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In my last video, we discussed the differences  between open and closed cell polyurethane spray  

foam. Their chemical compositions, physical  properties and performance. Today, we’re  

going to cover the pros and cons of both types of  spray foam. I’m going to incorporate your feedback  

and answer your questions from the previous  video. I’ll also discuss the one thing that  

absolutely terrifies me about this product. Let’s start with the advantages of spray foam.  

R VALUE R value is the measure of  

resistance to the flow of heat. Open cell foam  has a good R value of 3.5 per inch, but closed  

cell foam has an excellent R value of 6 per inch.  However, the R value test ignores the air sealing  

properties of spray foam. It positively  impacts all three forms of heat transfer;  

conduction, convection and radiation. Spray  foam is a high performance insulation product  

that is superior to traditional insulation. AIR SEALING  

1 to 1.5 inches of closed cell foam can act as  an air barrier while 3 to 3.5 inches of open cell  

spray foam acts as an air barrier. When applied  properly, it can improve the air quality in a  

building. It creates an airtight building that  keeps moisture, allergens and other airborne  

contaminants out. It can seal all gaps, even  in awkward areas and hard-to-reach places.  

Spray foam can stop uncontrolled air  leakage, which is the main source of  

energy loss. ENERGY SAVINGS  

It can lower utility bills in your home by keeping  conditioned air inside. It is estimated to reduce  

heating and cooling costs by up to 40%. It has  been called green or environmentally friendly  

because it reduces energy consumption,  greenhouse gas emissions and the HVAC  

requirements of buildings. CLOSED CELL FOAM  

Closed cell foam is impermeable to water. It can  protect attics and crawl spaces from moisture.  

It can reinforce exterior walls and increase  overall structural integrity of the wall assembly.  

It makes them more rigid and more resistant to  compression and shearing force. It can increase  

racking strength by up to 300%. Closed cell foam  is good in areas prone to severe weather like  

flooding, storm surges and high winds. LIFESPAN  

Spray foam has a long lifespan of up to 80 years.  It has a lower thermal drift or loss of R value  

over time than traditional insulation. It does  not sag, settle or deteriorate and is expected to  

outlast the life of a building. It also is  not a source of food for pests, rodents, mold,  

mildew and bacteria. EVOLUTION  

The spray foam industry is constantly evolving  because it is under unrelenting scrutiny. It  

used to be made with greenhouse gases that  contributed to the depletion of our ozone layer.  

Gases like CFCs or chlorofluorocarbons and  HCFC or hydrochlorofluorocarbons. Fortunately,  

they are not used anymore. Open cell foam  uses water as a blowing agent and closed  

cell foam uses a chemical with a very low  global warming potential of just 1.  

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first purchase of a website or domain. Now the disadvantages of spray foam.  

COST Spray foam has a high upfront cost, around 3  

times more than traditional fiberglass insulation.  The cost of both open and closed cell foam  

has fluctuated wildly over the past year because  of raw material shortages and supply chain issues.  

A rough estimate is 50 cents to 1 dollar per  board foot of open cell spray foam and $1.5 to $3  

for closed cell foam. A board foot is a  12 by 12 by one inch volume of material.  

However, it is important to remember that you  could see a pay back in less than 5 years thanks  

to the s energy savings SOUND  

It’s not a very good sound insulation product.  Open cell foam is 97% air by volume so it has  

some soundproofing potential but not as much  as you’d expect. Unfortunately, it traps  

soundwaves and creates a resonating chamber  that seems to amplify mid-range frequencies  

which are disruptive. The hardened foam also  binds layers together which couples the wall  

elements. This can increase sound transfer. STC or Sound Transmission Class is a rating of  

sound isolation in a wall assembly. The less  sound measured going through, the greater the  

transmission loss, and the higher the numeric STC  rating. Closed cell foam has an STC rating of 36,  

while open cell foam is 37-39. Far  lower than rockwool or fiberglass.  

NRC or Noise Reduction Coefficient rates how  well a material absorbs or reflects soundwaves.  

The greater the value, the better the  material is at absorbing or reflecting sound.  

Once again, spray foam’s NRC rating of 0.7 is  lower than that of rockwool or fiberglass.  

R VALUE Since the R value test is biased towards  

fibrous insulation, the spray foam may not meet  the minimum code requirements. Installing 4  

inches of open cell on the roof and 3 inches in  exterior walls isn’t enough in many cases.  

THERMAL BRIDGING If you don’t use a  

layer of continuous insulation on the outside of  a building, and only spray foam in between studs,  

those will act as a thermal bridge and reduce  the overall performance of the wall assembly.  

PERMANENCE Scheduling spray foam is tricky because it must be  

applied after electrical and plumbing work because  once it is in, you can’t make any changes. Spray  

foam adheres to the substrate it is sprayed on and  cannot be scraped off easily. Any renovations to  

the building’s structure in the future are going  to be very difficult. I predict an HGTV series  

30 years from now that centers on the destructive  removal of spray foam in flipped houses.  

