The Green Building Envelope
Insulation is the key to reducing fuel costs.
By John Wagner
The efficiency with which we keep the heat in or out of our homes (during winter and summer, respectively) has implications that reach far beyond monthly fuel bills. Just cooling U.S. homes costs $40 billion each year and consumes 15% of all U.S. power (90% of which is created with coal and fossil fuels). So properly insulating a home is a good investment environmentally.
Proper new insulation or retrofits can easily save 20% of fuel costs, to boot. But insulating a home has gotten a little complicated lately. Here’s why: When energy was less expensive, and structures were not built as tightly as today’s homes, moisture and mold weren’t a problem. That’s because air flowed (or was drawn or forced) through walls, and that served to dry them out naturally. Contractors could pack a wall with fiberglass insulation or cellulose (forget about vapor barriers), button up the walls, and never worry about a callback or lawsuit. Mold oozing out of switch plates was practically unheard of, unless the house flooded.
Insulation choices then were simple, too: It came in batts and product differentiation could be done only by changing the color of the fiberglass from white to yellow or pink.
With tighter houses, greater mold risks, indoor air-quality concerns, and a much greater understanding of the dynamics of heat flow, insulation has now become a highly specialized industry. Today you can buy a standard batt of fiberglass, but for a slight premium you can get batts with smart paper facing that changes its molecular configuration to allow moisture out or in, or blown foam that produces tiny chemical reactions that link cells to keep air and moisture out of walls entirely.
Coming Up to Batt
Loose fill cellulose, spray-fiberglass insulation, or blown foam applications—like those sold by BASF, Icynene, and Duraseal—are not items that a lumber dealer location stocks, per se. But well-trained yard personnel can make recommendations—especially for blown foam, which can have some very green attributes—as part of an installed sales program (see Blown Foam Choices).
The more likely items in your bays are batt insulation products. There are also some intriguing choices out there today that go way beyond the standard batts that got stuffed into walls in the 1970s and 80s.
Let’s take a close look at these, as they are generally premium products with good margins that offer desirable attributes to a contractor looking for low-tech ways to "go green.”
Formaldehyde Free, Mold Resistant
Formaldehyde is a known carcinogen, yet it is widely used in binders and adhesives sold in the U.S. When a traditional fiberglass batt is manufactured, the spun glass needs something to hold the thin glass strands together, and that’s the job of a binder. Batts and rolls that use binders are referred to as "bonded” fiberglass insulation. For people who are concerned about formaldehyde off-gassing into their homes—a major indoor air quality issue for green builders—there is a formaldehyde-free insulation from Johns Manville. Instead of formaldehyde, the company uses an acrylic binder. Indeed, Johns Manville offers the only complete line of formaldehyde-free fiber glass insulation.
Johns Manville has commissioned independent, nationally recognized laboratories to test their Formaldehyde-free insulation line to see if there are emissions of toxic volatile organic chemicals (VOCs) and formaldehyde.
The Formaldehyde-free line has passed the one of the nation’s toughest indoor air quality tests (the Environmental Specification 1350 test), which didn’t detect any formaldehyde in the batts. Johns Manville’s batts are also free of all VOC emissions. Even better, this insulation line is treated for mold-resistance (look for the MR Faced Batts). These batts are treated with an EPA-registered preservative that is used in food, which frustrates the growth of mold. The product Spider is a another formaldehyde-free fiber glass insulation from JM that sprays in almost dry, completely filling gaps and voids around electrical fixtures, pipes, and other obstructions for continuous insulation coverage. I’ve seen a live demo of Spider installation and it’s very impressive. That’s because excess insulation can be put right back in the hopper and used again. Unlike cellulose, Spider insulation will not settle or shrink, and it’s inorganic and naturally mold-resistant. (www.Jm.com; 800.654.3103).
Smart Batts, Smart Spray-ons
Imagine if you had batts of insulation that could open and close their pores in a smart way to control moisture when triggered by humidity conditions.
DryRight Fiber Glass Insulation from the ever-inventive CertainTeed Corp. is faced not with kraft paper but with something they call MemBrain. MemBrain helps to control moisture within wall cavities, and CertainTeed claims it can reduce the risk of mold and mildew by controlling moisture.
Here’s how it works: MemBrain has molecular-scale pores that open under moist conditions to allow moisture vapor to pass and dry the wall out. The pores close back up during the heating season to block airflow. The range in permeance goes from 1 perm to 30 perms, quite a swing. It’s available in R-13 and R-19 batts.(www.Certainteed.com; 800.233.8990)
A Warm Coat for the House
A great deal of heat, as much as 60%, can be lost or gained through radiant heat, one of three kinds of heat. (The others are conduction and convection.) Dupont Tyvek has a product called ThermaWrap that manages that heat flow.
Like Tyvek housewrap, ThermaWrap offers a vapor-permeable air barrier, but ThermaWrap has a low-emissivity surface that has an insulation value of R2. Think of it as Tyvek that insulates.
As it allows walls to breathe, ThermaWrap provides water-vapor transmission and water-penetration resistance, while adding to the thermal qualities of the house to boot. (www.Construction.tyvek.com; 800.448.9835)
Blown Foam Choices
Of all the recent insulation innovations, the one with the greatest positive impact on the building envelope is blown foam. Though it is relatively costly and has to be applied by a specialty contractor, it offers near-zero air permeability and great insulation properties. As a result, the building envelope has a high R-value and high integrity, two very green features. Moreover, these foams are self-adhering to walls, and they can be sprayed into the tightest spaces. Icynene and BASF have excelled here as national leaders.
Icynene insulation offers a continuous insulation and air-barrier system that creates a high-R-value barrier that is efficient, draft-free, and that has strong noise attenuation qualities. Icynene can prevent warm, moist air from entering the building, which is important, because when warm moist air meets cold air-conditioned air, it condenses out as moisture. If that moisture happens to be within the wall, you have a prospect of mold, rot, and indoor air quality problems. Icynene serves as insulation that can boost indoor air quality and mold prevention, too. (www.Icynene.com; 800. 758.7325).
BASF’s Comfort Foam closed-cell, spray-applied polyurethane foam offers near-zero air permeability and great insulation because it is self-adhering and seamless. Like other good spray foams, Comfort Foam can eliminate air leakage and thermal bridging common with batts. (Thermal bridging is the unequal transfer of heat through a wall; you see it on some exterior walls or roofs in the morning when the studs or joists beneath the sheathing appear as dew lines that linger even after the main wall has warmed up and dried out in the sun.)
Like Icynene, Comfort Foam helps control moisture, which reduces the risk of mold and the movement of vapor through a wall. Comfort Foam is also urea-formaldehyde-free, and uses ZONE3 zero-ozone-depleting propellants. (www. Basf.com/res; 888.900.FOAM).
There are a number of other insulation choices, of course, like rigid foam boards, stay-in-place insulated concrete forms such as those by Amvic and Amdek, and sheetgoods that combine insulation with a radiant barrier, like LP’s TechShield—a very high-performance product. Exhaustive coverage of each product would fill a book. And as Martha Stewart might say, "that’s a good thing,” because there are insulation products for every specialty application you can imagine, from low-VOC spot-application spray foams to batts pre-sealed in breathable plastic to keep the "itch factor” down during installation.
As always, the Internet is a great resource for further information on this topic. Search "insulation” on www.Epa.gov and you’ll get 9,168 articles. That’s plenty of great reading for the beach, the lake house, or the ski lodge.
|Roll the dice.||9.44%|
|Test the waters.||35.84%|
|Yes, this time.||33.96%|