The motto for building super high efficiency homes is “build tight, ventilate right”. When most people think of passive solar homes, they think of the homes built in the 70’s with huge south facing windows and concrete or stone inside the house for “thermal mass”. These homes were often epic failures in that they got way too hot in the summer and were very difficult to control. We’ve learned a lot since then.
Modern Passive Solar Design uses just the right amount of south facing windows. Instead of using thermal mass to store the sun’s heat, we simply don’t let the hot air escape by making the home extremely air tight. While it’s great to keep all of the hot air in the home in the winter, we still need fresh air to breathe. So we add a controlled mechanical ventilation system that ensures just the right amount of fresh air makes it into the house. This system, called an Energy Recovery Ventilator or ERV, moves fresh air into the home while exhausting stale air. A heat exchanger in the ERV uses the heat from the stale air being exhausted to warm the incoming fresh air, saving valuable heat in the winter. In the summer, we bypass the heat exchanger and bring in the cooler night time air to keep the home comfortable.