DIY EMC Tents for EMC/RFI testing?
Overlap the foil by 50%. That is, lay down foil edge-to-edge, then place a 2nd layer centered over joints of the first layer. The capacitance between layers will be enormous

C = Eo * Er * Area/Distance

C = 9 * Ef of air (The aluminum oxide should not dominate) * 1 meter^2 / 0.1mm

C = 10pF/meter * meter * meter/0.0001m = 10pF * 10,000 = 100,000 PF or 0.1uF

Thus at 1MHz the layer/layer capacitance will be ~ 1.6 ohms at 1MHz.