Spray foam is one of the most talked about insulation products. Mesmerizing videos of
expanding spray foam are widely shared on social media. DIYers recommend it for tiny homes,
van conversions and shipping container homes.
New homes in the suburbs are also moving from traditional insulation to spray foam.
In this video we’re going to discuss how open and closed cell spray foam insulation is made,
their performance and properties. We’re going to find out if one is better than the
other and where you should use them. Both open and closed cell polyurethane
spray foam is made of 2 parts. Part A contains very reactive,
low molecular weight chemicals called isocyanates which have a nitrogen-carbon-oxygen group. These
can be methylene diphenyl diisocyanate and polymeric methylene diphenyl diisocyanate.
Part A is standard for all manufacturers. Part B is a proprietary blend of chemicals that
provide unique properties in the foam. This part differs from one manufacturer to another. It
contains a polyol which is an organic compound containing hydroxyl or OH- groups.
It also contains initiating catalysts which help the reaction occur,
curing catalysts that allows the reaction to continue to its completion, flame retardants
that prevent the start or slow the growth of fire, blowing agents that form the gaseous part
of the foam and surfactants that reduce surface tension of a liquid and encourage foaming.
When the two parts come into contact with each other, an exothermic reaction begins,
heat is generated and polyurethane bubbles are formed. This is a simplified equation of the
chemical reaction. In open cell spray foam, the bubbles rupture, leaving behind only the struts or
the points at which two bubbles touch each other. In closed cell insulation, the bubbles don’t
rupture, creating interconnected closed pockets with trapped blowing agents. Open cell spray foam
uses water as a blowing agent while closed cell spray foam needs a chemical blowing agent.
The environmental impact of closed cell foam used to be a concern in the past,
but thanks to strict EPA regulations, companies now use blowing agents with an
incredibly low global warming potential of just 1. I recently visited Ambit,
a spray foam company in Dallas to see how both open and closed cell polyurethane spray foam
are manufactured. I met their chemists and toured their research lab, and manufacturing facility.
It was an incredibly educational trip. They also gave me these samples to experiment with
and review. Let’s now discuss some of the properties of open and closed cell foam.
Open cell spray foam expands over 100 times its liquid volume
so it can insulate hard to reach nooks and crannies. It is oversprayed and then shaved down.
It is soft and flexible. It has a low compressive strength and can be easily punctured and pierced.
Closed cell spray foam expands about 30-40 times its liquid volume
so it is good in tight spaces, where space is an issue.
It is undersprayed because it cannot be shaved down easily. It is hard and doesn’t compress.
Open cell density 0.4 to 1.2 pounds per cubic foot while closed cell spray foam has a density of 1.75
to 2 pounds per cubic foot. Lower density means a higher yield. You can get a lot more coverage
of open cell foam than closed cell foam for the same volume of raw ingredients.
Both of these products are very good insulators. They have a high R value which is a measure
of resistance to the flow of heat. The higher the number, the greater the insulating power.
Because it doesn’t contain any trapped air, open cell spray foam has a lower R
value of 3.5 per inch. Closed cell spray foam has a higher R value of 6 per inch.
Remember that the R value test ignores the very important air sealing properties of spray foam.
We discussed this in a previous video, I’ll link it up here. If applied correctly,
both open and closed cell spray foam will act as air barriers and prevent 98% of air loss.
In reality these perform far better than traditional R 3.5 or R 6 insulation.
The three main modes of heat transfer are conduction, convection and radiation.
The predominant heat transfer mechanism for open cell spray foam is conduction.
Closed cell spray polyurethane foam blocks heat transfer by conduction
because the trapped gas is a poor conductor.
Unlike traditional fiberglass insulation, both open and closed cell spray foam prevent heat
transfer by convection currents or air movement. 3.75” of properly applied open cell foam
creates an air barrier compared to 1” of closed cell foam.
Finally, radiation which is the transfer of heat through electromagnetic waves.
When installed under a radiant surface, such as a hot roof,
the interior surface temperature is significantly lowered, thus lowering the radiant heat load.
