# Material that limits air transfer? **URL:** \ **Category:** Factual Questions\ **Created:** [September 10, 2024, 3:59am UTC](https://boards.straightdope.com/t/material-that-limits-air-transfer/1007044 "2024-09-10T03:59:49Z")\ **Posts on this page:** 17\ **Page:** 2
**Author:** ![Sage\_Rat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sage_rat/32/399_2.png) [@Sage\_Rat](https://boards.straightdope.com/u/Sage_Rat)\ **Post date:** [September 10, 2024, 4:23pm UTC](https://boards.straightdope.com/t/material-that-limits-air-transfer/1007044/21 "2024-09-10T16:23:20Z")
> [@md-2000](#): > > It sounds like what you need is some insulation on the exposed wall to prevent solar heating. (Bonus if the outside is painted white) The outside wall is painted white. We’re south facing and the outside wall faces East. Usually, in the morning, there’s a layer of cloud that clears around 10am. Generally, it’s the garage door that gets all of the sunlight. ---
**Author:** ![Crafter\_Man](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/crafter_man/32/458_2.png) [@Crafter\_Man](https://boards.straightdope.com/u/Crafter_Man)\ **Post date:** [September 10, 2024, 4:24pm UTC](https://boards.straightdope.com/t/material-that-limits-air-transfer/1007044/22 "2024-09-10T16:24:15Z")
> [@md-2000](#): > > Plus you’d need a thermostat-triggered fan, to exhaust hot air. It should be located up high, since the hottest air rises. That was my first thought too - an exhaust fan. ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [September 10, 2024, 4:31pm UTC](https://boards.straightdope.com/t/material-that-limits-air-transfer/1007044/23 "2024-09-10T16:31:25Z")
Sadly, air doesn’t really count. [https://gchem.cm.utexas.edu/data/section2.php?target=heat-capacities.php](https://gchem.cm.utexas.edu/data/section2.php?target=heat-capacities.php) 540 lbs of air is about the same mass as a 3’x3’ slab of concrete, maybe less. ---
**Author:** ![Sage\_Rat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sage_rat/32/399_2.png) [@Sage\_Rat](https://boards.straightdope.com/u/Sage_Rat)\ **Post date:** [September 10, 2024, 4:48pm UTC](https://boards.straightdope.com/t/material-that-limits-air-transfer/1007044/24 "2024-09-10T16:48:28Z")
3 feet? I feel like I’d need to use a fair amount of energy to change the temperature of a cube of concrete of that size? ---
**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\ **Post date:** [September 10, 2024, 5:22pm UTC](https://boards.straightdope.com/t/material-that-limits-air-transfer/1007044/25 "2024-09-10T17:22:19Z")
> [@TriPolar](#): > > Heat in the garage is being transferred to the interior of the house and being replaced by hot air from the exterior and heat transferred through the exterior walls and door of the garage. The garage never gets much colder that way. There may be some slight reduction in temperature in the garage if there’s enough insulation and the vents are not very large. That’s like saying my radiator doesn’t cool my car’s engine because the engine never gets colder. > [@Sage\_Rat](#): > > My back of the envelope math would say that there’s roughly 540 lbs of air in the garage. I’d generally expect that to act as a reasonably large thermal mass, if static. Assuming a two-car garage (with two cars actually in it), then there’s somewhere between 6,000 and 9,000 pounds of (mostly) metal and (some) plastic in there too. The heat capacity of iron (on a mass basis) is about half that of air though, so instead of holding 11-17 times as much heat as the garage’s air, the cars only hold about 5.5-8 .5 times as much. > [@md-2000](#): > > Does the gas-powered hot water heater vent to the outside, or is it just pumping CO2 into the garage? (Mine’s electric and indoors) I suspect the vents are down low because CO2 is heavier, flows (from leaks?) more downwards. Flue gas from hydrocarbon combustion is a mix of mostly CO2, water vapor, and nitrogen. Assuming a stoichiometric fuel-air mixture (one that consumes all of the fuel and all of the oxygen), **[the density](https://www.pipeflowcalculations.com/tables/flue-gas.xhtml)** is almost the same as for **[air](https://www.google.com/search?q=air+density+at+0C&rlz=1C2GCEA_enUS930US1108&sca_esv=fb627f01e4917464&sxsrf=ADLYWIKhMYU7nsGi5uZCrLDB4v_sUP9bjA%3A1725988452349&source=hp&ei=ZH7gZqrSEuPw0PEPgrnL-A0&iflsig=AL9hbdgAAAAAZuCMdHPBGzWy_HDgnyS1bEILWbtTyxoQ&ved=0ahUKEwiqlNiE8LiIAxVjODQIHYLcEt8Q4dUDCBg&uact=5&oq=air+density+at+0C&gs_lp=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&sclient=gws-wiz)**. CO2 is more dense than oxygen, but water vapor is less dense, so the combined effects pretty much cancel each other out. If flue gas is sinking, it’s because it’s colder than the surrounding air - and garages just don’t get _that_ hot. ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [September 10, 2024, 6:51pm UTC](https://boards.straightdope.com/t/material-that-limits-air-transfer/1007044/26 "2024-09-10T18:51:24Z")
