[Greenbuilding] forced air heating vent placement

[RT]

Reuben;

As WatJohn has pointed out moving the supply air registers to the core  
partitions works for buildings with high-performance walls & windows and  
although doubling the R-value of the farmhouse walls and windows is a Good  
Thing, I have doubts whether the improvement will be sufficient to move  
the registers back to an interior partition parallel to the exterior walls.

The increased depth of the window wells will almost certainly create still  
air pockets at the bottom portions of the windows and that still air  
lingering against the R-2 or R-3 equivalent of the exterior-stormed  
windows (depending upon whether the original windows were single or  
double-glazed) can result in very serious condensation issues and possibly  
ice accumulation on the bottom edges of the vision glass and bottom sash &  
sills.

Since the existing registers will be buried by the added wall thickness,  
when you shorten the supply ducts to move the registers away from the new  
walls, it would be possible to run a smaller wide/thin duct extension from  
the end of the shortened duct/new end boot just beneath the interior wall  
finish under the window sill to a long,skinny slit-type register in the  
window sill that would provide enough upwards air movement against the  
glass surface to prevent the air against the glass from cooling down to  
the dew point.  You'd probably want to install a damper in that duct  
extension so that the volume can be adjusted to minimise noise (imagine  
the phenomenon of a whistle).

For an old farmhouse reno, it's likely that the budget would not allow for  
the storebought skinny registers that are more typically used in  
commercial work so you might make one out of wood. Easy to do on a table  
saw by ripping the slots on the top face with the blade set at half depth  
and then cross-cutting on the backside for the remainder of the depth.



On Mon, 28 Mar 2016 18:29:36 -0400, <jfstraube at gmail.com> wrote:


> Suffice it to say, walls with better than code insulation , good  
> airtightness (way better than 5 ACH and usually below 3) ‎, reasonable  
> window areas with very good to exceptional performance do work.


> home-nrg at dnaco.net

>> with all of the ducts in a central wall cavity


> From: Reuben Deumling <9watts at gmail.com>

>> I'm in the process of adding four inches to the inside of
>> the exterior walls on a 140 year old farmhouse and blowing
>> a ton of cellulose into those deeper cavities. There will
>> be exterior storm windows

-- 
=== * ===
Rob Tom  .  .  . T60BOM
Kanata, Ontario, Canada

A r c h i L o g i c  at  Y a h o o  dot C A
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