If you want to learn more about insulating crawl spaces, read expert recommendations from experts who know what they're talking about.
Growing up in a split-story house, the middle level was built on a crawlspace. We rarely went into it because there was a small opening in the back of the room that you had to go through to get out.
It fell to me (with a bit of help from my stepson) to clean out the old space before the new owners took possession. And I remembered just how creepy the old room had been.
The concrete floor is just as bare as it was when it was laid down nearly fifty years ago. Batts of sodden fiberboard hang loosely from the joists. A dim light filters through the gaps in the wall. Some evidence of rodent infestation can be seen, along with an accumulation of moldy wood.
During those times, standard building practices were to insulate the floors above the ground level and to leave the ground level's wall vents open, thereby allowing moisture buildup to escape through the ducts to the outside — a massive design flaw, as we now know.
Condensation formed inside the walls because they were not insulated enough. When warm moist outside temperatures entered through the openings, the humidity trapped inside caused the fibers to degrade and sag.
It was no surprise that Mom always worried about mold spoiling her rugs.
Crawl spaces need to be sealed off from the rest of the house. Insulation must be installed between the crawl spaces and walls. And, if
Today, energy experts have a different prescription for crawl spaces based on the idea that they should be part of the home's conditioned space (the heated and cooled area). If conditioned, condensation is eliminated, which minimizes the chance of mold and mites. Energy loss from air ducts is reduced, and first-level floors become warmer in winter. Drafts are also minimized.
Before doing anything else, eliminate sources of moisture in the crawl space.
Keep up with regular maintenance by extending downspout pipes, maintaining gutter systems, and grading walkways, patios, and gardens. Also, if needed, install a basement waterproofer or sump system.
Insulate the walls but not the roof.
Rigid boards may either be installed using construction adhesive or mechanical fastening devices. If you want to install insulation mats, you could use them instead of wooden boards.
Insulate your house with something that won't absorb moisture.
There are several types of rigid boards used for building roofs. Polyisocyanurate is the most common choice. It comes in sheets ranging from 1/4" thick to 3/8". Remnants and seconds are sometimes available at commercial roofing suppliers. You have to ask.
Seal all vent openings.
Vent covers, installed from the exterior, are available in standard sizes. Or make your own from plywood and caulk them in place.
Ensure that hatchways to the exterior are sealed.
If you want to keep out pests, use heavy-duty weatherstrips to ensure a tight seal. Or buy an already manufactured crawl hatchway.
Seal rim joists and sills.
Cut out rectangular pieces of rigid board insulation to fill the ends of joists with insulation. Seal the seams with foam sealant, such as GreatStuff. Then use caulk or another type of sealer to seal the joint between the bottom of the crawlspace wall and the floor.
Cover the floor with an air and water barrier and tape it to the wall.
Plastic vapor barriers are commonly used in basements and crawl spaces to prevent moisture from seeping into walls and ceilings. They come in sheets of varying thicknesses, and if you're planning to store items inside your basement, make sure you pick one that can handle foot traffic. Most manufacturers also provide encapsulating services, so check out those options too. I've heard good things about Basement Systems' products but haven't personally tried them.