We’ve had several inquiries during the recent Tour of Homes about the 17’ vaulted ceiling in our featured home. Mainly the question was about heat being captured in the vault leaving the lower areas cooler and less comfortable.
Read on to learn about why vaulted ceilings can be miserable in older homes yet work so nicely in a Passive House:
Comfort in a home is determined by many subjective variables, however what makes a home ‘thermally comfortable’ is well known. Below are the four comfort measures, that, when in balance make for a very enjoyable living space:
- Air Temperature
- Temperature of surrounding surfaces (ie walls, windows)
- Speed of air (draft)
Let’s say in our typical home, we set the thermostat to 72°F to keep the chill off, anything much lower than that often feels chilly. Then we look at the temperature of surrounding surfaces, inefficient windows, doors and walls will be cooler or cold to the touch. When the heated 72°F air hits those colder surfaces interesting things happen. One thing is that cold air is heavier than warm air, as the heated air cools off on the cold surfaces, it sinks. So, imagine the heated air coming from the furnace is lighter than cold air, it stays ‘high’ up in a room until it starts to cool off on those cold surfaces, it starts to sink, while being replaced by more light, heated furnace air, and so it goes. In older homes this movement of air would be called a… draft. In many older homes, when combined with air leakage this looping of air can actually feel breezy. It’s very uncomfortable.
Then there is humidity. This makes things even more interesting in our quest for comfort. High humidity levels play a big part in why 72°F doesn’t always feel warm enough in our older homes. For example, imagine a winter day in Colorado, at 28°F with low humidity levels, you might actually ski in a long sleeve t-shirt and be very comfortable. While, the same day in Olympia, WA at 50°F with humidity levels above 45% will have you drinking tea in your hot tub.
The other juicy thing about unbalanced humidity in your home is that it can cause loads of condensation on cold windows and walls resulting in serious deterioration and mold issues. Not good.
In a Certified Passive House, we don’t have inefficient, cold windows, doors and walls and we have no air leakage. With super insulation and critically efficient windows and doors, we avoid all that looping of sinking cold air and rising warm air… no draft! The temperature at the vault peak will be within a couple degrees of what it is at floor level. Given that, there is no need to crank up the heat to 72°F to overcome all that air movement found in an older home, in a Passive House 65°F feels exactly like 65°F no matter where you are in the room!
In our Passive Houses, those comfortable, ambient temperatures combine with a fresh air delivery system for a delightful synergy of human comfort, efficiency and durable structure. Passive Houses are so simple and work so well. Pretty cool.
Posted on October 14, 2010