Centex Goes 10 for 10 in Fort Collins

"The one who says it can't be done should never interrupt the one who is doing it."
- Murphy's Laws

A few years ago, one Colorado municipal utility conducted a detailed examination of the performance of' relatively new homes: those built between 1994 and 1998. While that study zeroed in on energy features required by a new energy code, its broader mission was to examine the interactive performance of those features. The utility's two key questions were, "Is it there?" and "Does it work?"

Answers to the second question identified 10 recurring concerns relating to energy efficiency, comfort, safe operation of combustion appliances and indoor-air quality. None of the study homes experienced every performance related problem. But the study's benchmark data helped quantify the rate of occurrence.

A few builders saw these issues as an opportunity. One of the first to do so was Centex Homes.

What follows is a listing of the recurring problems and how Centex Homes, starting in their new Fort Collins subdivision (Linden Park) is the first builder to address them all. Most of Centex's solutions involve multiple measures that interactively address a number of the potential problems. In the building science world, that's called systems engineering.

Background

In October 2000, the Colorado division of Centex Homes first learned the details being incorporated by a small but growing number of the Centex divisions around the country. By the middle of 2001, Centex/Colorado started experimenting with a few of those details and examining the benefits.

"Across the board, we decided to require the use of mastic on all of our ductwork," said Justin Jones, Centex special projects coordinator. "Then we said, `If we do that, why don't we draft-stop around tubs and fireplaces`? And if we do that, why don't we increase our levels of insulation?' One thing led to another."

All of these measures are part of the Environments For Living program, offered by Masco Contractor Services. Each of the 200 homes in Linden Park is being built to the highest level (platinum) of three performance levels in the EFL program.

Will Centex expand the systems first employed here to their other subdivisions? "A lot will depend on how it's received," said Jones. "We want to get some history here first. If it's well received, we will explore offering this program elsewhere."

The 10 elements

1. Comfort. Between 70 percent and 75 percent of homeowners surveyed complained of comfort problems on second floors: too hot during the summer or too cold during the winter.

Centex system solution: Perform room-by-room calculations to determine how much conditioned air needs to be delivered to each room. Next, design the ductwork to assure that amount can be delivered; a full range of 4-inch to 7inch supply ducts are being installed. Then seal the ducts with a permanent sealant (like mastic) to increase the likelihood that the proper amount of air will be delivered; install dampers to adjust, if necessary, the amount delivered; and test the ducts after installation to confirm that proper airflow is in fact being delivered. Additionally, increase wall insulation to R-21, upgrade window performance, and tighten the building shell.

2. Health and safety. In one-third of the new homes tested, combustion gases that should exhaust up water heater and furnace flues were susceptible to being drawn into the basement rather than being vented up the flue. In virtually all homes, provision of fresh air was left to noisy bath fans plus uncontrolled ventilation by air leakage.

Solution: Centex/Fort Collins prevents backdrafting of combustion gases by installing combustion appliances that are either direct-vent, sealed combustion or power-vented. On a controllable basis, a special controller called an AirCycler will bring in fresh air through a duct hooked to the return-air duct; the furnace blower then circulates that air through the normal ducts to all rooms in the house.

3. Architectural problem areas. Certain architectural features-such as rooms over garages, cantilevered floors and dormers on second floors-were frequently linked to comfort problems.

Solution: All cantilevers plus floors in rooms above garages are dense-packed with loose-fill cellulose insulation. This both boosts the R-value plus eliminates the chance for air infiltration to bypass the insulation. Solid backing is provided behind attic knee walls to prevent air infiltration that can reduce the effectiveness of knee wall insulation.

4. Common thermal defects. Three features in most new homes-tubs, showers and fireplaces against exterior wallsusually allowed air leakage from the outdoors, often leading to comfort problems.

Solution: Provide a durable air barrier (draft stopping) covering the insulated cavities before installing tubs, showers and fireplaces. (For a sample detail, contact Matt Thornberry at E-Star Colorado at 303-297-7498 and ask for a faxed sample detail, or order EEBA's Builders Guide: Cold Climates from www.eeba.org.)

5. Conventional windows. Nearly all homes in the study were equipped with standard double-glazed windows, plus metal windows in the basement.

