This article is about how to install mineral wool in attic or between the ceiling studs. This type of isolation is very efficient both summer, when it keeps the cool air inside rooms and during winter, when it reduces heating costs. The process of installing mineral wool insulation is not very complex nor time-consuming, so even a diy-er can get the job done. This product is a very good heat insulator and sound absorber, so it is used on a large scale. In addition the benefit-cost ratio is very good as compared to other materials.
The biggest drawback of mineral wool is represented by safety consideration, as it can irritate the eyes, skin and the respiratory system. Mineral wool comes in different forms and dimensions: 2′x4′ (50 cm x 1 m) strips, batts (2″ X 16″ X 48″ 32 panels, 3″ X 16″ X 48″ 24 panels) and so on. You should choose the products, whose dimensions are the closest to your needs (measure the distance between the studs and the studs thickness).
Installing mineral woolor fiber glass insulation might look as a complex or costly project, but we can say from our experience, that the investment will pay off in a couple of years as the heating cost will decrease significantly. You could start by insulating your ceiling by fitting mineral wool bats between the wood studs. Afterwards, you could also try to insulate your attic by installing the mineral wool between the sloped ceiling.
Generally speaking, there are four types of insulation: rolls and batts, loose-fill, rigid foam and foam in place. Rolls and batts are flexible (mineral wool, fiberglass), loose-fill are fibers that are blown between the studs, rigid foam is the most efficient insulator but is more expensive than fiberglass, while foam in place (such as polyurethane foam) is used to insulate door, windows and other small areas .
You can choose from many types of mineral wool, as it comes in the form of batts or rolls and in more thicknesses. We recommend you to buy the mineral wool according to your needs (measure the thickness of the wood studs and the space between them), but you have to remember that the greater the thickness the higher the R-value (thermal resistance). Therefore, if you double the thickness of mineral wool batting (by installing two layers) you also improve the thermal resistance. In addition, if you install drywall over the wood stud frame, you will slightly increase the R-value.
If you want to install mineral wool insulation, you need the following:
- mineral wool
- safety gloves and glasses, respiratory mask
- carpenter pencil, tape measure
- scissors and exacto knife
- avoid as much as possible the contact with the mineral wool
- use safety glasses, gloves and a respiratory mask
How to install mineral wool between studs
In order to insulate our ceiling, we have used both fiberglass rolls and pre-cut batts. The mineral wool rolls we bought, were about 50 feet, but the rolls can have up to 100 feet. In addition, they might be faced or unfaced.
In order to fill the space between the wood studs, you have to cut the rolls to the needed length, by using a sharp utility knife and a straight edge.
We also used mineral 4” thick wool batts to insulate the ceiling. The batts come in different lengths and widths, therefore you should buy the product which requires the least amount of cuts.
Batt insulation is available with and without facing. We recommend you to buy faced fatts, as they will be easier to install and because the paper layer has the role of an anti-vapor barrier. If you buy batts without facing, you’ll have to attach a plastic foil.
Before installing the mineral wool insulation, you have to measure the thickness of the wood studs and the distance between them. In our case the space between the wood studs is about 24” on center, just enough to fit 23” wide mineral wool bats.
Nevertheless, you should use 15” wide insulation when the studs are 16” spaced.
How to cut mineral wool
You have to cut the mineral wool batts or rolls to fit them into place, in a professional manner. Therefore, you have to use a tape measure to calculate the needed length at which you have to make the cut. Next, use the tape measure to set the cut line and place a large piece of plywood under the mineral wool (to protect the floor). Last but not least, cut the mineral wool with a sharp utility knife, by using an aluminum straight edge. Remember that you have to wear a respiratory mask while you work with mineral wool, as the fibers are very toxic.
Installing mineral wool insulation
If the wood studs are thicker than the mineral wool, you should install a second layer of insulation. This aspect is very important, as a double-layer of mineral wool would be much more efficient (thermodynamically and acoustically) as compared to installing a single layer.
Start installing the mineral wool from one corner of the room. If the batts are faced, then you have to staple through their flanges to the inside of the wood joists. If you use unfaced batts or rolls, the friction will hold them into place.
Nevertheless, you can secure the mineral wool layer with wire, as you can see in the image. The process is straightforward: use a hammer and install several nails in the wood studs and then using the wire make a network, as to support the mineral wool. The pattern shouldn’t be geometrically perfect, but should be dense enough to support properly the boards of mineral wool.
If you have to install drywall directly to the wood joists, we recommend you not to secure the batts with wire, otherwise you won’t be able to hand the boards level.
The next step is to install a second layer of mineral wool, as to fill in the gap between the metal studs and the future drywall ceiling. In addition, as we have previously mentioned, the second layer will also improve the thermal and acoustical insulation.
In order to fix the mineral wool strips, we have proceed exactly in the same way, as in the previous steps. Make sure you cut properly the mineral wool, as not to leave any gaps between the boards or layers. Any gap would affect the efficiency of the insulation.
After we have finished installing the second layer of mineral wool on the whole surface, we decided to fix an anti-vapor and moisture barrier, as we have used unfaced batts.
Consequently, we started by installing a double adhesive tape on the metal track, all around the room’s perimeter. This is a the proper method to attach the polyethylene foil, as it prevents air moisture and vapors to form.
Next, measure the surface of the room and cut the plastic foil to that specific dimensions, using an utility knife. Start with one corner of the ceiling and attach the anti vapor foil to the ceiling joists. If you do not want to use double adhesive tape, you could just staple it along the walls every 5” / 15 cm.
Afterwards, continue fastening the foil, until you got to the other wall. Remember that you have to make cuts if necessarily (using the utility knife) around light wires, ventilation pipes or attic ladders.
Thank you for reading our article about how to install mineral wool and we recommend you to check out the rest of our projects. Don’t forget to Like and share our projects with your friends, by using the social media widgets.