RE: Paper-faced floor insulation in crawl spaces

[Guest guest]

In the summer during air conditioning, ground connected crawl spaces (some of the walls below grade) are cool and humid. Additionally, People are climatizing themselves cooler and operating their home in the summer below the outside dewpoint, without an effective vapor barrier/retarder below the wood joists and sub-floor there is a risk of mold developing at insulated surfaces where the insulation does not block moisture vapor from the cold surface it is insulating. In addition as we add thicker insulations in this situation the potential increases.

Code IS an issue in that the Kraft paper facing is Flammable, the International Building Code (if you want the reference I'll get it for you) as many other Codes have required for years, specify that flammable backings of insulation need to be installed in substantial contact with the surface that it is insulating, meaning that Kraft paper insulation and many mylars (by Code) cannot be installed facing up into the Attic or into the crawl space. If they do, they violate code. This warning is on every major manufacturers product and has been since at least 1973. There are new generation packaging of fiberglass in sleeves that have the fire rating necessary to do be installed toward the crawl space and attic (flame spread less than 25), and there are true foil backed (not mylar) insulations that allow the backing to be installed into the crawl space.

Now as to the insulation placement, first of all in vented crawl spaces or attics, an acceptable practice is to staple the tab on the insulation backer to the side of the structure instead of along the bottom of the chord. It is impossible to get a air or vapor retarder when stapling to the side of the structural member. As I indicated, it is an acceptable practice to install it to the side, and easier ergonomically and faster to do the installation (that is why they allow it) and is shown in the major manufacturers installation guides and I believe on NAIMA's guides also. If the tabs are installed across the bottom of the Joist where the overlaps and joints can be sealed with tape you have a better chance of creating a barrier. However, now you have installed your paper to the humid space, good luck with that. Installing it against the floor, I'm unclear in the concept unless it went in before the floor, hopefully this is untypical as most floor sub-bases go in before dry-in which would make the insulation vulnerable to rain events. And if the paper is stapled to the floor after the sub-base is installed now you are purely relying on the glue and friction fit to keep it in place, again good luck with that.

Our philosophy is Not to (as in never) vent the crawl space, Place the insulation on the vertical foundation wall and install a vapor barrier on the walls when they are below grade and on the floor if it is dirt. If it is concrete, put a vapor barrier 5 to 10 mil polyethylene, and 1 1/2 to 2" insulation board under the slab. We also sometimes put in a 1" recess along the edge recessed to a drainage sump with a sump pump, If water weeps in we want to get it out. Depending on the site and if the crawl space or basement is below the natural grade outside we recommend footing drains to help keep water away from the walls and floor.

When the home is heated, heat pockets at the joist level keeping mold away, in the summer when air conditioning, the water vapor is allowed to migrate to the home due to the vapor pressure difference. Energy efficiency is very good as you stop your heat loss and moisture gain at the perimeter.

Now with that said, on our Tennessee home basement we did not install the insulation under the slab but use the ground connection for passive cooling in the summer and we only put a 3/4" of insulation on the side walls. We do keep a dehumidifier running in the basement to keep the dewpoint below 55 degrees so that the walls and slab don't sweat. The benefit, we can sleep down there at night in the summer and require a blanket, no need to air condition the upstairs.

When making the conscious decision to create a vapor barrier up into an attic or even down into the crawl space think of the number of pipes, wires and structural members your attempting to seal to try to get an effective barrier.

Out company's motto Crawl space ventilation- Never! Attic Ventilation- Never in Humid Climates! We practice what we preach, and have several installations of closed attics and crawl spaces over the past 15 years that are clean. Palm Beach County and Monroe County have had closed attic assemblies for over 60 years.

Hope that helps,

Ron

From: iequality [mailto:iequality ] On Behalf Of AirwaysEnv@...Sent: Thursday, April 20, 2006 10:45 AMTo: iequality Subject: Paper-faced floor insulation in crawl spaces

For the building scientists:The following was copied from the "Recommendations for Installation in Residential and Other Light-Frame Construction" on NAIMA web site:Vapor-Retarder-Faced InsulationThe vapor-retarder facing should usually be installed toward the warm-in-winter side of the construction. This means that in ceilings the vapor retarder faces down, in walls it faces the inside, and in floors over unheated spaces it faces up. In hot, humid (Gulf Coast) climates, vapor retarders can be installed facing the outside. Check local practices and/or building codes.OK, I have heard home inspectors comment that the Kraft paper faced floor insulation in a crawl space was installed upside down a number of times when it was installed paper face down. I have seen it installed both ways in my area (central NJ) many times each. I have asked but never heard an explanation from a home inspector or anyone else as to why the paper should be facing up.I have seen serious condensation problems on the underside of floors in wet crawl spaces due to air conditioning causing the floor materials to reach the dew point.My question is, "How should paper-faced (on one side) insulation be installed in a ventilated crawl space when the rooms above are air conditioned (paper facing down or up) and why?"Is fire code a major consideration or is the decision based upon optimal moisture control? See below copied from same site.Always follow these rules when working with vapor-retarder-faced insulation: Standard vapor retarders are combustible and should not be left exposed. For this reason they must always be covered. (Only special low flame-spread vapor-retarder facings can be left exposed.) Consult individual manufacturers' installation instructions. Included are such spaces as garages, storage rooms, utility rooms, and laundries. Covering standard vapor retarders is a requirement of the model codes issued by Building Officials and Code Administrators International, the International Conference of Building Officials, and the Southern Building Code Congress International.Thanks in advance for your answers,Steve Temes