A recent test revealed a high concentration of radon in my house. It looks to me that ventilating the area under the floor might solve the problem. However, since my floor is made of tiles, I think that the ventilation system will take the air from above the tiles through the cracks and not all the area under the house will be ventilated. What I would like to know is how can the floor tiles be sealed between each other. What material should be used. Thank you.