I want to block or reduce the amount of wireless cell signals coming into my house through my window(s) by using some type of mesh (screen). I could use a sheet of metal but then I wouldn't be able to see through the window. I am initially planning on standard window screen made of aluminum (not fiberglass), and I would ground the screen to an earth ground outside my house. The wireless signals are from a new cell tower across the street from my house. It has 3G, 4G and is supposed to get 5G. So the frequencies I believe would be 850MHz-1.9GHz for 3G, 700MHz-2.6GHz for 4G and 2.5-30GHz for 5G. What would be, or how would I calculate the maximum hole size to block these signals? Does the thickness of the screen matter? Would I be trying to interfere with the frequencies or the amplitudes of these signals? PS: My house has metal siding but the roof is asphalt. My EMF meter typically has higher readings throughout the house the higher it is to the ceiling. Any other suggestions would be greatly appreciated.
Mesh attenuates in the range 10dB to 50dB. For anything more than that you'd need sheets of 1mm to 2mm thick, made of copper or steel.
It is not true that holes smaller than the wavelength block or shield an EM wave. Also, findings of the Faraday cage -not box- for electrostatic fields (familiar to many from Physics classes) are often misleadingly extrapolated to electromagnetic fields.
Brick, wood, cladding all attenuate but do not shield, so it's not just your windows but also the walls, blank doors.
Metal chimneys and vents will also guide waves inward.
When testing our RF circuits we use a shielded chamber, made of copper plate. Even the door has a copper coil, installed like a draft stop. It provides more than 100dB attenuation, which is adequate to perform sensitive noise measurements in our circuits. Supply and network cables leading into the chamber are throttled with chokes.
Cell towers transmit at 40dBm or more. That's one transmitter at one frequency. Add a few up, at different bands, and from different towers, and you can see how an attenuation of 20dB does not accomplish much if you are close to the source.
As for your question, here are some examples of materials with attenuations higher than mesh.
From an engineering standpoint I'd say you will be throwing too little money at a problem for which there is too little evidence.
You pointed to a shielding paint. The manufacturer, Yshield (Germany), reports their in-house RF tests with 40dB attenuation after 1 coat, and 50dB & 60dB after resp. 2 & 3 coats. These are notable numbers.
For 60dB, $230 covers perhaps 150 sqft of wall/ceiling. Do the math for your home: a 2000 sqft 2-story home has 3400 sqft of surface needing coverage, and costs $5200 (very ball-park).
This is the attenuation through the paint, and does not account for imperfections in a realistic space (doors, windows, other orifices etc..)
Another issue is entrapment of EM waves: whatever gets in, or originates from within, is reflected between walls until it decays away. With purely reflective protection there is no EM escape. The report does not split the attenuation between absorption and reflection, but they do quote the resistivity. Absorbers would be the carbon paint, the furniture etc. and -ironically- human bodies.
You still need to cover the windows, which require a metallic foil. Metallic heat and UV shields also provide EM attenuation. Some office buildings with darkened windows are notorious for poor cell phone reception inside. (And I don't believe the foil is grounded)
The supplier you mention has those as well: