What's Changed in the Past 25 Years
Trace the last 25 years of applied building science through the eyes of one knowledgeable homeowner.
In November my Denver home celebrated its 25th birthday. I’ve owned it since it was new and built it with a number of energy-conserving features. The building materials in 1983 were different than they are today… or are they?
The home my wife and I purchased in 1983—one year before Home Energy published its first issue—was twice the size of our original home, built in the 1970s, but the newer home actually had lower energy bills! I’ve worked in the insulation industry for my entire career, including my present job at Johns Manville, and so I had a good idea of what energy conservation features should be included in my home and what other construction details were important.
Then and Now
If you look at the underside of my roof, you see plywood, the common roof sheathing in 1983. Today it would be more common to see oriented strand board (OSB). Sometimes today you might even see foil, as foil-faced roof sheathing is used to keep attics cool. In my attic, you also would see roof trusses made from 2 x 4s attached with truss plates. In a new home today, it would look pretty much the same. In my basement, you would see dimensional lumber used for floor joists. Today it would be more common to see a wooden I-joist or a floor truss. Under and between my floor joists there are metal ducts to move air from the furnace to the rest of the house. At least, that is what they are supposed to do. My ducts were not sealed. It wasn’t common in 1983. A new home would have metal ducts sealed with mastic, fiberglass ducts, or flex ducts. No-added-formaldehyde fiberglass duct insulation available today was not available in 1983.
When my home was being built, I had my builder add an exhaust fan over the shower in my master bathroom. He told me it wasn’t needed, since there was a fan over the toilet, which was in a separate room, but he would install it anyway if I really wanted it. Of course I wanted it, since it would help remove moist air from the bathroom to keep a low humidity level to prevent rot and mold. It’s done its job. Fans available today are quieter and have more-sophisticated controls that can turn on the fan when humidity is sensed or when outdoor air needs to be drawn into a home. The fan installed in 1983 still can be purchased today.
In 1983, the architectural covenants for my development restricted roofing materials to cedar shakes. While many types of roofing were available in 1983, I had no choice but cedar shakes. Aesthetically they are pleasing; however, they didn’t stand up to 2-inch-diameter hail in 1991, when they were replaced with another cedar shake roof. Since then, the architectural covenants have changed, due primarily to the fire risk posed by cedar shakes. I know how well they burn, as I use the ones that fall off the roof as kindling for starting fires in my fireplace. The roof was replaced in October 2007. A stone-coated steel roof mounted on battens and counterbattens replaced the cedar shakes. While a metal roof isn’t new (my grandparents installed one in 1917), installing it on battens and counterbattens is a new idea developed at Oak Ridge National Laboratory as a way to keep attics cooler in the summertime. A big change for residential roofing is the availability of cool colors that help attics stay cooler during the summertime, and other methods for keeping the attic cool.
I was on the bleeding edge with my sealed crawlspace. I would like to tell you that it was planned, but it wasn’t. The builder made a mistake. He forgot to specify venting. A bright building inspector recognized that the sealed crawlspace was no different from a basement with a low ceiling, but that it needed a supply-and-return duct. It has worked fine for the past 25 years. In 1983, craw spaces were vented. Today, building scientists are promoting sealed crawlspaces.
Insulation—Always in Fashion
My home has wood frame walls using 2 x 4 and 2 x 6 framing. Homes are constructed in much the same way today. However, while the other homes in the neighborhood are sheathed with OSB, my home is sheathed with polyiso insulation made with a now-banned chlorofluorocarbon blowing agent—with plywood in the corners to provide racking strength. Today’s more environmentally smart polyiso foam is blown with pentane but has a lower R-value per inch. I took an infrared (IR) photo of my walls from the inside, and the polyiso is still doing its job, keeping the studs close to room temperature. Foam sheathing isn’t very common today; it is installed on only 6% of homes in the United States. Today, most wall sheathing is OSB or plywood. If I built a new home, I would still install polyiso sheathing, but much thicker than the 5/8 inch that was installed in 1983.
|Foundation insulation was not required when my home was built, but I had the builder install extruded polystyrene (XPS) on the exterior of the foundation walls.|
In 1983, polyethylene vapor barriers were touted as the best material to keep condensation from occurring within a wall. The leading manufacturer of polyiso showed this vapor barrier with polyiso wall sheathing. This is the system on my home. The building science community has since learned that air infiltration is a greater source of moisture in walls than diffusion through walls, and that walls need to be designed to dry to the inside. Today, there are many options for a vapor barrier, including a nylon membrane that increases its perm rating as it becomes wetter. There is also a renewed interest in kraft facing, which performs like nylon by allowing more moisture flow as it becomes wetter. Another option is to use no vapor barrier; some experts think this does a better job than a vapor barrier of managing moisture in the building envelope.
Foundation insulation was not required when my home was built, but I had the builder install extruded polystyrene (XPS) on the exterior of the foundation walls. Upon walking through my basement just a few months after the home was built, my father-in-law commented that it was the warmest basement that he’d ever visited. I attribute it to the foundation insulation. The basement stays 65°F all year. I made a mistake, though—the foundation insulation was not extended above grade, which is readily obvious in the IR photograph of my home. The uninsulated portion is much warmer than the rest of the exterior. Foundation insulation has changed a little over the past 25 years. One system uses a fiberglass board to act both as a drainage plane and as exterior insulation. Sprayed polyurethane foam is being used in a few homes. Insulated concrete forms (ICFs) using polystyrene foam are offered by many manufacturers. Today fiberglass blankets are installed on many basement walls.
