what my Boss spent on custom closets:crap2:

[LeRoySmith]

my garage attic and garage stay 72 to 74 degrees all day. Costs about 10k to get it like mine and for us well worth the expense, because of the needed attic storage space....so maybe not worth it for villa attics??? I can't say because i've never been in a villa attic. I can say that the cool garage buffer space keeps the whole house cooler and my main ac will work less. Our house faces west and after noon the garage doors will fry your hand and or a ribeye. Before enacting my upgrades our garage was easily 120 degrees in the afternoon. Cool garages are achievable and less than what my boss spent on custom closets:crap2:

swmbo. 😃

[BigDawgInLakeDenham]

swmbo. ������

She has an attic full of Christmas she could not part with.... yet.....sequela is I get a climate controlled garage to play in lol. I take full credit for designing and implementing the climate control. I put my foot down at majic stairs and elevator....told her to go back to work and buy a premier home with a 4 car garage and that ended the conversation. She happily got up in the attic as I pushed all the boxes up the ladder....since it was only 72 degrees up there

[LeRoySmith]

She has an attic full of Christmas she could not part with.... yet.....sequela is I get a climate controlled garage to play in lol. I take full credit for designing and implementing the climate control. I put my foot down at majic stairs and elevator....told her to go back to work and buy a premier home with a 4 car garage and that ended the conversation

Way to put your for down!

I'm thinking about insulating and installing a mini split. I love to tinker but it's pretty warm out there. I just insulated and installed a mini split up north and it was about 2500 bucks all in. I asked someone for an estimate to blow in insulation in this garage (3 car with 2 for extension) and they wanted 1500). Ouch.

[BigDawgInLakeDenham]

Way to put your for down!

I'm thinking about insulating and installing a mini split. I love to tinker but it's pretty warm out there. I just insulated and installed a mini split up north and it was about 2500 bucks all in. I asked someone for an estimate to blow in insulation in this garage (3 car with 2 for extension) and they wanted 1500). Ouch.

The key to it all is 10k and thinking outside the box and spray foaming in the trusses, the front, and making a wall to enclose the attic....just like a cooler. I now control the environment....I'm acting like a liberal Democrat lol:sing: Ceiling insulation, that everyone buys, is a waste of money when it comes to an unconditioned space. You've added insulation to a hot space that stays hot and your garage doesn't change Temps much afterwards. I love to tinker but chose not to install a split myself because I may sell my house and want all the proper permitting, a Mitsubishi, and a company to back up their work. I'm insulating my garage doors myself because my research said my plan would be best for me and my west facing doors. Conklin Construction did my spray foam and attic ladder. Kalos did my Mitsubishi. More than pleased with results

[jrref]

If you want insulation blown in the attic, call the Solar Guys. They run specials periodically and you can use the cost of the project as a credit on your income tax. Their prices are reasonable.

What no one is talking about is insulating the garage ceiling will prevent it from superheating and cracking. If you don't insulate, the ceiling will crack no matter what you do. Same for the Lanai ceiling.

Whether to insulate or not depends on your garage's exposure. If you have a West or Westerly exposure in the afternoon, you want to insulate your garage and the attic above it. You will have a cooler garage when the door is down and your ceiling won't crack. That's it.

As far ar replacing your garage attic ladder. Did you know that you are supposed to install a fire rated ladder? Your garage has a 20 minute fire rating meaning all the sheetrock is 1/2 inch to prevent fire from spreading to the rest of your house for 20 minutes. The building code does not address attic ladders specifically but does say if you make a penetration, like installing a ladder access way, you need to fill the penetration with 20 minute fire rated material such as 1/2 sheetrock. In the case of installing an attic ladder you need to install a fire rated attic ladder to be code compliant. You can get these at Home Depot but they are special order and no one that I know of except myself has ever installed one or even knows about this requirement.

[BigDawgInLakeDenham]

If you want insulation blown in the attic, call the Solar Guys. They run specials periodically and you can use the cost of the project as a credit on your income tax. Their prices are reasonable.

What no one is talking about is insulating the garage ceiling will prevent it from superheating and cracking. If you don't insulate, the ceiling will crack no matter what you do. Same for the Lanai ceiling.

Whether to insulate or not depends on your garage's exposure. If you have a West or Westerly exposure in the afternoon, you want to insulate your garage and the attic above it. You will have a cooler garage when the door is down and your ceiling won't crack. That's it.

As far ar replacing your garage attic ladder. Did you know that you are supposed to install a fire rated ladder? Your garage has a 20 minute fire rating meaning all the sheetrock is 1/2 inch to prevent fire from spreading to the rest of your house for 20 minutes. The building code does not address attic ladders specifically but does say if you make a penetration, like installing a ladder access way, you need to fill the penetration with 20 minute fire rated material such as 1/2 sheetrock. In the case of installing an attic ladder you need to install a fire rated attic ladder to be code compliant. You can get these at Home Depot but they are special order and no one that I know of except myself has ever installed one or even knows about this requirement.

Does your "solar guys blown in insulation " and "special order ladder" slow the "super heating" of the garage ceiling thusly slowing it's cracking and before bursting into flames, so you can test out your ladder's fire rating just before the structure collapses? Is the "super heating" caused by an evil maxi mirror designed to relect heat into the drywall? Asking for a friend because nobody is sure how fire became the topic. We will need Fire Marshall Bill to tell us about fire....but my garage is 72 degrees

[barbara828]

Everything thing you can do helps. Attic fan, attic barrier [ saved 15% on electric too], Insulate garage door, new windows.

[jrref]

Does your "solar guys blown in insulation " and "special order ladder" slow the "super heating" of the garage ceiling thusly slowing it's cracking and before bursting into flames, so you can test out your ladder's fire rating just before the structure collapses? Is the "super heating" caused by an evil maxi mirror designed to relect heat into the drywall? Asking for a friend because nobody is sure how fire became the topic. We will need Fire Marshall Bill to tell us about fire....but my garage is still 72 degrees, fire free, with special fat man ladder made of aluminum. Just putting this out there...fire rated drywall is 5/8" and I doubt there is any fire rated drywall in my house or yours....you don't see sprinklers in the builds, do you?

You are correct, fire rated sheetrock is 5/8". The building code here states 1/2" gives you a 20 minute rating and that's only used if there is no living space above the area in discussion. For us here in the Villages, usually the attic space above the garage is open to the rest of the attic over the living area. If a fire breaks out in the garage, when it penetrates the ceiling it quickly spreads to the rest of the home. But as you mentioned, this is not the topic of this thread.