To find the average R-value the correct way, we first need to transform R-values to U-values. R represents resistance, as in resistance to heat circulation, so the greater the number the better when we’re talking about building materials. U-value, the heat transfer coefficient is the reciprocal of the R-value, so the lower the number, the better.

The equation for average U-value is:.

Average U-value formula, to find the average R-value of insulation.
Taking the attic as 1000 square feet overall and putting in 1/R for U, we get:.

average u-value for R-50 & R-10.
Taking the reciprocal of 0.06, we get the average R-value of about 17, which is much lower than the R-30 we had actually get by improperly balancing the R-values.

Conclusion.

As I stated above, heat takes the path of least resistance, so the amount of additional heat going through the R-10 half far exceeds the additional heat flow that’s stopped on the R-50 side. Instead of getting an R-30 average, the lumpy attic has an R-17 average.

In practical terms, this means that if you see an attic with lumpy insulation, act with a rake and smooth it out. In the example I simply exercised, you ‘d almost double the R-value without including any extra insulation!

Another common example of the flat-or-lumpy conundrum is an attic that’s completely insulated except for one little location, say the pull-down attic stairs. We can go through the exact same steps as above and show that an attic that has a uniform R-30 over 99% of the area and 1% at R-1 (the pull-down stairs) will have an average R-value of 23.

That’s right. Those pull-down stairs can reduce your overall R-value by 25%. One little uninsulated location can dramatically reduce the R-value.

The Spray Foam business is hard, and harsh winter weather makes it much harder. This is especially true in the far north, but a sudden drop in temperature can cause significant problems that affect your bottom line even in mild and warm environments.

Everything is more difficult in the Winter; the logistics of getting your foam sets to your shop, warming and prepping your chemicals, getting the rig to the Jobsite, setting-up the Jobsite, and lastly, prepping the substrate to spray. A savvy contractor will plan, prepare, and compensate for difficult winter conditions to keep the crews working as efficiently as possible.

The most important changes required to maintain profitability in the Winter are:

• Order several days in advance.
• Store material in a heated area.
• Warm the job structure starting the day before spraying.
• Heat your rigs.

Generally speaking, trucking companies do a pretty great job of getting our chemical from the factory or warehouse to your shop. Still, a weather event can stop or slow traffic making on-time delivery impossible. Weather delays might not be only in your region, trucks could be held-up hundreds of miles from you, and there’s simply nothing you can do about it. Ordering a few days to a couple of weeks in advance can mean the difference between your jobs getting done, and you get paid or not.

Heat makes everything easier. Chemicals flow, foam sticks, yields remain acceptable, and your crew will appreciate being warm. Store your sets in a warm room at your shop. This could be an insulated shipping container or a dedicated, warm room in your warehouse. Spray foam in the walls and ceiling, store your drums on pallets with fans to blow the heated air throughout and under your drums to get them warm and keep them warm. This can save hours on every job since the crew won’t have to warm the chemical enough to get it to spray. The primary heaters on your proportioner can only raise the temperature so much, and hose heat is less effective in the Winter, so start with a warm chemical every day. You’ll be glad you did, and so will your crew.

The heated chemical and a rig prepped and ready to spray solves half the winter challenge. The other half is heating the substrate you’re spraying. It’s important to apply heat without adding moisture to the structure, which can condense and cause even more delays. This means you’ll need indirect propane or a diesel-fired heater. With an indirect heater, the temperature of combustion is exchanged to the air in the building across a heat exchanger, and the flue gas stays outside. The flue gas’s moisture does not go into the building, so it can’t condense on your substrate. It’s necessary to use dehumidifiers and heat in some regions to dry the framing members below 19% moisture content. Heating the building the day before spraying is often the only way to heat the substrate deeply enough to make the foam stick and so it doesn’t shrink or crack.

If you’re not familiar with indirect-fired heaters, ask your tech rep about them. Fast and thorough heating can make or break your profit on the job. Even if you had to spend $75 on fuel, operating in a warm environment and spraying warm surfaces can save hundreds or thousands of dollars and every dollar saved goes straight to your bottom line.

Similar to the warm room and heating the structure, keeping the rig warm pays big dividends. Mechanical equipment starts and runs better, chemical flows, and the crew members prepping the rig can move more quickly through their job site set-up checklist. Attitudes improve as well as your profit!

Beware of metal buildings in the Winter. They can be nothing but trouble, especially for SPF. Metal does not allow any absorption into the substrate as OSB and plywood do. The small amount of absorption and attenuation common with wood substrates makes adhesion far more reliable than spraying on metal sheathing, and cold metal is the worst case for spray foam. 

One technique for spraying metal is to “prime” the sheathing with a thin coat of foam. Some call this a “flash coat,” and many manufacturers do not approve of this practice. ArmorThane does recommend it with their foams, so be sure to ask your ArmorThane tech rep for guidance on how to do this effectively. Another essential winter practice is to get closer with your spray gun and use a smaller tip.

If your foam is slow to react, sags on vertical surfaces, or drips when sprayed overhead, then it’s too cold. You might have all the right settings on the proportioner, but it’s still too cold, probably due to a lack of adequate hose heat. Make sure your hose is well insulated, especially around the Fluid Temperature Sensor (FTS), and lift your hose off the ground, when it’s cold, wet, or covered with snow. The hose can be supported by small bags of scrap foam or foam blocks made for this purpose. The hose will conduct heat to the ground or snow many times faster than to the air, so get it off the ground. Automatic hose heat control is very important. Yes, there is a by-pass method on most rigs to set specific amps if the FTS or sensor circuitry fails, but this is intended to be used only to get you through the day until you can repair the problem, not as a permanent operating procedure.

Some sweet spots have become industry standards in the spectrum of polyurethane spray foam densities. About ½ pound per cubic foot of open-cell foam is a sweet spot for low density, R-Value, yield, and sprayability. Two-pounds per cubic foot density are ideal closed-cell or medium-density foam based on R-Value, yield, sprayability, and dimensional stability. Less than 2-pound closed-cell foams might have a slightly higher yield, but they tend to lose dimensional stability in cold weather applications and curiously don’t necessarily lose adhesion. This becomes difficult when the foam shrinks and cracks but remains tenaciously adhered to the substrate, making it extremely challenging to remove to correct the defect.

Simply put, there are three primary solutions to cold foam problems: add heat, add heat, and add heat. Add heat to the chemical in storage and transportation, properly functioning primary heaters, and temperature-controlled hose heat. Add heat to the substrate. Call your cold-weather expert for advice. ArmorThanetech reps have years of experience with cold weather spraying, and they can help maximize your crew’s productivity.

If you’ve chosen a proven formula like ArmorFoam 2.0®, you should be able to spray most days of the Winter as long as you heat your chemical, your rig, as well, as the substrate. 

To protect your profit, stick to true 2-pound foams designed for winter application, such as ArmorFoam® Winter Formula.

The performance was judged for dimensional stability and R-Value retention through -40°F winter weather and ArmorFoam® passed with flying colors! ArmorFoam® Winter is a cold-weather foam you can trust from a company you can trust. Call ArmorThane to learn more about heating-up your winter profits.