Eliminating Air Infiltration

Please forgive me, as I'm not a professional writer or blogger and I'm trying to make this site more user-friendly by modifying the layout.

Good afternoon.

Today I’m going to discuss the following benefits of using spray foam insulation:

2. It eliminates any air infiltration into the thermal envelope of the house, which allows you to use a much smaller AC system, saving you a great deal of money.

3. It keeps dust, pollen, mold and allergens from entering the house through the walls.

When you use spray foam insulation to insulate your walls, you first must understand the physical properties of foam as well as its installation. The foam used for insulation is a polyurethane (plastic) material that is blown into the walls wet, foams up and cures (dries). The foam is blown in the walls as a liquid so it’s able to get into every nook, cranny, crack and void in the wall assembly. It then foams up, expanding everywhere it’s able to, and locks into place. What this means for you is that no air is able to enter or exit the home through the walls. That’s a good thing.

If you’ve ever felt a cold draft coming through the wall at a wall outlet, you understand that you’re losing hot air in winter and cold air in summer. That means that you’re paying good money to condition and de-humidify air for your comfort and that air is escaping the home. Typical practice is to increase the size of the AC unit to compensate for this known occurrence (more about this later). It’s just the way it’s done. Not anymore. With foam, you eliminate this leakage, you don’t feel the draft, and you stop wasting money on utility bills. Because your home is not leaking air, your AC system doesn’t have to be so large to compensate for the leakage and you can now use a smaller AC system to effectively condition your home.

Foam keeps dust, pollen, mold and allergens from entering the house because the typical paths (holes/gaps) into the house no longer exist. With foam filling all nooks and crannies in the exterior walls of the house, air can’t leak in or out and all of those harmful, air-borne particles can no longer come into your house. If you have problems with asthma, this will have a significant impact on your health and comfort. Just as important is the fact that tightening the thermal envelope of the house significantly reduces the probability of mold forming in your walls, as mold can travel in the air. A less critical but equally enjoyable benefit of tightening the envelope is that your home will have less dust on the furniture!

I know that as you read a lot of this material, you might be tempted to raise objections to the benefits of foam insulation. I welcome your questions and look forward to discussing your concerns. To go one step further, I will establish a list of common objections to foam insulation I’ve heard from builders, architects, AC subcontractors and homeowners. Check back soon, as I continue to walk you through the benefits of spray foam insulation.

Have a great day.

-James

8 comments:


Anonymous said...

so why would you put foam in the walls when it is much

better for hot humid climates to use foam to the exterior of the wall..stopping thermal bridging..insulate with conventional insulation in walls and incorperate air tight drywall approach to interior.

I just don't get why foam companies push foam for walls...then only fill the wall cavity partway full. Around here...condensation forms between foam and sheetrock and mold grows.

save foam $$ in walls and foam the roofline.

are you pushing open cell or closed?


March 19, 2010 9:03 PM

James Davis said...

Anonymous,

Who said it is better for hot, humid climates to use foam to the exterior of the wall? It's not. Stopping thermal bridging isn't the only benefit of foam. Foam's PRIMARY benefit is that is stops air infiltration through the wall.

The problem with using conventional insulation is that 10 years later, it sags in the wall and you have insulation on the bottom third of your wall. What are your options then?

Airtight drywall? I'll believe it when I see it. There are so many opportunities to fail at attempting "airtight drywall."

The reason foam companies push foam for walls, and then, only fill the wall cavity partway full is AGAIN, it eliminates air infiltration. You don't need to fill the cavity to eliminate air infiltration because you accomplish it with the first few inches.

Around here? Where might that be? The reason mold grows inside a house that has foam is because the AC system wasn't properly downsized to factor in the lack of air infiltration. When you keep the same beefy AC system (sized based on SF) and you no longer have the air infiltration (leaking of conditioned air out of the house), the AC will "short cycle", meaning it turns on and off much more often and doesn't run long enough at a time to draw the humidity out of the air.

Am I pushing open cell or closed? I recommend them for totally different applications. Closed cell is best in freakish conditions like wine cellars or refrigerated warehouses. It's also widely used on the exterior of homes and hotels up north. Open cell is most economical and logical for the walls and roofline of a home here in the South.

Anonymous, keep researching foam. You have some fundamental misunderstandings in your logic. Good luck and I hope you make the investment.


March 30, 2010 11:42 AM

Theresa Allison said...

Hi James,

I'm currently researching spray foam for our new home and I keep hearing a wide variety of opinions on it. One thing I hear is that open cell is not "really" open and that spraying it against the wood in the attic will cause wood rot when the roof leaks and the water has nowhere to go. Can you address this?

Also, the quotes I'm getting are close to 5x the cost of traditional insulation, can you address the time of payback for this type of investment? Thanks!


May 2, 2010 3:26 PM

James Davis said...

Hi, Allison.

Open cell is, in fact, open due to microscopic cracks in the foam cells caused by the heat from the chemical reaction. I've seen them myself.