Solution: For all their above-grade windows, Centex selected a high-performance product, typically with a Uvalue of 0.35 plus a Solar Heat Gain Coefficient of 32 percent (depending on window type). That means it insulates about 50 percent better than standard clear double-glazing against wintertime heat loss. It also reduces unwanted summertime solar gains through windows by about 50 percent compared to standard double-glazing.

6. Heating and cooling equipment. On average, the study showed that the average furnace is about 25 percent larger than needed, while the air conditioner is nearly twice as large as the average home's calculated cooling load. The latter can cause comfort problems, increase energy bills, decrease equipment lifetime, increase initial cost and be a burden on local utilities.

Centex solution: A key starting point is performing accurate calculations vs. the usual "rules of thumb" approach to sizing. EIC, a Pennsylvania-based engineering firm affiliated with Environments for Living, runs the calculations. All the other energy details described herein allow for considerable downsizing of HVAC equipment.

7. Duct problems. Performance testing during the utility study confirmed that Front Range homes have some of the leakiest ducts in the nation.

Solution: There's a four-step process here. First, to return air to the furnace, Controlling Systems-Centex's HVAC contractor-uses nothing but hard ducts. Eliminating the use of building cavities for return air solves the largest single source of duct leaks. Second, the amount of ductwork is reduced, due to the lower heating and cooling loads resulting from the better-insulated building. Third, instead of using "temporary tape," they seal all duct joints with mastic or other permanent sealant. Fourth, the ducts are tested to assure tightness.

8. Air conditioning. Installation of residential AC systems is skyrocketing along the Front Range. This increases summer peak demand costs for utilities, which end up paying more for that peak power than they receive from residential AC customers.

Solution: Since windows can contribute up to 50 percent of unwanted solar heat gains during the summer, the goal is to select windows that significantly reduce those solar gains. If cooling equipment is eventually installed, the installation of properly designed and sealed ductwork will both assure delivery of sufficient cool air and reduce demands on utilities and their customers.

9. Sun's impact ignored. In some homes, controlling solar gains is difficult without manipulation of the home's orientation to the sun. Large glass areas can let in uncontrolled amounts of solar gains year round. As one homeowner in the study put it, "the sun is my enemy!"

Centex solution: Start with the low solar-heat-gain window glass. Then orient all homes in the subdivision such that the largest window areas face north and south. This combination minimizes unwanted summertime solar gains, allowing homeowners their best chance to avoid the purchase of a $2,000 air conditioning system.

10. "Does it work?" The study showed that some key performance elements of a home-its air-tightness, the tightness of ductwork, airflow delivered by individual ducts, etc.-are rarely tested.

Solution: Centex has Steve Byers (EnergySmiths in Berthoud) perform E-Star ratings and performance testing on each home in Linden Park. Based on his testing of ductwork in Centex's first four homes, Byers is impressed. "This is head and shoulders above anything I've personally tested to this point."

Byers' most recent test in a Linden Park home showed the return-air ducts had zero measured leakage. Furthermore, the total duct system leakage of 128 cubic feet per minute was only 7 percent of the leakage found in the utility study's average home (1,860 cfm). Finally, the air flowing out of every register either equaled or exceeded the amount specified by the HVAC system designer.

No free lunch

Centex says the initial cost for these upgrades runs around $3,000 for these homes priced between $210,000 and $230,000. Energy savings will offset most of the increase in the mortgage payment for a Linden Park home. Significantly, the slightly higher purchase price hasn't slowed sales.

Jessica Warren, working on community sales at Linden Park, says the energy features have provided a strong boost to early sales since the mid-November opening. "This new approach has helped immensely," she said. "Today's buyers are more savvy about energy efficiency. Three-fourths of our early sales have gone to engineers. After some explanation and hard-hat visits while the homes are under construction, they understand and appreciate what we're doing here that's different and why we're doing it. It's given buyers a rational reason to make an emotional buying decision."

Steve Andrews consults with builders for E-Star Colorado and writes on energy issues (sbandrews@att.net). E-Star (www.e-star.com), is a nonprofit home energy rating system that works with both new and existing homes statewide.

2008 Built Green Colorado

Home Builders Association of Metro Denver, 9033 E. Easter Place, Suite 200, Centennial, CO 80112
(303) 778-1400 fax: (303) 733-9440  info@builtgreen.org

Last Updated: 10/05/2007