Building a Home – Insulation

Cellulose bails on the insulation truck.

Before discussing insulation in new construction, it’s important to understand how it works. Insulation is used to limit the transmission of heat across a distance. For example, we try to limit how much heat is transferred into a home from the outside during summer months. Likewise, we try to limit how much heat we lose from inside a home during the winter. The thermal resistance of a material such as insulation is expressed in something called an R-value. The higher the R-value of a material, the better it is at limiting the transmission of heat. Video of insulation being blown into walls.

Close up of cellulose insulation.

Different materials have different R-values. Ideally, you want to balance the cost of the insulation material with the energy savings. In our case, the best application was also one of the most economical. Cellulose insulation consists of flame retardant organic fibers (i.e. recycled newspaper). Its thermal resistance isn’t quite as high as fiberglass or spray foam, but it is quite a bit less expensive. Cellulose is also very practical in the sense that, unlike rolled fiberglass insulation, it can be wetted and blown onto vertical walls and will fill small voids that rolled insulation can’t. Video of insulation being vacuumed and blown.

An exterior wall with blown cellulose insulation.

Insulation is only necessary in exterior walls (i.e. walls exposed to the outside of the house), though it may be desirable in some interior walls for noise reduction. Cellulose insulation comes in 18 pound bails. The bails are fairly compact and rigid, so they’re fed into a “grinder” that breaks down the bail and fluffs up the cellulose. It’s slightly wetted in the grinder so that it adheres to the vertical wall spaces as well as other cellulose particles. It exits the grinder into a hose from which it is blown out. After it’s blown into the wall, a crew member would run a scraper down the walls so that the insulation was even with the wall studs.  The particles that are scraped off the wall or don’t adhere are vacuumed and sent back to the grinder to be recycled. Video of insulation being scraped.