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What is Spray Foam Insulation?

Spray foam insulation is a cutting-edge solution for sealing homes against air and moisture intrusion, saving on costly utility bills, and minimizing noise pollution. Its unique liquid form expands into a solid cellular plastic, filling gaps with precision. Intrigued by how this technology can enhance your home's efficiency? Discover the benefits and considerations in our comprehensive guide.
Deborah Ng
Deborah Ng

Spray foam insulation is a type of building insulation that can be used in walls, ceilings, crawlspaces and other parts of buildings. It is used to keep the heat inside when it is cold outside and the hot air outside when the weather is warmer. This type of insulation comes in spray cans and is composed of resin and certain chemicals, such as polyurethane or other isocyanates. When sprayed, the chemicals and resin create a foam that expands and solidifies in place. Spray foam insulation originally was recommended to be applied by professionals, but do-it-yourself kits are now available, although safety measures are heavily advised during application.


A closeup of spray foam insulation.
A closeup of spray foam insulation.

When the foam insulation is sprayed, it coats the surface and quickly expands as it solidifies. It dries quickly, providing insulation that is relatively permanent and will not sag. If the foam expands beyond the desired area, the excess insulation can be trimmed or cut away to the desired size.


Spray foam insulation is somewhat dangerous to people when it is being sprayed. Particles can get into the eyes, on the skin or breathed in through the mouth and nose if proper safety equipment and clothing are not worn. The chemicals can irritate the eyes and the respiratory system and can cause inflammation or rashes on the skin. It is recommended for a person to wear goggles, a breathing mask, gloves, long sleeves and long pants when spraying foam insulation.


Spray foam insulation on a house.
Spray foam insulation on a house.

Like any insulation, there are pros and cons to spray foam. Spray foam insulation is more expensive than fiberglass insulation. The process isn't neat, and the foam can be accidentally sprayed into places other than the intended target. If too much insulation is sprayed in, walls that are thin might buckle as the foam expands. Safety also is a concern for anyone who is attempting to apply this type of insulation.


Polyurethane foam insulation.
Polyurethane foam insulation.

Cost and cleanliness aside, there are clear benefits to using spray foam insulation. As a spray, it can get into and fill tiny nooks and crannies, providing better insulation. This can eliminate drafts and keep the building warmer when it's cold. No cold air can escape in the summer, either. These advantages can help lower the building's utility bills. By filling cracks and crevices, foam insulation also helps keep bugs and vermin from getting into the building, which can help save on extermination bills.

Safety goggles and a breathing mask should be worn when performing spray foam insulation.
Safety goggles and a breathing mask should be worn when performing spray foam insulation.

Spray foam insulation also adheres well to surfaces, so it can stick to the inside of walls or can be applied to the underside of floors and insulate from underneath. Homes that are insulated with spray foam often have a higher resale value than those that use fiberglass insulation or other types of insulation. There are environmental advantages as well; most notably, there aren't any fiberglass particles floating around in the air. Spray foam insulation also does not cause itching when it is touched, and it inhibits mold growth because it doesn't absorb water.

Insulation Projects

Spray foam insulation expands and solidifies when applied.
Spray foam insulation expands and solidifies when applied.

Do-it-yourselfers can purchase cans of spray foam insulation at most home improvement stores. Along with normal uses for insulation purposes, it also can be used to fill cracks around doors and windows as well as gaps around pipes and fixtures. If an insulation project is too large or difficult, however, it might be in a person's best interest to call in a professional. This might be more expensive, but it usually will ensure that the job is done properly.

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Discussion Comments


The whole problem of this post, although I'm sure it's to help inform everyone of these issues, is, how would one know who knows what their talking about and who's throwing the proverbial bullcrap?


The problem with someone having spray foam installed is that they are changing the gain and loss load of the home. If your home's load calculation was 36,000 BTUs, which equal three tons and you have a 3 ton system installed, then your air conditioner, which is a dehumidifier, will run enough to be able to remove moisture from the home. If you greatly change the insulation values in your home and don't need a 3 ton, but instead a 2 ton, for example, but keep your 3 ton system, you have an oversized system. This oversized system will run a lot less and since it is oversized, will run much shorter cycles, and not have the run time required to remove moisture from the structure, so if you change the load of your house you need a new load calculation performed on the house to see if your system is still sized properly.

