[Greenbuilding] Back to Rumford fireplaces, tight homes & backdrafting

[Keith Winston]

I think it's a huge mistake that we've all been lead to believe the 
bigger the exhaust fan (kitchen, bathroom) the better. And I'm 
incredulous that no fan manufacturer has figured out a direct-vent 
option of any kind associated with their fans (i.e. an electronically 
controlled make-up vent in the kitchen, to keep from depressurizing the 
rest of the house, and only on when the fan is on, perhaps even to the 
same level).

I'm sure it'll happen soon. Maybe.

Keith


Tom St. Louis wrote:
> Builder has installed Rumfords in two SIPs homes. The homes are so tight 
> that when the kitchen fan is turned on, the chimney backdrafts (even with 
> the combustion air supply open at the side of the fire box), this gets worse 
> as more fans and the clothes dryer are turned on. Even the 'supposed' sealed 
> combustion Rinnai on-demand water heaters backdrafted. Oh dear!
>
> More make-air sources are going to be added or maybe a larger single source 
> possibly behind the kitchen stove. Looking at adding sealed glass doors to 
> the Rumfords to add extra insurance to prevent backdrafting.
>
> Will a wood fired Rumford firplace work having air-tight sealing 
> ceramic-glass or other high temp glass doors with outside combustion air 
> source? Can they be converted to gas log Rumfords with airtight sealed doors 
> and still work?
>
> Big reminder for everyone.........
> Add up all the maximum CFM capacities of all exhaust air fans and appliances 
> in your buildings while still at design stage, then plan and specify make-up 
> air source(s) equal to worst case for air being sucked out. Must have 
> incoming make-up air equal to what is being exhausted.
>
> Add an adjustable barometric type or electronically controlled damper to 
> allow needed make-up air to prevent backdrafting or sucking air through 
> cracks in the building envelope. Some homes with those modern stainless 
> steel 700 to 1500 cfm kitchen fans or down draft stove fans would require a 
> fan to bring make-up air in.
>
> Tom
>
>  
>
>
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-- 
Keith Winston
Earth Sun Energy Systems
Hyattsville, MD 20781
301-980-6325
send me mail at 
keith at the company below
www.EarthSunEnergy.com