I just toured a property with a mold expert. Not a mold remediation contractor,(who may be hoping to find a big problem to work on) but a Certified Industrial Hygienist. (CIH) He brought a moisture meter and other equipment. He checked under each sink looking for leaks. With the probe he checked a ceiling spot that looked like an old leak, but he said no moisture present there. You are going to be looking for water intrusion (roof, wall leaks, plumbing problems.)because those are spores you are smelling. a CIH can do air samples as well to see if spores are in the air. The fact that you could smell a change after rain suggests a roof leak or a crack along a wall outside. Can you go up into the attic space with a flashlight? A home inspector who checked the house out when you bought it wouldn't have found anything necessarily because as a new home ages it settles. You can find cracks around the fireplace flashing up on the roof because that caulking cracks sometimes with a change of season. Recaulk. Send a registered letter now to the builder detailing the fact that you gave notice earlier, and now the problem is worse after a rain. If you installed satellite or cable and the installers made holes for their equipment on the roof or just walked over the roof--that could be the area water is entering.

Success! After a long battle, we finally figured out the problem. It turns out, there was a bad check valve, near the recirculating pump that allowed the cold water to get into the system. the same check valve failed on both systems. We opened it up, and both of them were encrusted with calcium deposits and hard water debris not letting the valve close. Just for future reference to anybody with a similar problem here is how we tackled it: -We checked the dip tubes on both hot water heaters , and both of them were fine. -next, my plumbers isolated the hot water heater to make sure the heater was running properly. all checked out fine. -We turned off the radiant heat systems and bypassed them with the built-in valves. -My plumbers opened up each shower fixture and closed off the water valves to take those out of the equation. the hot water still ran cold. - Next, the plumbers removed the recirculating pump and checked the system. the water still ran cold. at this point it had to be the check valves, since nothing else would cause the cold water to come back into the system. - The plumbers then starting removing the check valves beginning with the one near the recirculating pump and discovered the broken valve. If this still didn't work, they would've kept going to check every check valve in the system(three total). the plumbers installed a temperature gauge to be able to see the change in water temperature. now the temperature holds solid and 120� when the hot water is turned on. I can't wait to take a piping hot long shower. Below is a picture of the plumbing system if you were curious. Two water heaters, one for each unit with the radiant heat manifolds. Radiant heat system by Warmfloors, Napa Ca Installation by AG Quality Plumbing San Francisco, CA(the best plumbers in San Francisco by far) Thanks all! Here is a link that might be useful:

Hi, Thanks for the ideas. I hadn't thought of any of this stuff. I won't be home for a few days, due to new grandchild, but will check those things when I get back. This has been a baffling problem. We're on a slab. We have a good plumber, but sometimes try to trouble shoot stuff before we call him. Of course, every time we've done that in the past, he's had to come out and take care of it, lol. Maybe this time will be different. Linda

Check above the rooms (under the roof) for dead animals in the attic. Squirrels and mice are common invaders. If you have a chimney on an outside end-wall of the house and the chimney goes though the peak of the roof, that may be an entry point. Builders may frame the house and roof before the chimney is built (full brick chimney). After the chimney is built, there may be a gap where the eave box meets the chimney and the top side is bridged by roofing shingles, but underneath, the eave box does not meet the chimney. This is were squirrels entered my house. They got inside the eave box, moved down to the soffet (where the rain gutters are) and now had a lateral run the length of the house. They could enter the attic anywhere they pleased.