[Greenbuilding] Natural ventilation.

[RT]

On Mon, 29 Aug 2011 20:20:01 -0400, Frank Tettemer <frank at livingsol.com>  
wrote:

> The walls are 8'-3" at the truss plate, and the central high point in  
> the ceiling is 10'6".
> The home will be heated with an ESSE wood cooker, and has a 4" diameter  
> ABS pipe emerging from the floor, behind the ESSE, bringing in fresh  
> air, from below ground, and will be ducted to the combustion air inlet  
> on the wood stove for the winter.
> During the summer, a 4" TEE in this air pipe will allow earth-cooled  
> outside air into the home.
>
> Back to my original question around ventilation. How do I open and close  
> that 4" ceiling vent?

In my previous reply to this thread I got so carried away with yammering  
on about F.H King's natural ventilation system that I forgot the raison  
d'être for my posting -- Frank's question about the ceiling vent.

In my own home for the combustion air inlet that is a 100 mm  I.D. pipe  
run from outdoors -> under the under-slab insulation -> to the woodburner  
located at the geometric centre of the floor plan, I installed a short  
section of thick-walled (6 mm)steel pipe at the point where the inlet pipe  
emerges from the floor and inside of the pipe, a stainless steel round  
disc, precision-fitted, mounted to a brass rod (16 mm dia) fitted through  
the diameter of the steel pipe, ends of the rod extending out from the  
pipe far enough to accommodate washers, lock washers, hex nuts and a lever  
to indicate the orientation of the disc as well as providing a means to  
rotate it. (SS and brass components to minimise the possibility of moving  
parts seizing due to rust from condensation) -- basically an automotive  
carburetor throat.

The leading edges of the disc are bevelled (ie for half of the  
circumference on opposing faces) to enable the disc to move to and from  
the fully closed position (same idea as bevelling the latch edge of a  
door). I don't use that supply inlet. (see note below)

To operate the damper from 4 ft down from a 10 ft ceiling, it would be a  
matter of providing some mechanical linkages (ie a sash cord + pulleys,  
like on old-fashioned Venetian blinds or a couple of short rods).

If that sounds like too much trouble, perhaps there might be some  
honking-big carburetor in the Big Trucks graveyard that could be salvaged  
and butchered for the job and keep the throttle mechanism so that you step  
on a gas pedal to operate the butterfly ? (Nyuk, nyuk, nyuk)

That being said (this is the Note Below), it might be a good idea to have  
a look at Norbert Senf's comments on the necessity, utility and dangers of  
providing outdoor combustion air ducted to wood-burning appliances in  
air-tight houses , taking note of the potential for the supply duct to  
inadvertently becoming a flame-spouting chimney (and as such, the  
inadvisabilty of using plast-eccchhh! components in that duct run :

  http://www.repp.org/discussion/greenbuilding/199901/msg00481.html


Another approach (instead of the butterfly valve) might be to install  
something like the site-made damper for the 150 mm (6 inch) exhaust vent  
on my downdraft kitchen range -- not unlike the blast gate that is used in  
the duct runs of woodworkers' dust collection systems.

http://www.leevalley.com/en/wood/page.aspx?p=51506&cat=,62597


The advantage of this approach is that the the blade or "gate" can be made  
as an insulated panel. (I used a 20 cm x 20 cm (8" x 8") piece of 50 mm (2  
inch) eXtruded PolyStyrene wrapped with 30 gauge galvalume on the business  
faces of the sliding panel), site-bent galvalume channels for the tracks  
in which the panel slides, site-made sheet metal collars etc. all mounted  
onto a piece of 10 mm plywood so that the whole schmozzle is easily  
attached and air-sealed over the vent opening.

And all that being said, I am more than a little sceptical of the efficacy  
of a 100 mm ID passive supply air inlet for whole-house cooling. I suspect  
that we'd be talking more along the lines of something
with at least 10x that in cross-sectional area.



-- 
=== * ===
Rob Tom
Kanata, Ontario, Canada
< A r c h i L o g i c  at  Y a h o o  dot  C A >
(manually winnow the chaff from my edress if you hit REPLY)