Regardless, your concern seemed to be the theory that your roof will rot if the foam doesn't let the water move away from the roof decking. Assuming you haven't read my previous posts, the water WILL pass through the OPEN CELL foam. It will not pass through closed cell foam. The only thing I can suggest is for you to get a contractor to bring you larger foam samples (1' x 1' or 2' x 2') so you can put water on them and see whether it passes through or not. When the water passes through, it gets away from the roof decking and will not rot it out.  The bad thing about some contractors is that they'll tell you a lie to sell their product. I'm not a foam contractor anymore and have nothing to sell you.

As far as the pricing you're seeing, I don't know what market you're in but in Houston, foam is about 3-4x as expensive. At that multiple, the payback period was still 3 to 4 years. These are some of the items that impact the payback period.

1. You'll have a smaller AC system (saves $).
2. Your electric bill will be smaller because of #1 (saves $).
3. Your foam on the underside of the roofdeck will reduce the heat load on the house which lessens discomfort and thus, cooling requirements (saves $).
4. You won't leak conditioned air through the walls of your home or have hot air leaking in, which reduces the work load of the AC system (saves $).
5. Foam is more expensive (costs $).

Let's assume you're building a 2,500SF home. Normally a house like this will take 5 tons of AC equipment and fiberglass insulation might cost $2,000. This same home with foam would take 2.5 tons of AC (at $1,000/ton on average, you save $2,500). The foam will cost (in Houston) around $8,000 (or a $6,000 premium over fiberglass). Assuming an energy bill of $200 with fiberglass and an energy bill of $100 with foam (both very realistic, if not conservative, in Houston), you save about $100/month.

So, you pay $6,000 extra, save $2,500 on AC equipment and are left with a $3,500 increase. Divide the $3,500 increase by your $100/month savings and your payback period is about 36 months.

If you look at it another way, if you finance the foam into the cost of the house, an additional $6,000 adds about $35/month to your mortgage. If you're saving even $100/month in electricity, it's a positive cash flow decision from day one. Moreover, the foam will help you sell your house down the road because it lowers the operating cost for the new owner as well. If you paid that extra money to the utility company instead, you'll never see a return on it.

Allison, I hope this helps you.

-James


May 5, 2010 11:03 AM

Anonymous said...

hi everybody,

While I don't sell/install foam insulation, I'm a contractor myself with a good understanding and a whole system approach to houses. As such I can tell you that foam insulation is the BEST insulation available period. There are some limits of use in commercial applications, but nevertheless it's the best thing in residential construction.

Well, there is no reason to be upset about the fact that it is more expensive at the same time. If it wasn't, nobody would be using any other insulation.

Author of the above blog made a mistake saying that among the benefits would be less dust on the furniture. Correct me if I'm wrong, but majority of the dust in house is an affect of human and animal habitation and the materials used inside the home, thus making the outside sources not really important. But, it's a small mistake that does not take away from all the advantages the foam carries.

The bottom line is this: if you can afford it, foam it! Cut down on interior finishes if you have to get the foam in. But you can always spend on that interior remodel later while it would be insanely expensive to redo bad house insulation with foam later on.

Should you use foam in wall cavities too: absolutely yes!!!

Does the foam fixes all the problems in house construction? Of course not. But it gives a good bang for your bucks.

Cheers

-Greg Olchwski

November 15, 2010 3:33 PM



James Davis said...

Good afternoon, Greg Olchwski.

You said "Author of the above blog made a mistake saying that among the benefits would be less dust on the furniture. Correct me if I'm wrong, but majority of the dust in house is an affect of human and animal habitation and the materials used inside the home, thus making the outside sources not really important."

As Lee Corso says "not so fast, my friend." If air is blowing through gaps in your wall and air can carry dust and pollen, then said dust and pollen can blow through said gaps in your wall. Now, it might not be a continuous journey from start to finish and that dust and pollen might settle inside your wall and catch the next gust in, but it will use drafts as a vehicle to enter your home, unwittingly, of course.

I concede that other things cause dust besides outside sources, but dust, pollen and crud, in general WILL transfer through the wall assembly.  I never said "eliminates dust, pollen, etc.", I said reduces.

But, alas, we ARE in fact splitting hairs. Most readers would take MORE dust in their house, if they knew what it would do for their utility bills, right?

I do appreciate your opinion, but still stand by my original statement.

Cheers.


August 10, 2010 9:22 PM

Anonymous said...

James,

I have a friend who is building his own home and i would like to foam my own home. Together we are looking to either buy our own unit or rent one. Do you know of any economical units for the do it yourselfer or any way to rent?

December 7, 2010 2:58 PM



James Davis said...

Anonymous renter,

I wouldn't take on foaming a house with a ten foot pole, if I weren't a foam contractor already. The only foam job a "rookie" should take on is buying a small kit of TigerFoam and foaming maybe one wall of a room, say your mancave in the garage or something like that.

If you're talking about doing a whole house or two, you'll lose your collective asses. Professional systems can cost tens of thousands of dollars and would take rookies FOREVER. I truly mean no disrespect.

I talked to a gentleman once who got a truckload of TigerFoam-type kits and hired some laborers to spray his new home. It cost him about twice what it would have to hire a contractor and it took him more than a month to get it done!!! I could have done his house in two days!!

As I was once told, take my advice and do as you please. I personally would pay the professional. After all, we pay Red Wing to make our boots and Smith and Wesson to make our pistols, don't we?

Good luck.