Trained Eye

 
 
 

Cold Room in Basement

Question:

We recently purchased a home, which has a cold room, and in the cold room the two concrete foundation walls are partially covered with what we believe to be black mold. We are wondering what is the best way to go about removing and preventing the mold from reoccurring? Is this something that I can do myself or should I get a professional to come in? Currently the cold room is not vented to the outside.

Thanks for your help and hope to hear a response from you as soon as possible.

Answer:

Proper removal and cleaning of the mould on the foundation walls is dependent on the extent of the growth. If there are small to moderate patches of mould in several areas, you may be able to clean it yourself. If the walls are mostly covered, or if there is a heavy growth, professional remediation may be required, but it will be costly.

If you feel that the amount of mould is not too large to handle, the first thing to attempt is simple cleaning. If the mould is dry, the surface of the concrete can be cleaned using non-toxic soap and water, ensuring that you protect yourself with a respirator, rubber gloves and long sleeves. The room should be sealed off with polyethylene sheathing to prevent mould spores from spreading into the house during cleaning. If an externally vented central vac is available in the home, it may be used to suck up excess dirt and spores before removing the plastic sheathing. All clothing worn during cleaning should be removed and washed as soon as possible to avoid contamination of other areas of the home. Once the mould is removed you can take immediate action to stop it from coming back.

The key to preventing reoccurrence of the mould is simple, but you may not like the solution. The answer is to eliminate the cold room. In my experience, and in our climate with several months of the winter heating season, cold rooms in basements are always a bad idea. The lower temperature and limited air movement in these types of rooms are ideal conditions for condensation and moisture build-up, which may promote mould growth. When the warm, heated air in the home hits the cool concrete walls of this area, it will reach its “dew point” and condense on the cold surface. The moisture from this condensation will not dry easily because there is limited ventilation or heat to allow for evaporation. Dirt and dust on the walls will provide a medium for the mould to grow, and the problem begins. If the cold room is returned to the same temperature as the rest of the surrounding area and air circulation is improved, there should be little or no condensation on the walls, no moisture, and no more mould.

As I have stated in several previous articles on this topic over the years, mould requires a few simple items for growth. The two main items are a source of moisture and an organic, cellulose based medium to grow on. Limited air movement also helps, by preventing evaporation. All of these conditions may be present in your cold room, and all can be easily eliminated by opening up this area to the regular heat source and ventilation enjoyed in the rest of the basement. Periodic cleaning or vacuuming of the foundation walls after initial cleanup will also help prevent a source of food for new mould growth by removing dirt and dust accumulated.

Another item to consider after cleaning and opening up of the cold area is proper insulation. Once the mould is removed, either by your self or professionals, insulation of the cool foundation walls and the floor joist cavities above may help prevent condensation and reduce energy consumption. Use of moisture resistant extruded foam insulation may be ideal in this situation. Care must be taken to properly install and caulk the insulation and vapour barrier to prevent air leakage behind. Also the insulation must be covered with drywall or proper sheathing for fire safety.

Although installation of a cold room in the basement may seem like an economical way of providing a storage area for preserves and other items it can lead to serious mould growth, as you have witnessed. Many older homes had cold areas or cellars for vegetable and preserve storage that were not prone to this problem, but they have a fundamental difference. These older basements were very cool, uninsulated spaces with drafty windows and floor joist spaces that allowed adequate air movement and fresh air infiltration to prevent condensation on the foundation walls. When we insulate and seal the rest of the basement, in modern homes, and leave one isolated area cold we are asking for trouble. My recommendation would be to eliminate the cold room, altogether, and purchase an extra, energy efficient refrigerator as a replacement.