moisture
Another Potential Fire
February 25, 2009 by David Helm · Leave a Comment
Why do home inspectors enter attics? There are many things for the inspector to check in the attic including ventilation, insulation, wiring, plumbing pipes, termination of bathroom vent fans, moisture levels and the picture shown below.
- No Clearance
This photo shows a B-vent pipe (in this instance, a chimney for a free standing natural gas stove). The requirement for B-vent clearance is one inch of air between the chimney wall and insulation or any other flammable material. There was adequate clearance between the chimney wall and the wood framing so the fix for this potentially hazardous condition is relatively easy. Remove insulation from around the pipe, put in a 12 inch high baffle that gives the one inch all around clearance (aluminum siding works well) and close the circle with foil tape. Insulation can then be replaced up to the outside of the baffle. A nice simple fix that costs very little, but may save a house fire from happening.
moisture
Crawl Space Ventilation
February 6, 2009 by David Helm · Leave a Comment
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.
Louvered vent
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
