The skinny on insulation
I choose 2 x 6 wall construction based mainly on this information and facts about insulation:
Fact #1 – The thicker wall cavity provides room for actual R-19 to R-21 wall insulation.
Fact #2 – There is more space for insulating around piping, wiring, and ductwork allowing for better closure of air gaps.
What is insulation R-value?
R-value insulation ratings are used to measure insulation’s ability to resist heat flow. The higher the R value, the more effective it is. Home insulation should be purchased based on its R value, not thickness or weight.
- Insulation R-value of blown-in cellulose insulation is about 3.70 per inch.
- Insulation R-value of fiberglass insulation is about 3.14 per inch.
- Insulation R-value of open cell is about 3.8 per inch.
- Insulation R-value of closed cell is about 6.8 per inch
The BEST WAY to insulate is…
…two words for you: Spray Foam.
Actually to be more specific, closed cell spray foam is what you need. It’s the best choice for almost every possible situation.
Open cell spray foam has a lower R-value, but more importantly it does not provide a vapor barrier. Additionally, the outside shell of open cell insulation is part of the R-value. When you see them shaving it off to make it pretty, they are actually doing more harm than good.
The main drawback is the initial price. It may cost more up front, but spray foam will pay for itself in the end.
It helps to keep in mind that insulation is a 24/7/365 thing, and a necessary element in both heating and cooling effiency. Keep in mind that very low energy bills are a great selling feature if you want to sell your house in the future.
The 2nd BEST WAY to insulate is…
…with Polyiso Insulation in a board form.
Polyiso is one of North America’s most widely used and cost-effective insulation products. It is a rigid foam board insulation used primarily on the roofs of commercial buildings and schools, and as sheathing for homes.
This product is readily available, light weight and easy to cut and install. It comes in various thicknesses so you will probably be installing it in layers. Just take the time to seal each void as you go as best as possible during installation. Don’t forget the house wrap for an additional vapor barrier.
The great compromise is…
…a spray-bat combo or spray-poly foam-board combo.
This solution is created by applying at least one inch of closed cell spray foam and then adding a secondary layer of Poly foam-board or fiberglass rolls (bats) over it. This will greatly aid in making the home more energy efficient, without breaking the bank. This layer of spray foam provides an excellent R-value of almost 7 plus an additional crucial vapor barrier. The batts provide additional R-value at a fraction of the cost. Don’t forget the siding and drywall adds some additional value as well.
How to Install Insulation
In the grand scheme of things, putting up pre-cut batts in a wall with a staple gun sounds easy, right? But it’s a bit more complicated to do it properly.
Here are some tips from the DOE on installation of fiberglass insulation.
- When batt insulation is installed, it is fit between the wood frame studs, according to the manufacturer’s instructions. The batts must be carefully cut to fit around obstructions, such as window frames, pipes, wires, and electrical boxes with no gaps.
- Don’t compress the insulation to fit behind pipes or wires. Instead cut to the middle of the batt’s thickness so you have one flap under the pipe or wire and the other flap over the pipe or wire.
- One common mistake is to leave narrow places between close-spaced wall studs uninsulated. Even though these spaces may look like a very small part of the wall, small uninsulated areas can greatly reduce the insulation performance of the whole wall. Strips of insulation should be cut off and stuffed into such tight spaces by hand.
But you just said you can’t compress it?
Water is one of the biggest factors in regards to R value and home insulation. If moisture/water gets into your house insulation, it lowers the R value by about 5 percent or more. The moisture can also weigh down the insulation by opening up gaps at the top. This is something almost all carpenters have seen a time or two.
It’s also crucial to take into consideration the entire wall. Wall R-values are that of a wall with just the studs. This doesn’t include framing, windows, doors and exterior corners.
I have also read that approximately 10-12 percent of your home is not insulated properly. This is primarily due to the way it is constructed “with lumber”. Wood studs create a thermal bridge from outside to inside. These cold spots can affect the insulation and lower the overall R-values of the whole wall. Additionally, because the R-value of wood is different from the R-values of the walls, a cold spot could occur and lead to condensation problems.
The R-values of wood wall studs are wall studs are stated as 1.25 per inch.
A 2×6 or 5.5″ x 1.5 = about 7
A 2×4 or 3.5″xX 1.5 = about 4.5
Remember how important insulation is for the long-term efficiency of a home and the energy cost associated with keeping it comfortable…even a smaller, Cozy Home.