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

[Norbert Senf]

At 03:23 PM 12/5/2006 -0800, 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?

Yes. Check out the "Washington state certified" Rumford on Jim Buckley's site
www.rumford.com

There will be a link to a source for some nice very minimalist airtight ceramic
glass doors. You need to install the "Wolf's Mouth" air supply that is used
on the Washington state fireplaces.

>  Can they be converted to gas log Rumfords with airtight sealed doors
>and still work?

Yes.


>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.

Yes, to a point. You can subtract the existing leaks in the house, which are an
unknown until the house is actually built and tested with a blower door.

We've got "R-2000 Makeup Air Guidelines" online here:
http://mha-net.org/docs/R2000-2.pdf

it provides a very good diagnostic technique for determining and supplying
the correct amount of makeup air, after the fact.

also, a consulting report on makeup air for a new 
house with 6 large open fireplaces:
http://mha-net.org/msb/docs/rept-makeup.PDF



-------------------------------------------
Norbert Senf---------- mheat(at)heatkit.com
Masonry Stove Builders
25 Brouse Rd.
RR 5, Shawville------- www.heatkit.com
Québec J0X 2Y0-------- fax:-----819.647.6082
---------------------- voice:---819.647.5092