Also, your a/c does not dump moisture from your house into your attic as a previous poster stated. That is just nonsense. Air from inside your home is pulled through your filter returns across your a/c evaporator coil. The coil is very cold, so moisture in the air that is going through the coil reaches the dewpoint and runs down the coil into the coil drain pan and into the trainline on the coil that exits the house. The then-dehumidified air comes back into the house through the supply ductwork/or supply air grills. So your hvac system takes moisture from inside your house and dumps it outside. It's like taking a Coke out of the fridge and walking outside in 95-degree weather. Moisture from outside will reach the dewpoint on the outside of the can, so the can will sweat in your hand. So you recently removed moisture from the air around the can.

Also hvac systems don't remove moisture from areas they don't condition, like attics or moist crawl spaces. That's why some contractors are starting to seal crawlspaces under new homes and semi conditioning them, so there is no moisture to condensate on duct work surfaces or to be absorbed by wood subflooring.


150894 - Read about "Rising Truss Syndrome."


Anon4303 is correct except for the part on exhaust fans.

Negative pressures are never OK, create IAQ problems, and are dangerous. Exhaust fans without makeup air should never be used. Building pressures should be designed as neutral or slightly positive. Infiltration is always bad, but a slight EXfiltration is OK if the air is filtered and conditioned.

Using an exhaust fan without makeup air produces negative pressures. In a “standard” built house using fiberglass, the makeup air ends up coming from infiltration. This infiltrated air carries moisture, mold spores, pollen, and other outdoor contaminants. Even the fiberglass fibers themselves become an indoor contaminant and allergen. The home now becomes a “vacuum cleaner,” concentrating these pollutants within the home over time. Further, the fiberglass acts as a filter, and ends up holding some of the moisture and mold spores that have infiltrated through. You've created a “diaper” in your wall, and you know what diapers hold. Misapply a vapor barrier without an integral thermal break, and you've also created a pretty nice condensation plane for the infiltrated air.

In a truly “tight” home, such as when spray foam is used, different problems arise when only exhausting. You've solved the infiltration problems, and infiltration is never a good thing, but you've created other problems, potentially just as dangerous. As was mentioned with the standard home, an exhaust fan will create a negative pressure, but in this case, where does the makeup air come from? It has to come from somewhere! You can't suck air from a bottle! So either you end up exhausting much less then you think, or the air comes from somewhere, and it does: from chimneys, fireplaces, flues, plumbing fixture drains and vents; yep, an equally hazardous situation. You may also see condensation around defects in the construction you might never have otherwise seen, as again, the air has to come from somewhere.

In both of these situations, the problem is solved by first, always providing positive combustion air for all fuel burning appliances. This is required by the mechanical code for a reason; obey it. Second, *never* exhaust without providing an equal or slightly positive amount of filtered and conditioned makeup air. Using dedicated ventilation systems such as HRV's or ERV's make this simple.

For those with chemical sensitivities, or homes that have IAQ problems, these can be mitigated by keeping the building under a slight positive pressure with fresh clean air, maintaining a slight EXfiltration. If your building is leaky (which most are) this won't be cheap on your energy bills, but you will have a healthier home.


@anon229957: You need to learn what a convention current is and why it transfers heat. Not all insulation is about air gaps.


For the argument that spray foam seals a home too well, why don't you consider what is actually inside the home? It's 100 percent sealed sheetrock with baseboard moulding, with spackle and with caulk. If you can breathe through a sheetrocked room the size of a coffin and not feel ill, then maybe you are on to something. Homes have always been airtight. You are arguing about the air that we do not breathe. I'd rather seal it so that mold can't grow and I have better insulation.


I am remodeling part of my house and had closed cell spray foam applied about 1.5 weeks ago. It still smells. Is this normal? I have been trying to ventilate but with the hot weather the air has been on. I am concerned if this is an issue. Was it applied properly? Did it cure properly? Was it applied too thick? Can I cut out a portion to see if there is a problem?


Build tight and ventilate right.


