Types of Insulation
Types of insulation: how, where, and why
It is important to understand what insulation does, where it should be used, and how much should be used. Insulation is measured in R-Value. R value is a way to measure how much resistance the insulation has to heat flow.
The higher the R-value, the more the resistance and the better the material is at insulating a home. Different insulation materials also have different R-values per inch. They also resist air flow differently.
R-6 to R-7. Air tight
Open Cell Spray Foam:
R-3.6 to R-3.9 Air Resistant
Polyisocyanurate Foam Board
R-6.5 to R-7. Air tight
Cellulose (Loose-Fill)
R-3.1 to R-3.8. Leaks air
Cellulose (Dense-Pack)
R-3.5 to R-4 Air Resistant
Fiberglass (Batts)
R-2.9 to R3.8. Leaks air
Approximate R-Values needed by location
- Attic R-49
- Walls R-20
- Basement R-14
Attic
In most cases, we like to use a blown in cellulose product. This type of insulation is treated with a boric acid and is mold resistant, fire retardant, and critters don’t like it. On top of that, it also has a much better coverage and gets in every nook and cranny versus fiberglass batts.
Heat likes to escape through the attic, so it is essential that the attic is insulated and air sealed properly. Cellulose is especially preferred when the attic space is flat and you have sufficient space to reach building code. If there is no attic space, or room is limited, a foam product can help reach the desired R-Value while using less space.
The attic is usually where you can find some of the largest opportunities to save energy in your home. By adding insulation in your attic, you can maintain the desired temperature throughout your home much better. Combined with attic air sealing, it can also help to alleviate the formation of dangerous ice dams in the winter.” -energystar.gov
Basement/crawlspace
When insulating your basement or crawlspace, we use a combination of spray foam and rigid foam board to insulate the walls, sill plates, and rim joists. In cases where the crawl space is damp or moist, we install a vapor barrier which helps keep mold and the musty smell out. When we insulate, we like to focus on exterior walls rather than the flooring directly under your feet. Why might you ask? The answer is simple. The walls are where you are losing your heat.
On top of this, there is usually plumbing underneath the floor that needs to be kept warm to prevent from freezing up. Another factor is that many homes have a furnace or boiler that is producing heat which can go into the living space and keep your home warmer. Keeping the walls insulated versus the floor can also help keep your home cooler in the summer!
This is what energystar.gov has to say on insulating basements.
“In most cases insulating the basement walls—and possibly the slab—results in better performance. Insulating the basement walls, rather than under the first floor, brings the basement within the thermal envelope or conditioned space of the home and connects the basement thermally to the rest of the house. This will keep the basement warmer during the winter. In the summer, a conditioned basement will usually be dryer than the alternative.
A warmer, dryer basement can have much more value as a functional, usable space. It also provides better conditions for HVAC equipment. In extremely cold climates, insulating the basement walls may be critical to keep temperatures in the basement above freezing (which is important if there are any mechanicals or plumbing in the basement). If heating equipment is located in the basement (e.g., a boiler or furnace, water heater, ducts, etc.), the heat losses from this equipment may provide all the heat needed to keep an insulated basement comfortable and usable. During the summer months, because the ground is generally cooler than the air within the home, connecting the basement to the conditioned space will reduce the cooling load. It’s true that good basement wall insulation will limit this cooling effect, but even a home with a well-insulated basement will generally require less air conditioning energy than the same home with insulation beneath the first floor”
Walls
The walls of your house make up the biggest surface area to cold exterior temperatures, so it is vitally important that they are insulated properly.
In retrofits we like to use blown in cellulose through a process called “dense packing”. This process helps you get the insulation you need while reducing the air leakage seen in typical fiberglass batt construction.
Dense packing is done by removing siding, cutting a hole through the sheathing, filling the wall cavity, and then replacing the siding.
In new construction we do spray foam or dense packed cellulose walls. Fiberglass batts can be used, however we always recommend spray foam or dense packed cellulose.
Building code for new construction has changed and now requires continuous insulation along the house, not just in between the studs. Rigid foam board can be used to help achieve continuous insulation.