Humidity Venting

[sailfast]

115 year old house is considered new???
Fresh air needs to be supplied for the oil furnace as well.

Crawlspaces in older houses are generally best sealed as part of the building envelope.
If a furnace needs fresh air to operate then that should be addressed directly too

 

[the old grind]

IIRC, Michigan building codes require 'atmospheric venting' on all new builds, and they're typically piped to mechanical room so high-efficiency furnaces and power-vent water heaters don't backdraft each other or fireplaces & woodstoves within the envelope.

Had a rental on a crawl with ground floor furnace in a hall closet behind louvered doors. Poly sheeting over sand in the crawl-space helped some, but I replaced the bi-folds with solid doors and screened a hole in the floor to have combustion and draft air drawn from below to circulate. It was just enough in this particular situation. When I sold the rental the first thing the NO did was cover the hole without understanding its purpose. I just shrugged.

I'm sure the details of OP's situation will confuse many of us offering help/suggestions, would recommend considering several proposals till he finds what works best. (better IMO to be on-site and see the 'package')
Hopefully this'll be a 'one and done' deal for him.

 

[widefat]

Update - some progress. After uncovering some of the wall space, I found a vent hole hole through the wall, an open hole about 12"x9" to the exterior. The previous owner had covered the hole and filled the space with insulation. I opened the hole, and the humdity dropped from 75-80 down to 60-65 in a couple of days. The average humidty here has been around
75, so I think I made a leap forward. I ordered an 8" inch exhaust fan, and I think I will connect it to a timer as Ralph posted.
I also found the biggest Garter snake I have ever seen laying in the insulation.

 

[s219]

Just keep an eye on airflow, because the fan is going to pull replacement air from somewhere beyond the cellar. Could be from inside the home through all the gaps, cracks, and joints in the construction. You don't necessarily want to be sucking conditioned are from inside the home to exhaust it through the cellar wall. That would also mean you're pulling outside air into the home through other gaps, cracks, joints, leaks, etc. Home airflow is a fickle thing, it will always balance somehow, and usually that comes at the expense of your heating/cooling bill!

 

[sailfast]

Update - some progress. After uncovering some of the wall space, I found a vent hole hole through the wall, an open hole about 12"x9" to the exterior. The previous owner had covered the hole and filled the space with insulation. I opened the hole, and the humdity dropped from 75-80 down to 60-65 in a couple of days. The average humidty here has been around
75, so I think I made a leap forward. I ordered an 8" inch exhaust fan, and I think I will connect it to a timer as Ralph posted.
I also found the biggest Garter snake I have ever seen laying in the insulation.

As a building envelope professional i have to tell you this is a bad idea.
Will likely have unintended consequencesas and possibly actually increase the humidity.
I recommend you consult with a local professional.

 

[CalG]

Update - some progress. After uncovering some of the wall space, I found a vent hole hole through the wall, an open hole about 12"x9" to the exterior. The previous owner had covered the hole and filled the space with insulation. I opened the hole, and the humdity dropped from 75-80 down to 60-65 in a couple of days. The average humidty here has been around
75, so I think I made a leap forward. I ordered an 8" inch exhaust fan, and I think I will connect it to a timer as Ralph posted.
I also found the biggest Garter snake I have ever seen laying in the insulation.

How do you think the cellar space was able to achieve a lower RH than average ambient?
I wish i could do that, the de-humidifier has run none stop for the past three days.

 

[CalG]

As a building envelope professional i have to tell you this is a bad idea.
Will likely have unintended consequencesas and possibly actually increase the humidity.
I recommend you consult with a local professional.

WTF is a building envelope professional?

How much does the framed certificate cost?

 

[widefat]

As a building envelope professional i have to tell you this is a bad idea.
Will likely have unintended consequencesas

Could you throw out a couple of examples of what may happen and why it is a bad idea? Seriously....I like to learn about these things.

 

[widefat]

How do you think the cellar space was able to achieve a lower RH than average ambient?
I wish i could do that, the de-humidifier has run none stop for the past three days.

eh, it didnt last....the level came up to the ambient outside.

 

[dadster4]

I would look for additional vents around the crawl from outside the home. If none are found...make one on the opposite side from the one you did find. Normal atmospheric pressures will ventilate the crawl over time. Heavy plastic sheeting laid over any exposed earth will help, but not a lot, if not properly sealed at joints and around perimeter walls. The best you can do is to let the crawl "breathe" so the Rh is not higher than outside. A "leaky" house that has been standing that long with no moisture damage, rot, or mold will not benefit much from a dehumidifier pissing a few gallons of water everyday unless the ground moisture is controlled and a dehumidifier will also raise the temperature in the space. Are you considering air conditioning at all...it would solve all your problems.