Spray foam is sprayed between the joists. Would the moist air not travel through the joists and to the outside?


the original problem of the walls inside moving or buckling is caused by the contractor putting the drywall on before the foam has fully cured and expanded. until the foam has released all its gas, it will keep expanding to a degree. the contractor needed to leave enough of a gap for the foam to have somewhere to go.


My husband and I built a house this past year and we used foam insulation in the walls, on the roof ceiling and under the floor in the crawlspace. I will say it keeps your energy bill down; however, we used trusses and the foam has somehow made our house so tight that the trusses (I don't know) can't breathe. Now the house moves-- the walls move up and down from summer to winter. One of our walls sitting on the bottom floor of our 2 story house raised about 1/2 inch off the floor.

We have the same problem with our ceiling above the attic (the wall came off the roof truss and the sheetrock tape has came off. Everything was inspected and built to code. We used the same trusses on our previous house we built 2 years ago, but did not have this problem with regular insulation. So I don't know how well this foam stuff really is, considering the minor damage it causes. The outside walls pull away from cabinets, and other walls. Just to answer-- no it is not the foundation.


I have fiberglass insulation in 2x6 outside walls. Cut a hole through "vapor barrier" to run wires and the back of the sheathing was frosty.

Why?? Condensation..If I spray foamed no air would hit the sheathing and no frost would form.

I'm in HVAC and all you need is an air to air exchanger. Problem solved. Brings fresh air in and exhausts stale air. Wish I had built this house because it would all be spray foamed.


I leave in central texas where the humidity is extreme. I am feeling a combo of wall foam with a blown in attic that is vented is the way to go. Any thoughts? --JS


Save yourself some worries. use fiberglass insulation in walls, blown-in insulation in your crawl spaces, and spray foam (great stuff by dow) around all of your plumbing and wiring projections and other holes, nooks and crannies. coupled with proper caulking around windows and doors, foam pipe insulation around your water pipes and foam gang-box insulators, your house will be very efficient and still be able to breathe. the end.


No matter what type of insulation is used in your home spray foam or otherwise, it is extremely important to exhaust air from the living area. Just the fact that people are living in the home washing clothes and dishes, cooking and showering, and not to mention breathing, emits a large volume of moisture. Any moisture in the home has the potential to create mold.

The home's humidity levels are safe around the 30 to 50 percent level. Any higher than 50 percent and your run the risk of mold, any lower and you run the risk of cracking hard woods, and breathing issues. Do yourselves a favor and put a hygrometer in your home. They are about twelve bucks at Radio Shack.

Always use exhaust fans and dehumidifiers if need be, and hey, remember, sometimes the humidity is higher outside so just opening a window doesn't cut it.


re new home in 78572 with spray foam. Home walls are brick with 2" gap to 2x6 vented through soffit. Roof is clay tile. Thanks


I install foam for a living and the only thing it's hard on is the installer, and if you don't want it then good but if you do great. And your house will still breathe through the vents in the roof.


I am a mechanical engineer with 35 years experience in engineering and construction. 98 percent of the stuff written here is mostly conjecture and not proved on any true facts. If I were to take the advice from these posts, we would all do better to just live in a tent.

Anyone adding foam, open or closed cell, to an existing structure better hire an engineer to properly size and balance things. Do not go to an architect because they are not educated in this field.

Moisture moves due to pressure differential between the inside and outside of the structure. Sealing up a structure has serious building and health considerations. Do not depend on Bubba or the guy doing the install for your technical guidance. Hire an engineer and let him/her design your total system. He/she will have to put their PE license on the line and they are prepared to do so. The biggest waste of energy is Bubba the HVAC contractor sizing HVAC equipment and installing crappy ductwork.


I am having a house built with closed cell spray foam of two inches and then fiberglass batts over that. Also will have a complete air to air exchanger, radiant heat and low temp radiator panels. My understanding, super efficient. Comments?


I have a client that sprayed foam one year ago. The home was inspected and mold free at the time. One year later the entire crawl space is a petri dish. Does anyone have any suggestions on removing foam or cleaning mold on it?


You are all right and wrong. Spray foam is the future of insulation, but it must be done properly. There is a huge debate right now over "hot roofs". Now you haters know what to call the application you're hating on.

