Insulation and Knob & Tube Wiring

Insulation and Knob & Tube Wiring

This time of year Mother Nature reminds us how powerful she can be. We receive numerous inquiries from prospective customers wanting to know if we can inject spray foam insulation into existing walls. While we can most certainly do this if the wall cavity is empty, the first thing our Salespeople and Certified Applicators look for is Knob & Tube wiring within the structure. If there is any, we always recommend bringing in a certified electrician.

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While we are definitely experts in spray foam insulation, we would never undertake wiring a home. We here at Iowa Spray Foam always refer to a professional electrician for their services.

Why is insulation and Knob & Tube a bad combination?

Knob & Tube wiring needs space to keep it cool. When spray foam insulation (or any insulation for that matter) is installed around it, the insulation restricts the wiring from dissipating the heat in the wire when electricity is energizing the circuit. If the heat is not properly dissipated, the wiring could overheat and potentially cause a fire. This is part of the reason that the tubes come into play: they prevent the wire from touching the framing or other materials, preventing fires.

You must also keep in mind that some of this wiring could be as old as 80 years old. We have witnessed some homes where the protective insulation wrap around the wiring has fallen off or has even been chewed off by rodents. So while most people don’t really want to spend money on upgrading their homes, it is really a good idea.

Don’t believe us? See what This Old House has to say about Knob & Tube: “Faced with drafty houses and high heating bills, homeowners often add thermal insulation to their attics and walls. Insulation on top of knob and tube wiring is a major fire hazard.”  They go on later to state,  “In 1987, the National Electric Code prohibited the placement of insulation in contact with this type wiring.”

These concerns come into play not only inside a wall cavity, but also in attics, crawl spaces, or even basements when installing spray foam insulation. This is just another reason to make sure you are looking for professionally trained and certified spray foam insulation contractors for your projects. Call us at Iowa Spray foam for your next home project.

Building Science 101: Heat Transfer Methods and Flip Flops

Building Science 101: Heat Transfer Methods and Flip Flops

flip flops
I know that I have written a lot of blogs in the past years, but this may be one of the least intriguing. However, the topic is important.
There are three basic methods for heat transfer: conduction, convection, and radiation. We are going to talk about conduction in this particular blog and we will follow up later with the other two methods.
What is Conduction?
Conduction is a heat transfer method that requires two materials to be physically touching each other to occur. This is unlike the other two methods of heat transfer that can occur without physical contact.
An example of conduction includes putting a pan on a burner of a stove and turning on the heat. The heat from the burner or flame transfers through the pan’s metal, warming the food in the pan. Another example would be walking on the sand at the beach while barefoot. As you may have experienced, the sand is hot and it will transfer that heat to your feet. So to keep your feet from burning you put on a pair of foam flip flops.
Now that you have a basic idea how conduction works you are certainly wondering what this has to do with spray foam insulation. In fact, it has a lot to do with building construction in general or even more to the point, how your building can lose energy and be uncomfortable.
Thermal Bridging
Thermal bridging is heat transfer via conduction. Have you ever driven down the road and noticed on a cool, frosty morning that you can see the lines from the trusses on someone’s roof? Or maybe on the siding of the wall you can pick out every stud? This is also known as “Ghosting”.
The reason you can pick out every stud is because wood has an R-Value of about 1 per inch. So when we install an R-21 of spray foam insulation into the wall, the insulation slows down the convection of heat through the wall, much like the foam flip flop keeps your feet from burning on the sand. The wood stud allows it to transfer heat faster and thus you see the lack of frost on the wall where the stud is. This also works on roofs when insulating the underside of the roof in a vaulted area because the drywall is attached directly to the roof joist and the sheet is attached to the roof joist from the other direction.
How Do We Stop This?
We need to provide a thermal break between the wood and the exterior of the wall. This is done by attaching foam sheeting, or in some cases applying spray foam over the trusses in a complete manner. The picture below shows the spray foam insulation installed over the purlins on the roof underside. The purlins covered will not conduct thermal bridging here.
How Much Energy Are You Losing?
Keep in mind you have a stud every sixteen inches in an exterior wall. If you add those up you could have anywhere between 15-30% or more of your wall conducting heat transfer. The 2012 IECC code has this figured out. They allow for a provision to have an R-13 cavity insulation with an R-5 continuous insulation such as a foam board.
Adding spray foam to a home is just part of building a warm and comfortable home. Stopping conduction via thermal bridging is another key part. Before heading out to the beach this cold winter and putting on those foam flip flops, call a Building Science educated Spray Foam Insulation contractor to keep you warm and comfortable!

