Geiger tube housing

I have the mightyohm kit and for a week or so I upload the data. (The past days the readings are higher, as I put it on my stone kitchen workbench, just to see the difference...)
I am wondering what influence the housing of the kit has. All example I see heve open space around the tube. So in another test, I put some alu-foil around the kit to see if the readings drop. But no difference.. As I do not want to have the influence of the concrete walls, I am thinking of putting the kit in a waterproof housing of plastic.

Anyone that can be of any help? Maybe just add 10% to the value or 'plastic does not filter'...

Next to that, you only want to be alerted if the values go up steep (Let's say some accident somewhere...), not if they stay in the same bandwith.

Thanks!

René

I have tried various housings. As we are measuring gamma and generally hard beta, the material makes little difference unless it is made of fairly thick/dense metal. I have tried acrylic tubing which is not good in strong sunlight.  Likewise polycarbonate. I now use small standard waterproof electrical boxes.