The key to using spray foam in your entire house is sealing the thermal envelope. When you vent a hot and humid attic with hot and humid air, you still have a hot and humid attic. When a house is impermeable to air and moisture, there is no dew point. The attic space is typically 8-10 degrees warmer than the conditioned space below as it is now semi-conditioned.

Firestopping/sealing all penetrations between floors prevents convection and caulking plates, band joists, sistered studs, etc. eliminates other sources of infiltration. When you use SPF, you save money because not only do you run your hvac less, you are able to use smaller systems to achieve the same level of comfort.

If you're still unconvinced you either can't convince your wife to spend 30k+ insulating your house or you enjoy venting money into the lower atmosphere.

On a side note, spray foam is highly toxic when being applied. If you want to "check it out" while it's being applied "cause it looks cool" or simply because you want to see why you're paying so much for insulation, you must have a mask with organic vapor cartridges, as well as eye and skin protection. Some people can have severe allergic respiratory reactions from being around the vapors. The stuff will kill you eventually if you're not careful.

Once cured and the vapors gone, it is as harmless as your dashboard or $10 boogie board.


I just purchased a house built in 1930, with balloon framing, no insulation in the walls, and lots of leaking through the roof. Despite the leaking through the roof, the house is mold free, because it breathes.

At one point, I was going to use foam insulation on the walls, and like many who posted here, I now believe this can be a mistake as it will take away the ability for the house to breathe, and likely create mold problems.

So, this is another vote for being careful with insulation. What you save in energy costs you may lose in replacement of damaged structures.


Because of the extremely high price of foam insulation, it should be used only where installation is difficult and space is limited, such as within existing walls. You can very easily and cheaply insulate your attic with blown-in cellulose.


Skelly makes sense to me in #17. Here are my observations: You have a totally enclosed, encapsulated structure. In fact, we have fixed windows in all areas except where we must by code have single-hung windows for egress. We might get a little draft from doors and the few windows, but it is really sealed if we use foam from top to bottom.

So, now, let's look at the inside environment. Pipes, whether you use copper or PEX, have fluid running through them that is at a different temperature than the air around it. They will generate condensation. You have an air conditioner that lowers air temperature by removal of humidity in the air. This occurs in our attic in the coils or the heat pump in our case. So the A/C is pulling humidity out of the air, but a lot of it escapes in the attic where it is removed--that is why attics are often more humid than outside or in the living area. So there is two sources of humidity.

Next, let's say that the air in the attic is less humid than outside. That creates a differential humidity, and physics dictates that like osmosis, if there is less water inside than outside, it will pull moisture from the outside, by wicking it through any wood that is exposed to both the inside and outside. Now, all this moisture is inside of a trapped environment with no way to vent off the humidity, so it builds up, or comes to rest, or otherwise stays, on the wood surfaces--your interior wood framing, paper backed sheetrock exposed in the attic, etc. Inside the house, you are generating tons of humidity by using hot water in sinks and showers, cooking, whatever. Can you turn on a vent fan? Absolutely! But I ask you this: If it is a sealed house, how can you vent inside air out without replacing it with outside air?

Your HVAC can have a fresh air system on it, but that isn't going to prevent a vacuum from being created when you turn on a vent fan. So the fan runs, but not much air is leaving because it can't draw air in to replace it in such a tightly sealed house. Okay, so you get a nice 16 SEER A/C with a two speed fan, and it runs on low for 30 minutes per hour, which removes the humidity, right? Where is that humidity going? Into your attic, which makes it more humid, and then back into the house, or further rotting the wood in the attic. Plus, think about how much humidity is there when you take a shower--that is a heck of a lot of A/C for the entire house to dehumidify one room every time you shower or cook. And the vent fan is back to a negative-pressure problem. What does a vacuum cleaner do when you block the nozzle? Does it quit running? No, it speeds up, because it can't get air from anywhere and so it loses suction.

