by Mason Knowles
Residential remodeling is a vast industry and it is expanding. The U.S. Census Bureau estimates residential improvements in 2005 will be approximately 162.4 billion dollars.1 This remodeling boom is helped by low interest rates, home equity loans, and by consumers who want to add entertainment space, efficiency, comfort, value, and aesthetic elements to their home. According to the National Association of Home Remodelers (NARI), remodeling a kitchen, bathroom, or basement can add up to 80 percent of the remodeling costs to the value of the home.2
Following the industry trend, this author and his wife decided to make improvements to our townhouse in Reston, Virginia. Remodeling the kitchen and adding landscaping to the walkout section near our basement were both fairly easy—we just decided on what features we wanted, hired a contractor, and went to work. However, two years ago, when we added an entertainment/family room and bathroom to the basement, it was a far more complicated situation with several obstacles to overcome.
Townhouses in Reston are typically multi-story units with basement, middle, and top floors. Most of the units are very drafty due to leaks, cracks, and crevices from sheathing, doors, windows, and framing (e.g. ceiling/wall, floor/wall, and roof/wall). This unwanted infiltration and exfiltration led to a stack effect. As many design professionals know, stack effect occurs in buildings as air is sucked into the interior in the lower floors and goes out through the soffits and vents in the attic and roof. This creates different climate zones throughout the house. For example, on a 29-C (85-F) day, with the temperature set at 20 C (69 F), the following conditions were typical:
- the basement was a chilly 19 C (66.5 F);
- the middle floor a comfortable 22 C (71.5 F); and
- the top floor (i.e. the bedrooms) was an uncomfortable 23 C (74.5 F).
We learned to live with the ranges by adjusting our thermostats depending on the rooms we were in, but if we were to spend a lot of time in the proposed basement, this temperature variation needed to be decreased.
Not only did we have different temperatures in each level, but the winter and summer humidity ranged from a skin-cracking 10 percent in winter to more than 65 percent in summer. The extremely low humidity in the winter and high humidity in summer would severely limit the type of materials suitable for the basement. For example, we wanted to have a hardwood flooring system, but could not have humidity more than 60 percent or the wood would swell and bulge. Conversely in the winter, low humidity would open gaps in the material.
Water damage from ice dams
Northern Virginia is a mixed climate zone, which means some winters are very mild with barely freezing temperatures, while other winters can have tons of snow. This author knew ice dams could theoretically cause water damage, but until we had 0.6 m (2 ft) of snow on our roof in 2003, the joys of actually experiencing one were still unknown. Since the attic was not well-sealed, warm air inside the house escaped into the attic, heating the underside of the roof deck. The snow next to the deck melted, running down into the gutter where it re-froze, causing the system to function improperly. As more water came to the gutter, it escaped down the interior walls of the home, saturating walls, and causing damage (Figure 1, page 24). Most of the water eventually seeped into the unfinished basement, with damages exceeding $15,000. While the insurance company picked up the lion’s share of the costs, we were ordered to fix the problem, as it would no longer be covered. Of course, the damage would have been much worse if the basement had been finished.
One might think that after this author had spent 35 years working in the spray polyurethane foam (SPF) industry, the material would be omnipresent throughout his home. However, it is not always practical to take an existing house, tear out the gypsum wallboard, and install spray polyurethane foam (SPF) . Nevertheless, using sprayfoam became a far more attractive option when it became clear a creative solution was needed before the basement-remodeling project could begin.
Sprayfoam to the rescue
To stop the air from coming into and out of the building, an spray polyurethane foam (SPF) contractor was hired to remove the 152 mm (6 in.) of fiberglass batt from the basement walls and sill plate (R-19), and the 305 mm (12 in.) of blown-in fiberglass from the attic floor (R-38).3 While assisting the contractors in removing the fiberglass batts from the sill plate (i.e. the 305-mm perimeter section between the ceiling of the basement and the first floor), dirt, leaves, and other outside debris cascaded down on us—the air movement was so strong it blew this author’s hat off. The applicator then installed 76 mm (3 in.) of 2-lb (0.9-kg) density spray polyurethane foam (SPF) to the floor of the attic (R-18), 25 mm (1 in.) to the walls of the basement (R-6), and 76 mm (3 in.) to the sill plate (R-18). Immediately after the installation of the spray polyurethane foam (SPF) in the attic and the basement, no air movement could be detected.
The temperatures in each level of the house were then measured. At an outside temperature of 29 C (85 F) and the thermostat set at 20 C (69 F):
- the basement was 20 C;
- the middle level was 21.7 C (71 F); and
- the top level was 22.2 C (72 F).
While the humidity was still fairly high at 55 percent, it was still considerably lower from the 65 percent of the previous day.
Having successfully addressed the various obstacles, work began on the basement. Nine months later, the finished project not only added an additional 83.6 m2 (900 sf) of living space, but also made the home more resistant to the weather and stopped the ice dams (and consequent water damage).
In May 2005, after enjoying our new basement for a couple of years, we decided to replace the furnace and air conditioner—both units were about 12 years old and required significant maintenance. The spray polyurethane foam (SPF) provided another nice surprise when the HVAC contractor downsized the AC unit from a 2.5-ton unit to a 2-ton model and also reduced the furnace 25 percent in BTU size.
1 Visit http://www.census.gov/construction/c50/c50index.html#. 2 Visit www.nari.org. 3 As insulation formulation may vary from manufacturer to manufacturer, design professionals should consult the suppliers’ specification sheets to understand the exact properties over time, including the actual R-values. Factors affecting the R-value include thickness of application (i.e. the thicker the foam plastic, the better the aged R-value), the substrate, and the covering systems used (i.e. the lower the perm-rated covering and substrate, the higher the aged R-value).
Mason Knowles is the executive director of the Spray Polyurethane Foam Alliance (SPFA). He can be contacted via e-mail at firstname.lastname@example.org.