Blog

Understanding C02 Emissions in Buildings

8/22/2013

When is there too much CO2 in a building? Let’s take a look at the air quality inside a building. First, we must consider the carbon dioxide content CO2 of the air. The presence of carbon dioxide inside buildings is largely due to human respiration, because the metabolism of cells converts oxygen to CO2 when it is breathed out. A person at rest or a low level of activity will produce 0.7 g CO2 every minute. The diagram shows some concentrations

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

7/11/2013

The core of heat recovery is the heat exchanger. There are various types of heat exchangers availabe 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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Understanding the Summer Bypass Function

7/3/2013

As the season approaches for cooling in North America, we want to share some information on Summer Bypass, or Night Cooling. Most of our units provide for automatic Summer Bypass and utilize programming that senses when the inside temperature is warmer than desired, and the outside temperature is cooler than the inside temperature. A damper is automatically opened that routes the outgoing warm air around the heat exchanger, and allows the cool outside air to come directly into the house, through

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ASHRAE Standard 62.2-2010

6/10/2013

So much talk in the building industry these days seems to be about ventilation, and specifically, ASHRAE 62.2-2010. This is the standard that is being adopted by many states for code compliance, as well as by weatherization programs across the country. With the new standard comes plenty of confusion, and plenty of scrambling to understand and implement the standard. In reviewing the ASHRAE 62.2 -2010 standard, it becomes clear that compliance is a challenge with a conventional exhaust only (bath

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Understanding the Summer Bypass Function

3/27/2013

As the season approaches for cooling in North America, we want to share some information on Summer Bypass, or Night Cooling. Most of our units provide for automatic Summer Bypass, and utilize programming that senses when the inside temperature is warmer than desired, and the outside temperature is cooler than the inside temperature. A damper is automatically opened that routes the outgoing warm air around the heat exchanger, and allows the cool outside air to come directly in to the

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Frost Prevention in HRVs and ERVs in North America

2/21/2013

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

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ASHRAE Standard 62.2-2010

11/6/2012

So much talk in the building industry these days seems to be about ventilation, and specifically, ASHRAE 62.2-2010. This is the standard that is being adopted by many states for code compliance, as well as by weatherization programs across the country.Â Â With the new standard comes plenty of confusion, and plenty of scrambling to understand and implement the standard.Â In reviewing the ASHRAE 62.2 -2010 standard, it becomes clear that compliance is a challenge with a conventional exhaust only (bath

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Combining HRVs/ERVs and Heating/Cooling

9/12/2012

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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HRV vs ERV

8/28/2012

We are often asked, “Should I use an HRV or an ERV?” Building professionals sometimes assume that the use of an HRV versus an ERV can be determined by geography, but itâ€™s often not that simple. Much of the country uses an HRV and one could generalize that ERVs are better for humid climates, but what about those climates that are both dry and humid during the year? For New England, often building professionals use an HRV, but one could realistically use

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