So basically we are talking about a trade off: getting a house sealed from dust and pollen and everything bad, not letting much cool or hot out, but countered by a problem of humidity handling, which requires a massive amount of forethought and expense to get fresh air in so you can vent out the humid air you don't want. And then you are introducing pollen and dust and other stuff. I suppose you could open any window in the house every time you turn on a vent fan and it wouldn't draw a vacuum and the vent would work, but I don't think my skinny little wife is going to dig me opening a window when it is roasting/freezing outside (we're in Texas after all).

So what about if you use all foam, so it doesn't settle like blown fiberglass (Spider), and has a decent R value, and seals better than other insulations, but we put all the vents in like normal (ridge vents, soffit vents, attic fans) to keep that humidity moving out of the house (in the soffits-out the vent fans--no vacuum). With a source of air from the attic, the inside vent fans will work as well.

Am I missing something here, socratically speaking? Is my logic flawed? (please don't even answer that if you sell foam insulation, because my experience is you are so brainwashed that you are incapable of anything but toeing the party line of "give me foam or give me death!"


we have been in the foam business for seven years now and our customers love it. It's nice to go into your attic at 84* when its 104 outside.

And what's with all this your house needs to breathe hot air? fresh air intake systems are controlled through your HVAC. In 10 years spray foam will be in 80 percent of custom homes. Use spray foam America and save 30 percent to 40 percent on your power costs.


I have been thinking about spray foam and its effects on the wood framing for some time now.

I fear that the performance of the foam with force moisture migration to the outside through the framing itself. this moisture will condense at the dew point somewhere in the wood studs (or roof joists). This could rot the stud prematurely.

If you add a vapour barrier to the system, it might help but stopping moister from getting into the wood, but it might cause dry rot since now any moisture humidity in the wood has no where to go.

I am hearing that .5 pound foam is more permeable and will allow a minor amount of moisture migration, and that they recommend a semi permeable Latex paint "membrane" on the interior face of the wall.

the system described above makes some sense since it allows the wall framing to breath to the inside a bit as well as to the exterior through the building wrap.

I have also heard that a layer of 1.5" insulation board R5 on the outside of the sheathing board makes a huge difference because it moves the dew point to outside the sheathing plane in most climates and therefore totally eliminates moisture condensation and that stops migration since no moisture is changing state.

Any comments or discussions on any of these assemblies should be appreciated.


Spray foam is truly a new and better insulation material than some might think. i have found some excellent ideas for spray foam for my home online. it is a product that has its faults but what product is perfect?


I have spent most of my life in the construction trades. Repairing and remodeling and all the other bright ideas that were introduced through the years.

I will hold my breath and spare your ears from the disasters being introduced over the years. It has made me skeptical to the point of doing my extensive research.

As far as spray foam/closed-cell and specifically on the back sides of rafters. I would reserve some caution to this procedure.

Conditions and observations:

1. Overheating of materials/ expansion and contraction/ sweating.

These are some serious topics that are being passed on by most of the above comments in previous posts. Yes it does wonders for insulation and R value standards. But this still does not answer the observations and conditions.

So when someone tries to answer a dryrot/sweating/overheating problems that "will" occur if it is applied to the back of roof sheeting/rafters without addressing the issues, then its very questionable.

I spent a lot of time researching this topic and everyone that is usually in favor of this application method is ignorant of the issues or is selling the product.

In 15 years the application companies that sprayed foam will probably not be in business and an entire roof replacement is going to be on the homeowners tab.

Insurance does not cover mold,dry-rot,wet-rot.

Knowing how much "sealed" wood I have personally replaced over the years I would be cautious as to the concept being tried and true.

For someone to say it is, then I too have a bridge to sell you.

Spray foam has been around in residential construction for over 25 years, but its application processes have changed.

IE: Florida siding panels or MDF -- was approved by the agencies and was pushed very hard by the manufacturer. Unfortunately simple logic in many minds ($$) did not win until it was too late.

Lawsuits and code changes adapted to this product as it was banned in Florida mid early 1990's. So everyone was saying this was also a fantastic product, but moisture and humidity won out over lack of common sense.

Who gets to replace all these bad products and procedural methods that only the newbies in the industry are selling different colored bridges? Not them for sure. They are long gone with your money and you're stuck with a experimental product and or a bad application process.

Yes building structures "breathe" and "move." The concept is like a living thing. Basic principles are always thrown out the door with new products, which is a failure to understand the basics of materials for longevity.

