By now, you have a good idea of how important ventilation is to your comfort and health. And in order to have control over ventilation, you need to seal your house against unwanted airflows. That means adding or improving your insulation.
The financial and environmental benefits of insulation are clear. If more than half of the money you spend on energy goes to space conditioning, as it does for most of us, any amount you can save there will have great impact. And by reducing your consumption of heating fuel, you both conserve resources and cut down on emissions from combustion.
Insulation does more than just keep indoors warmer in winter and cooler in summer, though. Combined with a thoughtfully designed ventilation system, it helps you manage the flow of air, moisture, and heat between the indoors and the outside. That includes exhausting stale air, filtering out allergens, preventing mold and mildew, and maintaining a comfortable balance of temperature and humidity.
In other words, the real value of insulation goes beyond savings on heating costs; insulating products that seal air leaks effectively provide the greatest number and degree of benefits.
Other Properties of Insulating Materials
All insulation should help keep heat on one side of a wall and cold on the other. Beyond that, it can have several other characteristics, which you should bear in mind as you consider different materials. Here are the most common features mentioned for insulation:
- R-value—resistance to heat flow; a reference for comparing different materials
- Resistance to fire—marginally increases safety within the insulated spaces
- Moisture control—determines effectiveness at preventing water damage and mold
- Weight—affects ease of installation and likelihood of settling later
- Stability—provides estimated loss of insulating capacity from settling
- Convective heat loss—transfer of heat through solid materials, not air
Most insulating products currently available fall into these categories:
- Structural insulated panels made of various materials
- Loose fill, such as recycled cellulose
- Rolls and batts, usually fiberglass and often with paper or foil facing
- Rigid foam boards, using polymers such as expanded polystyrene
- Radiant barriers, panels that help reduce convective heat loss
- Reflective insulation, which resists conduction, convection, and radiant heat transfer
- Insulating concrete forms, wall sections that combine concrete and insulation
Spray-Foam Insulation
The most visible difference between spray-foam insulation and other materials is the way it is installed. The foam begins as a liquid, and is sprayed on wall cavities, between joists, and in other open spaces with a high-pressure, low-volume applicator.
This liquid fills even the smallest gaps and contours in the receiving surface, and expands by 100 times its liquid volume to form a semi-rigid layer of light foam. As it expands, it continues to fill small spaces, sealing the area against air infiltration. When the foam dries, it can be trimmed flush to the studs or joists with just a handsaw.
By sealing the open spaces, spray-foam insulation reduces fuel consumption and costs, keeps out allergens and pollutants, and prevents some outside noise from entering the house. One thing it doesn’t do is trap moisture.
Managing Indoor Air Quality
The spray-foam insulation known as Icynene has open cells, like a sponge. It’s breathable. Because it minimizes air infiltration, though, it does not draw moisture from the outdoor air. When water gets in a space insulated with sprayed foam, the moisture runs through or
evaporates freely. This reduces condensation, and the growth of mildew and mold.
This also means spray-foam insulation helps you focus on the intentional flow of air through your house, which gives you control over pollens and pollutants. Following the builder’s motto of “seal it tight and vent it right,” you can keep respiratory problems, such as
asthma and allergies, in check.
Even during application, spray-foam insulation makes breathing easier. For example, Icynene is water-blown, and contains no HCFCs, HFAs, HFCs, HCs, formaldehyde, or VOCs. It does not cause corrosion, is the only insulation certified by the Envirodesic air quality
improvement certification program, and meets energy efficiency standards set by ALA Health House, EarthCraft, and Energy Star.
Also, thanks to its efficiency at filling spaces, spray-foam insulation helps reduce noise entering the house, and even noise transmitted from one part of the house to another.
Saving Energy and Money
All insulation products, correctly installed, will help improve indoor comfort and reduce heating costs. Spray-foam insulation is particularly good at sealing the envelope, so it brings the added benefits of minimized air infiltration.
In new construction, spray-foam insulation can seal a house well enough for a smaller, more fuel-efficient boiler or furnace to provide all the heat the house needs. This may also help the homeowner qualify for favorable mortgage rates, rebates on heating equipment,
or even tax advantages. The payback period is short, and, amount you save on fuel will only increase as energy prices rise. And, any house built for energy efficiency will both cost less to own and bring a higher resale price.
Remodeling projects that include the use of spray-foam insulation may require a different application method. Using Icynene as an example again, it is also available in a pourable version, which can be added to existing spaces without tearing out walls or floors. The
liquid can be poured through small holes, but will expand to fill and seal large areas. This makes expanding foam an effective material for insulating irregular and hard-to-reach spaces.
Back to Basics
R-value is the one characteristic on which all insulating materials are judged. Numbers are given in value per inch of thickness. Sprayfoam insulation has inherently high R-values, higher than fiberglass batts or loose fill and comparable to rigid foam sheets. But its sealing
properties virtually eliminate airflow, so it is more effective than its R-value alone indicates.
The U.S. Department of Energy acknowledges the limits of information provided by R-value. Real-world conditions such as material compression or settling, air gaps, and conduction through adjacent materials—including the building’s framing members—all affect the performance of insulation.
Perhaps a better measure is actual energy costs after installation. A house sealed with spray-foam insulation costs less to heat than one with batts, loose fill, or rigid foam sheets. Estimates vary from 10 to 50 percent, but one thing is constant: a house with spray-foam
insulation always saves more on heating.
