crawlspace

Crawl Space Ventilation

The purpose of crawl space ventilation is to keep the moisture/humidity level in the space at as low a level as possible.  This is important because wood destroying organisms thrive in moist environments.  Anobiid beetles (most common and most destructive wood eating insect in Western Washington) for instance, thrive in a wood moisture level as low as 13%.  An unventilated, or inadequately ventilated crawl space is apt to have high moisture levels.  Most newer homes are provided with adequate ventilation through building codes.  Homeowners often defeat this ventilation by installing foam block inserts, thinking they are protecting water pipes.  The proper way to protect water pipes is with pipe insulation.  Closing off foundation vents does not allow moisture to leave.  Older homes often have inadequate ventilation. Standard building practices require one square foot of vent area for every 150 square feet of crawl space.  Vents should be evenly distributed and within a few feet of corners to promote air circulation. One example of inadequate ventilation is the louvered vent cover shown below.

This type of vent actually has only half the vent surface area that it appears to have.  This restricts air flow.  A better solution would be to replace the louvered vent screen with 1/4 inch mesh galvanized hardware cloth.  This would give full ventilation surface area.  I always advise my clients to do this.  To sum up; keep vents open.  The only time, in this county, to block vents is when we are having a serious northeaster with the temperature and wind chill down around O degrees fahrenheit, and only for the duration of the northeaster. 

As always, thanks for reading.

David Helm, Bellingham home inspector

http://www.helmhomeinspections.com

crawlspace

Tales of Inspecting

I know that many home inspectors have stories (some of them horror) of inspections that did not go exactly as planned.  I have heard one story about a very dangerous person, with gun, that happened to be in the house.  My own little story is nowhere near as nasty as that one, but it had me worried for a bit.  I always save the crawl space for last.  It is a dirty place and I don’t wish to take any of the dirt back into the home.  This particular day, my client was in California, the realtor came to open the house and left, so I was alone at the site.  The crawl space was a particularly tight one, but one I could traverse with some effort. As I was coming down the home stretch, so to speak, I came to  an area that had flexible duct work that was pretty close to the ground.  Since I needed to see some plumbing nearby, I decided that I could probably push my way under this duct (after all, it was flexible).  I got about halfway through when I found that I could not make it any further.  Okay I think, I’ll just back out from under it.  WRONG!  Here I am, stuck in a crawl space, my cell phone is in my tool bag outside the entry.  I can’t move forward, backward or sideways.  What a predicament!  After struggling for a good 5 minutes (seemed like hours), I figured I needed to stop, relax and think this through.  I wear heavy duty rain gear in crawl spaces.  First thing I did was remove the rain coat; it felt like I could move a little, but not enough.  It was winter, so I had a fairly heavy shirt on; removed it.  Now I am naked from the waste up and feeling really ridiculous.  My next move was to very slowly inch my way backward.  After about 5 minutes of this I was free.  Put my shirt and raincoat back on and went the long way to get out.  While laying there thinking what to do, I was seeing the headlines: “Home Inspector found dead lodged in crawl space!”  What a time!

Thanks for reading.

David Helm, Bellingham home inspector

www.helmhomeinspections.com