47 Ways We Reduced Mold Risk when Building our House

Video tour of the house:  https://www.youtube.com/watch?v=cRhksJI28Aw

1. Dry climate (If you follow many other ideas, you can still do well for a dry house even in a wet climate, I believe.)
2. Ground built up higher before building
3. Ground around sloped away from house
4. Large vegetable garden (needing lots of watering) is downhill from the house
5. Drainage ditch carrying water away from the house
6. Gutters with long downspouts to carry water far away from house
7. Gravel under slab
8. Shallow, insulated slab (reduces risk of water wicking up through slab)
9. In-slab heating (reduces risk of condensation on cold slab in winter)
10. Slab cured over 30 days before building
11. Douglas fir framing (more mold-resistant than some woods; less thermal bridge than metal framing although metal framing can be insulated. Metal framing is especially helpful in climates where termites are a problem and the house occupant is chemically sensitive to pesticides.)
12. Metal z-piece flashing over house sill
13. Steel siding (not a reservoir siding so it doesn’t hold water or have risk of mold growth on it in normal circumstances)
14. Steel roof (will hold up against leaks much longer than a typical shingled roof)
15. Steel interior ceiling (Zero diffusion of vapor into attic. It could still sneak up through openings, but we were careful with light fixtures, etc.)
16. FlexWrap on window sills (no seam at corners where moisture could find its way easier because it is a continuous coverage/wrap)
17. Plastic window frames (to reduce condensation risk/thermal bridging with metal windows, but there are some good metal ones out there I think, with thermal breaks)
18. Hardly any wood outside, just around exterior doors, treated with beeswax/coconut oil
19. No foundation plantings or watering close to the house
20. No trees overhanging or shadowing the house (lots of sunlight for drying)
21. No sheathing
22. No wood sub-floor
23. No plywood at all in the actual house materials (very little plywood in furniture either)
24. Thorough insulation, no thermal bridges
25. Sheep’s wool insulation (it regulates humidity)
26. No interior vapor barrier or reducer in the walls (no plastic at all except water pipes) so that the wall can breathe
27. No drywall (Plaster walls, which are mold-resistant. Plaster walls also reduce air leaks into walls because you can create walls with fewer gaps.)  https://www.youtube.com/watch?v=lQmdEb1ZKjU
28. Cement-bed tiling on floor, so no thin-set (Thin-set can apparently grow mold.) Here is how to do it:   https://www.youtube.com/watch?v=ZePENUCnZcA
29. No sealant on floor tile grout, so if a spill happens, the grout can dry out. If it were sealed, an imperfect sealing job could let water through but prevent it from drying out. This also allows us to see if water is coming UP through the tile, such as when the toilet leaked underneath.  Update:  I would NOT do this if there is wood of any kind underneath the tile. There is too much risk of the wood absorbing water through unsealed grout, wicking under tile, and not drying out.  Rock-hard cement has much less risk.
30. Exposed pipes under sinks, no sink cabinets
31. Exposed pipes with free-standing tub. The supply line is in the wall, but many connection points are open to the room, so this allows us to find & fix leaks fast. 
32. Free-standing tub fixed away from wall so there is no connection with the wall at all.
33. Exhaust fans in bathroom and kitchen, both vented outside. Many kitchen stove “exhaust” fans vent right back into the kitchen, dispersing the humidity but not taking it outside.
34. Ductwork for exhaust fans insulated (to prevent condensation in cold attic)
35. No other ductwork, no HVAC
36. Window a/c unit which we dry out at least every two days 
37. Dishwasher open to the room on all four sides. The back side is fairly close to the wall, however, it is still out from the wall enough to see what is going on, no hidden places that could gather water.  This photo is looking down at the gap between the back of the dishwasher and the wall.  The silver poles are the metal leg/frame of the worktable under which the dishwasher is installed.  The white “tube” in the middle of the photo is the water supply line to the sink and dishwasher. (The supply line is in the kitchen next to the wall instead of inside the wall.)   This set-up also allows airflow behind the dishwasher to reduce humidity risk.  We open windows and run fans blowing out while using dishwasher, also.       
38. Dishwasher installed under metal worktable, no wood close by
39. No pressboard or plywood in kitchen or bathroom or laundry room
40. Metal cabinets in kitchen
41. Industrial refrigerator with no drip pan and also several inches above the floor, so dirt and humidity are not trapped
42. No freezer inside the house
43. Plumbing all on the side of the house opposite bedrooms, so if an issue arises and needs to be remediated, it can be more easily blocked off from sleeping areas.
44. Dehumidifier for bathroom (etc.) when it is humid outside. We clean it every two days and have recently learned that vinegar in the collection bin may help reduce mold in the bin by changing the PH of the water.
45. One level (no upstairs plumbing)
46. Only one bathroom
47. House all tile, no carpet or other flooring to hide accidental moisture

(For more info, see our book:         Building a House for Multiple Chemical Sensitivity: a Mold-Resistant, Low-Tox Home )

Christa Upton      Black Hills Picture Books     Edgemont, SD  57735