Insulating wood framed crawl space floor

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Author Message Lynn Javoroski CSI CCS LEED AP SCIP Affiliate Senior Member Username: lynn_javoroski Post Number: 321 Registered: 07-2002 Posted on Saturday, March 25, 2006 - 11:17 am:    Problem: how to insulate a wood framed floor in an 1863 house outside Iowa City. The room is over a dirt crawl space (the rest of the house has a basement). The Douglas Fir (or pine - the guy who did the refinishing though it was Doug Fir)) wood flooring is directly fastened to the floor joists - no sub-flooring. The crawl sapce is approximately 24 inches high/tall. Joists are about 10 inches deep and randomly spaced (as you'd expect). Questions: What type of insulation would you recommend? Vapor Barrier? What goes where? Ron Beard CCS Senior Member Username: rm_beard_ccs Post Number: 115 Registered: 10-2002 Posted on Saturday, March 25, 2006 - 01:50 pm:    Lynn: The first question you should consider is: To Vent or Not to Vent. Check out << http://www.eere.energy.gov/buildings/info/documents/pdfs/29238.pdf >> for DOE’s position. With limited space to work, your choices are batt or foam. I’m assuming that there is only a small access opening. Whether you vent or not, you still want a good vapor barrier. Insulating the perimeter walls requires substantially less coverage area than the footprint area so there is a cost saving by insulating the walls. In a recent similar project, I used Icynene foam insulation. Foam can be easily applied to stone or any other rough foundation wall. Wood flooring directly on the floor joists was typical construction of the era and still found everywhere throughout the country. With a sealed crawlspace, air passage through the floor should not present a problem and is actually a benefit. I would, also, consider a louver between the basement and crawlspace, if possible. The vapor barrier should be at least a 10-mil sheet with a low perm rating with sealed edges and seams. Reef Industries’s “Griffolyn 10-Mil Green” is a product that I have used successfully in the past. There are many other similar products on the market. See the following Discussion Group Topics for further information: Crawlspaces: Vented or not vented? Sprayed foam insulation Sorry we wouldn’t be able to see you at the Convention. Ron Ronald J. Ray, RA, CCS, CCCA Senior Member Username: rjray Post Number: 56 Registered: 04-2004 Posted on Saturday, March 25, 2006 - 02:12 pm:    Prior to making the decision NOT to seal off the crawl space from the occupied areas, one might want to have the craw space tested for the presence of radon gas being released through the soil. See http://www.epa.gov/radon/ for assistance. Harold S. Woolard Senior Member Username: harold_woolard Post Number: 23 Registered: 12-2003 Posted on Saturday, March 25, 2006 - 03:21 pm:    The crawl place should remain vented no matter who's vapor-retarder you use. If Radon Gas is available a ASTM 1993-98 product should be used. W. R. Meadows makes a product PMPC which has been tested to stop radon gas from entering a structure. The vapor-retarders meeting ASTM 1745 either 10 mil or 15 mil have a WVT rating of 0.01 WVT while PMPC WVT is 0.00045 grains/per hr. http://www.wrmeadows.com/wrm00061.htm Test results are available on request. Phil Kabza Senior Member Username: phil_kabza Post Number: 163 Registered: 12-2002 Posted on Saturday, March 25, 2006 - 04:45 pm:    If you're considering insulating the crawlspace sidewalls, give thought to the problem of providing a non-inspectable path for termites and carpenter ants (the latter are fond of polystyrene). http://www.buildingscience.com/ includes a white paper on the topic of insulating/venting/ conditioning crawlspaces that is worth reading. Joe L. is a national expert. Ron Beard CCS Senior Member Username: rm_beard_ccs Post Number: 116 Registered: 10-2002 Posted on Saturday, March 25, 2006 - 06:05 pm:    Ronald/Harold: Your points are well taken. The crawlspace I was referencing was in the Tidewater area of southern Virginia, a very low radon area, so radon was not an issue. The project had considerable mold and mildew and the HAZMAT consultant agreed with the non-vented scenario. Iowa City appears to be in a high radon area so Ronald’s point is quite significant. Depending how much radon is present, if any, vapor retarders can still effectively seal the crawlspace. As previously stated, there are many, many choices for vapor