What is Cement Board Underlayment?
Cement board underlayment (CBU) is a type of insulation material used in construction projects. It consists of concrete or other materials mixed with sand and gravel. It provides structural support without requiring excessive amounts of energy or space. In fact, it can be built into walls with little effort.
The main advantage of using CFR is its ability to withstand extreme temperatures, such as those found underground. However, it does not provide enough insulation to keep heat from escaping during cold weather conditions. In addition, it tends to crack and crumble over time due to exposure to moisture and environmental factors like water infiltration. Because of these drawbacks, it has been replaced by other types of insulation products that are better suited for your needs.
How Does CBU Work?
CBU is made up of two parts: the cementitious matrix and the epoxy resin. The cementitious matrix acts as a barrier between the building materials and the outside environment. It helps insulate against temperature changes, moisture penetration, and UV radiation. The epoxy resin is a thick liquid that hardens when exposed to air. When combined with the cementitious matrix, it forms a rigid structure that allows for good thermal performance while maintaining strength at high temperatures.
CBU is made up of two parts: the cementitious matrix and the noncementitious matrix. The cementitious matrix is a mixture of aggregate, such as sand, gravel, clay or crushed rock; and filler materials such as fiberglass, gypsum wallboard or cellulose acetate. These fillers help to form a solid structure around the concrete.
CBU is popularly used as a supplemental heat source for hydronic tubing. It can also be used with a radiant heat system, in which case it must be placed on top of an already-installed layer of hydronic tubing. If left exposed to the ground, the CBU will eventually crack and deteriorate due to the expansion and contraction of the soil. The noncementitious matrix is simply the liquid that gets poured over the mixture of fillers and aggregates to hold the structure together.
The most common types of noncementitious matrix used are vinyl ester resin, acrylic resin, or polyester resin. Each of these resins has its own level of flexibility and hardness. Vinyl ester resins are softer than acrylic or polyester resins, but they allow for more elasticity in the board. In order to prevent this from happening, it must be secured with furring strips and plywood decking.
CBU can be used as a substitute for traditional wood framing when constructing new buildings or as an addition to an already-finished wall. For instance, when used as a structural support, it is installed on the interior side of the walls. When used as an insulator, it is installed on the exterior wall. Acrylic resins provide greater flexibility than vinyl ester resins, but they are less flexible than polyester resins. Polyester resins provide the greatest flexibility of the three.
Other types of noncementitious resins can also be used, such as urea-formaldehyde and phenolic resins. However, these materials are not as commonly used due to health risks. Urea-formaldehyde can release toxic gases when exposed to heat or moisture. Phenolic resins are not as flexible as the other types of resins and are more likely to crack.
It’s important to note that CBU is not designed for use in wet areas like a bathroom or kitchen. When installed in an area that gets damp, it can cause the the CBU to crack and deteriorate prematurely. To remedy this problem, the building should be constructed so that water is diverted away from the walls.
CBU is not a good insulator when compared to other materials on the market. It does not perform well in extreme temperatures, and it can only handle temperatures between -20 degrees Fahrenheit and 160 degrees Fahrenheit. If exposed to extreme heat or cold, the material can crack, warp or even ignite.
Other types of foam can be used as an alternative to CBU. These are usually made of the same types of resins, but the foaming process is different. Some types of foam require an open-cell structure to provide an insulating effect. Closed-cell foams do not have any air inclusions and do not provide as good of an insulating value.
Foam insulation can be beneficial in some cases where walls need to be created quickly. The main downside to using foam is that it is not as strong as other types of insulation. It can also have a negative effect on indoor air quality, especially for people who have allergies or other respiratory problems.
Foam insulation boards are another type of residential foam that can be used as an alternative to CBU. These types of boards are usually made of polystyrene or polyurethane. They can be installed without the use of adhesives, but most manufacturers recommend installing them with a bead of sealant along the edges for added strength and water resistance.
The rigid foam insulation board is made by a similar process of blowing open-cell resin into a rigid plastic form. Unlike the standard type of foam board, this board can be used as a drop-in liner for countertops and other flat surfaces. It’s also usually made to be fire resistant, so it can be used in buildings with strict fire codes.