ENVIRONMENT Polyurethane spray foam is plastic, so  

many people think it is as bad for the environment  as single-use plastic. They don’t realize that it  

is a long-term use plastic that plays a  vital role in the decarbonization of homes.  

It is not biodegradable and will head  to a landfill at the end of its life.  

But so does contaminated fiberglass, rockwool  and other traditional building products.  

The difference is that spray foam lasts much  longer, and provides greater benefits during  

its life. FIRE  

Neither open cell nor closed cell spray foam are  fire resistant. However, they do have some flame  

retardant chemicals. They charred and burned but  the flame was extinguished as soon as I pulled  

the fire away from it. BUILDING SYSTEM  

A building acts like a system. Replacing  one component will affect others.. While  

new homes can be designed to take  advantage of spray foam’s qualities,  

existing homes may not. Homes with a gas furnace,  fireplace or water heater draw combustion air from  

the attic. But if the attic is sealed with foam,  those appliances will not work properly and they  

can be very dangerous. Many people with sealed  attics have noticed that vent hoods don’t work,  

the bathroom fan doesn’t pull air out, and that  wet towels don’t dry. The humidity levels inside  

such homes can be very high. Spray foam needs  an ERV or energy recovery ventilation system,  

a fresh-air ventilation system or a dehumidifier  to draw clean, fresh air into a home and remove  

stale air. HEALTH  

PPE or personal protective equipment  is vital when using spray foam.  

Exposure to spray foam before complete curing  can lead to asthma, sensitization, lung damage,  

breathing problems, skin & eye irritation.  You must also wait 24 hours after application  

before entering the space without PPE. PREPARATION  

Spray foam is a very finicky product. Meticulous  preparation is very important. You must make sure  

the substrate is dry. Spray foam can pull back  from the studs if it comes in contact with oil,  

grease, dust or other contaminants. Technique  is important too. If spray foam is undersprayed,  

it pulls away from sides, allows air infiltration  and reduces R value. Overspraying can lead to  

messy floors and damaged studs. RATIO  

The ratio of raw materials is very  important. Most spray foam systems  

have a mixing ratio of one-to-one, or one part  isocyanate to one part resin blend by volume.  

However, since the 2 parts have different specific  gravities and viscosities, the drums may not empty  

at the same time. An excess of Part A isocyanates  will result in a glassy cell structure,  

brittleness or friability. It will easily break  into smaller pieces. The density will also be  

higher than the manufacturer's specifications.  An excess of Part B resin will result  

in soft and spongy foam with a lower density  than the manufacturer's specifications.  

SPEED The speed of reaction is important when applying  

spray foam. A reaction that occurs too fast or  too slow can affect the cell structure, density,  

adhesion to the substrate and layers, surface  texture and tensile and compressive strength.  

But the one thing that terrifies me about spray  foam is that it is not a DIY friendly product,  

despite what novices on YouTubers tell you. It is  very messy and requires a lot of experience to get  

it right. Mixing the chemicals is an exact science  with a small margin of error. Spray foam experts  

are trained for weeks on the proper methods of  spraying. They know how thick the layers must be  

and how to test whether it is curing properly.  I was told that spray foam raw ingredients have  

a shelf life of just 6 months and that they  can smell after that “best by” date. There are  

specific blends to use in summer and winter. Using  the wrong product at the wrong time of the year,  

at the wrong humidity and temperature levels  will cause delamination and improper curing.  

The cheap DIY spray foam you can buy at your local  hardware store is a watered down consumer grade  

product that will not last. Remember that  tub refinishing video I made a while back?  

The 2 part epoxy started peeling off after a year.  Well, at least that was visible. I’m worried about  

spray foam deteriorating or off-gassing  behind a wall without you knowing.  

I was on the fence about spray foam’s future in  the construction industry until I visited Ambit’s  

lab here in Dallas and spoke to the chemists.  I have a whole new respect for the product.  

Unfortunately, there are a lot of misconceptions  about it and false articles on the internet  

about how spray foam is destructive because it  releases greenhouse gases into the atmosphere.  

The industry is under constant scrutiny and  pressure. They have to spend a big chunk of  

money on R&D, compared to traditional insulation,  even though the embodied energy of the latter is  

much higher. Just like with any other building  material, spray foam has its advantages and  

disadvantages and is not right in every instance.  If long-term building performance is important to  

you then it should be something you consider.  Let me know what you think about spray foam in  

the comments below. I’ll also link my Patreon  page in the description. If you can support me,  

I’d really appreciate it. A big thank you  to everyone already supporting me. Don’t  

forget to hit the like button and subscribe  to my channel. Thanks for watching. See ya.