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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.