Moisture Myths and Spray Foam

Moisture Myths and Spray Foam

Here at Iowa Spray Foam, we get a lot of questions about spray foam and appropriately so. One of our most common questions is about whether or not spray foam will cause moisture issues. The simple answer is no. However, let’s go into detail rather than just taking my word for it.

Myth #1

Some people assume that when spray foam is applied to a metal surface (like a metal pole barn) that the moisture will get trapped on the surface of the metal, causing it to rust out. This is not true.

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By using some basic building science logic, we can easily disprove this. Moisture movement requires air movement. When you have an air seal you stop the moisture movement. Spray foam is an air seal which effectively stops the moisture movement. Condensation occurs when warm, moist air hits a cold surface which then leads the moisture-laden air to reach its dew point. Insulating with spray foam stops the moisture-laden air from reaching the surface, keeping it from reaching the dew point and then the water vapor in the air does not turn into a liquid.

Do you want to test this yourself? On a hot summer day, fill a plastic or glass cup and a foam cup with ice water. Set them outside for an extended period of time. Which one condensates? Of course the plastic or glass cup will condensate, but the foam one doesn’t. But why? The foam prevents the cold water from meeting the warm air resulting in a lack of condensation.

So you may not believe a spray foam contractor telling you all about the great things about foam. How about a building science professional? John Straube, a building science professional from Building Science Corporation explains condensation and how it is related to insulation:

“Cold-weather condensation is primarily the result of outward air leakage. Diffusion usually does not move sufficient quantities of water vapor fast enough to generate a problem. To control damaging condensation inside enclosure walls and roofs, air barriers are used to stop airflow and vapor control layers (vapor diffusion retarders or barriers) are used to limit diffusion flow. Air leaking outward through the enclosure wall in cold weather will contact the back of the sheathing in framed walls. This condensation can accumulate as frost in cold weather, and subsequently cause “leaks” when the frost thaws and liquid water drains down, or cause rot if the moisture does not dry quickly upon the return of warmer and sunnier weather .In walls with sufficient exterior insulation, the dewpoint temperature of the interior air will be below the temperature of the back of sheathing: therefore condensation due to air leakage cannot occur within the studspace. If an assembly is shown by calculation to be safe against air leakage condensation (using the method described below), then diffusion condensation cannot occur, even if absolutely no vapor resistance is provided inside of the sheathing (i.e., no vapor barrier or other control layer), and even if the sheathing is a vapor barrier (such as foil-faced insulations).”


Moisture Myth #2

Myth: You have to use closed cell spray foam on metal pole buildings. Open cell spray foam will allow moisture to get to the metal surface.

Remember that open cell spray foam is also an air barrier. Sealection500, the open cell spray foam used at Iowa Spray Foam, only allows 0.001 L/sm2 of air to pass through at 50ps. 50 Pascals of air movement is equal to about 16 mph wind. So with a 16 mph wind a very little, almost unmeasurable amount of air is passing through open cell spray foam. Even when tested at 300 Pascals — or around 50 mph — a very small amount of air moves through open cell spray foam.


The Questions to Ask

The best question that needs to be asked but consequently never is, is: how do we control moisture in the building? Simple things like vapor barriers under the basement slab or in a crawl space can do the trick. Controlling and removing excess moisture due to cooking, bathing, and laundry goes a long way as well. Check out this video from Anderson Windows on other ways to eliminate moisture:



The next time someone tells you that foam insulation traps moisture, tell them they are all wet! A spray foam contractor as well as a building science professional proved it to you with a foam cup! Contact Iowa Spray Foam for all of your spray foam needs.

