Cement crawl space ventilation

sheslostcontrol · 05-21-2010, 09:22 PM

Hi -- new to the forum..

My 20'x30'x6' crawl space has cement floors, and stays very humid. Even with a large dehumidifier running the humidity is around 70%. The crawl area is where my furnace, hot water heater, and washer/dryer are located.

I ordered a 200 CFM powered crawl space vent which has a built-in thermostat and humidistat.. It will be installed on one side of the space and a standard non-powered vent on the other side.

My question for the forum is whether I should run a fan inside the crawl area to circulate the air, or just let the vent fan draw air from the standard vent?

**beenthere** · 05-21-2010, 10:48 PM

Depending where your located at. The power venting could make the crawlspace worse. Since it already has fresh air coming into it.

sheslostcontrol · 05-22-2010, 07:56 AM

sorry -- I'm in Georgia.

The humidistat will turn the fan & standard vents off if the humidity rises above a set level (like during a rain storm).

As of today there is no air coming into the crawlspace. No ventilation whatsoever.

**beenthere** · 05-22-2010, 08:02 AM

IS your water heater connected to a chimney? If it is, then air is being drawn into the crawl.

If it isn't, then the water heater is causing your humidity problem.

sheslostcontrol · 05-22-2010, 08:18 AM

It may be, but before the water heater was filled up & turned on I still measured 70% humidity. I'm currently at 70-75% with the water heater operational.

**beenthere** · 05-22-2010, 08:23 AM

A chimney drafts/draws air up through it, weather or not the water heater is filled or not, and weather the burner is on or not.

sheslostcontrol · 05-22-2010, 08:25 AM

I do not have a chimney -- there is a flue for the furnace, but that is closed off to crawlspace air as best I can tell.

I was planning to place the powered vent near the top of the wall, to pull the most humid air.

**beenthere** · 05-22-2010, 08:39 AM

Ok.

Where does the water heater vent to. Does it have a chimney. Or does it just vent into the crawlspace.

High humidity in a crawlspace, often comes from the crawlspace being vented.

sheslostcontrol · 05-22-2010, 08:48 AM

The house sat without power and water for several months. During this time, with no water in the heater (drained), and no ventilation, the humidity was around 80%. The previous owner had zero ventilation in this crawl space. I haven't added anything other than a dehumidifier (which feeds into a bucket I empty about once a day).

**beenthere** · 05-22-2010, 09:32 AM

Sorry.

Since you don't answer my questions.

I'll leave someone else help you. Good luck.

05-21-2010, 09:22 PM	#1
sheslostcontrol Member Join Date: May 2010 Posts: 158	Cement crawl space ventilation Hi -- new to the forum.. My 20'x30'x6' crawl space has cement floors, and stays very humid. Even with a large dehumidifier running the humidity is around 70%. The crawl area is where my furnace, hot water heater, and washer/dryer are located. I ordered a 200 CFM powered crawl space vent which has a built-in thermostat and humidistat.. It will be installed on one side of the space and a standard non-powered vent on the other side. My question for the forum is whether I should run a fan inside the crawl area to circulate the air, or just let the vent fan draw air from the standard vent?

05-21-2010, 10:48 PM	#2
beenthere An old Tradesmen Join Date: Oct 2008 Location: PA Posts: 19,069	Cement crawl space ventilation Depending where your located at. The power venting could make the crawlspace worse. Since it already has fresh air coming into it.

05-22-2010, 07:56 AM	#3
sheslostcontrol Member Join Date: May 2010 Posts: 158	Cement crawl space ventilation sorry -- I'm in Georgia. The humidistat will turn the fan & standard vents off if the humidity rises above a set level (like during a rain storm). As of today there is no air coming into the crawlspace. No ventilation whatsoever.

05-22-2010, 08:02 AM	#4
beenthere An old Tradesmen Join Date: Oct 2008 Location: PA Posts: 19,069	Cement crawl space ventilation IS your water heater connected to a chimney? If it is, then air is being drawn into the crawl. If it isn't, then the water heater is causing your humidity problem.

05-22-2010, 08:18 AM	#5
sheslostcontrol Member Join Date: May 2010 Posts: 158	Cement crawl space ventilation It may be, but before the water heater was filled up & turned on I still measured 70% humidity. I'm currently at 70-75% with the water heater operational.

Cement crawl space ventilation