The main disadvantage of rigid foam insulation is that it isn’t as strong as the other types. This means that it can be more prone to punctures or tears, and it can’t be used in load-bearing walls.
CBU in the Home
CBU can be a good choice for some home insulation projects. It’s relatively easy to work with and can be fairly effective when installed correctly. One of the most common applications of CBU is for the foundation walls. It can also be used on an exterior wall or within an attic.
The first step in installing CBU on the exterior foundation walls is to make any needed repairs. Patch any cracks or holes with mortar and let it dry before applying the foam. If the top of the wall is sloped, add a skim coat where the siding will be installed later on.
Next, measure the spaces in between the studs. For this example, we’ll be using 2×4 studs that are 16 inches on center. Measure, mark and cut a sheet of foam to fit in between every stud. Some types of foam have paper or plastic on one side. Make sure you’re cutting the good side facing out.
Using a trowel, apply a thick layer of adhesive on the wall. You should also wear disposable gloves, a dust mask and protective eye wear while working with the adhesive. The adhesive will need a few hours to set up before applying the foam.
After it has had time to go off, fit the foam into the wall. You’ll need to cut the foam to shape and trim away any excess material. When you’ve finished fitting it in place, use a notched trowel to spread another layer of adhesive on top of the foam. Let this dry and then repeat the process one more time.
After the adhesive has set thoroughly, you can finish the wall with siding or other types of sheathing. It’s important to keep these exterior foam walls ventilated since they won’t allow moisture to escape. Install at least one intake vent and one exhaust vent to allow for air circulation.
Installing in the attic is a fairly straightforward process. If you’re lucky, the attic may already have a few walls that are insulated with fiberglass or cellulose. You can usually use these walls as a starting point.
Measure the area and then cut a sheet of foam to fit between the framing members. You can use the same foam cutter that you used for the exterior walls. Make sure you wear eye protection throughout the installation process.
Using the notched trowel, coat the foam with adhesive. You may want to wear a dust mask or respirator for this step since the dust and debris from the foam can be irritating to your lungs. Let the adhesive set up for several hours before installing the next sheet of foam. Also, make sure you leave vents in place to allow air to circulate. Without air flow, the foam can become a potential fire hazard.
Keep repeating this process until you’ve finished the project.
Insulating with rigid foam in an attic is a fairly simple process. It can be more cost-effective than using more traditional methods such as fiberglass, and it’s also a lot lighter. If you’re lucky, your attic may already be insulated with fiberglass or even cellulose. You can always use these as a starting point and then add on top of them with your rigid foam insulation.
Remember, you’ll need to apply a thick layer of insulation to compensate for the “empty” space between the studs. If your walls are not completely filled with foam, then they will not be an effective insulator.
Installing rigid foam above the roofline is also an effective way to prevent ice dams. Ice dams occur when moisture from inside the home melts and runs along the roofline. Typically, this happens along the eaves of the roof.
The water then refreezes and builds up until it’s heavy enough to break free. It then flows down the roof and into the gutter. From there, it makes its way into the soffit, blocking the drain tubes that lead to the roof. This causes water to back up and leak through your ceiling. Installing rigid foam above your roofline will prevent this ice from forming.
As an added benefit, this will also prevent heat from escaping your home. Keep in mind that you can’t install rigid foam on your roof with just any kind of spray foam. There are special kinds for use on the roof.
If you choose to work on a ladder, then be very careful. It’s always a good idea to have someone assisting you on the ground in case you need help climbing down. This is especially true if you’re using a roofing ladder.
Your typical extension ladder leaning against the house is not nearly sturdy enough to provide a safe working platform.
You now have several options for insulating your walls: fiberglass batts, rigid foam board insulation, or spray foam. You can also use a combination of these materials. All three provide R-value insulating and all are suitable for all climate zones.
There are pros and cons to each type. The type you choose will ultimately be a matter of personal preference, availability, and cost.
Fiberglass batts are the traditional insulation material. It is widely available and fairly inexpensive. Before installing fiberglass batts in an existing wall, it is important to make sure the wall is sound and does not have any holes or weak spots. Holes and weak spots in the wall could allow the fiberglass to poke through and protrude into your home. This could be very dangerous.