Air Sealing New Homes

Air Sealing a New Home

According to the Department of Energy, 40% of heat loss in a building is due to air leakage. If this is not reason enough to air seal a new home, let’s consider another idea: air leakage is air movement. Air movement carries moisture. Moisture fuels mold growth. So if you stop the air movement (the air leakage), you greatly reduce the chance for mold growth in the walls of your home.

How to Air Seal

There are many avenues you can take when considering air sealing a home. There are a few low-cost things you can do to start air sealing your home. A simple step like caulking double studs and top and bottom wall plates is a great place to start. Great skill nor expensive tools are necessary to complete this project: all that is needed is a caulking gun and a step ladder.


Keep in mind that it can take several cases of caulk to air seal a home depending on the size and how the house was framed. This is a project that anyone can do, including a prospective home buyer who is looking to save some cash. For great results, you must pay great attention to detail. This video has great ideas as to how to air seal your walls:

Window Sealing

The next step in this project would be to seal all protrusions in the exterior walls. This includes electrical boxes, plumbing, and AC lines. Any other protrusions should be sealed up and a great way to do this is with canned spray foam you can find at your local hardware store or lumber yard.

Most quality windows are sealed very well. However, when installed in a rough opening of the wall there can be a gap up to an inch. This area also needs to be air sealed. It is important to be careful when sealing these areas up because the window manufacturers have specifications as to how it should be done, and it varies from manufacturer to manufacturer. You can seal these gaps with caulking or canned spray foam.

When using canned spray foam around windows and doors, it is extremely important to utilize the proper type. There are two kinds of canned spray foam: minimal expanding (or door and window) and regular expanding. When working with windows you definitely want to use the minimal expanding canned spray foam. Using the regular expanding spray foam can cause the window frame to bow which leads to wedging the window shut, damaging it. Another important tip when using canned spray foam: be patient. Use a small amount and allow it to expand. Make several short passes and wait between applications to allow it to expand fully. Failing to do so results in using too much product and having to trim it off, resulting in wasted material.

Ceiling Sealing

The best time to seal the ceiling is after the drywall is hung. Once again, any protrusions through the ceiling needs to be air sealed (including electrical boxes, wiring, can lights, duct work, etc.). Also don’t forget bulk head areas over cabinets or chases. Canned spray foam can work well for most of these areas. It might also be required to use a foam board to cover the protruding area and then to seal around it.

For more air sealing tips, you can download this book from Green Builder Magazine.

Spray foam insulation is also an air seal. Choosing Iowa Spray Foam to install open or closed cell spray foam in your new home can seal up many of these areas mentioned in this blog and more. Open or closed cell spray foam insulation finds all of the cracks and gaps the wall or ceiling areas may have. Give Iowa Spray Foam a call and let us show you how to stop up to 40% of the heat loss in your new home.

Basement Insulation and Moisture Management

Basement Insulation and Moisture Management

There is a widely spread misconception even in today’s construction of new homes that people believe they don’t need to insulate basements. There are many reasons why basements need to be insulated.

Why Insulate a Basement?

Some people believe that because a basement is typically protected and surrounded by dirt that the dirt will insulate the basement. Think about it this way: during the winter the frost line can be anywhere from two to four feet deep. The dirt surrounding the basement is not completely up to the bottom of the siding. Up to six foot of the basement wall is below 32 degrees Fahrenheit: basically 75% of the outside of the basement wall is below 32 degrees Fahrenheit. If it’s 32 degree outside wouldn’t you wear a coat? This is the equivalent of insulating your basement walls.

Most basements are about the same equal exterior wall area as above ground walls. So if you don’t insulate the basement over half of your exterior wall is not insulated. Interestingly enough, it takes about four feet of dirt to equal the same R-Value of a two inch thick piece of foam board.

