Sprucing up the crawlspace could bring a breath of fresh air
By Hannah McKenzie
Q: The fiberglass insulation in my vented crawlspace has transformed from pink to gray. It looks damp in some places and has fallen down. I’m planning to replace the insulation but what can I do to make sure this doesn’t happen again?
A: It is confusing to see insulation deteriorate when you can’t see the culprit. The best course of action is to fix the unseen problems before replacing the insulation. Otherwise, you’ll find yourself in the same spot in a few years.
Dirty insulation is often a sign that air is moving between the interior of your house and the crawlspace. The insulation acts like a crummy air filter by capturing some airborne dust as crawlspace air enters your home. The conditioned air from your house is likely leaking into the crawlspace as well. This air movement often wastes money, makes your house smell musty, brings in excess dust, welcomes pests and may affect your health. The solution is to use caulk or foam to air seal holes where pipes and wires pass through the floor. If ductwork is in the crawlspace, air seal the duct joints and around the duct parts that touch the floor. Big holes can be covered with scrap wood or rigid foam and then sealed around the edges. Stuffing fibrous insulation into the holes is not effective air sealing, just a crummy filter.
Excess moisture in the air can cause fiberglass batts to fall apart, giving the appearance of insulation melting away from the floor or pink icicles drooping down. Moisture can be dramatically reduced in the crawlspace by covering all exposed soil with a vapor retarder, which is simply plastic sheeting that is 6-mil or thicker. Seams should be overlapped a minimum of 12 inches and taped. The vapor retarder should extend at least six inches up the foundation wall and piers.
The sources of standing water should be investigated and solved. Look for plumbing leaks, ground water entry points, clogged gutters, clogged HVAC drain lines, soil sloping towards the foundation or even rain water dumping through foundation vents. Uninsulated air conditioning ducts and disconnected dryer ducts also add unwanted moisture to the crawlspace.
Proper installation of insulation is critical for comfort. Just as you need a blanket to touch your body to keep you warm, insulation must touch the subfloor to truly work. Make sure the insulation stays fluffy, because compressed insulation loses its R-value and doesn’t adequately insulate. It is essential to carefully cut insulation to go around plumbing, electrical and HVAC components. The North American Insulation Manufacturers Association has a series of critical details, technical tips and videos of fabulous fiberglass floor insulation installation that can be viewed here: www.naima.org/insulation-knowledge-base/residential-home-insulation.html
Crawlspaces are my least favorite DIY home improvement area because I’m constantly listening and watching for mice, spiders and the dreaded “Mister No Shoulders.”
Don’t hesitate to get pricing from an insulation contractor to do air sealing and install a vapor retarder and insulation. You may be surprised to find the price is close to doing the work yourself since installers purchase insulation at a fraction of the retail price. Be upfront about the quality of workmanship you expect so you can reap the benefits of comfort and energy savings. If you want a super top notch job, hire a home performance contractor. They will have additional experience finding, sealing and insulating all the bizarre crevices under an old house.