Go to Europe in some areas to fully understand this concept on structures 800 years old made of wood. We lose sight of the basics in the glare of technology.

I think the sprayed foam is a fantastic product but its application methods need serious refinement as we will see in the near future of closed cell application, and it won't be pretty.

There are applications of foam that respect a structure to vent/off-gas yet keep a conditioned attic but is not being used in 99 percent of its applications.

So I would not have it blown on my rafters except keeping the venting principle in play. I would use the product on my own home but in a veryY different application method than what is currently being used today.

Remember even the surgeon general in the 1950-1960s were recommending in magazine ads what type of cigarettes they smoke? Well 30 years after that blunder we know better. Common sense won over again in the end. --Skelly


Simply said: There are two thermal dynamics at work when it comes to heat buildup and humidity in a home. Compounding heat takes place when radiation, conductivity and convection can all interact with each other in an enclosed environment devoid of enough airflow potential to sustain rapid relief.

Humidity buildup is also a compounding process that takes place when temperature extremes of hot and cool are allowed to clash. Basically, when the sun comes up and hits the roof, two things happen at once.

First, the roof gets hot (conduction), the attic gets warm (radiation) and the air in the attic beams start to expand (convection).

Second, the air that's in the attic from the night before (usually 60 percent more humid than the air of the day) is now subjected to that heat oppression and the insulation blanket becomes impacted with heat of the day. This of course leads to both an unbearably hot attic and a wet attic through out the day. The humidity is not born from inside the building envelope, it is coming at the structure from outside, and therein lies the problem.

Foam is an incredibly good insulator but it's still thermal mass and its heat reflectivity and absorption rate are dramatically better than traditional insulation products. But that's only half of the issue. Foam will retain that heat gain roughly 70 percent longer and that means once it's hot (usually about eight days of 100-plus temperatures) it never cools off, and your air-conditioner is now fighting 110 degree attic temperatures because of your insulation.

What's worse? The water has no place to go but into your wall studs and rafters. There's no doubt AC costs will go down with an encapsulated insulation blanket, but the cost for having it is unbelievable. P.S. Check out solar powered fans for a whole different idea.


I echo the concern of post #10. A company has proposed spray-applied closed cell insulation on the underside of the roof which also seals all venting in the attic. We have been told by professionals that eliminating attic venting in Florida is subjecting the attic space to the possibility of mold later. The attic venting has been tried and true for years in Florida and we are skeptical about this foam application on our older home. Would appreciate further input from roofers, engineers, architects, inspectors, energy experts. We have tried to back out of our contract and are facing probable loss of our deposit.


We built an addition and had it insulated in foam, it was the best thing we ever did, that and putting the radiant heat pipes on top of the floor and not underneath the subfloor. As we can get to it, we are going to rip out the rotten fiberglass insulation in the main house and replace that with foam too including spraying the underside of the roof. I have to say, I was against doing the roof, but the difference between the addition and the main house is amazing, especially noticeable with snow. We had a professional do it, and I believe he used open cell foam, and he explained it all, and knew his stuff and we have had not one problem. No ice dams, no heating problems, no mold, no water condensation. We removed so much insulation that was riddled with mouse holes and mouse droppings. (we use to have a crawl space under the house that mice loved in winter). They absolutely love the fiberglass insulation for making their nests out of. Do this experiment, Take hold of a foam cup of hot coffee or hot tea, what do you feel- nothing right? That is how good a very thin amount of foam can insulate. Put a cover on it and watch how long it takes for your coffee to cool enough to drink. The stuff is amazing! I have to say one more thing. Builders like building the way they know how. They don't really want to learn about anything new and certainly don't like anything if it changes the way they have to do things. They want to hang radiant heat pipes under the wood underlay and tell you that it will heat the floor just as well as it would if the pipes were on top of the floor- well a child could figure out that they were wrong, but often we are convinced because we assume they know more since that is their profession. ( by the way there is a great study out now about that). The same goes with the foam, it's new, it's not the way it's been done, spraying the ceiling doesn't allow for that "cold" attic, that supposedly will stop all ice dams if only done right (except that no one ever can seem to do it right). Go with the foam, pay the price to have it done right and you won't be sorry.


