What is the r-value of concrete?

The article aims to answer the question “What is the R-value of concrete?”. It will also discuss how you can calculate the R-value and how this R-value is related to concrete insulation. 

What is the r-value of concrete?

R-value is the insulating capacity of concrete. In terms of thermal resistance, R-value evaluates the ability of a concrete slab (or other material) to resist heat flow or the efficacy of insulation. 

The U-value, on the other hand, is a measurement of the amount of heat that is transferred from the ground to a confined area through a concrete slab. 

Lower density concrete offers superior thermal insulation than higher density concrete because of the inverse relationship between density and thermal insulation. 

Finally, to determine if the reinforced concrete slab can resist heat transfer, the R-value and U-value of the slab under consideration must be calculated.

How can I estimate the R-value of concrete?

It is possible to measure the thermal resistance of a standard concrete slab using an R-value between 0.1 and 0.2 and multiplying it by the thickness of the slab. ASTM C 168, on the other hand, provides the following formula for calculating R:

R-value = temperature difference X area X time / heat loss

Temperature, area, duration, and heat loss are all measured in Btus for a concrete slab with an outside and inner temperature differential of 30 degrees Fahrenheit.

It may be found in the ASTM C 168 document that ASTM C 168 provides two more equations to determine R-value.

A distinction should be made between American and European standards when comparing R- and U-values.

Divide 1 by the R-value and multiply the result by 5.682 to get the European U-value. A European U-value is multiplied by 0.176 and divided by 1 to translate to an American R-value.

How can I increase the R-value of concrete?

Continue reading the article to understand how you can increase the R-value of concrete:

Stopping outside air from entering is one of the greatest methods to maintain a comfortable inside temperature. If a concrete block wall settles or shifts, air may escape through the cracks in the joints between the blocks. 

Another common location for leaks is under the rim joist, the board that rests on the edge at the top of the block wall. Apply a layer of mortar to fill up any gaps. Outside air should be kept out by sealing the gap between the top layer of cinderblocks and the top rim joist.

Large, lightweight sheets of rigid foam may be installed directly on the surface of concrete blocks. Rigid foam panels may be used to cover a whole wall if you’re insulating a storage space or an unfinished room. 

Because the panels are light enough to be glued in place, no nails are required. Only use glue specified for stiff foam and masonry, and follow the manufacturer’s instructions exactly. The rigid foam may be “eaten” by certain glues, resulting in a sticky mess. 

To ensure that the wall is completely airtight, special tape is supplied for use over the seams. Building the wall with furring strips and then insulating between them is a better option if you want to dwell in the space. 

It’s basically the same method as framing a regular wall, except that the wall studs usually fit flat along the block wall. You can cut and install rigid foam insulation into 1.5-inch-thick stud gaps provided by standard two-by-four studs. 

It’s a bit more time-consuming, but you can complete the wall by installing drywall over the studs. The Outside Insulation Finishing System (EIFS) may be applied to exterior blocks when it is not possible to insulate the inside of a block wall. 

Although EIFS is not a masonry product, it is applied in the same manner as stucco. Over the block wall, the EIFS contractor places a moisture barrier, then rigid foam insulation, steel mesh, and lastly the stucco-like material. 

EIFS must be applied by a professional contractor, and you may require a permit since the EIFS will add around 3 inches to the external wall measurements.

How to insulate concrete walls?

To insulate concrete walls:

  • Build a stud-framed wall out of wood first. The wall should be framed like any other wall in your home. In most cases, a single bottom plate and a double top are used in the construction process. 
  • Depending on the thickness of your insulation, you may want to adjust the wall thickness. R-13 typically requires a 2×4, whereas R-19 through R-21 need a 2×6. It’s OK to utilize 2×12 or double-stud walls if you’re constructing a Passive House with R-40 wall insulation.
  • Allow a 2-inch space between the studs and the concrete wall. In the case of batt insulation, this area allows for a little amount of ventilation. If water manages to seep through the concrete, it will be carried away by gravity and eventually end up in a drain. 
  • However, if you’re going to use spray foam, you’ll want to insulate this space. For best results, use the foam to fill any spaces and gaps between the studs and the studs themselves. If you want to keep water out of your home, use closed-cell spray foam. A layer of firm foam insulation may also be used to fill up this space before the stud wall is built.
  • Some masonry screws may be necessary to attach the stud wall to the concrete. However, it isn’t required.
  • If you’re using batt insulation, push it down between the studs so that it’s snug against the sides of the studs. The insulation should be held in place by friction. An incorrectly-cut insulator or too-closely spaced studs might be to blame.
  • Don’t squeeze the insulation. If you have to squeeze the insulation in during the wallboard installation, this indicates that your studs are inadequate. The R-value of batt insulation is reduced when it is compressed.