Moisture Management

For most people it does not occur to them the moisture that is in a home is due to a “dry” basement. They are misled to believe that homes have a “dry” basement. Many new homes never get a vapor barrier. To learn more about vapor barriers, visit this blog post.

Most people believe concrete to be waterproof but this is not true. In fact it is exactly the opposite: while it may not let water in it allows capillary water transfer. According to EnviroShield, “Moisture problems are not necessarily caused by hydrostatic pressure. Concrete is hydroscopic: like a sponge it will absorb moisture from the air and if the humidity on one side of the concrete differs from the other, it will move moisture to the drier side.”

The video below will give you a good explanation as to where to install your vapor barrier and capillary breaks. It also gives you a good overview of different ways to insulate a basement:

Insulating Basement Walls

Basement walls can be insulated inside or out. But also keep in mind that you will need an air barrier. One of the biggest issues with insulating the outside of the basement comes from having to attach the insulation to the concrete wall. Another large problem occurs when attempting to protect it from damage when backfilling the basement over dig. A main concern for many home owners is that insulation on the outside of the basement is not aesthetically pleasing.

Therefore, your best option is to insulate from the inside. There are a variety of options to choose from: you can attach a foam board to the wall or hang vinyl-backed fiberglass rolls from the rim joist area down. The fiberglass method has become the favorite for the “Economy Production Home Builders” you see now. The fiberglass rolls are often called “diapers” in the construction world because they look like diapers and have a tendency to absorb water in the same manner.

vinyl backed fiber glass basement

The last way to insulate the basement is to stud it up like an exterior wall would be and install batt insulation or spray foam insulation. This is the best way to insulate the basement wall. If you install fiberglass insulation in the basement you will need to be sure to control moisture in the concrete. If moisture is not controlled the perfect environment for mold growth is made.

The simplest and most recommended way to insulate a basement wall is with closed cell spray foam insulation. To learn more about the specifics of closed cell spray foam insulation, visit this link.


Closed cell spray foam insulation is an air barrier, a vapor barrier, a drain plain, and insulation all in one simple step. It solves all of these problems in one. Wood foundation basements can also really benefit from close cell spray foam insulation.



Many home basements are not insulated. When finishing a basement this is a great time to insulate it. Give Iowa Spray Foam a call and let us help you insulate your basement with closed cell spray foam insulation.

Common Bonus Room Issues


What are bonus rooms?

Typically a bonus room is a room that is located above a garage. They are called a bonus room because people think that they get an additional room in their home without much added expense. These rooms are typically used for entertainment purposes.

Problems faced with bonus rooms

Usually at this time of year when the first cold nights start to hit we get many calls about cold bonus rooms. Many houses, including ones that are being built even today, have problems with cold or hot bonus rooms (or rooms above garages). Some of the most common problems found in these bonus rooms are a lack of insulation, air sealing issues, and installing duct work in poorly insulated areas.

Most codes, depending on your climate zone, require at least an R-38 in the floor are of a bonus room. This alone is not enough to keep the floor and the room warm.

What are knee walls?

Up in the side attic areas that most bonus rooms have are what are called “knee walls.” These walls are usually less than three feet in height and are used to support the rafters in the building construction. It is very common for most contractors to simply install insulation in these knee walls and then cover them will drywall.


Notice the dark color of the fiber glass insulation shown above in the photo. This is due to the air passing through the fiber glass and it trapping dirt in the insulation, just like a common furnace filter. The fiber glass insulation in these side attic areas is exposed directly to the vented attic and can suffer from air flow passing over it, lowering the insulation’s effectiveness. The 2012 IECC building code now requires these knee walls to be covered with an air barrier to be in contact with the insulation.

Check out this great animated video to get a better visual reference as to what is taking place:

To get the best insulated knee wall we suggest insulating and air sealing the knee wall with spray foam insulation like this picture below:


Another common mistake is to install duct work in the triangle areas behind the knee walls or in the floor in the bonus room. Installing duct work in an unconditioned attic space is not a good idea. Check out this previous blog from our sister company KC Spray Foam about attic insulation here.

