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I did a rough calculation and I will need about 13-14 sq. ft. to fully cover the back and bottom of my trunk carpet in my HTC. So, from Amazon I just ordered two of these for $39.97 each: "E.F.R Aluminum Thermal Heat Shield Protection with Fiberglass and Self-Adhesive Backing Heat Barrier- 8 Sq Ft (24x48 Inch)". It has pretty good reviews and is pretty light - 8.4 ounces each.
If you want to get a little more extreme, you could also wrap your exhaust headers and catalytic converters with appropriate material (NOT the above heat shield). I would first try using the heat shield in the trunk and see how that works.
Insulation just slows heat transfer, it doesn't stop it. Eventually the interior temperature will equalize at a point where the heat coming in equals the heat going out.
What I'm getting at is you may not want to insulate the whole trunk liner. If there is an area of the trunk exterior that is cooler you may want to leave insulation off that area to let the heat input vs heat output equalize at a lower temperature.
Insulation just slows heat transfer, it doesn't stop it. Eventually the interior temperature will equalize at a point where the heat coming in equals the heat going out.
What I'm getting at is you may not want to insulate the whole trunk liner. If there is an area of the trunk exterior that is cooler you may want to leave insulation off that area to let the heat input vs heat output equalize at a lower temperature.
100% Correct. Only the back side facing the engine compartment and catalytic converters (I guess maybe I should have called this front, but I was measuring from the back of the car) and the bottom side above the muffler. I am leaving the trunk cover and side facing the back of the car as is, without the thermal barrier. The goal is for the thermal shield to slow the energy transfer from the engine/exhaust, while the energy transfer out of the trunk lid and side facing the back of the car remains the same. It will not be as effective as if there were an air gap with air flow between the thermal barrier and the carpet, but that would probably interfere with too much of the trunk space.
Before I actually use the adhesive to fix the thermal barrier in place, I am going to compare a temperature measurement with the stock configuration to a temperature measurement with the thermal barrier set in place, but not yet attached to the carpet with the adhesive. I'll post the results here.
I went out and drove for 15 minutes with a meat thermometer in my trunk. Outside temp was 90 deg. F. When I got home I measured the temperature on the bottom of the trunk (on my cargo liner) with an infrared thermometer and it read 103 deg. F, which is 13 deg. above ambient. The meat thermometer read 99 deg. F, which is 9 deg. above ambient.
I placed the thermal barriers behind the carpet and drove for another 15 minutes. I have one barrier covering the bottom and extending part way up the engine side of the trunk, and the other one slightly overlapping but extending all the way up the engine side of the trunk. This time the infrared thermometer read 102 deg. F, which is 12 deg. above ambient. The meat thermometer again read 99 deg. F. Not much different.
So, I think it is safe to say the Self-Adhesive Backing Heat Barrier from Amazon is not very effective for this particular application, at least not based on my results from 15 minute drives in 90 deg. heat. Maybe there would be a bigger difference in cooler weather.
Perhaps the TKO Performance Blockit Ultralite Heat Shielding performs better - I don't know. The test in the video (I suspect it is a sponsored video) showed a 30 deg. difference, but the test conditions were completely different - 32 deg. ambient vs my 90 deg. ambient. Also, I have the cargo liners in my trunk, which themselves probably act as a thermal barrier. In the TKO video there were no cargo liners.
If anyone tries the TKO heat shielding, please post your results.
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Thanks, this is good data. I've considered adding the insulation but I'd like to see other people's experiences first (backed up by data).
Right now I use a large food delivery bag in the trunk with synthetic ice packs in it when I want to keep things cool.
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Thanks, this is good data. I've considered adding the insulation but I'd like to see other people's experiences first (backed up by data).
Right now I use a large food delivery bag in the trunk with synthetic ice packs in it when I want to keep things cool.
After giving this more thought, I suspect my cargo liners play a big part in keeping the temperature rise in my trunk under control - the cargo liners in the trunk sit over the muffler area. Stock my temperature rise (13. deg. on the cargo liner and 9 deg. in the trunk) was significantly less than the temperature rises shown in the TKO video, even after the TKO heat shield was applied. Again, I had a much higher ambient temperature, which probably changes things. Nonetheless, my stock temperature rises are pretty good in comparison.
