Joists are the main elements that create the frame of a home’s ceiling and floor. Generally, ceiling and floor joists are built out of engineered or 2x lumber. The joists are placed about 16 inches on center apart. The wood that wraps around the edge of the floor framing is called the rim joist or band joist. Looking at the outside of a home as it is being framed, the rim joist is the solid band of lumber spanning along the side of the floor frame.
The main purpose of a rim joist is to give stability and strength to the other floor joists. Floor joists are held into the rim joists by nails which prevent the boards from falling over to the side and tie the flooring system together. The rim joists keep the floor joists upright and level.
Many homes are improperly insulated on the rim joists, allowing cold air around the foundation to easily enter the home. Insulating rim joists prevents drafts, cold temperatures, moisture, mold, pests and structural damages.
When a home has uninsulated rim joists, the only layer between the interior and exterior of the home is the housewrap, sheathing (which is only about 1/2 in – 3/4 in thick) and the siding. Rim joists are considered above grade and should be insulated to a minimum of R-20 in climate zones 5-8 and a minimum of R-13 in climate zones 1-4. Rim joist insulation is now required by most current building codes.
The most common products used for rim joist insulation are foam board and spray foam. Each product has unique benefits and differs in cost. Read below to learn more and decide which product is best for your home. Also, feel free to contact our certified technicians for a free quote and assessment for your rim joist insulation. Call: (833) 244 -7283.
Spray foam is one of the most effective and easiest forms of insulation to install in a rim joist. The foam expands to cover the area, filling any cracks or gaps in the structure as well.
Spray foam creates an air seal which blocks out drafts, pests and moisture. Finally, spray foam boats extremely high R-Values (the measure of an insulation product’s effectiveness) with closed cell spray foam at R-7 per inch and open cell spray foam at R-3.8 per inch.
Foam boards can be cut in order to fit snugly in place as rim joist insulation.
The edges must then be lined with caulk and any bigger gaps insulated with expanding foam.
The R-Value of foam boards is about 4.7 per inch.
Fiberglass can be used to insulate rim joists and has an R-Value of about 2.2 to 2.7 per inch. The downside of fiberglass is that it may retain moisture and harbor the growth of mold.
Some building codes may not allow fiberglass insulation. Therefore, insulating rim joists with foam is the best option.
If you have any questions regarding our rim joist insulation in Rockford, IL, please get in contact with us at 833-244-7283. We will gladly answer any questions you may have and assist you in any way that we can. We look forward to working with you!
