What is the cheapest most efficient insulation?
To determine the most affordable insulation we want to determine how much insulation will cost per square foot at a certain R value. Lets test insulation costs at an R-15 value to compare them. There are numerous choices of insulation with differing costs and performances. Blown in cellulose, Mineral wool batts, fiberglass batts, foam boards, closed cell and open cell spray foam.
| Blown in Cellulose | Mineral Wool Batts | Fiberglass Batts | Foam Boards | Open Cell Foam | Closed Cell Foam | |
| Cost per Square foot of coverage | $.32 | $.63 | $1.27 | $1.15 | $1.05 | $1.125 |
| Cost per Square foot per R Value | $.017 | $.042 | $.042 | $.115 | $.135 | $.18 |
| Total cost per Square foot at R-15 | $.25 | $.63 | $.63 | $1.73 | $2.03 | $2.76 |
The clear most affordable insulation is blown in cellulose. It is very cheap and can cover larger areas. However blown in cellulose isn’t the best choice in all applications. When you need to fill a cavity that is not parallel to the ground you need something that will stay in the stud-bay being filled.
Is insulating a house worth it?
When you are insulating a house you are making an improvement that is raising the property value and decreasing future cost of utility bills. This doesn’t even include the gain to the environment as the structure will consume less energy. Insulating will almost always be an instant return on investment and is totally worth it.
You will also have a higher quality of life as the house will provide the desired temperature and humidity with no draftiness. Spending money on insulating will certainly have a return on investment but some insulations will have higher ROIs than others.
How does insulation pay for itself?
Investments in insulation can have a dollar for dollar increases in the home value. That means you are not actually expending any money by insulating. Any dollars you spend will stay within your net worth as the value of your house appreciates. Insulating behaves more like an investment than an expense as it provides a return on investment and a residual income stream. This residual income stream is the saved money from lower utility bills over time.
The stock market provides on average an 8% return annually. When you are investing in insulation you stand to see a higher rate of return than the stock market. Lets consider a 1700 SqFt home will cost $3000 to insulate the attic and the walls. You could see savings of $50 per month in energy costs which is $600 per year. Saving $600 per year on a $3000 investment is a 28% annual return on investment! Thats 3.5x the stock markets average.
What is the most economical insulation material?
The most economical insulation choice is blown in cellulose fiber. It is the cheapest insulation per square foot but can also deliver serious R-value when applied in thick layers. This is applied in unconditioned attic crawlspaces. Most older houses will have an unconditioned crawlspace. Think multi feet layers of blown in insulation. It comes in bags and is applied with an insulation blower.
What is the cheapest way to insulate an attic?
If you are rehabbing an old house and need to fill an attic crawlspace and the walls, the best and cheapest choice is blown in fill insulation. Blown in cellulose will cost around $.32 per square foot when done DIY. A $16 bag of cellulose will cover 48.8 SqFt up to R-19. An attic can quickly be covered in many feet of blown in insulation you can also fill the walls.
What is cheaper blown or batt insulation?
Blown in cellulose is the cheapest insulation hands down. R-15 of mineral wool batts costs $22 and covers 34.8 sqft, meanwhile R-15 of blown in cellulose costs $12 and covers 48.8 sqft. Blown in costs $.32 per square foot while mineral wool batts cost $.63 per square foot. Thats nearly 50% cheaper per square foot.
Why is cellulose the most affordable insulation for house rehabs?
This is the best choice for house rehabs because it is the rock bottom cheapest option and will fit with the other steps of the house rehab. Blown in cellulose doesn’t have a very high R-value per inch but it doesn’t matter because it is so cheap many feet can be blown in at a low cost. Blown in cellulose is also eco friendly because it is made of recycled material.
Does blown in cellulose work in new home builds?
You can also use blown in insulation for a new house build too but it may not be a fit if you are creating a conditioned attic or basement space. This is a space in the house where the mechanicals like the furnace, AC system and ducts are kept in an insulated enclosure that wont be affected by temperature extremes.
Keeping your ducts in conditioned space will increase the efficiency of your HVAC systems. Blown in insulation is is a great method but the use of a conditioned space will boost energy efficiency much more on a new house build.
What is most affordable insulation for a new build house?
If the house is a new build the best choice is to use mineral wool batts. Mineral wool batts will cost $.63 per square foot. In particular if you are trying to create a conditioned attic or basement space you can’t put blown in cellulose in the stud bays of the roof in the attic. The best option is to fill the roof stud-bays with mineral wool batts.
Typically the rafters of the roof will be 2x6s or 2x8s. This will leave 5.5 inches or 7.5 inches of depth that can be filled with the batts. On a 2×6 deep rafter you can get R-20 and on a 2×8 rafter you can get R-30 with mineral wool.
Adding R value
If you require more R value you can add extender strips of wood onto the edge of the rafter to add more depth to the stud bay. More depth means more space to add another layer of mineral wool batts to push the R value from 30 up to 50. This will allow to keep your attic space at room temperature allowing your mechanicals to perform much more efficiently.
Why are mineral wool batts most affordable insulation for new home builds?
Mineral wool batts can be laid inside the wall cavity prior to drywall being installed. Mineral wool batts are a good choice because they have high R-Values per inch density. Getting R-15 out of a 3.5 inch deep stud cavity is pretty good. A $22 bag of mineral wool will cover 34.8 SqFt up to R-15. They are fire resistant and good at deadening sounds. The material is also not made of oil based products but made of stone.
What insulation is the easiest to install DIY?
Blown in cellulose is the easiest to install and most affordable insulation. This is because it can be sprayed out with a machine and doesn’t require to be put in wall cavities by hand. For 200 sqft of space it can take 30 minutes to cover with cellulose. That same job may take 2 hours when installing mineral wool batts.
How do I prepare my attic for insulation?
Before installing blown in cellulose or mineral wool batts there are many things that need to be done to prepare.
1. Use a can of spray foam to cover any holes or leakages in the attic. Air sealing is a major component of insulating. Some people decide to spray foam the entire attic but that can very expensive. I prefer to use a spray can and touch up any holes. This will stop air from leaking in from the outside and will also keep put pests.
2. Put blockers over areas that cant be covered by the insulation. The big one is having blockers over light fixtures as you don’t wan insulation to be in contact with electrical wires. Also you want to make sure any vents or soffits are not covered as well so there can be airflow along the roofline.
3. Put a sheet of foam board on the topside of the service door. There will be a service door where you can access the attic and typically these doors are made of thin wood. You don’t want your service door to be a leak area so make sure the door itself is insulated with a sheet of foam board.
Conclusion: What is the most affordable insulation
Installing insulation is an investment that will certainly yield a return on investment. By implementing the most affordable insulation to your situation you will make the job of insulating easy
More resources: https://www.energy.gov/energysaver/insulation