Engineered Systems - October 2008 - (Page 53)

Cold Climate HVAC Challenges a significant concern in cold climates. The development of sustainable buildings with better energy efficiency has driven a general improvement in building envelope design. However, the desire for better indoor comfort has increased the use of humidification within buildings. Low indoor humidity can lead quickly to dry, itchy skin and noticeable discomfort in the human eye and nose. Providing an indoor environment with a minimum moisture level provides, as a minimum, relief from this discomfort and has been tied to improved healing in medical spaces. The dewpoint of spaces without humidity control can be as low as 25°. However, the dewpoint of humidified spaces can rise as high as 50°. In short, if any surface within a humidified buildings drops below the dewpoint of the indoor air, there is a strong potential for condensation to occur on that surface. Even with improved building components, it is sometimes difficult to keep all exterior envelope surfaces above these humidified space dewpoints. There have been instances of moisture forming on windows, window frames, window sills, doorframes, wall surfaces, and floor surfaces. These examples have been the result FIGURE 1. Typical VAV system with central return fan. (Schematic couresty of Trane Engineering.) of overcooling of surfaces due to cold exteriors, lack of proper insulation, lack of proper air movement, or lack of proper control. If condensation persists, and the surface temperature drops below freezing, ice and frost can form, making the symptom even more obvious and objectionable to the occupant. Another problem with persistent condensation is that it can result in high moisture levels within the building material itself. This can lead to mold and mildew once warmer weather arrives. Built to be the Best ™ www.Laars.com Input 209 at www.esmagazine.com/instantproductinfo | 800.900.9276 ©2008, Laars® Heating Systems. All rights reserved. ESM10084Laars.indd 1 w w w. esmag a zin e.9/22/08 com 9:25:24 AM 53 http://www.Laars.com http://www.Laars.com http://www.esmagazine.com/instantproductinfo http://www.esmagazine.com

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Engineered Systems - October 2008 Contents Editor’s Note Letters Back2Basics HVAC Challenge Case in Point Commissioning Building Automation HydroTech HVACR Designer Tips Special Insert: Engineer's Technical Library Fall 2008 Living Wild! Chilled Beams in Chicago Phoenix Convention Center: On The Rise Cold-Climate HVAC Challenges Humidification Strategies For Data Centers & Network Rooms Special Advertising Supplement: Tabb Talk Computers & Software Issues & Events Products Literature & Catalogs Glossary Classifieds Advertiser Index Tomorrow’s Environment

Engineered Systems - October 2008

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