Insulating Vented Crawl Spaces

How to Insulate Vented Crawl Spaces

By Mark J. Donovan




A vented crawl space is effectively exposed to the outside air temperatures. Insulating vented crawl spaces saves money on energy bills as well as keeps a home warmer during the winter months.

A vented crawl space typically has at least two vents installed in it that are left open during hot, humid times of the year and closed during cold, dry times of the year.

This said, vented crawl spaces are still cold even when the crawl space vents are closed during winter months, and consequently they can cause lower level floors within the home to be uncomfortable.

Insulating Vented Crawl Space Materials

Insulating vented crawl spaces is an easy DIY homeowner project and won’t break the bank in material costs. To insulate a vented crawl space, you will need caulk, faced fiberglass rolled insulation (R-19 value), pipe insulation, a vapor barrier (large sheets of 6 mil polyethylene plastic), duct tape, and some sand and gravel. Also make sure to wear clothes that cover your entire body, goggles, gloves and a mask to protect you from the insulation while installing it.

Insulating Vented Crawl Space Instructions

First, caulk around any holes in the subfloor to prevent any air infiltration into the finished rooms of the home.

Next, install the fiberglass roll insulation in-between the floor joists by tucking it up snuggly against the subfloor and holding it into place with metal wire hangers or chicken wire. Also, make sure to insulate in-between the floor joist bays near the band joists.

In most areas of the country the faced side of the insulation should face upwards toward the subfloor, however in areas of the country where the temperature and humidity are fairly high all year round, the face side of the insulation should face downward away from the subfloor.

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The general rule of thumb for installing faced insulation is to have the faced side (vapor barrier side) face the warmest side of the wall or ceiling. So for example, in the northern part of the country, the faced side of the insulation should face the interior finished room as this space will normally be warmer than the crawl space area.

Next, wrap any exposed heating or plumbing pipes with insulation.

Finally, apply a vapor barrier to the floor to complete the insulation of the vented crawl space. The vapor barrier should go up the sides of the crawl space walls by about 1 foot and should be taped with duct tape along the length of the wall.

Cover the vapor barrier with sand and then gravel to protect the vapor barrier from being damaged when you crawl or walk on it.

Insulating a crawl Space

By installing a vapor barrier on the floor of the crawl space the humidity levels in the crawl space will be dramatically reduced and thus prevent the insulation from becoming damp and moldy.

So save this year on home heating bills and enjoy warmer and comfortable floors by insulating your vented crawl space.


For more help on Basement Additions, see HomeAdditionPlus.com’s Basement Remodeling Bid sheet. The Basement Remodeling Bid Sheet will help ensure that your hire the right contractor so that your basement remodeling project is done correctly and you get the project finished on time and budget.

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