A growing family and a small house can be an uncomfortable combination, especially if the house is old. Chris and Katie Conger, who live in Coconut Grove in Kailua with their two young sons, knew they would have to remodel, but the question they always asked was if they could turn a 1960s-era home into a modern, eco-friendly environment.

The answer is a resounding yes.

Their remodeling project took about 18 months, and the finished home includes a variety of green touches, most of which are designed to take advantage of natural air flow and lighting in order to reduce energy costs.

"We knew we didn't want air conditioning but we wanted a house that was cool," said Chris Conger, a 37-year-old coastal geologist with the University of Hawaii Sea Grant College Program. "It wasn't that hard. I guess it depends on how you approach it."

Even so, it was an ambitious job expanding the 970-square-foot house into a 2,300-square-foot house. At roughly half a million dollars, it was also expensive — but the Congers view it as an investment in a home they will use for decades.

Their home went from three bedrooms and one bathroom to four bedrooms and two bathrooms. The couple added a sun room, opened up the kitchen, reorganized the interior and built a garage. They also moved the entire house to another spot on their flag lot.

New building materials help the finished home protect the interior from the sun's baking rays: The plywood in the roof is backed with material containing air bubbles and reflective foil to repel heat, the attic is vented by solar-powered fans and exterior walls are now a sandwich of insulating material.

Even the eaves got the treatment.

"We took our overhangs on our roof and extended them to the maximum length and that gives you more shade time," Conger said. "That cools the walls. You have less heat going into the house."

The energy use at the Conger home, despite growing 230 percent, is almost exactly what it was before couple started the project.

But the home still uses a lot of natural light to brighten the interior. Eight highly reflective tubes bring in sunlight but not heat, contributing to the ambiance and not the family's Hawaiian Electric Co. bill.

It feels homey, natural and anything but hot.

"The coloring of the light, the texture of it, the feel of natural light is completely different," Conger said

"The advantage of the tubes is you don't get a heat transfer. If you have an open roof with a skylight, you get a lot of transfer of heat."

One of the key features of the couple's plan was to govern exactly what went into the construction effort. They researched green products for months before coming up with a specific list for their builder.

The process even included child-tested use of an inexpensive but durable bamboo flooring material. They wanted to use bamboo because it is a more sustainable wood and, as it turns out, performed well when they handed their sons, now aged 3 1/2 and 2, a set of hammers.

Conger admits to one downside he hates to ponder much: the carbon footprint the couple left after driving all over town for eight months looking for the best materials.