retarders including those with multiple-plies and reinforcement plies, and a whole host of other characteristics including radon acceptable performance ratings. For any of them to work properly, they must be completely sealed per manufacturers instructions at every seam, at edges, and at penetrations. When used with a foam insulation on the walls, there is an additional seal when the foam covers the edge seam of the turned up vapor retarder. Harold: <The crawl place should remain vented no matter who's vapor-retarder you use> I used to agree with you but I keep remembering the saying: “Never say never.” I have currently come to the conclusion, after a LOT of reading on both sides of the issue, that one must consider every project on an individual basis and respond accordingly. Hey, isn’t spec writing interesting. Nothing ever stays the same, even the topics and constructions methodologies we once thought were non-debatable are now long passed over. Many of us can remember when asbestos was the greatest new material since sliced bread. Radon and indoor air quality was never an issue because most projects weren’t that tight ...and VOC’s - never heard of them. Ron Eugene A. Groshong, Jr., CCS (Unregistered Guest) Unregistered guest Posted on Wednesday, March 29, 2006 - 10:05 am:    <The crawl place should remain vented no matter who's vapor-retarder you use.> I disagree. If radon is a concern, venting the space below the vapor retarder would be better than venting the crawl space. I would test for radon first. A loop of perforated pipe that pokes through the foundation wall might do fine if the radon level is low, but if it is at all significant you probably want to add a drainage mat or some gravel over the entire surface below the vapor retarder. Lynn Javoroski CSI CCS LEED AP SCIP Affiliate Senior Member Username: lynn_javoroski Post Number: 324 Registered: 07-2002 Posted on Wednesday, March 29, 2006 - 10:29 am:    Thanks for all the input; I'm sure my son and his wife will be buying a radon kit in the near future! But back to the original question, if you'll humor me: where does the insulation go and where does the vapor retarder go? If they insulate the walls of the crawl space (and I like that idea), where should the vapor retarder go? Up against the floor joists? If they don't insulate the walls, what other options would be best? Batts or rigid between the joists? And then where does the vapor barrier go? Right now, there's cold air coming up through the floor; it would be nice to stop that. They've made this room, which I think used to be the back parlor, into the library. It should be cozy. Ron Beard CCS Senior Member Username: rm_beard_ccs Post Number: 117 Registered: 10-2002 Posted on Wednesday, March 29, 2006 - 10:38 am:    Vented or not, the VB should always be placed directly on the ground with sealed seams and sealed edges. Ron Curt Norton, CSI, CCS Senior Member Username: curtn Post Number: 109 Registered: 06-2002 Posted on Wednesday, March 29, 2006 - 11:10 am:    Lynn--the key to comfort and energy efficiency is stopping air flow, not vapor. Fiberglass insulation will not stop air flow and a simple poly vapor retarder will eventually allow air to leak at seams or penetrations because it has no structural support. The best option in my mind is a spray foam insulation in the joist space and a vented crawl space. Vapor migration will not cause near as many problems as moist air flowing through the floor. Insulation the walls is an option, but it may be harder to get a good seal at the ring and then you have to be concerned about a vapor retarder for the floor. With the spray foam in the joist space, I don't see any real value in using a vapor retarder on the floor. John Bunzick, CCS, CCCA Senior Member Username: bunzick Post Number: 498 Registered: 03-2002 Posted on Monday, April 03, 2006 - 11:12 am:    I would recommend the following to create a conditioned space: 1) Don't vent to the exterior. 2) Provide separate mechanical ventilation to the crawl space. I cannot remember the standard which recommends this (ASHRAE 62.2? or perhaps IRC?), but the volume requirement is very low, I think 50 CFM continuous. 3) Use a good vapor retarder applied to the surface of the soil to keep moisture in the soil from coming into the space. 4) If radon is an issue, vent it from under the vapor retarder to the exterior. 5) Insulate the walls with foam, extending horizontally onto the soil--distance per local energy code.