DEAR TIM: There has been so much news lately about mold that
I am very concerned about what might happen to my family and myself in my new
home. When I was growing up, mold was never and issue. What is different now?
Why is mold such a problem with newer homes? Older homes seem to be somewhat
immune. Chad G., Birmingham, AL
DEAR CHAD: As much as I hate to say it, I think the mold
problem is just starting to raise its ugly head. For many years I have witnessed
building construction practices that, in my opinion, contribute to
severe mold growth and subsequent structural failure from wood rot. The
problems can be traced to several things. First and foremost among them, many
modern builders simply do not understand the dynamics of water vapor,
condensation, ventilation and exterior moisture protection. In the years ahead,
I predict that mold discovery and mold related issues will reach epidemic
proportions in recently built homes.
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Let's discuss the older home you grew up in and the
thousands of older homes that are still occupied and in excellent condition in
your community and others around the USA. Older homes simply were not built
as tightly as the homes of today. The weatherstripping around doors and
windows was poor or non-existent. Many homes had little or no wall insulation.
The houses were drafty. Inexpensive heating fuel allowed these building
practices to exist. Residential central air conditioning had yet to be invented.
Builders understood the importance of tar paper beneath wood siding. Brick
structures were two or often three courses thick. Indoor humidity in the winter
time was very low.
Because of these factors and several more, water that triggers mold growth
didn't collect inside of wall cavities, on interior wall surfaces and in attic
spaces.
The drafty nature of the construction allowed the water to
rapidly evaporate into the atmosphere. Mold most certainly did grow,
but only in places where water leakage had become a chronic problem.
The energy crisis of the 1970's turned the residential construction industry
on its ear. There was a rush to seal air leaks in houses and improve the
weatherstripping on doors and windows. Vapor barriers in exterior walls became a
building code requirement. In many areas of the nation, forced air heating and
central air conditioning with its necessary duct work replaced traditional hot
water or steam radiant heating systems. Along with the duct work came whole
house humidifiers. Humidifiers are a good thing, but if not operated properly,
they can become mold's best friend.
The rapid growth in the overall population created a housing boom. This led
to an influx of builders and sub-contractors into the residential housing
industry that had little or no formal training. These individuals, without
knowing it, started a trend of poor building that was, and continues to be,
unknowingly passed on to subsequent builders and sub contractors. Just because
an individual has been doing something for 20 or 25 years doesn't mean it is
right!
For example, go back in time and you would never see a roofer caulk metal
flashing in place. Sure, modern caulks are a far cry better than old brittle
butyl caulks, but they can and do break down over time. On the other hand, 40
pound tin flashing embedded 3/4 inch deep into a mortar joint has been known to
last 70 years or more.
Old builders discovered well over 100 years ago that overlapping layers of
ordinary 15 pound tar paper stopped rain water and snow melt from touching vital
wall sheathing and wood framing members. Today we have modern air and water
infiltration barriers, but many houses are
built without this vital
secondary moisture protection. Wind driven rain can and will get behind
all types of siding. It can also penetrate the single layer of brick veneer that
so many homeowners think is waterproof.
To stop mold growth, your builder must be well educated and be able to
demonstrate a knowledge of how to use modern building materials in such a way
that water does not condense within wall cavities and attic spaces. He needs to
build your home to standards that exceed what the building code
states. The building code is a wonderful set of guidelines but many
code officials will agree that is a set of minimum standards. If he does not
agree with this point, it is time to re-open the bidding process on your new
home.
If you have mold growing on a surface, it can be removed by using different
types of bleaches. Not all bleaches are the same. The most common bleach that
most people use is chlorine bleach. It is a liquid purchased at just about any
grocery store. The chemical name for chlorine bleach is sodium hypochlorite.
Chlorine bleach is a very effective mildew and mold killer, but its fumes
can bother some people. Mixing a 50/50 solution of chlorine bleach and water is
often all you need to do to make a powerful solution. Spray it on the mold and
mildew and let it sit for several minutes. Scrub it with soap and water and then
rinse.
If you want a less toxic bleach, you may want
Oxygen bleach. Oxygen bleach is a
powder you mix with water. It produces no fumes and it also does a good job or
removing mold and mildew, but it doesn't do it quite as fast as chlorine bleach.
The Oxygen bleach solution is also safe for any vegetation and nearby plants
should you be working with it outdoors.