Historic preservation and environmental concerns occasionally clash, usually over issues involving windows, solar panels or, less often, exterior insulation.

The most common conflict occurs when homeowners decide to replace single-pane windows with thermal- or double-pane ones that insulate better.

Modern windows can be adapted to look like historic ones in new buildings. But when remodeling older structures, city historic-preservation rules call for preserving the original materials.

One way to solve this conflict is to install modern double panes in the old wood frames. But a more economical and common method is to install exterior storm windows. This way, not only is energy saved, but the historic window behind the storm window is protected from weathering.

David Rasch, head of the Historic Preservation Division of the city Land Use Department, said Santa Fe's architectural style already saves energy in that it calls for small windows on large expanses of walls — mimicking real adobe buildings.

But Rasch said the loss of heat through windows has been exaggerated. "I know people claim that it's a big energy loss, but that's just a wives' tale," he said. "There are many other energy losses that are worse than the windows. The roof is one of them. When you look at the building envelope ... 10 percent or less is (glass). Your walls leak more heat than the 10 percent of (glass) does."

The next most common conflict between green building and preservation involves solar collectors.

City code promotes solar panels for space heating, hot water and electricity. But in historic zones, solar panels — like rooftop appurtenances for heating, air conditioning and ventilation, as well as satellite dishes and antennas — must be hidden from view of the streetscape.

Usually this means increasing the height of the parapet, but it could also mean placing the solar panels elsewhere, such as on the ground, or otherwise disguising the panels.

In the summer of 2005, David Groenfeldt and Annette Cantor were forced to remove solar collectors on the roof of their house at 1021 Camino Santander. Cedar Mountain Solar had installed 10 4-foot-by-8-foot panels in October 2004 without seeking Historic Design Review Board approval. The city red-tagged the work after a neighbor complained.

Groenfeldt replaced the original panels with collectors measuring 10 feet by 16 inches, mounted horizontally so they only rise a few inches above his roof parapet. He also painted their metallic surfaces to match the exterior stucco and planted evergreen trees along Camino Santander to further hide the panels.

The new panels, designed by a retired Sandia National Laboratories engineer, don't work as well as the others would have, Groenfeldt said. Also, he said, the new panels do not qualify for state tax credits because they were manufactured by a firm not certified for the state tax program. Groenfeldt said he appealed this to the state Energy, Minerals and Natural Resources Department, but was turned down.

The 2007 state law that extended tax credits for the installation of solar collectors included a provision that forbids a county, municipality or private covenant or deed from restricting the installation of solar collectors. But the bill, sponsored by state Sen. Phil Griego, D-San José, specifically exempted historic districts.

In rare instances, exterior insulation can cause a conflict. Adding spray-on foam insulation to the outside of a Pueblo Revival-style building presents no problem because it only means a more rounded, bulbous, lumpy surface like real adobe. But that doesn't work so well on Territorial-style buildings, which have sharp exterior edges.

Although conflicts between green-building techniques and historic preservation occasionally cause conflicts, Rasch said, these are more than offset by what is known as "embodied energy." For example, he said, the woodwork in old windows often is made of old-growth trees with thin wood grains that are more durable than the wide grains of trees grown for lumber.

"All the raw materials that go into making a window, shipping it to the factory to make the window, shipping the made window to the site, hiring someone to install it — that all is energy that's embodied in that building," Rasch said. "It's much more cost-effective for the planet to maintain it instead of demolishing it and carting it to the dump. So the embodied energy makes historic buildings green by their mere existence. The green thing to do is maintain the existing building and add to it — not take away from it."

Contact Tom Sharpe at 986-3080 or tsharpe@sfnewmexican.com.