Systems

Ventilation

Download Earthtube Ventilation System Diagram (32k PDF)

Introduction

How best to draw fresh air into any home is a question of debate among professionals and designers. In older homes, indoor air quality is often good in part because they are so leaky. This comes with the disadvantage that much heat energy is lost through these air leaks (being replaced with fresh but cold outdoor air and felt as drafts).

As buildings became more airtight in an effort to reduce heat loss, they at the same time began to require a different way to bring in fresh outdoor air. This is additionally true (in fact a building code requirement) if the house has indoor combustion devices that consume oxygen, such as a propane range oven, gas boiler or wood stove.

The traditional response has been to install a heat recovery ventilator (HRV). This mechanical device uses a fan and a series of baffles to partially pre-heat incoming cold exterior air with the heat given off by exhausted stale indoor air. While HRV's are quite capable of performing this task, they are not inexpensive to purchase and install and they can consume a fair amount of energy. HomeAlive has been designed to cut out the energy requirements and expenses.

Instead, Home Alive uses an historical "free" method of drawing in fresh air, an Earth Tube Natural Ventilation System.

Earth Tube Natural Ventilation - How it Works

Earth Tubes consist simply of a pipe that is buried below the frost level (the maximum depth to which the ground freezed in the winter) and surfaces both inside the house and outside the house.

Inside the house heat from the Hydronic System warms the air above the floor. This air rises creating a low-pressure area. The low-pressure area essentially creates a void into which new air moves. This effect pulls or sucks air up from a floor vent connected to the interior side of each earth tube.

At the depth of burial, the earth is consistently 4*C all year long. So in the winter months, the fresh incoming air is preheated from whatever the outdoor air temperature is to something closer to 4°C. Home Alive makes use of this cool air before releasing it into the house by passing it through an insulated cold storage area - effectively an above ground root cellar.

What's more, in the summer, the earth tubes can be used to draw in cool air, again at 4°C as natural air conditioning. It also takes the humidity out of the air, thus creating a very comfortable ambient temperature indoors. No mechanical parts. No energy consumption. No need to build another coal-fired energy plant to keep this house cool.

Sometimes the best solutions are the simplest.

For More on Earth Tube Natural Ventilation

• Learn about the HomeAlive systems hands-on. Everdale offers seasonal workshops on different aspects of the systems. You can also take part in guided Saturday Tours of HomeAlive. Visit www.everdale.org
• Check out the HomeAlive Buyer's Guide for suppliers and equipment of these systems.

> Back to Top