The Consequences of Bad Ventilation

The concept of proper ventilation is a key concept in attics and crawlspaces. The fact of the matter is that water vapor needs an escape from the area. When water vapor is not allowed to leave an attic or crawl, a true recipe for disaster is created. Care should be taken when improvements are made. I have come across many older homes with retrofitted ceiling fans in the bathrooms. This is a great feature to get excess moisture vapor out of the bathroom. All too often, the fan is allowed to terminate in the attic space creating a moisture problem in the attic space. Below is an example of just such an installation. The proper installation would have the fan exhaust all the way out of the attic and through the roof.

1 Bathroom fan that terminates in the attic

Another example of an improvement going bad is when extra insulation is added to the attic. Care must be taken that the extra insulation added will not interfere with the ventilation of the attic. One way to ensure that the vents will not be covered is through the installation of baffles that will allow air flow down to the soffit vents. Below is an example of adding insulation without allowing for ventilation.

2 blocked vents with insulation

The results of such an installation are as follows: condensation problems, overheating attic, and crating a condition that will allow mold and mildew growth. Mold and mildew can be used by some buyers to scare sellers into expensive concessions during the selling process. Below is the result of not allowing proper attic ventilation.

3 wood damage and warping with obvious growth

Here a simple thing like no ventilation had caused the wood decking material to warp and separate. Trying to seal the area is only a stop gap approach to fixing the problem. The ventilation needs to be restored and only then can the wood decking be addressed. The other problem that this improper ventilation has caused can be seen from the roof.

4 Visible ripples noted

The warped decking has created a visible ripple on the roof shingles. Also, excessive wear has been caused by all the underlying problems. It is important to check with professionals when doing home projects yourself. Also, just because you have paid someone money to do work at your house, this does not make them professionals.