> [@Machine\_Elf](#): > > That’s like saying my radiator doesn’t cool my car’s engine because the engine never gets colder. Cold coolant is recycled through your engine. No cool air is entering the garage. And once the water pump and thermostat in your car start the coolant circulating your car engine does not get any colder, it maintains the same temperature. ---
**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\ **Post date:** [September 10, 2024, 7:28pm UTC](https://boards.straightdope.com/t/material-that-limits-air-transfer/1007044/27 "2024-09-10T19:28:37Z")
> [@TriPolar](#): > > Cold coolant is recycled through your engine. No cool air is entering the garage. And once the water pump and thermostat in your car start the coolant circulating your car engine does not get any colder, it maintains the same temperature. Just as hot air doesn’t need to enter a garage to heat it, cold air doesn’t need to enter the garage to cool it. heat transfer is heat transfer, regardless of whether it takes place via fluid convection or via conduction through walls. Note that “cooling/heating” and “temperature change” are two separate things. If I’m heating a thing with a heat source while simultaneously cooling it with a cooler, then my cooler is definitely cooling it, even if the temperature of that thing remains constant. ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [September 10, 2024, 7:43pm UTC](https://boards.straightdope.com/t/material-that-limits-air-transfer/1007044/28 "2024-09-10T19:43:43Z")
> [@Machine\_Elf](#): > > Just as hot air doesn’t need to enter a garage to heat it, cold air doesn’t need to enter the garage to cool it. heat transfer is heat transfer, regardless of whether it takes place via fluid convection or via conduction through walls. But in this case the air in the garage is being heated by conduction through the walls and through air vents. So you can say the garage is being cooled because some of that heat is transferred to the interior of the house, but the garage still doesn’t get any colder, it’s just maintaining the temperature. There will be much more wall and door area through which heat is transferred to the garage than the tiny amount of heat transferred through the interior wall. The interior wall should be insulated and have a double layer of drywall on the interior which is not going to make it a good conductor so the garage will continue to increase in temperature until the exterior gets colder than the garage and heat transfer to the exterior occurs through the walls, door, and vent. ---
**Author:** ![phs3](https://avatars.discourse-cdn.com/v4/letter/p/8491ac/32.png) [@phs3](https://boards.straightdope.com/u/phs3)\ **Post date:** [September 11, 2024, 12:37pm UTC](https://boards.straightdope.com/t/material-that-limits-air-transfer/1007044/29 "2024-09-11T12:37:30Z")
One data point: we have a 2-car attached garage. In 2017, we had a garage system installed that included wall-mounting for shelves/brackets and a pull-down ladder to the attic. Since then, I’ve been collecting all the bubble plastic from Amazon shipments in recycling bags. When one is full, I put it in that attic. The garage is much, much cooler in summer and warmer in winter than it used to be. I don’t know, of course, whether it’s the added insulation on the walls from the plastic mounting or the effect of the many bags of bubble plastic in the attic. I tend to think the latter. Not sure if this helps! ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [September 11, 2024, 2:12pm UTC](https://boards.straightdope.com/t/material-that-limits-air-transfer/1007044/30 "2024-09-11T14:12:10Z")
> [@Machine\_Elf](#): > > Note that “cooling/heating” and “temperature change” are two separate things. If I’m heating a thing with a heat source while simultaneously cooling it with a cooler, then my cooler is definitely cooling it, even if the temperature of that thing remains constant. I think we understand what each other means here. There is heat being transferred from the garage to the cooler interior and that process can be called ‘cooling’. ---
**Author:** ![Chisquirrel](https://avatars.discourse-cdn.com/v4/letter/c/6bbea6/32.png) [@Chisquirrel](https://boards.straightdope.com/u/Chisquirrel)\ **Post date:** [September 11, 2024, 7:49pm UTC](https://boards.straightdope.com/t/material-that-limits-air-transfer/1007044/31 "2024-09-11T19:49:47Z")
What’s the insulation for the rest of the garage like? The garage door might be the wall that’s getting all the sunlight, but the roof is almost certainly getting a massive dose of it as well, and over a much larger area. Unless you’re going to actively cool the garage, the best you’re going to get is to slow down the temperature cycling between daytime and nighttime. ---
**Author:** ![Kedikat](https://avatars.discourse-cdn.com/v4/letter/k/ed655f/32.png) [@Kedikat](https://boards.straightdope.com/u/Kedikat)\ **Post date:** [September 12, 2024, 2:48am UTC](https://boards.straightdope.com/t/material-that-limits-air-transfer/1007044/32 "2024-09-12T02:48:05Z")
I think he said only one wall and the door wall are outside walls. I think there is a room above the garage. ---