Fiberglass is also not very durable, so you should avoid installing it in high-traffic areas.
Rigid foam board insulation is very durable and can be quite effective. The chief drawback is that it is often more expensive than fiberglass. It can also sometimes be difficult to find contractors that are experienced in installing it. It’s also not readily available at your local home improvement store.
Spray foam is the most effective type of insulation, but also the most expensive and the most difficult to install. It is also potentially the most dangerous, especially if you don’t follow the instructions exactly. It’s not suitable for use in wall cavities that contain plumbing or wiring, so plan accordingly.
If you’re on a tight budget, then rigid foam is probably your best option. If your home already has good insulation and you don’t mind the extra work involved, then go with fiberglass. If cost is no object and you want the best possible insulation, then go with spray foam.
The first step in any wall insulation job is to remove the switchplate cover, light switch, and electrical outlet so you can get to the framing. Use a screwdriver to remove the screws that hold these in place. You can now pull back the drywall and gain access to the framing members.
Fiberglass batts are generally installed between the studs as you saw earlier in this chapter. Use a utility knife to cut open the packaging and slide the insulation into place. It’s best to space the batts out every couple of feet. Fiberglass batts are made with zigzags, so they can expand and contract without breaking down or losing their insulating properties. Spray some canned air into the wall cavity to remove any dust that has accumulated.
If you’re installing rigid foam board, then you must frame the area first. Mark the stud locations on the wall using a tape measure and framing nails. You can then install 2×4 or 2×6 framing members at the appropriate locations. The 2×4’s are sufficient for R-13 walls, while the 2×6’s are necessary for R-19 walls. Nail a piece of wood over the top of each stud so you have a flat surface to mount your foam board to.
Use wood screws to secure the foam board to each of the 2×4 or 2×6 studs.
Spray foam requires no frame, but you must first thoroughly vacuum the wall cavity to remove all dirt and debris. Use a small amount on each application and make sure you overlapping your work by at least a foot. It’s best to do short sections at a time.
It’s also important to wear a respirator, goggles, and gloves when working with spray foam. It is a very effective insulator and it will clog up your respiratory system, burn your eyes, and cause severe skin irritations.
Once the foam has been sprayed into place, you should not interfere with the insulation for at least 12 hours. After this time, you can install the drywall. There is usually some settling that occurs, so you may have to do a little touch up in some areas.
After the drywall has been installed, you can then re-install the electrical boxes and switchplates, and light switches. Make sure to turn the power back on before you start installing the new switchplates!
Sources & references used in this article:
- Natural tilings for zeolite-type frameworks (NA Anurova, VA Blatov, GD Ilyushin… – The Journal of …, 2010 – ACS Publications)
- Robotic tile placement: Tools, techniques and feasibility (N King, M Bechthold, A Kane, P Michalatos – Automation in Construction, 2014 – Elsevier)
- Highly porous aluminophosphates with unique three dimensional open framework structures from mild hydrothermal syntheses (Y Hao, Y Pan, Y Lin, L He, G Ge, Y Ruan, H Zhou… – …, 2020 – pubs.rsc.org)
- Radio controlled tiled video display apparatus and method (D VanDruff – US Patent App. 10/288,853, 2004 – Google Patents)
- Tile Your World: John Bridge’s New Tile Setting Book (JP Bridge – 2003 – books.google.com)
- IM-17: a new zeolitic material, synthesis and structure elucidation from electron diffraction ADT data and Rietveld analysis (Y Lorgouilloux, M Dodin, E Mugnaioli, C Marichal… – Rsc Advances, 2014 – pubs.rsc.org)
- Database mining of zeolite structures (P Guo, N Yan, L Wang, X Zou – Crystal Growth & Design, 2017 – ACS Publications)
- Crystal Chemistry and Topological Features of Mixed Frameworks in the Structures of Natural and Synthetic Ree-Silicates (SM Aksenov, SA Mackley, DV Deyneko… – XI Всероссийская …, 2020 – elar.urfu.ru)