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Making a 19th Century Cottage Into a Carbon and Energy Neutral Home

Making a 19th Century Cottage Into a Carbon and Energy Neutral Home

In 2004, architect Cathal Stephens and his wife Sarah bought a 19th century stone cottage in the northwestern countryside of his native Ireland. “Once we owned it, we realized we’d need to expand the building and that there were a lot of things that needed improvement,” he said. “We wanted to do a good job of it, and at the same time, make it sustainable.”

To do this, Stephens utilized Passive House Principles. Simply stated, the requirements are as follows:

  • A very high level of insulation around the roof, floor, walls, windows and doors, with virtually no gaps.
  • An airtight building, to avoid heat loss through cracks and gaps.
  • Constant ventilation with heat recovery, to provide fresh air while extracting stale air without loss of energy.
  • Maximize south-facing windows to increase the capture of solar energy on cold sunny days.

Stephens hired an energy consultant to help him with some of the complex energy calculations necessary to apply this technology. It helped that the cottage already had south facing windows. “I was ready for an interesting project and I wanted to experiment and push the envelope of sustainability,” he said. “Later I wrote papers about it and presented them at several European conferences.”

After stripping nearly everything out, he put super insulation under the roof, and then added insulation to the 18-inch thick outside granite walls. New triple glazed windows were installed, and on the north side, restored old windows were placed in front of them. This maintained the historic character of the house.

Then there was the issue of “thermal bridging,” which occurs where there is heat loss, most often around joints or where one insulation type meets another. “We located these,” he said, “and designed unique insulation details to eliminate them.”

The building then being a sealed environment, a heat exchanger was used to control ventilation. “Both the outside air and the inside stale air go into it,” he said. “They pass by one another but they don’t mix, so the cool incoming fresh air is warmed by the outgoing air. We’re not just throwing out the stale air; we’re capturing the energy it took to heat it.”

For electrical energy, a wind turbine was installed. This works particularly well in western Ireland where there are strong prevailing winds year round. “We make just about as much energy as we use,” he said. “It’s like we’re using the grid as a battery. On windy days, we’re exporting energy to it, and on calm days, we’re drawing energy from it.”

There are some cold days in winter when additional heat is required. That was solved by installing a small wood burning stove. It is sealed, has a door on it, and has its own ventilation.

A 19th century cottage is now in many ways a state-of-the-art 21st century home. “We now live here part-time every year,” said Stephens. “And besides being energy and carbon neutral, we find the house is very comfortable. It’s also very clean, because there’s very little dirt and dust coming in from the outside. As the designer and the homeowner, I’m very happy with how the Passive House principles have worked.”

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