Moisture problems can lead to mold or damage to wall coverings, and maybe more. As we improve the tightness of our homes, we should be concerned with indoor air quality as well. The first step is dealing with humidity.
In Houston, humidity has always been a problem. Air quality is also a problem, but most homeowners do not seem to be too worried about that fact. When following up on a home where I had done an inspection job, I spoke with the owner about dealing with moisture, since the structure had issues. He was greatly improving the building envelope’s seal, so there was a concern about air quality beginning with moisture. We discussed whole house dehumidifiers and HRVs (heat recovery ventilators). HRVs are not common in Houston, but we may wish to consider incorporating this technology as we create ever tighter buildings. My older home is slowly obtaining a tighter envelope as I continue my improvements, so I have been thinking about dealing with moisture too.
I was sitting in my living room when I noticed that the water level in my 250 gallon fish tank had dropped significantly. This can lead to a good deal of water in the air. I noticed the bathrooms, and how we have moisture build up there, so I began to investigate dehumidifiers. This appliance has really developed over the years. Portable units havemuch larger capacities now ( many have 50 to 60 gallons). The problem with these portable units is that they do use a bit of electricity. To reduce the amount of power usage, a whole house dehumidifier which would be installed as part of the HVAC system (your air conditioning) is the better option. Portable units with greater capacity run around $200 to $250, while whole house systems run between $900 to $1500. With either system, you could use the water for your plants. Since my goal has been to reduce my electricity usage, the whole house unit seemed the better choice; however, cash flow was my issue (I have a few customers who seem to think that they do not need to pay me).
Thinking about my humidity problem, I thought about how moisture can be removed from the air. Actually, if you are a crafter you may be familiar with a few moisture removing materials. They are called dessicants, and you have one in your kitchen cupboard: salt. Flour will also pick up on moisture in the air, but salt is better as a dessicant. I thought about having salt spread about the house picking up the moisture in the air, then the salt could be dried in the sun to release the water into the exterior air. Checking online, I discovered that this idea is the basis for do it yourself dehumidifiers. I figured that the idea could not be original.
Taking my cue from the whole house system, I built my dehumidifier into my air conditioning system. Some of the articles that I read on the topic stated that the salt will leak some water, so they incorporate a basin system. I was not sure if this would happen though. Many of these dehumidifiers included fans to blow the air across the salt to speed the air drying action. I wanted to use air which was already moving, so I would not need to use the fan. The pictures below detail my version of a whole house dehumidifier. The top portion is a cage made with chicken wire. Into this cage, I placed a sunscreen fabric. This fabric is plastic based, so the salt will not corrode it. The salt is not coming into contact with the metal from the frame to avoid this issue. To deal with excess moisture that may leak from the salt, I placed a roasting pan underneath the cage. This is one of those disposable pans that you may use for turkey. To lift my cage above this pan and so it will be in the air flow, I used pvc pipe as legs for the cage. This dehumidifier was placed into my return air chase. Having an older home, I only have one return air vent. Since this is where my filter is located, I can remove the dehumidifier when I take the filter out for cleaning each month.
I like the fact that this is a great passive dehumidifier, no energy from the utility needed. I am not fooling myself though. The air will pass through the salt here, but I will not catch all of the humidity in the home. I made portable units to help me out here. I took half liter water bottles. Cut off their tops. Made air vent slits in the sides. I took cuttings from my bamboo to wrap around the bottle. I used a rubber band to hold these in place. Then I painted the holder. I filled them with rock salt. I have these placed around the house. I can take the salt out to be dried when I do the one in the chase. I do not suspect that this will rid my house of all of its moisture; however, I have taken a step in the right direction. I do not like the look of portable units, and a whole house dehumidifier is too expensive at this time. There are smaller units which fit into closets, but I think that these may be a hassle. They need power, and they need a vent to draw air from the home.
I want to explore other passive methods to improve indoor air quality. At least methods which do not use much power. Live plants help. I heard that ivy, which is a great indoor plant, cleans the air well. My wife has had an issue with plants inside the house. I am not sure for her reasons, but she is always setting my pots outside. She has never explained her actions to me, except to say that they are a mess. We did have problems with the children digging into the pots, so that might be the mess. We will see.
Update: After a week of having this dehumidifier in place, air moisture has been decreased. Part of this decrease may be due to a change in habits though. I run my range hood vent when opening the door for my oven (I always ran it when preparing a meal on the cooktop). I am not taking hot, steaming showers as much (I jump into the shower when it is lukewarm- a habit that the rest of my family already had). The other big moisture problem is the aquarium, but I have not come up with a solution for that. As for the salt leaking water: I have not had a need for the basin. I am leaving the basins in place to see what will happen.
Second Update: After a little over two weeks, I noticed that the water catching system has not been needed. Others writing about making dehumidifiers, have reported that the amount of moisture can cause the salt to release water, so a bucket was needed. Is the moisture down in the house? Yes, but not as much as a proper system would have accomplished. I think that taking a step towards removing moisture from the home may be a good path. Drying clothes outside is one example. Keeping bathroom and utility room doors closed to prevent moisture from spreading. My big problem is the large fish tank; it is releasing quite a bit. My next step is to take measurements to see how well the salt may be working.
Third Update: I still have not dried the salt. There has not been a need to do so. I weighed the salt from last week to this week, and it is picking up moisture. Again, this type of dehumidifier is not going to be dealing with homes that have large amounts of moisture. Goes to show you, prevention is better than dealing with the result.