[Greenbuilding] tight additions open to drafty houses

[John Salmen]

I agree that you have to build to a tight standard for an addition (no point
in doubling the leakage). I have had clients that have refused the expense
of outboard insulation - but for that I design with framing on 24" centres
and specify roxul batts (r23) which makes a big difference - can generally
encourage the roxul upgrade by savings in framing (which there are) and
health issues of lung irritants. At least you are assured of the best you
can provide for in terms of the basic structure. The rest can be upgraded...

Also a small addition built tight will require makeup air... even if they
invested in day of interior air sealing of the original.


 If the addition is built to an air tight standard and a small space it will
require make-up air in any event which as you say the old house could
supply. 

-----Original Message-----
From: Greenbuilding [mailto:greenbuilding-bounces at lists.bioenergylists.org]
On Behalf Of Eli Talking
Sent: March-13-13 2:41 PM
To: Green Building
Subject: [Greenbuilding] tight additions open to drafty houses

I have a client I am trying to "Deep Energy Retrofit" their old house. 
Whether they do that or not, I think it is important to make the addition to
the new standard of tightness.  However, it evaluating the value, I am
confused by the impact of being open thermally to the 1930+- un-insulated 2
story clapboard house.  If not thermally separated, will the tight
construction of the addition get air from the drafty main house.

Though a Foyer and hallway needs to open to the old house, perhaps the
bedrooms, bath and closets could be separated by sealing and insulating
interior walls.  I would think that since the old house will be conditioned
to comfort, insulation is secondary to sealing.

Would that separation be needed to take advantage of ERV.  Maybe a simple
timer on bath vent could deliver the fresh air from drafty part of house.

I am a little on thin ice in that thermal efficiency is not their agenda. 
However, I feel an ethical responsibility to build new to a high standard. 
To build to the common practice is to build obsolete without consideration
of the embodied energy that will be consumed.  If we build to reduce and
ideally eliminate the consumption of non-renewable energy, we have not
depleted the resource used to make the house until the house is destroyed.

Eli 



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