Humidity and Older Homes

Humidity in Older HomesAt times, maintaining an older or historic home can almost be a Goldilocks situation: you don’t want too much, or too little, but it needs to be just right.

One area where this is particularly true is humidity. In the winter, dry air can drop indoor humidity levels to as low as 10 percent relative humidity; in the parts of the country that have hot, steamy summer weather, humidity levels can soar to more than 50 percent or greater.  This doesn’t just make your home uncomfortable, it can also damage both a historic home as well as your belongings.

How to spot humidity damage

Fortunately, there are many telltale signs that will indicate that humidity may be a problem in your home. High humidity and indoor moisture levels provide an ideal environment for mold, mildew, fungus and even standing water in the basement.

Homeowners may also be able to smell that there is a problem in the house. A dank or mildew smell in areas with poor ventilation or high humidity is also a tip off that humidity levels are high.

Look high and low in your home for more telltale signs: there may be rust or corrosion on metal objects or salt/mineral deposits, also known as efflorescence, on exterior and interior walls. Prolonged exposure to humidity can also cause wood – structural, flooring, even furniture – to warp, cup and even begin to rot. Damage to masonry can also occur, resulting in cracks and eroded mortar.

Though it’s not likely this can be seen from ground level, excess moisture can also affect your roof, leading to gutter issues and potential problems over time with missing shingles, roof tiles and/or slates.

Finally, how water moves around the foundation and basement of a historic home can also affect moisture levels inside. Missing downspouts, poor grading and locations of subsurface fields can all contribute to higher moisture levels inside the home.

All of these issues can be easily identified during a home inspection, especially with a licensed home inspector that specializes in historic homes. However, there is a greater benefit to homeowners in addressing humidity issues before such damage occurs.

Ironically, humidity and moisture can become a problem in a historic home after modern improvements are incorrectly added to increase a home’s energy efficiency. These improvements often fail to take into account the mechanics of moisture and moisture dynamics as well as historic construction methods.

For example, and this is a very simple example, many older homes were intentionally built so that air can properly circulate. Calking or sealing windows and roofing can create a moisture trap over time – humidity that enters the home from outside, as well moisture generated by simply living in the home via cooking, laundry, showering, has no way to escape.

Solutions to high humidity issues


Fortunately, there are things that homeowners can do to ensure that moisture levels stay within the recommended range year round. The first is to periodically inspect all elements of the house to eliminate any possible moisture infiltration, which can occur from the roof to the basement. A visual inspection can discover any leaks or cracks or areas where condensation and moisture can collect. Outside of the home, landscaping and foliage should be trimmed away from the home. Any exterior elements that could hold moisture – piles of firewood, furniture, awnings, etc. – should also be removed or relocated.

An interior inspection can also be helpful to discover if any mechanicals or piping is providing a moisture source. Condensation pans and drip lines should be checked. If regular day to day living is a contributing factor, additional and appropriate ventilation can be added to a home.

Most importantly, it’s important to monitor humidity levels year round. This not only ensures that a consistent relative humidity is established, but it also provides means for identifying a problem should one begin to occur.

Here at Towne & Country Building Inspectors, historic home inspections are our passion. If you are looking for a historic home inspector in Milwaukee, look no further. Give Towne & Country Building Inspectors a call to schedule your inspection today.