Sunday, December 6, 2009

Green Building Gone Wrong: Lessons Learned the Hard Way

Five years ago, I completed a green remodel of my family’s home. We included green features like solar electric panels, a solar hot water system, recycled lumber, Trex decking, and many other green products. But since the remodeling work was completed, we’ve had years of consistently high propane bills, and I began to question whether my house is actually any greener or more sustainable that the average home.

For the past three years, our home has consumed between 1,300 and 1,500 gallons of propane per year. That’s “sustainable,” all right — for the oil industry! I have since learned that while using recycled, reclaimed, and renewable products is a noble green building objective, it’s more important to produce an energy-efficient, durable, healthy building that conserves water. Once that’s done, you can supplement your energy with renewables and fill in with as many green products as you like.

An energy audit
Frustrated by our high energy bills, we hired Balance Point Home Performance Contractors to test our home and help devise strategies for reducing our energy use. These energy auditors performed a blower-door test to determine shell leakage, used infrared thermography to locate leaks, calculated the required heating and cooling loads according to Manual J from the Air Conditioning Contractors of America (ACCA), tested the safety of our combustion appliances, and measured the actual efficiency of the heating and cooling systems.

When we remodeled our house, we had chosen to install a radiant floor heating system. Although it was more expensive than other heating systems, it was supposed to be more comfortable and more energy efficient. The radiant tubing was installed in the joist bays below our subfloor. The HVAC contractor chose the less-efficient method of hanging the tubing in the bays instead of stapling it up to the subfloor with heat transfer plates. The contractor also connected the tubing to our uninsulated rim joists, which does a great job of radiating heat to the outdoors. I was advised to use foil-backed fiberglass batts underneath the PEX tubing to reflect heat upward. That’s fine, if you want to keep all the critters warm and cozy in your crawl space — because the fiberglass batts leak heat like a sieve.

Furthermore, it turns out that our boiler was considerably oversized. According to the Manual J calculations, our peak heating load is 46,000 Btu/h, but somehow we ended up with a 90,000 Btu/h boiler — twice the necessary size.

Fixing these problems won’t be cheap
Now, we’re facing the need to downsize the boiler, remove the tubing connections from the rim joists, add heat transfer plates in our joist bays, and install rigid foam insulation under our PEX tubing and at the interior of our rim joists. Then I’ll need to air seal the whole assembly. What an incredible waste of more energy — my energy!

The solar hot water system with a tankless water heater as backup has never operated effectively. Solar hot water systems will likely be standard practice someday, but for now they are expensive, and most plumbers aren’t experienced in the correct installation of solar equipment.

In retrospect, our tankless water heater was a mistake. Some tankless systems are designed for solar backup, but we mistakenly chose a model that was not designed to accept preheated (solar-heated) water. In general, tankless water heaters provide minimal energy savings, cost about three times as much as a storage unit, and actually waste more water than a storage unit due to the delay in firing. They do, however, produce an endless supply of hot water. But, how is that a green selling point in water-challenged California?

Stopping air leaks
Building shell leakage, in my opinion, are responsible for some of the worst energy losses in most homes. Air leaks are caused by builders’ lack of knowledge and poor workmanship. Air leaks into attics can be easily reduced by using spray foam to seal ceiling leaks and by installing an air barrier on the back side of kneewalls. Air sealing roof vent channels and interstitial cavities is not hard work; it just needs to be done. Reducing shell leakage is probably more important, more effective, and less expensive than the majority of green products on the market.

With the 50% California rebate we received in 2004, our photovoltaic (PV) system might appear as a grand success. But it will take approximately 15 years for the PV system to repay itself. It might be a fine investment for those with a big budget, but PV should be way down the list when money is limited. We cannot simply buy sustainability; we must achieve sustainability through careful workmanship throughout the building process.

On the positive side, we did make some smart green choices. We used structural insulated panels (SIPs) for our addition, and they have a high R-value and perform well. The Loewen casement windows also function well with minimal air leakage. And we love our interior cabinets, trim, and doors, all made from recycled Douglas fir and cherry certified by the Forest Stewardship Council (FSC).

Indoor air quality must be carefully considered when building a new home or remodeling. Tighter homes require a good mechanical ventilation system. Get fresh, filtered air from clean places, not stale air leakage from crawl spaces and attics. Test your home for radon. Test all gas appliances for combustion safety. Use carbon monoxide detectors, and be careful if your garage is attached to the house. Car exhaust and other toxins can leak into your home when it is under a negative pressure.

All new equipment needs to be commissioned
Finally, don’t assume that any particular building system or mechanical system will automatically be energy efficient. Regardless of the type of equipment you choose, any system can either perform beautifully or perform pathetically. Be sure that any work you do is tested by a home-performance contractor to be sure it performs to energy efficient, healthy standards. I wish I had known that five years ago.

E. Conrad Welch owns Dovetail Construction and works as a green building consultant.

A good example of what happens when green components are selected piecemeal without benefit of a fully coordinated green remodeling strategy and execution. Get an energy audit, then design the project to fit your needs.

Posted via web from David Bourbon