**Author:** ![md-2000](https://avatars.discourse-cdn.com/v4/letter/m/9d8465/32.png) [@md-2000](https://boards.straightdope.com/u/md-2000)\ **Post date:** [September 12, 2024, 1:20pm UTC](https://boards.straightdope.com/t/material-that-limits-air-transfer/1007044/33 "2024-09-12T13:20:26Z")
Based on my extensive research - watching old Holmes on Homes episodes - the insulation in the ceiling of built-in garages tends to be poorly done. In Canada, however, this manifests as cold bedroom above garage in winter. So another obvious question will be “how good is the insulation above the garage?” or of course, the insulation between garage and house in general. My dad’s old house had a thermostat-triggered fan to vent the attic. Modern attics tend to have vents in the soffits to let in cool air and vents high up on the roof to allow air to exhaust by convection as it gets hot from the effect of dark shingles in the sun. My question about the exhaust for the hot water heater was basically - does the hot water heater vent into the garage, or is there an exhaust pipe to the outside? I have never dealt with anything except an electric water heater. ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [September 12, 2024, 2:20pm UTC](https://boards.straightdope.com/t/material-that-limits-air-transfer/1007044/34 "2024-09-12T14:20:35Z")
> [@md-2000](#): > > Based on my extensive research - watching old Holmes on Homes episodes - the insulation in the ceiling of built-in garages tends to be poorly done. Sounds right for many older homes. Current codes would emphasize the need for heavy insulation over a built in garage in colder regions. Not sure what the hot zone requirements would be. Here in the Northeast insulation was pushed mainly to reduce heating costs but we may find A/C energy expenditures to be comparable in the future. ---
**Author:** ![filmore](https://avatars.discourse-cdn.com/v4/letter/f/7993a0/32.png) [@filmore](https://boards.straightdope.com/u/filmore)\ **Post date:** [September 12, 2024, 2:47pm UTC](https://boards.straightdope.com/t/material-that-limits-air-transfer/1007044/35 "2024-09-12T14:47:47Z")
> [@Sage\_Rat](#): > > I’ve added insulating tiles to the inside of the garage door Are the insulating tiles like ceiling tiles? If so, I’m not sure if those are the best things to use. I’m not sure how well they would insulate that kind of space. Plus, you’d have to worry about the convection of the hot air between the tile and the door. If the air can freely move along the door and above the tile, the space between the tile and door will get very hot and the hot air will flow into the garage. You can get garage door insulation kits at the hardware store. It’s rolls of fiberglass insulation that you stuff horizontally along the garage door section. It fills the space to prevent air movement and will greatly reduce the amount of heat that comes in from the hot door. For the south wall, one thing you might consider is to plant trees and bushes to block the sun. The more you can prevent the direct sun from hitting that wall, the less heat that will get into the garage. ---
**Author:** ![jjakucyk](https://avatars.discourse-cdn.com/v4/letter/j/3d9bf3/32.png) [@jjakucyk](https://boards.straightdope.com/u/jjakucyk)\ **Post date:** [September 12, 2024, 3:16pm UTC](https://boards.straightdope.com/t/material-that-limits-air-transfer/1007044/36 "2024-09-12T15:16:46Z")
> [@md-2000](#): > > does the hot water heater vent into the garage, or is there an exhaust pipe to the outside? A gas water heater must be vented to the outside. Venting into the garage would be nearly as dangerous as running a car with the garage door closed. ---
**Author:** ![md-2000](https://avatars.discourse-cdn.com/v4/letter/m/9d8465/32.png) [@md-2000](https://boards.straightdope.com/u/md-2000)\ **Post date:** [September 14, 2024, 5:28pm UTC](https://boards.straightdope.com/t/material-that-limits-air-transfer/1007044/37 "2024-09-14T17:28:14Z")
> [@filmore](#): > > > [@Sage\_Rat](#): > > > > I’ve added insulating tiles to the inside of the garage door > > Are the insulating tiles like ceiling tiles? I would imagine the simplest easiest insulation would be to use construction adhesive to stick those slabs of 2" thick styrofoam insulation to the door segments. There will be gaps where the pieces of door have to bend, but that would be only, say, 5% of the surface being less insulated. Here in Canada, most garage doors come insulated. I still see frost buildup between the segments, the seal is not perfect. > [@jjakucyk](#): > > A gas water heater must be vented to the outside. Venting into the garage would be nearly as dangerous as running a car with the garage door closed. Thanks. That’s what I thought, but I’ve never seen one in a garage so I thought I’d ask. [Previous page](https://boards.straightdope.com/t/material-that-limits-air-transfer/1007044.md?page=1)