Open cell foam has a perm rating of around 15 for a 2” depth so it cannot block water vapor. Closed
cell foam acts as a vapor barrier when thick enough, over 1.5”. It has a perm rating of less
than 1 perm for a 2” depth. Spray foam systems do not require a vapor retarder in southern
climates. In northern climates the need for vapor retarders and vapor barriers increases.
To test the water resistance of open cell foam, I poured some water mixed with a green dye
over it. The liquid immediately seeped through the gaps and the open pores. Open cell foam is
moisture permeable, meaning water can move through it but its performance depends on the brand.
Some retain only 5 percent of its weight in water, while cheaper brands retain as much as 75 percent.
Closed cell spray foam, on the other hand, is 100 percent moisture impermeable,
meaning it doesn’t allow water to move through it.
Liquid seeped through some cracks, but most of it just puddled on the top.
While the closed cell foam might sound like a better option, open cell foam can be better on a
roof deck. If a leak were to occur the foam would be discolored and it could be quickly repaired.
Closed cell foam will conceal the leak until the water builds up somewhere else
and causes much bigger problems. Before we move on to their surprisingly poor
fire resistance, I’d like to talk about the sponsor of this portion of the video,
Insulation4US. They are the largest US online retailer for insulation products. They ship
nationwide with over 800 locations in their huge distribution network.
Insulation4US is cheaper than big-box retailers and they offer a $60 flat shipping fee
on 80% of all products. Brands such as Owens Corning, Rockwool, Hunter Panels, Rmax, Kingspan,
Handi-Foam Spray Foam, Bubble Wrap and more are available online to purchase today and to
be delivered directly to your job site. Use Promo Code Belinda5 to receive an additional 5% discount
off your next order with Insulation4US.com. When open cell foam came in contact with
the flame, it immediately caught on fire and started to smoke. However,
the flame did not spread, and it was extinguished the moment I pulled the fire away from the foam.
Closed cell foam also had surprisingly poor fire resistance.
Both open and closed cell polyurethane foam are thermoset materials. They will char and flake when
burned, but will not melt and drip like a foam coffee cup. They meet Class I fire standards,
they have a flame spread index of less than 25 and a smoke developed index of less than 450.
As you can tell, their performance was very disappointing compared to Rockwool
or other mineral wool insulation. It is also plastic, so the smoke can be toxic.
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.
Finally, let’s discuss some uses of open and closed cell spray foam.
Open cell is good for soundproofing. It has about twice the sound resistance in normal
frequency ranges as closed-cell foam. Open cell foam is future-proof. If you need
to renovate a house or run new wiring, open cell spray foam is going to be much easier to
work with. Closed cell foam’s rigid structure and durability make it ideal for exposed walls
because it won’t be damaged if it is bumped by machinery or tools.
High density closed cell spray foam insulation can reinforce exterior walls when sprayed in
stud cavities. The National Association of Home Builders has shown walls installed with
closed-cell spray foam have a racking strength up to 300% greater than walls without it.
Open cell is better in warm climates where the inside of the structure needs to be kept cool.
In the states, that includes climate zones 1 to 4. Since it is vapor open, it allows homes
to dry out, preventing condensation and mold. Closed cell foam which has a higher R value is
better in cold climates when the inside of the structure needs to be kept warm.
In the states, that includes climate zones 5 to 8 and marine 4. Open cell foam should
not be used below grade, like in basements, because it is susceptible to water damage.
Flash and batt insulation is a hybrid system where closed cell spray foam and fiberglass are both
used to insulate a space. It is more effective than just fiberglass and less expensive than all
closed cell spray foam. It is not recommended to use open cell foam for this application.
I wouldn’t say one is better than the other. Your project, budget, location and other variables will
determine which spray foam is best for you. They offer many benefits to traditional insulation,
but they also have many drawbacks like risks to the environment and our health. I’ll discuss all
of them in my next video, so hit that subscribe button, notification bell and the like button
too. I’ll 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. Thanks for watching. See ya.