The stock cargo liners are $145 and cover both the trunk and frunk. In addition to apparently helping with thermal insulation, they look nice and work to keep the carpet clean if any fluid leaks from groceries or whatever else is being carried in the trunk and frunk. The cargo liners are very easy to put in place and remove, so they may be a good option.
After giving this more thought, I suspect my cargo liners play a big part in keeping the temperature rise in my trunk under control - the cargo liners in the trunk sit over the muffler area. Stock my temperature rise (13. deg. on the cargo liner and 9 deg. in the trunk) was significantly less than the temperature rises shown in the TKO video, even after the TKO heat shield was applied. Again, I had a much higher ambient temperature, which probably changes things. Nonetheless, my stock temperature rises are pretty good in comparison.
The stock cargo liners are $145 for both the trunk and frunk. In addition to apparently helping with thermal insulation, they look nice and work to keep the carpet clean if any fluid leaks from groceries or whatever else is being carried in the trunk. The cargo liners are very easy to put in place and remove, so they may be a good option.
Yep, I got the GM cargo liners the same time I got the splash guards. Reasonably priced for what they are.
Is the trunk airtight? Seems to me that in general, trunks, or any enclosed space that is in the sun can get not just to ambient air temperature, but hotter than ambient temperature, just from the infrared component of sunlight that is absorbed by the surface (or passes through glass) of the enclosure then transmitted to the interior space (like your attic space for example). Lots of surfaces will get much, much hotter than ambient air temperature in sunlight. The surrounding heat from the exhaust on the sides or below the trunk enclosure just contributes to that both from convection of hot air around the trunk, as well as the infrared heating much like sunlight on the trunk lid. White will reflect some back. A black trunk or car with a black top will get extra hot. Doesnt the shiny part of the insulation reflect the IR heat back some? A good way to alleviate the heating for enclosed spaces (like your attic) is to allow a little airflow. Visibly, the trunk looks well sealed but there may be an opening through where the latch is. I any case, I attached some photos showing how heat (or air) from the engine vent on the HTC could be circulating around the top of the trunk, around the seal. I am not saying it goes into the trunk, and I am not saying whether or not is airflow would add to the heat, or carry some away - just noting that this airflow is possible. You can see in the first photo that the rear landau cover vent is open to that space around the trunk. This is also where water will enter between the landau cover and the trunk lid. The water flows around the said, as you can see in the second photo, then down toward where the trunk pneumatic cylinders attach and out the rear vent (apparently). Since the landau vent opens to that space, it possible that both air (hot air?) and water will flow around the gasket on the trunk top. I was trying to see if there is already existing ventilation in the actual trunk but so far I did not see that.
It appears that the vent opens in the space that surrounds the trunk gasket. Water will also come in here, though the gap between the landau cover and the trunk lid. Water and air can flow along to the left and right sides of the trunk/trunk gasket, and down in to the space where the pneumatic cylinder attaches. You see daylight toward the back of the car - this looking past the pneumatic cylinder hinge and out through the rear vent of the car. I think this is the path for water flow but will also allow air to flow out as well.
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I didn't see ventilation holes for the trunk, but I was not looking for them either. The heat shielding I tried was fiberglass with a shiny aluminum coating. Theoretically, the aluminum coating should reflect radiant energy to some extent, but it is just being reflected back onto the trunk walls, and thus not really going anywhere. I think it would it work better if there were an air gap between the shielding and trunk walls for air to flow, but that is not practical in our cars - the carpeting would not fit very well. Anyway, I pulled the heat shielding out since it did not accomplish much. Maybe I will try the experiment again next winter when we get slightly cooler weather.
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I didn't see ventilation holes for the trunk, but I was not looking for them either. The heat shielding I tried was fiberglass with a shiny aluminum coating. Theoretically, the aluminum coating should reflect radiant energy to some extent, but it is just being reflected back onto the trunk walls, and thus not really going anywhere. I think it would it work better if there were an air gap between the shielding and trunk walls for air to flow, but that is not practical in our cars - the carpeting would not fit very well. Anyway, I pulled the heat shielding out since it did not accomplish much. Maybe I will try the experiment again next winter when we get slightly cooler weather.
I think the trunk must be vented in some way. Otherwise it would be hard to close. In the same way the cabin is vented so the doors close without popping our ears, or flexing the side windows.
