I’m trying to insulate our garage. I’ve added insulating tiles to the inside of the garage door which, though fairly cheap to do, doesn’t seem to have really changed how much the temperature inside differs from outside. I’m assuming that this means that there’s too much air transfer with outside (?).
There are two holes, each about the size of a brick, opened at the bottom of the side wall to the outside. I’m assuming that these are there as a safety precaution to gas leaks from the water heater (?), so I don’t necessarily want to plug them. I am wondering, though, if there’s any sort of material that would limit the rate of air movement between the inside and outside worlds to ensure that the room doesn’t fill with noxious gas but also doesn’t drain all the air out on the next mild breeze passing over the outside wall? I.e. it should allow air to flow but up to a max, allowable speed.
In general, the hope would be that it would find some medium temperature between the min and max of the day and not move much from there. In general, I’d expect it to be cooler than outside in the middle of the day and warmer in the middle of the night.
I assume too the rest of the garage walls are heated? And the ceiling?
If the holes are at the bottom, the low area of the floor might be cold due to flow, but higher up it should be warm-ish. If not, is there something stirring the air in the garage?
have you hung thermometers at assorted levels to see the temperature differential?
Are we talking freezing temps here? I assume the water heater pipes are insulated to prevent freezing?
Two walls and the ceiling are connected to the inside part of the house, which is temperature controlled. Otherwise, there’s nothing controlling the temperature in the garage and nothing moving inside it except the pilot light.
What material are the walls, door, and roof of the garage? If for instance there is only thin aluminium anywhere, your problem is most likely not air transfer …
Without a huge amount of thermal mass, the garage will tend to follow the outside temperature, with some amount of delay. If you want to even out the temperature, it needs to be very well insulated, and very air-tight.
Unknown. It’s possible that the outside wall is made of paper and copper wire. But, given that I can’t practically change that if so, I sort of have to assume that it’s air transfer until proved otherwise (assuming that it’s cheap and easy enough to stuff something in the vents).
I guess, technically, I could plug them for a couple of days just to test the theory…
I did just find a technology known as “static mixers” off the page for the Tesla valve. Some chance that I could get someone to 3D print something.
Putting some fibreglass insulation in the vent holes would slow but not stop air movement. Not sure if that might be a code violation. The tighter you pack the holes the slower the air movement. It will not rot, but can hold moisture.
There are vents with bi metallic actuators. They automatically open and close at certain temperatures. No motors or electricity required. If it is too hot during the day, install a couple high on the outside wall. This will allow air to flow out. But it will draw air in through the low vent holes. It won’t end up much, if any cooler than outdoor air temperature. But if the garage is heating excessively due to solar on the walls, it might help some.
Are the garage walls that you want to insultate in full sunlight during the day? In that case your issue might be heating by radiation (from the Sun) rather than convection (from outside air). Would it be possible to mount some kind of sheets at a distance from the outside of the wall, to block direct radiation? (According to the Stefan-Bolzmann T⁴ law an intermediate sheet of material much lowers radiative transfer). Or even cover that wall in solar panels?
Thermal mass tends to smooth out diurnal variations, but the outside temp is only one forcing input. As the OP mentions in post #6, two walls and the ceiling are mated to the house and temperature-controlled; that’s the other forcing input. So when the great outdoors is smoking hot, the air-conditioned living space is trying, through insulated walls, to keep the garage cool. Here in Michigan, I have the opposite situation: I have one living-space wall dumping heat into the garage in the winter, and it can keep the garage a good 20 degrees above the outside temperature when it’s very cold outside. It helps that the side walls of the garage are insulated, and the door is foam-core. Things could be improved further if I laid down some insulation in the attic.
You may want to dig further about this. If nothing else, the water heater needs fresh air to support combustion and to assure that the flue gas can rise up in the flue; if you hermetically seal the garage, there will be a problem with that. This PDF shows building requirements in Garden Grove (California?), and indicates that garage water heaters beyond a certain size (in relation to garage size) must have fresh air inlets in the garage wall. Your city may have similar code requirements.
Assuming fresh air vents are indeed required by code in your area, you might look into whether those vents can be fitted with air exchangers:
These are heat exchangers intended for bringing fresh air into (and stale air out of) well-sealed houses, while keeping heat in/out of the house. They might not be code-legal on a combustion air vent, but if they are, then these could bring in the fresh air your water heater needs while also preventing outdoor heat from coming into the garage.
Exactly. Thermal equilibrium isn’t necessarily the average air temperature outdoors. Because of solar gain, a hot attic above, etc. it can be noticeably higher. Also, don’t forget the added heat from the vehicle(s). Every time you pull your car into the garage you’re adding a lot of heat from the engine block, cooling system, transmission, exhaust, and at least during warm weather, nearly all the rest of the body and frame. That, on top of burping a bunch of air in and out when the garage door opens, can push that equilibrium temperature up even higher.
I don’t think your indoor A/C is cooling your garage at all. Heat will be transferred through the wall from the garage to the interior and transferred outside by your A/C.
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.
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.
I have an insulated garage, and the summer problem here in the Great White North is that without intervention, it retains heat, so when it is breezy cool outside in the morning, the garage still retains its summer heat from yesterday afternoon. This comes from a not-as-well insulated dark coloured garage door and some small windows. The one (insulated) wall it shares with the house, plus engine block heat, keeps it at or above freezing when the temperature drops well below freezing. (Biggest problem is the snow in car wheel wells melts, I’m forever fighting a big puddle all winter).
It sounds like what you need is some insulation on the exposed wall to prevent solar heating. (Bonus if the outside is painted white) Plus you’d need a thermostat-triggered fan, to exhaust hot air. It should be located up high, since the hottest air rises.
Without active cooling, obviously the best you can do is the outside temperature. However if it cools off at night, this should mean the fan should pull out the hot air and replace it with evening and nighttime cooler air. If you need to get fancy, a similar arrangement could be a fan blowing household cool air into the garage; but then you have to consider where the replacement air is coming from - and block any lower air feed in the garage, as cool air will flow downward and then out those holes. Plus, most building codes are very persnickety about ventilation openings that could allow car exhaust to get into the house.
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.
So to sum up - better insulation, some means of venting when it’s too hot.