Certainly worth a try. It should at least slow down the rate of heat transfer so it takes longer to get up to objectionable heat. Please report on how well it works. The factory styrofoam floor liner is a pretty good insulator too so it may be hard to tell the difference.

 

The factory styrofoam floor liner is a pretty good insulator too so it may be hard to tell the difference.

But with both in there it should make a difference. I don't have the liner in my boot as I have amplifiers installed across the floor and I don't think it gets any hotter without the liner.

 

For aluminum heat shielding to be effective you need an air gap. Note how the heat shielding that AR installed is rigid and has stand offs.

Also for aluminum heat shielding to work well it needs to be clean, bare aluminum--not anodized, not painted, not coated with clear plastic and not dirty. Aluminum foil works pretty well.

The optimum width for the air gap is a complex subject, but tiny air gaps do not work well.

 

@lockem do you mean like fins in a heat sink? Unfortunately the trunk is so tiny, if you created some sort of a Fin-ed aluminum structure to soak heat and cool it down, you'd take away space from the trunk. Also wouldn't the heat need to be vented and circulated out with fins?

I wonder, I think: any one sided aluminum will only work if there is a way to radiate the heat out and away? Like away and out of the bottom of the trunk?

 

@lockem do you mean like fins in a heat sink? Unfortunately the trunk is so tiny, if you created some sort of a Fin-ed aluminum structure to soak heat and cool it down, you'd take away space from the trunk. Also wouldn't the heat need to be vented and circulated out with fins?

I wonder, I think: any one sided aluminum will only work if there is a way to radiate the heat out and away? Like away and out of the bottom of the trunk?

No, the fins in a heat sink are intended to transfer heat to air, while aluminum heat shielding is intended to stop radiative heat transfer. Look at the heat shielding around your muffler for an example of how it can be done to work.

In this environment heat moves 3 ways

Radiation (IR).
Conductive (direct contact).
Convective (moving fluids, such as air).

As soon as you have a substantial conductive path for heat to move around, the other 2 mechanisms become trivial. Minimize conductive heat transfer by minimizing contact (adding air gaps) and/or using insulating materials. Insulating materials use fluffed up low heat conductivity materials to minimize contact area and implement a lot of tiny air gaps so that convective heat movement is minimized. Unfortunately insulating materials need to be thick to do much and are pretty much always fragile.

if your air gap is too small, the air will conduct heat across the gap. If your air gap is too large the air will start convecting and move heat across the gap. The width of the gap between thermal dual pane windows is not arbitrary.

Radiative heat transfer is strongly dependent on temperature differences. IIRC for modest differences the transfer varies as the 3rd power of the absolute temperature. To be more precise:

(T2^4 - T1^4) * scale_factor where T2 and T1 are the absolute temperatures of 2 parallel surfaces. "scale_factor" is really important here since for clean pure aluminum that factor is about 2% of the factor for a black surface. This is what aluminum heat shielding is doing, but it only works if there is no "thermal short circuit" caused by direct conduction (no air gap) or wrong width air gap.

A completely different means to control trunk temperature would be active cooling. In this case we need channels in the trunk flooring material (it may already have such) and a source of cool forced air (from the HVAC system? probably easier to just add a fan) to blow through combined with an exit in the body work. I think there are already exit vents mounted in the rear part of the rear fenders. This sounds simple, but I think is actually pretty difficult to implement. Liquid cooling might also be made to work and might be easier given the dimensional constraints.

 

$56 bucks is a lot cheaper than trying to run cooling fluid or air into a sealed trunk. Works, well, maybe works for me. I don't put our cats in the trunk. Maybe my solution is looking for a problem?

NV

 

I would be very surprised if your implementation helped at all.

How about sound deadening? I have a load of old sound deadening material that is made up of a self adhesive butyl rubber compound and a 0.1mm aluminium layer. Would this provide and heat insulation if stuck to the floor i.e. you have boot floor, butyl rubber then the aluminium?

If you replace the trunk floor with said aluminum layered sound deadening material and then do not put anything on the floor of the trunk you should get a substantial reduction in the amount of heat going into the trunk. However, with nothing on the floor of the trunk, did you fix anything? I thought the whole point was to keep from heating up stuff that is sitting on the floor of the trunk.

An inch of EPS or bubble wrap would likely be enough to make a significant difference in the temperature, but then you loose an inch of height from your already small trunk.

 

How about sound deadening? I have a load of old sound deadening material that is made up of a self adhesive butyl rubber compound and a 0.1mm aluminium layer. Would this provide and heat insulation if stuck to the floor i.e. you have boot floor, butyl rubber then the aluminium?

 

the Jeg's I put down has white mylar on one side, then about a quarter inch of some sort of felting insulation, then a layer of bare shiny aluminum on the other side. I put the aluminum side down. You can also buy two sided aluminum facing, and some shielding that is thicker. It is not adhesive on either side. Whether or not it makes a difference really isn't important to me, as I rarely have anything in my trunk. If you look around, there are lots of things to reduce heat/noise intrusion into cars. All the best, and stay safe. HC