09-04-2018, 09:41 PM
Our crawl space has too much moisture with a touch of water. I’m interested in hearing from the experienced folks here.
The questions are where would it be best to install fans to move the humidity out from under the house, how many fans, and how many CFMs are likely to be necessary?
This 20 year old house (roughly 1800 SqFt under H/A) is built on a stem wall on acreage where the grade runs downhill from east to west. Water primarily runs around the house although 2 places run straight into the eastern stem wall.
There is a slight downhill from south to north.
The stem wall in the southeast is 2 courses rising to 3 on the northeast and rising to 6 or 7 on the west wall.
There are 3 crawl space accesses:
1. Western end of the South wall
2. Western end of the North wall
3. Northern end of the West wall.
Accesses 1 and 2 are more or less in line at opposite ends of the house.
Looking down on the house from above, the stem wall would appear nearly as a rectangle with a plus sign connecting the perimeter.
Each section has a roughly 6’ opening which makes each section accessible to the other—the openings are bridged by precast concrete.
There is, however, one area in the southwest corner which is more like a vault—it is fully enclosed on three sides and has one small ventilation opening.
There were 2 single block ventilation holes on the east wall which were letting water enter the crawl space and which I have just sealed.
All the other walls contain one or more single block ventilation holes dispersed by the engineers.
- Above the stem wall are 12” I-joists, 1/2 subfloor, 3/4” T&G sturdi-floor, vapor barrier and finally 3/4” real wood flooring.
- Between the I-joists, we have 6” of blown in cellulose insulation sitting roughly 4” below the subfloor.
- The house is perfectly comfortable, inexpensive to air condition and doesn’t feel the least bit humid.
However, the insulation shows humidity ranging from 30-90% and the bottom of the I-joists also have high humidity.
Ever since Hurricane Irma it’s been wetter than we’ve seen in many years.
The humidity in the insulation is the greatest concern because it could create issues.
I estimate the maximum height of the crawl space to be 48” and the minimum about 24”.
I estimate there are 5 single-block ventilation openings at 24” or higher (no water intrusion issue) and there are 3 roughly 4’ SqFt accesses.
I believe I’ve sealed the only ventilation openings allowing direct water in.
Engineering ideas especially as it relates to installation and location of exhaust fans in the crawl space?
The questions are where would it be best to install fans to move the humidity out from under the house, how many fans, and how many CFMs are likely to be necessary?
This 20 year old house (roughly 1800 SqFt under H/A) is built on a stem wall on acreage where the grade runs downhill from east to west. Water primarily runs around the house although 2 places run straight into the eastern stem wall.
There is a slight downhill from south to north.
The stem wall in the southeast is 2 courses rising to 3 on the northeast and rising to 6 or 7 on the west wall.
There are 3 crawl space accesses:
1. Western end of the South wall
2. Western end of the North wall
3. Northern end of the West wall.
Accesses 1 and 2 are more or less in line at opposite ends of the house.
Looking down on the house from above, the stem wall would appear nearly as a rectangle with a plus sign connecting the perimeter.
Each section has a roughly 6’ opening which makes each section accessible to the other—the openings are bridged by precast concrete.
There is, however, one area in the southwest corner which is more like a vault—it is fully enclosed on three sides and has one small ventilation opening.
There were 2 single block ventilation holes on the east wall which were letting water enter the crawl space and which I have just sealed.
All the other walls contain one or more single block ventilation holes dispersed by the engineers.
- Above the stem wall are 12” I-joists, 1/2 subfloor, 3/4” T&G sturdi-floor, vapor barrier and finally 3/4” real wood flooring.
- Between the I-joists, we have 6” of blown in cellulose insulation sitting roughly 4” below the subfloor.
- The house is perfectly comfortable, inexpensive to air condition and doesn’t feel the least bit humid.
However, the insulation shows humidity ranging from 30-90% and the bottom of the I-joists also have high humidity.
Ever since Hurricane Irma it’s been wetter than we’ve seen in many years.
The humidity in the insulation is the greatest concern because it could create issues.
I estimate the maximum height of the crawl space to be 48” and the minimum about 24”.
I estimate there are 5 single-block ventilation openings at 24” or higher (no water intrusion issue) and there are 3 roughly 4’ SqFt accesses.
I believe I’ve sealed the only ventilation openings allowing direct water in.
Engineering ideas especially as it relates to installation and location of exhaust fans in the crawl space?
Gary
Please don’t quote the trolls.
Liberty, Freedom and Individual Responsibility
Say what you'll do and do what you say.
Please don’t quote the trolls.
Liberty, Freedom and Individual Responsibility
Say what you'll do and do what you say.