I agree with tradesman1; Everything I have ever known about the proper way to build a house says that it must be able to breathe and do so in a way that allows moisture to pass from the inside to the outside of the structure. Long ago when homes were sheathed with 1 x 6 lumber, builders would butt them together and rely on shrinkage over time to provide breathing passages for moisture to pass through. Today; Tyvex is used which is a breathable product. If this breathability weren't necessary then why not wrap the exterior in sheet plastic? Moisture in the home from cooking, bathing, etc. is most often drawn out by the sun through an area of the house that has nothing to do with the location of a vent and if it can't get out it may be a source of mold. Lastly, it was not too long ago when aggressive insulating and non-breathable vapor barriers were making people ill because of the trapped chemicals in the home from furniture, carpeting and glues in sub flooring material. I believe it is only a matter of time before lawsuits are brought about that will expose the health danger caused by whole house foam insulation. Personally, I'd stay far away from it.


what a load of crap, seems all of you have no understanding whatsoever on house building.


whats wrong with sealing the house and opening some widows?


I am trying to re-insulate my attic. presently with blown-in insulation, need to bring up to recommended r-value of 39, living in florida. One company wants to put the foam insulation in the attic on the underside of the roof. What concerns me is the heating of shingles during the day that this will cause. Is this concern valid? Any recommendations. Can add cellulose to present and achieve insulation R value. Florida is not at all cool during the summer heat and humidity. -- Undecided in Florida.


As the new owner of a 30yr old, 30ft geodome with one inch of foam sprayed down and another inch of cellulose blown over it, and no walls up in the thing (what do I do now?, lol)... I've done a bit of research myself and can see the people posting are talking oranges and apples. You can't devalue one system based on the merits of another system. Simply put.

Old systems are great. But you can spray foam an attic roof without ruining the ventilation qualities in the home and increase your R. An open room with a cathedral ceiling is probably also best with foam.

If you do spray foam an entire house, then interior home ventilation is still just as important as it was before, if not more so. If you're going to believe these people can lock in a home's air and care for it with machines as if you were in outerspace, keeping you free from all the invisible things we fear... then I've also got a bridge you might want to buy. Simply put, if you're not breathing fresh air, you will not smell fresh air, you will smell something else.

We've found insulating your home is not a one point solution, but a balancing act. If someone tells you your home has to max out airflow... then somethings wrong. Likewise, if someone tells you they can seal up your home... then somethings wrong. The type of home you have will determine how much air flow, how much sealing up, etc.


A lot of seemingly valid points are raised here. Some ask what about moisture and mold. Well first we need to know where this moisture and mold is appearing. If spray foam insulation is properly installed, then there should be no cracks and crevices for moisture to form in. Filling the walls of a pre-existing home it may be impossible to be certain that every crack and crevice is filled. New construction on the other hand should have every void filled leaving no-where for moisture to form.

Now there is the probability of mold becoming a problem in the living space of the home, but as a rental property owner I can say that it is caused more often than not by a lifestyle habit instead of ventilation in the home. Case in point: I haven't seen a problem with moisture or mold in my bathroom, but I have had tenants complain about it. Upon repairing the damage, I also check the condition of the ventilation fan. I have found them to not be functional, and when I tell the tenant "the exhaust fan is broken". They sometimes reply "I didn't know, I never use it." I repair it anyway, and request that they start using it.

I have entered a newly empty unit to prepare it for the next tenant, and found the range hood to be completely plugged by grease rendering it useless. The range hood is good for removing excess moisture from a home not to mention that being plugged by grease is a fire hazard.

Those are just 2 little things that seem like common sense, but a lot of the world just doesn't get it.

I have also purchased a few drafty old homes, and begun repairs only to find that there was a moisture problem, and they needed more repairs than I had initially planned on. The damage was cause by a moisture problem, and there was no lack of ventilation. I think this is more just blaming a product for problems before giving the product the benefit of chance.


