Kitchen exhaust really sucks!

Range HoodI think the title explains itself.  Commercial range hoods or downdraft exhaust are becoming popular in new homes and kitchen renovation projects.  You know they look cool or have the ability to hide in the counter top, and man can they suck.  Hold your hair piece around some of these because you could lose it.  They actually pull so much air out of the house, that they cause very harmful conditions in the home.  And I have been conducting energy audits on more and more of these homes lately and leaving with not so happy customers.

The issue that these exhaust units create is that they are pulling so much air out of the home that air has to come back into the home somehow and this is causing standard atmospheric water heaters and the less efficient furnaces that are still in operation in lots of homes to backdraft.  So anytime you turn on the exhaust, it actually pulls the combustion gases from your water heater into the home increasing ambient levels of carbon monoxide.  And this situation can occur in any old, new, large, and leaky home.

I mention not so happy customers because when I come across this condition, all incentives from the local utility to make efficiency improvements are halted until the back drafting issue is resolved because we don’t want to tighten up a home and make the conditions worst.  Although this is not really a green building issue, it is just that green builders and designers who look at how the house works as a system takes these kinds of issues into consideration.  Therefore here is a preview of a great article from on ways to prevent the back drafting from these high cfm rated exhaust fans that any homeowner, architect, designer & builder/remodeler should read if considering one of these units.

Makeup Air for Range Hoods

If your kitchen has a powerful exhaust fan, it may be pulling air down your chimney or water-heater flue

Most homes have several exhaust appliances. These typically include a bathroom fan (40-200 cfm), a clothes dryer (100-225 cfm), and perhaps a power-vented water heater (50 cfm), a wood stove (30-50 cfm), or a central vacuum cleaning system (100-200 cfm). But the most powerful exhaust appliance in most homes is the kitchen range-hood fan (100-1,200 cfm).

Every time an exhaust fan removes air from your house, an equal volume of air must enter. The air that enters cracks in a home’s envelope to replace air that is exhausted is called “makeup air.” Two trends affecting makeup air are causing increasing problems for homeowners: homes are getting tighter, and range-hood fans are getting more powerful.

So where does a powerful range-hood fan get its makeup air? If the house doesn’t have enough random air leaks around windows, doors, and mudsills, the makeup air is often pulled backwards through water-heater flues or down wood-burning chimneys — a phenomenon called backdrafting. Since the flue gases of some combustion appliances can include carbon monoxide, backdrafting is dangerous. In some cases, it can be life-threatening.

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Incorporating LEED into Project Specs

“A LEED rating system does not confirm sustainability,” Susan Kaplan, CSI, CCS, a specifier for HLW International in NYC, explained to CSI’s Sustainability Practice Group during a recent meeting.

LEED is not a complete roadmap for running a green project. There will always be new material and system requirements, regulations and standards, etc. These are all LEED “special needs.”

Although it uses a great organizational method that covers attributes including Sustainable Sites, Water Efficiency, Energy and Atmosphere, Materials and Resources, and Indoor Environmental Quality, LEED does not cover the entire life cycle of the project. was mentioned to emphasize that one needs to view the project from the stand point of the entire life cycle.

In the future, LEED will move toward a multi-attribute focus. ISO standards are beginning to address these attributes through LCA, and to look at products more comprehensively. Today’s owners do not necessarily understand that the products they are getting are not as green as they are made out to be. Michael Fuller, CSI, AIA., NCARB, CDT, LEED AP, member of the GreenFormat Program Management Task Team, believes that in the future, there will eventually be more comprehensive definitions of what constitutes a green or sustainable product.

Continue reading the article at CSI Blog