What To Do With Your Vented Crawlspace

Recently I’ve had several conversations with Atlanta homeowners who are asking for advice or guidance about their crawlspaces. With so many of us now working from home, we’re spending huge amounts of time inside our homes that we’ve never done before.
  • “Bob, I paid a company to encapsulate my crawlspace two weeks ago. I need you to come insulate my floors with spray foam.”

 
  • “Bob, I have a client who has an encapsulated crawlspace, and he insulated his attic with foam insulation. Yesterday he noticed green mold growing in the corners of one room. What should I tell him?”

 
  • “Bob, not even a year ago we replaced our floors with new hardwood flooring. They’ve started buckling, and the floor company said it’s due to high humidity in my crawlspace! Will you come see what’s going on? I need help!”

 
  • “Mr Bird, from time to time we can smell a musty smell in our house. I think it’s coming from our dirt crawlspace. Our home feels like it has high humidity inside. Will you quote a new moisture barrier for me?”

vented crawlspace
Vented crawlspaces under our houses present challenges these days that we used to rarely see. Why are the calls and problems with these crawlspaces becoming more frequent? I’m no scientist, but I’ve got 20+ years of experience in hundreds and hundreds of these dark, damp areas.

Living in a Sealed Butter Tub

Homebuyers are purchasing these older Atlanta homes and tightening the house with modern windows, attic insulation with airsealing, and installing modern HVAC systems. However, it seems that the crawlspace is the last place to get any help. And, since so many folks are working remotely from home, we’re finding things out about our homes that we’d failed to notice.

 

It’s the Stack Effect, Matilda

I wish I had a nickel for every time I’ve explained the stack effect to a homeowner! As your filtered, conditioned air leaks out of your house, it is replaced with unfiltered, humid air from the environment around your house. A huge source of this uncontrolled air infiltration is from the lowest, horizontal level of your home. And if you live above a vented crawlspace, it is a HUGE source of this trespassing air. Crawlspace air that is laden with moisture and unhealthy nasties that move into your home.

equipment for vented crawlspace

Here Are Some Suggestions To Consider

 
  1. Forget it and live with it. Well, the unintended consequence of this attitude may make you or a loved one a little unhealthy.

 
  1. Install fiberglass batt insulation under the floors. This has little to no effect concerning the moisture migrating upward into your house. And it’s a short term solution for floor insulation. As it sags, it leaves air gaps and those gaps have zero R value.

 
  1. Install a moisture barrier, (also called vapor barrier). This will help, but are the foundation wall vents open? And what about those bare foundation walls?

 
  1. Install closed cell spray foam insulation to the underside of your floors. Great choice, if you plan to leave your dirt crawlspace, vented. About 2” coverage is plenty. Works well for enclosed porches, or vented crawlspaces with no hvac or airducts.

 
  1. Encapsulate the crawlspace. Seal it up with a poly liner! A good choice. I strongly recommend installing a dehumidifier, and a wireless weather station so you can monitor conditions under your house. If there is a gas appliance (furnace) under your floors, get your HVAC tech involved in the conversation.

 
  1. Insulate your crawlspace. This is my favorite remedy for pesky, vented crawlspaces. Seal the dirt with a durable moisture barrier. And install closed-cell spray foam insulation to the foundation walls. We leave a 3” inspection strip directly beneath the sill plate, to inspect for termites. Install a dehumidifier and wireless monitor.

If you’re considering #4 or #5, be sure to address any bulk water intrusion before closing up your crawlspace. If there is a gas appliance (furnace) under your floors, get your HVAC tech involved in the conversation, unless your contractor has addressed the “Combustion Make-up Air”.

 

As for us, at Bird Family Insulation the most popular choice homeowners are making is evenly split between #3 and #5. Spraying foam insulation to the subfloor is a very popular upgrade. Sealing and insulating the crawlspace is equally as popular in our 20 years of business, particularly for clients with air duct systems under the house.

 

Air leakage from the duct system semi-conditions the insulated crawlspace, for a wonderfully bright, healthy, climate-controlled area!

 

I am told that dry, semi-conditioned, insulated and sealed crawlspaces are a huge selling point for a home. Dry wood is healthy wood, and promotes healthy Indoor Air Quality. 

 

And who doesn’t want to enjoy living (and working) in a healthy home? 

vented crawlspace
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