Re: Anon4303

There is nothing 'ridiculous' about a house 'breathing'. The fact is, there must be air and thermal exchange going on in a house or the thermal differentials will cause attrition while the air becomes stale. ASHRAE standards are fairly clear on this; a home must have air turnover consummate with it's volume/N-factor/inhabitants. A single bath fan is not the 'solution' when one hasn't even considered all factors. Foam insulation can make a home too tight, and it has serious drawbacks.


We recently had spray foam insulation installed in our newly built house. Some of the spray got on the exposed main wood beam that spans the cathedral ceiling. Is there a chemical that will remove it? I have tried sanding and scraping with a wire brush. The 24" beam is glued 2 x 8's x 30ft long and 17ft above the floor. Not an easy to get to project.


I own my own insulation company and I have had several customers here in South Louisiana call me with moisture problems because of foam. Most of them have been under floor, but I have had some attic and wall problems also. I have three customers that have had to rip out their entire subfloor because the foam rotted it. So to say that spray foam is the perfect insulation is outrageous and foam installers should stop lying about the truth of the matter. I also install radiant barriers and reflective foil, which my customers say is "the best bang for your buck" instead of paying 30-40% more to insulate your house. I know also a close family member that owns a company and sprayed his own house. While letting it air out the toxic and flammable fumes burned his own house down. I know for fact and have numbers to back up my statement that foil in conjunction with cellulose is the best way to go.


A traditionally built house uses a combination of a whole-house wrap, a moisture barrier, and a ridge vent on the roof to provide ventilation and to facilitate the movement of moisture out of the home. It may not be a perfect system, but it's a system that works; it has been tried and tested.

Perhaps I was not clear in my original post. It's the wooden frame of the house that is of major concern for mold, not mold within the insulation. Moisture is the only ingredient necessary to cause wood to rot. Sprayed foam insulation may be mold and moisture resistant, but the wood surrounding it is not.

To suggest that a bathroom exhaust fan would be adequate enough to remove moisture from a completely sealed house is not only foolish but dangerous. I hope this not what is done in the homes you're responsible for.

FACT: new construction with sprayed foam insulation requires an upgraded HVAC system with a superior dehumidifier and an energy recovery unit. The costs of this will be significantly higher than a standard HVAC system. Again, fact: the survival of the home's substructural components such as framing are completely reliant on your HVAC system. Fact: sealed, the house will become a heat sink, absorbing heat during the day and releasing it into the home at night. It will significantly reduce the life of roofing materials such as shingles (e.g. "baking the shingles off the house").


Re: Tradesman 1 comments

You should really know what you are talking about before you post. First of all, mold (like the kind you often see in fiberglass) does not occur in a home insulated w/SPF. Why?, because you need dust and moisture for mold to grow. Both of these are eliminated with the use of foam. This is well known. Another well known fact is moisture build up is often the result of warm moist air condensing on the cold surfaces of the attic. Again, because (with foam)the attic air is conditioned, condensation(moisture) doesn't occur. As far as a house "breathing" that is just ridiculous. Do you want Dust, pollen, allergens and drafts "breathed" in? Do you want your costly conditioned air "breathed" out? Of course not. Build Tight and Breath Right is how we do it. Air Handling systems are simple and inexpensive and can consist of a good quality bathroom exhaust fan and that's it. Problem Solved. Lastly, HVAC equipment can be downsized with the use of foam (By 10-20%). Also the HVAC equipment cycles less often and works less hard due to the air sealing efficiency of SPF.


What about moisture and mold? If a house is sealed there is no way for contaminants and moisture to escape on their own. I've heard the upfront cost can be triple, just in necessary HVAC work to properly ventilate the house. It's a serious concern building a house that 100% reliant on HVAC equipment for survival of sub-structural components such as framing. Conventionally built, a house can breath on its own, providing good opportunity for moisture to escape through ridge venting and sidewalls. If the past few years have shown us anything, it's that weather patterns are becoming increasingly more erratic and more extreme. This has placed significantly more strain on everyone's HVAC systems, causing more power usage, and if prolonged, possibly repair work. I'm not downgrading the necessity of greater efficiency in new homes or the need to progress with our building practices. Potentially incorporating this insulation with other innovations may be the answer. Though constructing an airtight home and placing the survival of it 100% in the hands of a costly HVAC system is not.

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