Reducing Spring Allergies in an Energy-efficient Home


The arrival of spring for many of us signals a return to the garden and hiking trails. Unfortunately, for some, it also signals the return of seasonal allergy symptoms. Pollen counts are currently at medium to high levels in most of the United States. Tree pollens, such as birch, ash, maple, and oak, are especially prevalent now, becoming airborne and leaving a noticeable layer of pollen dust on cars and waterways. Humidity levels are also on the rise, boosting dust mite populations

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Ventilation IAQ


Spring has sprung and pollen is in the air! It’s during this time of year that we focus on allergies and asthma and the air in our homes. We start to open the windows to let the fresh air in, and we start to sneeze. With the increased focus on IAQ, ventilation becomes an important subject. We’d like to discuss the different methods of providing fresh air to our homes, and how these different methods can have different results.  There are three methods

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Effects of Indoor Humidity


One of the functions of an energy recovery ventilator (ERV) is to lower the humidity entering the home in a hot, humid climate. To understand the true benefits of indoor humidity control, it is important to understand humidity and the effects it has on the body. Research shows that indoor humidity can contribute to illnesses and health conditions such as allergies and respiratory infections. It’s important to have a strategy to maintain comfortable and healthy humidity levels. What Is Humidity? By definition, humidity is

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What is an Energy Recovery Ventilator?


Today’s building requirements demand improved energy efficiency and air quality standards for residential and commercial HVAC systems. In addition, as new buildings become more airtight, there is an increased demand for contractors, engineers and system integrators to improve the performance of mechanical ventilation systems. How Energy Recovery Ventilators Work An Energy Recovery Ventilator, also known as an Enthalpy Recovery Ventilator (ERV) is an essential component in an HVAC system as it improves indoor air quality by bringing in the fresh air, reduces energy consumption

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The Comfort of a Heat Recovery Ventilation (HRV) System in Cold Maine


“Where are the driveways?” asks one guest visiting Belfast Cohousing & Ecovillage (BCE). “How strange, these houses don’t have any driveways!” Even the layout of the homes demonstrates that this is not a typical subdivision. But that’s just the beginning. My family recently purchased a high-performance house in BCE, a multigenerational community with 36 homes. Despite the cold winters here in Midcoast Maine, we have no furnace and no radiators. Our house is heated primarily from solar gains, its occupants, appliances, and modest

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How Critical are Heat Recovery Ventilators for a Healthy Indoor Environment in Energy-Efficient Homes?


Heat Recovery Ventilation (HRV) systems provide a range of advantages for a healthy indoor environment in high-performance homes. Over the course of their lifetime, individuals will spend an estimated 80 percent of their time indoors. If these individuals are exposed to poor air quality within the home, it can contribute to chronic and acute health conditions such as allergies and asthma. HRV systems ventilate homes with a continuous supply of fresh filtered outdoor air. Indoor Air Quality Good indoor air quality is a key

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What is Heat Recovery Ventilation?


Heat Recovery Ventilation (HRV) is a balanced mechanical ventilation system designed to bring in continuous fresh filtered air from the outside while retaining most of the comfortable room temperature. When in a leaky building, HVAC equipment is constantly heating or cooling the unfiltered, unconditioned incoming air depending on the season. The unconditioned, uncontrolled air can produce drafts and variations in temperature from room to room. Controlled mechanical heat recovery ventilation greatly reduces unconditioned infiltration from the outside and temperature variations between rooms

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Understanding Heat Exchangers- Cross-flow, Counter-flow (Rotary/Wheel) and Cross-counter-flow Heat Exchangers


The core of heat recovery is the heat exchanger.  There are various types of heat exchangers available including cross-flow, counter-flow (includes rotary/wheel) and cross-counter-flow. Through a heat exchanger, fresh-filtered air flows into the house continuously and an equal volume of stale air simultaneously flows out of the home. These airflows are allowed to pass by each other – separated only by a thin membrane.  The longer the two streams flow past each other, the higher the efficiency. How a Cross-flow Heat Exchanger

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Frost Prevention in HRVs and ERVs in North America


There are several options for preventing frost in HRVs/ERVs, and the following is a sampling of the most popular options. It is important to have adequate frost prevention and depending on your climate, there are best practices available. If you have questions about best practices for your region, contact Zehnder America for recommendations. Option One – Utilize a ground source Pre-Heater/Pre-Cooler. The Zehnder ComfoFond-L utilizes a ground loop of glycol and a small circulating pump to pre-heat or pre-cool and dehumidify incoming

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Problems with Combining HRVs/ERVs and Heating/Cooling


Zehnder has been dealing with this issue across the country, and newly collected data confirms our recommendation that you do not mix the two. There are two aspects of this practice that have had negative impacts on comfort, efficiency, and healthy environments. 1)  Heating/cooling the ventilation air – The biggest drawback here has been the tendency to over-ventilate to meet heating or cooling needs.  In winter this can lead to drying out of the indoor air, and in summer this can lead to

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