The other common problem with duct work is due to its physical size: it takes up almost all of the area in the floor joist of a bonus room leaving very little to no room for insulation.


The picture above shows that the duct work is left open in the unconditioned area of the garage. They added a register to allow the furnace to blow warm air in the garage as an attempt to keep the area warm. This is a bad idea for many reasons: the main reason being the carbon monoxide from the vehicles inside the garage can get into the occupied areas of the home. What should have been done in this situation is a bulk head should have been built around this duct work and properly insulated and air sealed.


The good news is that even if your home is finished we can help with the comfort level in your bonus rooms. When done correctly bonus rooms can add a lot of value to a home. Contact Iowa Spray Foam for free, professional advice on insulating and air sealing bonus rooms with open cell or closed cell spray foam insulation. We care about your safety and your warmth this upcoming winter season.

Combat High Heating & Cooling Costs

The bitter cold temperatures we have experience in Iowa this winter have been more than just unpleasant for many residents. They have caused financial strife for a record number of people as a result of heating costs significantly higher than previous winters.

In a previous blog we talked about the real value of spray foam insulation. When heating costs rise drastically, the value associated with spray foam insulation increases even more. Our insulation products can save you money over time, and the savings begin immediately through reduced energy bills.

If you’re in the process of building, these are factors to keep in mind as you make your insulation decisions. While insulation foam may be more expensive in terms of initial costs, you are making an investment toward energy efficiency that will help your home or building function better for years to come.

Our experts can also identify ways spray foam insulation can benefit your existing structure – through a remodel or addition of insulation in an attic or garage, for example. As you can imagine, when costs are high like this season, the ROI associated with spray foam insulation becomes much quicker.

Impact on the Midwest

According to an article from late January in USA Today, “Revised EIA (Energy Information Administration) estimates from earlier this month peg some home heating bills rising as much as 23.5% in the Midwest. But even those estimates may be too low.” The pinch may also vary based on whether you heat with electricity, natural gas or propane.

For those in Iowa struggling with energy bills related to propane, you might find assistance at the Propane Shortage and Heating Assistance Webpage through the Low-Income Home Energy Assistance Program (LIHEAP). Income requirements and guidelines are available on the webpage.

Take Steps to Save Money and Energy

The simplest steps you can take to save energy are to turn your thermostat down and wear more layers to remain comfortable. For additional energy saving tips, or for assistance, review information provided by the Iowa Utilities Board.

Unfortunately, forecasts by the U.S. Energy Information Administration don’t show improvement in cost. In fact, according to the chart below, costs for natural gas and electricity are forecasted to rise from 2014 to 2015.

US Energy Information Adminstration

Improve Insulation, Improve Efficiency

Consider using spray foam insulation to improve your home’s energy efficiency in the future. Doing so will equate in lower utility bills and a more comfortable home. Our experts are available to meet with you to review your insulation needs, our products and related energy savings you might expect.

Is Spray Foam Fire Proof?

This is a question we get from time to time. It’s important to know that while spray foam insulation has fire retardants mixed in, as with most building materials, it is not fireproof. Most spray foams are a Class 1 spray foam and have better smoke development, flame spread numbers and auto ignition points than wood.

For example, SEALECTION 500, one of the products we use, has a flame spread index of 21 and a smoke developed number of 216 – which are both very good. As you can see on the product’s technical data sheet, the spontaneous ignition temperature for SEALECTION 500 is 1040°F. In comparison, the spontaneous ignition temperature for wood is 662°F. Watch the Demilec APX Spray Foam burn test video below to see how spray foam might perform in a fire situation.

While the spray foam product in the video does not have an ignition barrier or ignition barrier coating, most spray foam products will always need some kind of ignition barrier or thermal barrier. Be sure to consult the Evaluation Service Report (ESR) for the detailed uses of ignition and thermal barrier needs for the product you intend to use. All spray foams have individual reports, like this one for SEALECTION 500.

People also wonder if smoke from spray foam is more dangerous, but it is not. Like other organic materials, including wood, smoke from spray foam is a mixture of many gases. The major components of smoke from Icynene spray foam insulation are carbon dioxide and carbon monoxide.

