The main cause of poor/erratic signal is reflections/mirroring and not insulation from the signal in the first place (unless you are living in a concrete or lead lined bunker). That's why one minute your mobile phone signal may be 40% and the moment you try to make a call it drops to 5% as the error correction goes into overdrive by resending your data until an unbroken packet gets through. Radio signals are highly directional and subject to reflections. If your phone (or Wi-Fi) is sending and receiving data then that data may travel via a window or doorway and maybe bounces off a few local buildings, but if that same data is also reflected up and down a foil-lined room a few times before it then travels along the same route, errors and collisions will occur. For each successful packet that gets acknowledged you may have many times more that fail or arrive as duplicates, all the time eating up the bandwidth that should have been available for sending the data you actually want to send.
The OP would need to create his Celotex house at 1:1 scale and install every other surface that might cause reflections (including the bricks and plaster) in order for it to be a fair test. At which point he has built his house...
The OP would need to create his Celotex house at 1:1 scale and install every other surface that might cause reflections (including the bricks and plaster) in order for it to be a fair test. At which point he has built his house...