Innovations in designing green chemicals are emerging in nearly every U.S. industry, from plastics and pesticides to toys and nail polish. Some manufacturers of cosmetics, household cleaners and other consumer products are leading the charge, while others are lagging behind.

For decades, many manufacturers used the most powerful weapons in their chemical arsenals, with scant attention to where they wound up or what they might have been doing to people or the planet.

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Heat Recovery Ventilation (HRV) systems are a relative newcomer to the cold climate construction scene, yet have become almost indispensible in today’s super-insulated, air tight homes. They are also becoming an increasingly common element in the current weatherization and insulation retrofitting trend. As older homes are undergoing energy facelifts, and becoming tighter and better insulated, they are also facing the same indoor air quality challenges one would see in new construction. In this article I am hoping to provide a basic understanding of how HRV’s work, their applications, and their advantages.

The HRV is principally designed to supply a regulated exchange of fresh air to the house, while simultaneously expelling stale indoor air. This is of particular importance in a home that is too tight to do so on its own, through passive means. At the core of the HRV unit is a heat exchanger where the airways exhausting the warm, moisture laden indoor air, flow next to the air passages bringing in outside air. At this junction, the cooler incoming air is warmed by the outgoing exhaust air, recovering a substantial amount of heat that would otherwise simply be lost. Typical heat recovery percentages can range from 70 to over 90 percent, depending on the unit and the controls. This is where the HRV shines in comparison to a simple exhaust fan that blows warm air directly outside.

A typical HRV system is designed such that its ducts supply fresh air to bedrooms and living areas while exhausting stale, humid air from bathrooms, kitchens, laundry rooms, and crawlspaces. The HRV should not be substituted in place of a cooking fan, so a range hood should still remain the primary vehicle to remove grease and smoke from above the cook stove. The HRV is designed to be balanced so that it takes in as much air as it exhausts, maintaining close to neutral pressure. Consequently, it is important to note that it is not meant to be a means of supplying air to combustion appliances. Because the system is neutral, it does not present potential back drafting hazards such as one might find in conventional unregulated exhaust fans, which can possibly create excessive negative pressures. Most units run efficiently, using about as much power as one 60 watt bulb when operating, and the industry is constantly improving energy use and performance. As with any appliance, the HRV requires some minor maintenance. Every fall would be a good time to check the built in filters and clean or replace them as necessary.

In addition to regulating air flow in a home, HRV systems can also perform several other important functions. After talking with Rich Musick and Bill Reynolds at Solutions to Healthy Breathing, I learned that it is now possible to install an in-line filter system directly after the inbound fresh air leaves the HRV unit. This allows the home owner to filter the incoming air for particulates and odors. One application in this regard might present itself this winter to those people who may find themselves in neighborhoods with poor air quality due to excessive wood or coal smoke. The potential for pollution levels to increase in Fairbanks this winter is very real, and people with asthma or other breathing issues could benefit from this option.

One other feature worth mentioning is that with the right controls, an HRV can be made to operate in a recirculation mode. A humidity sensor in the unit insures that it meets the house’s air exchange needs, after that it can be programmed to default into recirculation. This would be an excellent feature for people who are using a woodstove as a major source of heat and need a means to distribute that heat to hard to reach areas in the house.

Up front an HRV system may seem like a significant expense, but it is also important to look at it as an investment. By improving indoor air quality, the HRV can help to insure peace of mind by providing a healthy living environment year after year. It also helps contribute to the longevity of the structure by removing moisture before it has the opportunity to do real damage. Keep in mind that in this climate, indoor moisture problems are a big concern not only to the house, but also the occupants if mold is allowed to proliferate. If you own an older unit, a control upgrade may be an option, and prove quite cost-effective and beneficial. If you are thinking about purchasing a system, as always, it pays to learn about specifics, and find an installer who is willing to educate and stand behind their product.

Ilya Benesch is the Building Educator at the Cold Climate Housing Research Center (CCHRC). For questions or comments please contact CCHRC at (907) 457-3454

One of the main goals in building a high energy efficient home in our extreme climate is to seal the inside of the home as tight as possible. This eliminates any heat loss through air leaks and saves real money on the heating bill.

But of course that tightness comes with a considerable trade off. If no heat can escape the home then no fresh air can infiltrate into the home, and the tighter the home the more this becomes an issue. This is a very important fact which needs to be considered carefully—as we all need to breathe. Lots of fresh air, at all times.

That is a fact—and in our climate a healthy and comfortable climate can only be achieved by mechanically exchanging the house air. That’s why every tight home needs a Heat Recovery Ventilator (HRV) to work properly. Everything else is a short cut, which will not work as desired by the homes occupants.

So, what does an HRV do? First and foremost it supplies fresh outdoor air to the inside of the home while exhausting the inside air to the outside via a balanced ventilation system. Of course, if the fresh air is cold, it will need to be warmed up, and that costs money. A heat-recovery ventilator uses the heat in the outgoing stale air to warm up the fresh air. A typical unit features two fans: one to take out household air and the other to bring in fresh air.

What makes an HRV unique is the heat-exchange core. The core transfers heat from the outgoing stream to the incoming stream in the same way that the radiator in your car transfers heat from the engine’s coolant to the outside air. It’s composed of a series of narrow alternating passages through which incoming and outgoing airstreams flow. As the streams move through heat is transferred from the warm side of each passage to the cold, while the airstreams never mix.

HRVs can recover up to 85 percent of the heat in the outgoing airstream, making these ventilators a lot easier on your budget than any passive system or opening a few windows. But what about electricity costs?

Yes, of course an HRV is not only expensive to install, but also requires energy in form of electricity to work. But at fuel prices over three dollars the payback outweighs the costs by a big margin. In the end however the main question is—how much is a healthy house environment worth? It is priceless.

Thorsten Chlupp is owner of REINA Properties Corporation an Energy Star & GREEN Builder and recipient of the first Platinum certification on GREEN build homes in the State of Alaska. Mr. Chlupp is also a member of the Interior Alaska Green Building Committee Council. He has been building in the Interior since 1997 and has focused on GREEN build since 2005.