Info-to-Build-On Venting Hot Air by Raoul Hennin November 26, 2003 The biggest challenge in a new home is establishing a balance between ventilation and efficiency.

A modern home is expected to be comfortable, efficient and durable. The best way to make a house last is to keep it dry. But our desire for warmth in winter and cool temperatures in summer can actually create moisture problems in the building envelope.

Condensation occurs when warm, moist air comes into contact with a cold surface. This happens during summer months when humid air infiltrates the house and hits cooler surfaces. In winter months, the moist air is inside the building trying to escape and condense on surfaces inside the building envelope.

When it is cold outside, warm air inside aborbs moisture from all available sources: cooking (especially turkeys) and shower steam, inhabitants breathing, humidifiers, and even plants. Not only is the trapped air inside the house unhealthy to inhabitants, it also creates a problem for the building itself. Warm, moist air inevitably finds stealthy ways to escape an otherwise air-tight house. As this moist air escapes through minute crevices, pinholes, or improperly trimmed windows, it leaves a layer of condensation on all available cold surfaces. Through time this condensation can cause serious damage to the building envelope.

A good way to stay one step ahead of condensation is to create slight negative pressure inside the house by installing an efficient, quiet fan which constantly exhausts humid air directly to the outside, while pulling in a steady trickle of clean, fresh, dry air. This way, the building envelope only experiences the dry winter air and no moisture or condensation ever has a chance to build up inside the house. Panasonic offers some very helpful guidance on sizing a fan for your house on their web site. "Sealed Combustion" for furnaces, boilers, and any other combustion-based heaters is a necessary part of the negative pressure strategy. It is also possible to install a fresh air supply duct - often referred to as a passive inlet.

At Shelter Institute, one of our goals is efficient design. We build dozens of beautiful, energy efficient timber frame homes each year. These houses are virtually air-tight and super-insulated, easy to heat and cool and very, very comfortable to live in. The line of fans we recommend and carry in our store is manufactured by Panasonic. These super efficient fans are incredibly quiet and durable. They are rated for continuous operation - which means we turn them on in the fall and leave them on all winter. We recommend to each of our timber frame clients that they install and use continuously one of these fans in their new house! In conjunction with compatible whole-house systems, these fans solve a variety of moisture related problems in existing structures as well.

Riddle: Why do other manufacturers make their bathroom fans so noisy?

Answer: To remind you to turn them off because they are so inefficient.

The efficient, quiet Panasonic Whisper Ceiling™ Fans are the ideal replacement for an existing bathroom fan. You can purchase one on our web site or visit the Panasonic site to see answers to frequently asked questions on efficiency, sound levels, and flow rates.

Gaius specs the Panasonic fans for every house we build.