If we can help answer questions you have about spray foam insulation, give us a call. We are always available to help you!

Top 10 Building Science Secrets: Put Iowa Spray Foam insulation to work for you!

The practical purpose of building science is to optimize building performance. This course of thinking looks at a building as a whole and how the many systems – like insulation, and HVAC, etc. – work together. At Iowa Spray Foam we invest in training and equipment to provide insulation systems that complement our customers’ needs. This includes many years of qualified experience.

We recently came across this article that highlights the “Top 10 Building Science Secrets,” and thought there were a few interesting points to share with you. The author, Dr. Allison Bailes posts regularly about building science on the Energy Vanguard blog if you want to learn more from his perspective.

Here are our thoughts on some of the points addressed:

1 – Housewrap isn’t installed to be an air barrier.  People ask us if they use spray foam if they still need housewrap? You don’t need housewrap to stop air movement if you use spray foam, however, you need to ensure your home or building has a drain plan. The real problem we see with housewrap is that it is often installed incorrectly. Watch this video to see how it should be done.

3 – A house does not need to breathe.  Build them tight, ventilate them right. Most homes are not too tight; windows leak plenty of air. We do recommend installing Air to Air exchanges properly calculated by a professional.

4 – A small insulated area can make a huge difference in heat loss or gain.  (This also leads into 6 – Ductwork is important.) Missed areas can cost you big in performance!

5 – The quality of processes, more than the quality of products, determines the quality of the house.  Just because you spend a lot of money to install spray foam insulation does not mean it is going to work well with your home’s systems. You get what you pay for. Make sure you work with an experienced contractor who has a solid understanding of building science and the proper products and equipment to complete your installation right the first time. It is an investment that will pay off for years to come.

8 – Duct systems should not be in unconditioned attics, especially in hot climates.  Running ductwork outside of the thermal envelope is like taking a shower and then running around the outside of your house to get a towel. It puts the heated air into an unheated environment and then back in. Ductwork is usually only insulated to R-6; Zone 5 requires R-49 in the attic. Does it make sense to insulate duct work in an attic to only R-6 but the attic to R-49?

If you have questions, give us a call anytime – we would love the opportunity to share our education and experience with you!

Spraying in the Cold: Leave it to the Pros

Proper training and equipment is need to successfully install spray foam insulation in cold weather.

You can count on Iowa Spray Foam’s experience and equipment to complete your job right – regardless of weather.

As we get into the cooler seasons of the year, folks often start thinking about improving their home insulation to keep the heat in and utility costs down. While this is a natural line of thinking and certainly a good time to get your home sealed well, there are some points related to adverse weather homeowners need to keep in mind with respect to spray foam insulation.

Most foam insulation contractors will limit spraying conditions to above 40 degrees to 50 degrees surface temperature. When you spray in cold conditions you have to adjust the equipment and techniques to get a good form. All of our contractors participate in a 32-point training with sections devoted entirely to product knowledge and equipment. You can trust our team to know how to manage your project appropriately, regardless of adverse weather.  We have mobile units designed to heat and process the chemicals to produce their maximum yield.

SPF from Iowa Spray Foam can be applied any time of the year.

In cold weather it is important to maintain adequate SPF material temperature to ensure proper metering and mixing of the components.

Other spray foam equipment operators might buy lower end equipment that doesn’t have the heating capacity to spray properly in inclement conditions. Care should also be taken to store the products within the manufacturer’s suggested temperature ranges. When this doesn’t happen, the chemicals in the foam can degrade and change viscosity, making the foam difficult or impossible to apply correctly. The same goes for the equipment. Not everyone stores their equipment indoors like we do. It takes extra time and energy for these steps, but we feel they are critical to ensuring the best application for each project.

Having the knowledge and experience is what sets us apart. We have successfully sprayed well below zero in many applications. If you have questions about your project or want to learn more about our products and how they could benefit the function of your home, give us a call. Wishing everyone a safe and Happy Halloween!!