Can I insulate concrete walls with spray foam?

Yes, using spray foam to insulate a concrete wall is the most effective method. However, it is available in two variations: closed-cell and open-cell.

Spray foam with closed cells has a higher R-value and is more water-resistant than open-cell spray foam. You may apply it in any area that gets wet since concrete is notorious for this. There are no little spaces around cables, pipes or vents that are not sealed by this natural water barrier.

Spray foam’s major drawback is its hefty price tag. It’s not something you can pick up from a shop and put together yourself. Because spray foam contains chemicals, some homeowners aren’t interested in using it. 

You may get ill if the insulation isn’t installed appropriately by a professional. However, it is a great concrete insulator when properly built. Insulating a concrete wall with firm foam boards is the next best option. Aside from being easy to do yourself and inexpensive, this is the most common approach.

An average of 2 to 6 R-values per inch may be found in rigid foam, which is also water-resistant. Once the boards are in place, I suggest caulking and taping all of the joints. Placing them flush against the concrete, with no space between them and it is safe.

A Foam board is most effective when the R-value you need is selected and the foam board is adequately sealed to produce a robust vapor barrier. House wrap tape made of Tyvek (or comparable material) and silicone are excellent choices.

“Great Stuff” foam in a can is the best way to seal around any holes in the foam board for cables or pipes or any other penetrations.

Insulating a concrete wall with a foam board and fiberglass composite is one of the best and most economical options available. The finest of both worlds is at your disposal. This combination of stiff foam and batts provides an excellent vapor barrier and dense insulation. 

If you utilize batts near concrete, ensure there is absolutely no water in the area. You’ll be using caulk, tape, and can foam to seal a layer of foam board right up against the concrete. Frame a stud wall in front of the foam board, and you’ll be done! 

Always remember to figure out how much R-value you’ll need for your insulation. As the R-value rises, so does the thickness of the batt insulation. Make sure the studs are the same thickness as the insulation. 

Compressing batt insulation might cause it to break down. Your studs are too tiny if the insulation becomes crushed when installing the wallboard. That’s why it’s important to match the stud thickness to the insulation.

The batts should be tight when they are installed in the stud cavities. They shouldn’t fall out due to friction. If the studs are too wide apart, they will fall.

How to install electrical cables in concrete walls?

To install electrical cables in concrete walls:

  • You may wish to consult an A/V expert for this task. It’s best to avoid running A/V cables too near to circuit electrical connections so that the distance between the site of usage and the service connection is as short as feasible. 
  • The distances involved should be documented on a materials list. To cover the distance, you’ll need more than the bare minimum of cable. Allow additional time for connections to be made and for the removal of any impediments. 
  • Ten to fifteen percent additional cable is a reasonable rule of thumb when purchasing cable. In addition to the cable, you’ll need wall plates, connectors, low-voltage electrical boxes, and nail plates for the studs in which you’ll be drilling.
  • Make holes in the studs and other frame parts using a drill and spade bit for the cables. Using a drill, drill a hole in the middle of each stud that is big enough to enable the wires to pass through, but never more than 40% of the stud width. 
  • In order to prevent drywall fasteners from coming into touch with the cables, nail plates should be affixed to the front of each hole.
  • The holes may be used to suck in wires. A fish tape or a fish stick may be used if you need to transfer cables through the wall plates and onto a level above or below your current location. 
  • Keep a few extra inches of cord on each end just in case. Using suitable staples or clamps, secure cables at 4-1/2-inch intervals. Make sure you place the clamps approximately 1 foot from each connector.

Conclusion

Thermal resistance, or R-value, refers to a wall’s capacity to impede heat movement from one side to the next. There are several advantages to using concrete blocks as a wall, but its low heat resistance makes it a less-than-ideal option. 

The thermal resistance of an 8-inch thick block wall with no additional insulation ranges from R-1.9 to R-2.5, depending on the density of the blocks.

Frequently asked questions (FAQS): What is the R-value of concrete?

What is the r-value of concrete?

R-value is the insulating capacity of concrete. In terms of thermal resistance, R-value evaluates the ability of a concrete slab (or other material) to resist heat flow or the efficacy of insulation. 

The U-value, on the other hand, is a measurement of the amount of heat that is transferred from the ground to a confined area through a concrete slab. 

How can I estimate the R-value of concrete?

It is possible to measure the thermal resistance of a standard concrete slab using an R-value between 0.1 and 0.2 and multiplying it by the thickness of the slab. ASTM C 168, on the other hand, provides the following formula for calculating R:

R-value = temperature difference X area X time / heat loss

Bibliography

Glenda Taylor. How to Increase the R-Value of a Concrete Block Wall. Home guides. Retrieved from: https://homeguides.sfgate.com/increase-rvalue-concrete-block-wall-54431.html

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