My home was insulated with three different types of foam. I mentioned the polyiso wall sheathing and the XPS foundation insulation. The third foam is sprayed polyurethane, which was used to seal around doors and windows. Today there is a low-expansion version of sprayed foam to reduce the risk of bowing the window and door frames. Also, sprayed foam is being used to seal other penetrations, including holes for electrical wires and drain waste vent pipes. I’m glad I had the builder air seal around the windows, but I’m slowly air sealing other leaks in my home, including my ceiling recessed-can lights. These days, homes are better air sealed than they were in 1983, especially if a HERS rater checked the home.
The can lights in my home are IC rated—that is, they can be in contact with insulation. It was state of the art in 1983. I’ve been able to seal some of the original can lights, and today airtight IC-rated can lights are available.
Light and Heat
My can lights originally had incandescent bulbs. My wife was responsible for marketing demand-side management programs for the local utility, so we switched out a few bulbs to the first CFLs that were available. These didn’t stay in place long, because they took a long time to start, they flickered, the light quality was poor, and the light color was odd. We now have some of the newer CFLs, and they are much better. CFLs have improved; as more sizes, types, outputs, and light colors have become available, and some CFLs are dimmable. LED lights are just now coming on the market for residential lighting.
Being in the insulation industry, I wanted an efficient furnace in addition to an energy-efficient house. I convinced the builder to install a 97% efficient gas-fired furnace-water heater combination. This decision may have helped the planet, but it was a constant source of aggravation. Reliability was value-engineered out of the product. It had to be repaired at least three times a year, until I finally replaced it when it was seven years old. The replacement furnace is 93% efficient and more reliable. A wider variety of efficient and more-reliable furnaces is now available, including ones with a sealed- combustion system that uses outside air, keeping the furnace from depressurizing the house.
When I replaced the furnace in 1990, I also needed a new water heater, since the old furnace provided domestic hot water. I replaced it with a power-vented gas-fired tankless water heater, an Aquastar, one of the few available at the time, designed to handle 3 to 3.5 gallons per minute. Other building scientists have thanked me for being on the bleeding edge of technology, due to my original choice of furnace and tankless water heater. The water heater mostly worked okay after I insulated all the accessible water lines and installed low-flow restrictors in all water outlets. My wife and I quickly found out that we could use hot water for only one thing at a time. We also learned that enough hot water had to be used to prevent the water from cycling from hot to cold. Actually my cold water wasn’t very cold; it was 85°F until our neighborhood changed from well water to 45°F Denver city water. While I got colder water, the tankless water heater could raise the temperature of Denver water only to 90°F. Our showers were too cold. Finally, the tankless unit was replaced with a power-vented conventional water heater.
Today, there are more options. Condensing-type water heaters are available, and the new tankless water heaters are modulating and don’t pose all the problems that my family encountered. Did I mention that the original tankless water heater was less reliable than a standard water heater, only one contractor could service it, and parts were expensive and hard to find?
My home was built with two masonry fireplaces. Each is supplied with outside air and has glass doors and a heat exchanger. I don’t see many wood-burning fireplaces in the Denver market, as wood burning is restricted on many winter days due to pollution. Before I used either fireplace, I installed metal chimney caps to prevent sparks from landing on my cedar shake roof.
Windows in Time
Windows are a crucial element of walls, as they have higher heat gains and losses than the opaque part of a wall. In 1983, I thought that it was a big improvement to move into a home that had windows with wooden frames and double-pane glazing. It was a big change from my previous home, which had aluminum-framed windows with single glazing. How things have changed! There now are more options for windows than there were in 1983. Windows are rated for U-factor, solar heat gain coefficient, and visible transmittance. Low-e glazing is now standard.
My kitchen windows helped educate me on building science. I learned that gravity causes water to flow downhill. The lesson involved the windowsill. Unfortunately, water flowing downhill flowed toward the house. Who would have guessed that a wooden window frame would rot in seven years in Denver’s dry climate? The replacements were low-e windows with metal-clad wooden frames. The windows in my study also added to my building science education. A few months after my wife and I moved into the home, it rained 4 inches in one hour. We were shopping when it rained. When we got home, we noticed a puddle of water on the inside windowsill. The builder sent the window contractor to check. The window had no head flashing! The contractor claimed that it wasn’t necessary, because an overhang protected
the window. Severe weather happens. Wind blows rain sideways. After head flashing was added, there were no more leaks. These days there are many new products for sealing around windows. Flexible flashings weren’t available in 1983, but they are today.
The More Things Change …
The style of homes has changed during the past 25 years. Homes are much bigger today, but they are built pretty much the same way in 2008 as they were in 1983. There are a few new products, and some improvements on old products. But homes do what they always have done—provide shelter from wind, water, and extreme temperatures. Would I build the same home today? No. I would build a net zero energy home, one that was much more energy efficient than those built today. I would use currently available building materials, as they can be used to construct net zero energy homes.
Home ownership—it’s not just a home; it’s an adventure and an education.
John B. Smith, P.E. is currently the global leader for Johns Manville’s Building Science Platform and resides in Centennial, Colorado. He’s been in the insulation industry for 36 years.
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